gtm

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Everything posted by gtm

  1. quote: Originally posted by: David Burgess I've used both. Piezo film is much cheaper than a phono cartridge. Much less fragile, harder to damage. Don't need to figure out which of the four phono cartridge wires to use. Easily used from any position (sideways or upside down) Will handle larger amplitudes than a phono cartridge. ... Also works well as feed for a spectrum analyzer or FFT program PIEZO FILM Hi David and all: Not meaning to be contentious but I see some drawbacks. The color codes and pin-out of cartridges are standard in the industry. Yes there is a significant difference in cost, in this case I have many. Tone arms can be made to work sideways (jukebox) or upside down by adjusting the counter balance. Thankfully I don't have a lot of experience dropping un-dampened tone arms though not known any to be destroyed. That said I can agree the strip appears to be more robust though doubt that is needed for this application. As for amplitudes I again question how it's attached to the surface... weighted, taped, or clamped. Any of these could cause false readings whereas the needle would not have these problems. Consider what happens when the tone arm goes skating across the grooves, it isn't destroyed. If I am to believe the drawings there are areas which would be overlapped by the strip thus having shadows not knowing what was being sampled especially using a larger size. We are also talking about a monural source if that matters. By design you can hear the left side of an orchestra vs the right, rotate 90' it may recognize front to back.(???) If true I could see as a real plus in determining wave source. It could be the needle will be too sensitive and I miss the point so to speak. There are so many unknown variables that it could be just a waste of time and the real proof is just following the thinning drawings and be done with it. Cheers, gtm
  2. quote: Originally posted by: Tim McTigue Sorry, I really don't. ... I have very little information or experience, and if I've represented myself otherwise, it's most assuredly not intentional... Hi David, Tim and all: Woops, that was a generalized statement about starting from scratch and not about plate tuning. I've followed your progress and take my hat off to you for your work. ............ David, I know nothing about a piezo strips nor know why they would be better? The phono can be adjusted down to less than 1 gram or up 10 grams for I don't have a tracking or skating issue. I could load them up sideways with a feather if I thought placement and wave form was being distorted. Cheers, gtm
  3. quote: Originally posted by: Tim McTigue quote: Originally posted by: Andres Sender look at Martin Schleske's website. The stuff he's doing is where all this actually starts to get interesting, Wow, that site is a revelation! gtm, take the photo tour there - a number of pictures look like what you're attempting. ... Also check out platetuning.org - that site looks like a gold mine... quote: Originally posted by: gtm ...Honestly didn't know what I was faced with ... ...every step of the way feels like that. There are layers upon layers of depth to this endeavor, which is why I guess so many spend a good part of their lives pursuing it... Hi Tim,Lyndon,Andres,Mark and all: By no means did I read all that was offered on those sites. I did reject the use of microphones if I am to use a speaker and given tones. It would be impossible to isolate the source and the effect. The other aspect was to not become so involved requiring sophisticated electronic measuring equipment. I now have diagrams of known areas to address. Once I have mapped some of these I should have a better idea if the phono cartridge is a valid method to _hear_. I think it's important to have some recorded data so should I undertake another I have a reference point of where to begin. Tim you have a considerable leg up on this for you have been at it for over a year with loads of reading and planning behind you. I'm coming in after the fact with a very narrow limited knowledge base and a plethora of ideas on how I should do something without adequate information. I just found out how to plot the highs and lows on the top and back with a simple tool thanks edi malinaric. Combined with the diagrams at least I will have some basis for trying something. Thanks, gtm
  4. gtm

    Calipers

    quote: Originally posted by: edi malinaric Hi GTM - you wrote... ... "found mention that the indicator stylus is 4-48 thread so that may be an international standard just like ball bearings are in inch sizes." Negative, negative, negative - on the international standard that is... Always be aware that the metric system is for real and healthy in the great wide world. ... There's nothing special about it, just another standardised system like ACME, BA, BSW, BSF, NGT, NPT, SAE, UN, UNC, UNEF, UNF .... I have both imperial and metric thead gauges to avoid "close enough" engineering. Wrt to bearings, Google for FAG bearings and have a loook in their catalogue for the range of metric bearings that are available. As for stringing up my plywood calipers - I've tried a couple of plywood cellos - didn't care to much for them so I'll pass on that one. Hang loose - cheers edi Hi edi and all: Strange that the "tip kits" are inch sizes. The mm gauge I was looking at (Chinese?) mentioned they were inch threads sizes. I'm well aware the Metric system is here to stay, I believe it's the standard in engineering schools. My kids will frequently state a size in metric measure and sometimes have difficulty with inch sizes. Be aware that Japanese metric threads are not the same as European metric. While the measure is metric the actual profile is different. It is their contention that the sharp point of the thread causes galling thus their's is rounded. The difference is subtle but not beyond normal eye inspection. However try to find a tap and die set for these... I'm well aware that bearing outside measures are mostly metric, it's the actual balls which will be in inch sizes. That's according to a SKF employee many years ago when looking for a highly specialize metric thrust bearing for a roller crank. A quick Internet search could not establish this. As a matter of course any time I pick up an unknown source ball I'll check with mike only to find it's in inch size. It may be the US has all the important patents for manufacturer tooling and metals including chrome. For many years the balance of trade with Japan was higher because they imported more automotive making machinery than they exported in cars. You couldn't possibly get by without metric pitch gage if you didn't recognize standards especially in the automotive industry. ............ I seem to recall they do make a bias ply plywood though may be like finding hen's teeth. I've not found any guitar I would own made from plywood, the sonority just _ain't_ there. I suspect you would have better luck laying up your own carbon fiber laminate even if you have to build your own press and molds. Onward, gtm
  5. gtm

    Calipers

    quote: Originally posted by: edi malinaric ... - and why not string it up with a violin E-string on both sides to achieve that extra stiffness and at much less weight! Don't forget to get a good fit at the bridge feet. cheers edi Haaay, let's not get carried away with turnbuckles, toggles and marine eye's. :-) Actually I see no reason these cannot be fitted to your plywood calipers. ............. Was looking at mm dial indicators and found mention that the indicator stylus is 4-48 thread so that may be an international standard just like ball bearings are in inch sizes. I'm really not concerned with the flex, as long as it returns to zero when the excess load is taken off. I could buy some flat corner braces in steel and glue or screw them in. Initial checks of the top are mostly on the fat side though there are a couple areas that are already almost at spec. Cheers, gtm
  6. gtm

    Calipers

    quote: Originally posted by: edi malinaric Hi GTM - I should have put these up before you started making shavings. This one works a treat for tracing the plate contours. ... The little drop of nail polish on the setscrew is useful when tracing the contours. Adjust it by 1 turn and you have the next contour exactly 1mm higher or lower. Half a turn gives you a 1/2mm difference. Makes beautifully even contours and picks out the high/low spots beautifully. cheers edi Hi edi and all: No shavings yet, probably a week away at the rate I'm progressing. That's slick, I like it. Are you using bore gauge, vernier caliper, or inside outside caliper to set the desired thickness? Do you use these in pairs as a go,no-go gauge? Change pencil lead colors when your work area gets too cluttered with marks? .............. Hot dang, hot dang, light bulb moment.......... Since I have plenty to work with on the throat with my Plexi caliper why not glue a pair of blocks outside on the upper and lower arms at say 2"-3" inboard of the dial? I can't see any angular torsional deflection causing a problem. For that matter I could glue another pair on the other side at different a location. This way I wouldn't increase the flex I reported earlier by drilling additional holes in the arms. Good idea??? I would like to install brass threaded Slimsert/Keensert on the adjustable screws. You can find small ones in plastic parts of high end electronics and older computer parts for salvage. These may not have outside threads but splines and molded into the plastic. If you crush them slightly they act like a "nylock" nut and they can be pressed and/or glued into place. We are not talking major tensile or compression loads on any of this. Cheers, gtm
  7. gtm

    Calipers

    quote: Originally posted by: edi malinaric As I wrote... "TSK, TSK, GTM - Us old fogies should know better.... Getting old quickly. cheers edi Hi edi: Speaking of old fogies... I'm about 90% complete with the Plexi caliper. Actually it's working fine but there is 0.005" of flex when I apply a bit of pressure beyond that of the dial spring. The arms ended up being 1.5 wide and the throat is 9.25 deep to the dial center. I can shorten the arms for it was an arbitrary length based on the original plastic size. I can drill another shorter location for the dial and anvil and leave the existing holes. An alternative is to determine just how much throat depth is needed for a violin and put a steel or aluminum bar strap bridging the 2 arms. Gut feeling is it would reduce the flex down to .001". The advantages of this are that they could be moved diagonally if I need a deeper throat for violas and maybe cello's. I've needed this tool a few times in my life and have always had to invent some substitute method of measuring. The other advantage is I can clamp the end in a 3" suction cupped equipped vise and I can run the top plate 3/4 the full length rather than having to work at right angles. Cant say I'm impressed with some of the tips which have sharp 90' corners for they want to dig into the wood. I'll have to chamfer them or find a plastic cap like a wire nut and sand it smooth. Don't say a word about my screws, they will get changed. Also thinking of buying just another dial gauge so I don't have to keep breaking down my magnetic base unit. Here are some picts including an antique hour glass just acquired. http://home-and-garden.webshot...album/562839445EXdweX Cheers, gtm
  8. Bad news of sorts. The "100% pure tung (china oil) oil I received from Leevalley apparently has had the UV catalyst properties removed. The first coat allowed to dry for 12 overnight showed no hardening change after 1 hour in the sun, a 2nd hour with same results. After 48 hours it still was still soft enough to load up 220 sandpaper. When I tried the white steel wool synthetic pads equal to 0000 it picked up slivers at 48 hours. At 60 hours I was able to get a second coat which was exposed to the sun for one hour, 9 hours later it could take another coat if I did not sand. There are still pores to be filled so I may apply the 3rd when the sun is up enough to warm the box. I might try mixing 25% Minwax tung which has driers and photo non reactive to see if that has any effect on another side. Also note the odor is not the same as what was used on my boat. I will write the supplier and see what they can suggest. Previous applications of Minwax yielded a high gloss rather than the satin which I found more desirable. Bummers Cheers, gtm
  9. quote: Originally posted by: Andres Sender You might want to read Keith Hill on area-tuning the violin, I believe some or all of his articles are now on the web. Then read up on plate-tuning, which is described also in various sources on the web, as well as a detailed writeup by Al Carruth which is in one of the GAL's Big Red Books now. There used to be a highly detailed discussion of steel-drum tuning on the web. ... look at Martin Schleske's website. The stuff he's doing is where all this actually starts to get interesting, ... Keep in mind that lots of people make very fine violins without any of the above. Just because some people might use (to make up an example) a microscope and a caliper which reads to .001 mm to make violins doesn't mean they are necessary to the process of making a fine instrument. Hi Andres, Mark, Lyndon and all: Thanks for all the good reading info, is there going to be a test? :-) While I can clearly hear tonal difference using the tap method I question my ability to properly make adjustments to correct what I am hearing. I use to have pretty good relative pitch and know when a guitar string was vibrating false when the root was in tune. I'm not ready for a hearing aide but obviously something more than a tuning fork is needed to keep me honest. In envy those who can look at a piece of wood, scratch here and there to make it sing. I think we call them professionals. It would be years if ever before I attained those skills. For certain I'm a lot more comfortable with tools and measuring as a way to compensate for my lack of intuition. It's this plate tuning which has me uncomfortable, not suggesting I'm heavy handed with my 9' disk grinder but I sure don't want to be seeing daylight while I'm chasing a perceived tone. (joke with the grinder) Honestly didn't know what I was faced with to the degree that has been dumped in my lap. I knew of thinning as a means to achieve a desired tone but no idea how involved it was. The phono cartridge seemed to make the most sense to prevent too many mistakes as I chase those magic tones. Tried several tappers and the best found to date is a ping pong ball to give the crisp sound without denting the surface. I was looking at the Vigdorchik tone strips and was talking with someone who has been using them for some years. If I can depend on that I surly can put a phono stylus and see what I have. Then comes the question of how to support the top. An instant solution is to cut the top shape out from a cardboard box and support the ends with stryofoam cups. This will also give me a mount platform for the tone arms and the box can house a speaker. Cheers, gtm
  10. Hi all: Watching TV show "How it's Made" for steel drums and noted the tuning process and was thinking of various possible methods of attempting same for violin. In the case of the steel drums they had microphone(s) / pickups used though they seemingly kept that info secret. They did mention it was being fed into a computer/laptop but again nothing shown. I was under the impression that it was not sophisticated or beyond the average pocketbook. I have seen colloids used to visually display a sound/ pattern though don't know that a specific frequency was assignable. Using glitter might not be as effective or reliable because it's following the curves in the surface. Hopefully the colloid in a freezer bag would give more detail. I could see amplitude changes would be helpful in isolating where they can be found. I've read in other threads here that the tap / rap methods have been used and employed. I am interested in something which is more definitive and perhaps less subjective which can be fed into a computer and monitored. I can impose a source tone from a speaker and then record what is actually happening in various areas perhaps in stereo or even quad sound. Borrowing from some research phono cartridge(s) would be used fed into an amp and then into the computer. I have several cartridges though not all the same which were left over from making tone arms from reeds rather than bamboo. Has anyone else has tried using this method? Cheers, gtm
  11. Here are a few of violin and first coat of tung oil on cigar box. Was late night and no power sanding. Daylight will expose to sun and hopefully have more coats and high speed orbital sander. I'm interested to see how it will fill in what appears to be fairly porous wood and how many coats it will take. http://home-and-garden.webshot...album/562839445EXdweX Cheers, gtm
  12. quote: Originally posted by: David Burgess quote: Originally posted by: gtm I don't know if he was fired from his former employer but something went on there. gtm Former employer? ________ has been on his own for close to 25 years. Who examined and appraised the bow at Butterfield & Butterfield? _______ also examined it and then appraised it? quote: Originally posted by: gtm The man was drooling over the phone when we first made contact indicating how much he would like to have it. Can I assume your first contact was by phone? He was drooling over a bow he had never seen? quote: Originally posted by: gtm I even tried the FBI WCC since there were other ongoing investigations. Investigations of what? Are you saying that ____ was being investigated by the FBI? Hi David and all: I think you may find it's a lot less than that. ............ If the B&B name is important I can dig it up, it's one of those memory lapse things. He might even be a member here. .......... First contact was to have him look at it, second was to establish repair costs and appraisal AFTER it arrived. .......... I certainly tried, if you know anything about the FBI WCC so I have learned they will _not_ disclose anything. Twice I have hand delivered papers and floppy disks for different things to Wilton's Waffle. They take them, make copies and give them back. Follow up phone calls may get you a person's name but they will not tell you if they are investigating or if it went to archives. I presume if there were a court case I would be contacted. I also contacted the field office for the region but never returned my call. Unlike the bigger cases with millions of dollars from several major orchestras this may have been a singular event. At the time I called the regional FBI they were combining offices and I was of the impression there was only one agent... good luck. I understand the need for secrecy and I have to accept that to some degree. The other case took almost 2 years, it was a case of hacking into the Los Angeles school system computers and harassing people including myself. As it supposedly turned out no harm done according to newspaper reports. Who was it, the school police chief's son who only got a slap on the hand. Go figure. Cheers, gtm
  13. quote: Originally posted by: Jacob Very well, I'm not about to question the merits of your case. What I'm questioning is you sniping at the guy on an Internet forum from behind a "user name". To me that's terrorism. Either pursue your case via legal channels or shut up, and live and learn without involving the rest of the world in the process. When you get burned by someone big time you may take another stance. However, I see no relationship to terrorism. How else is someone to learn of a business person's character if all that is offered are glowing testimonials when there is a dark side not reported. In good faith you take your car in for repair, would you not want to be an informed customer before you were ripped off. There are now consumer laws to protect you from automotive repair shop abuses. There are no consumer laws for this, just ask several members of the St Louis Symphony. The dichotomy is do I listen to you(singular) and shut up or do I have a voice and a right which you may not want to hear... Would it not be a failure of abdicated responsibility... You have every right to have an opinion just as I do. The difference is how handle objectivity without resulting in implied terrorism tactics. It is not my name that is call to question. Certainly Mat Roop may not agree had he thought to use his services. If you have a personal thing with me take it to PM. Thanks, gtm
  14. gtm

    Calipers

    quote: Originally posted by: GMM22 ... I would liken it to misplacing ones keys, something I do with such frequency that if viewed in isolation, it would leave most casual observers wondering how I even manage to function from moment to moment. Hi G and all: What's that saying about repeating something and expecting different results... Cheers, gtm
  15. quote: Originally posted by: Jacob ... Or the flip side of the coin - could the accused party institute legal proceedings for defamation? Hi Jacob and all: I wish he would. I cannot count the dozens of unanswered emails and phone calls. Calls even to his / wife's Internet provider to verify they were still customers. The problem was he was 1200 miles away. Mounting legal action in another state possibly superior court would have been more than what he and Butterfield & Butterfield initially appraised it. On top of that it was my daughter who actually sent it who was a minor at the time. The man was drooling over the phone when we first made contact indicating how much he would like to have it. That was the last call ever answered until the police were called to verify he still lived there. I even tried the FBI WCC since there were other ongoing investigations. Why would he _not_ sue me, easy, he would not want to open up his business dealings to public scrutiny. I don't know if he was fired from his former employer but something went on there. The lesson, never will I ever send anything of value out of state to someone I've not looked in their eye. I will continue to speak the truth about ________ till the day I die. This is not the first scam that has been pulled in this business and I'm sure not the last. Cheers, gtm
  16. quote: Originally posted by: Mat Roop Doug thanks so much....great information I would not have had otherwise.... Thanks, Mat Hi Mat and all: There are a couple of give away things to look for if you think you have a valuable bow. Frogs and screws can get changed or stolen. What I look for are the threads on the screw,before the industrial revolution these were hand made in a die of sorts. The die was made in 2 halves of plate steel with each half having each thread cut into the steel. Needless to say they had to be a mirror image continuing the thread. To make the screws the blank was put between the 2 halves which were indexed with pins and then struck with a hammer thus forging the thread. When the screw was compressed some would squeeze out along the part line. They would then rotate the screw 90' and strike again, this would then fold the flash back into the screw. It would be repeated several times, however that first strike leaves a very fine line right down each side. It sometimes has to be seen with an eye loupe but it's the criteria used. The nut on the frog can also be used if you can determine it was made by hand These were filed square and sometimes weren't always square and you could see the file marks. Now the bow, the slots were cut by hand thus you will see chisel and scratch marks at the ends and along the sides. Again it may take an eye loupe to see these. Take a bow such as this apart and you will see it's too well machined and all the parts will look well made. This is not to say these things can't be forged but I've yet to see any fake forged adjusting screws. I had a Lupot bow, the real thing which _________ stole from me when I sent it for repairs. I have pictures and know every mark on it, I saw a Lupot got sold for $24,000 back in 2002-2003. I called the local police who showed up on his doorstep, at first he denied it but when I made the 2nd call they again went and revisited, suddenly he remembered it was sent Priority Mail with signature. What he sent back unrepaired was a piece of junk not worth $300 dollars. What a snake, some day he will get his, maybe the IRS will examine this huge profit. Bummers. gtm
  17. gtm

    Calipers

    quote: Originally posted by: GMM22 You could also try applying heat to help loosen the threads. ... Some penetrating oil applied and left overnight might also help. ... The tip of the indicator is replacable if need be. Personally speaking, if I knew for certain it was threaded, I could never allow such a small screw to defeat me. Hi GMM22, Jacob and all: I'm with you, _ain't_ no screw going to get the best of me. If I understand correctly the needle is pointing at 9 rather than 0, this would then mean it's too wide so he would have to ADD material to bring the needle to 0. In C.B.Fiddler's lower picture I see a rectangular shape at the extreme left end. Is this a removable cover hiding a set screw???? Something has to keep the threaded anvil in position. In an earlier post someone mentioned the tips for one of these units were replaceable with different types. A url was given for a shop in Pasadena Calif What am I thinking, they offered PayPal so I ordered a set for my own use hoping at least the anvil ends will fit what I'm making. LittleMachineShop.com http://www.littlemachineshop.c...ductID=1783&category= I don't know if there is an international standard for these threads, these say 4x48. Including shipping and tax, $9.26 Alternately there are services which repair gauges, try the phone directory for something local. A good machine shop should have staff who are familiar with these and may be able to help. Please keep us updated. gtm
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    Calipers

    quote: Originally posted by: Jacob How does one adjust the screw underneath the bottom "point" of the caliper in H. B Fiddler's attached image? I have a caliper like that, it is over-reading by 0.1mm, but I can't get the screw to turn. Hi Jacob and all: I know nothing specific about this gauge. I will standby until your question is answered and the problem solved. First, the gauge appears to have an outer ring, some makers have a thumb set screw/knob which locks this in position though I don't see one here. You could try rotating the ring CW or CCW as a means to zero the instrument. This changes nothing internal with the gauge for it's only the dial which rotates with the ring. A thumb and forefinger should be enough force to move it. However I note there is a lever and pawl and I cannot determine if they are acting on the ring and dial. If the lever prohibits rotation then lift it enough to clear the dog. This isn't rocket science but your question is well founded and I can understand being nervous at these prices. Ideal is to have the needle at 12:00 as _edi_ and I were discussing. Is this time for a confessional, you lent it to someone, the grand kids were driving nails, someone bounced it off the floor, someone was measuring the unmentionable... bla bla bla?? Second,the "anvil" has slipped adjustment. Here I am even on less solid ground without seeing it. In the case of micrometers this is pressed into place and is not meant to be changed. Any adjustment is done at the barrel and knob to zero it. Again as edi were discussing it could be the anvil is adjustable because it is threaded into the base. If there is no set screw and yet it's threaded then they may be relying on friction between threads so it doesn't move. I hate butchers, if I see so much as bruised paint or scratches on metal I will know. ASSuming it's threaded: So what I'm about to suggest must be done with some care and knowledge. Put some duct tape on the face where the anvil seats so your pliers don't scuff the finish. Cut a strip wide enough to extend above the straight sides of the anvil and wrap 2 layers, gently apply pressure with the pliers while trying to rotate CCW. If the pliers slip on the tape apply more pressure, if they cut the tape while turning, STOP and get help. If you have a manual see if they show diagrams and possible options for a different shape anvil as an option. See if it's threaded, that may be your answer. Hopefully I speak for everyone in solving your problem, there are enough qualified contributors to make sure you get the best answer. Iffn not und chrg isn 1 beer virtual beer/hr. I've read your replies elsewhere and I'm sure you know that one hand washes the other. Wish we had a forum where we could kick things like this around so the thread doesn't go off topic yet valid questions such as this can be answered. Cheers, gtm
  19. gtm

    Calipers

    quote: Originally posted by: edi malinaric Hi GTM ... wondered how long since the parachute had been repacked. On grit size - just happen to have some 600 grit. Mind you there is also a small tube of 1 micron diamond that I could use. Seems a waste just for chisels and planes. cheers edi Hi edi and all: Nuttin like living on the edge and then think about the parachute. :-) For what it's worth if memory serves 4 microns will stop a water molecule. Commonly found in fuel injection filters which tells you that fuels and any additives are smaller. ............ Back on topic, any suggestions for size now you have 20/20 hind sight? Not wanting to make a federal case and spending $15 in gas I bought a 12.5x6 x .5 clear Plexiglas which looks like I have plenty to work with. Cheers, gtm
  20. quote: Originally posted by: yuen Hi gtm. Good for you and we will be delighted to hear your successful result. (armchair quarterback, I am) Hi yuen and all: Hahaha, you didn't think you were going to get off that easy?? To ground or not to ground that is the question? I see a lot of beautiful modern violins with the body left with natural finish but the neck, peg box and scroll have some color added. What to do? .......... Violin arrived today with only the blocks glued so the fun begins. Cheers, gtm
  21. quote: Originally posted by: yuen Hi gtm; Are you talking planning or you are actually performing these operations? My gut feeling sample or varnish (different thickness of coating etc) won't make mush of difference in tone. The easiness of vibration will make greater difference. That is, how solid is your violin. Wood being used, weights density and thickness of each its parts are out weight the varnish.. Sorry yuen hadn't answered your questions. Thanks for reminding me I really need a check list for I want to weight before I do any work and then at various stages. I'm planning to do this when: The violin and the tung oil arrive. The violin should arrive Monday from Colorado. The seller says the wood is from "his" 50 year old trees but doesn't say if aged. The fingerboard is not glued to facilitate top removal for thinning which he recommends and is sending diagrams for areas to be thinned. Since this will be a new process I have no idea how long it will take... 1 day, a week? I will have to make a thickness dial indicator for that aspect. The tung oil should be in the early part of the week so I can proceed with test samples to verify it's what I want to use. If all goes as planned and I can get 2+ coats dried in a day and should have some initial results within a day or so including microscope examination. In the long range I agree it probably won't affect the tone, it's the loudness which may be affected. If it's hard but not brittle as varnish then it may be canceling out/suppressing some sympathetic overtones or harmonics. I will be at the mercy of someone to play, for that to happen a sound post needs to be made and set. For this reason I am inclined to not attempt a recording before removing and thinning for another would have to be made again. Cheers, gtm
  22. gtm

    Calipers

    quote: Originally posted by: edi malinaric Hi GTM - re sailplanes. ... - I'll swear that they were about 2m higher than normal. ... By comparison the wooden wings didn't seem to have moved at all. Baltic plywood/Finnish Plywood - same place. Adjustable anvil. I just like the zero on the gauge to be at 12 'o clock. Looks neater somehow. The neck of the gauge is locked into place by a guillotine type of arrangment and moving the gauge to exactly get the needle vertical is a pain - so - I added an adjustable anvil. ... The wear pattern on the micro-abrasive says that the surface is bumpy. The plane blade however shaves hair and makes 0.0003" shavings so I'm satisfied - for the moment. I have three pieces of 10mm glass and might drizzle some oil and some 600 grit silicon carbide onto the surfaces and do that "three card trick" to work them flat. edi Hi edi and all: 2m!!! I know I'd be wearing my lunch. I'm not versed enough to argue the fine points though sometimes having something too rigid can then lead to catastrophic failure without warning. ........ I have seen some lesser quality "Baltic" with fewer laminates from other Scandinavian countries. The 19mm if memory serves were 11ply to which I added my cherry veneer. ........ Funny how some of our brains work, I too am fussy about the 12:00 clock position. I think it has to do when you are bent over upside down you still know which way the needle is swinging. If it's at 10:00 you have to think about it and that detracts from what you are trying to achieve. ......... Doesn't it make you feel good when your shaving have pencil marks on both sides. If it ain't broke don't fix it... ......... Eons ago, a friend of the machine shop owner (Bunny Phillips) brought in 2 hand scraped surface tables which he was going to lap together. One maybe 6x8 and the other 4x4, he worked at it for a couple of days. Came the weekend he left, Monday morning these tables could not be separated. We spent the better part of a day and gave up. The guy had to call a special mover and trailer just to take them away. Last we heard he never had gotten them apart. I got to thinking on this and came up with a trick I've used since. In this case drill through one and partly into the other, tap the hole for a grease zerk and use a hand lever grease pump. They put out 10,000 psi and have never failed when needed, unlike air it doesn't explode when the part releases. Point here is do not leave your work stuck together, stand on edge or put wooden blocks between them. The 600 sounds a bit coarse unless you are looking for opaque, 3000? Cheers, gtm
  23. gtm

    Calipers

    quote: Originally posted by: edi malinaric Hi GTM - until we consider carbon, sapphire or boron fibre composites, wood is your best bet for mass/stiffness ratio. Something that de Havilland Aircraft Co knew over 60 years ago. No plastic aircraft flying as far as I know. ... Use 16mm aircraft ply if you can - marine ply next and common or garden plywood as a last resort. No trouble tapping the wood without any lubricant. I did apply a blob of Pliobond contact adhesive to the mouth of the hole before screwing in the base anvil setscrew. This makes it abit difficult to adjust but ensures that the zero won't wander. The only reason for making the lower anvil adjustable was - why not? Lightening holes are unnecessary - I had planned to cut them but on completing the "horseshoe" and comparing it to the aluminium job I realised that it was unnecessary. Brian enthuses at how much less tiring it is to use compared to the all-metal one. Using up some of the useful offcuts and scrap in the workshop sure beat ordering (at great expense) the genuine article. I did splurge on the Kefer gauge because that is the important bit. cheers edi Hi edi and GMM22: Nice to see there are those willing to try the unconventional. I was thinking that a couple of those delta winged were plastic skins. And it's going to take a lot of convincing before I accept that sailplane wings don't flex. When I've used GMM22's method I use an Allen cap screw and a driver bit in my battery drill to run the threads. Completely agree the plywood you find in this country is made from junk. The only nice stuff is cabinet grade but then the grain is wrong and it's not exterior glue, the best stuff I found came out of Finland. The lightning holes aren't critical so may be omitted. Give me some arguments for an adjustable anvil? Should I then consider making the throat wider than needed? ............... Wanted to make mention of analog and digital gauges. They each have their place but for this application I would favor an analog. You are looking for trends and it's a lot easier watching a needle swing than having to constantly read a digital and remember if it were getting thinner or thicker especially when you run over a speed bump. If you are needing an absolute then digital is the way to go. I did like the stand idea I saw as long as it can be fixed so you can slide your work around while observing thickness. ............ I didn't get to the plastic store for I got involved with my new worktable surface plate inspection. Ha ha ha, what I had thought was 1/2" plate glass turned out to be .740". I've not tried weighing it on the bathroom scale but must be 125-150 lbs which ain't light when you consider it's 30x60, I'm thinking it was bullet proof for a bank or something similar. The most deviation I've found is 0.004" which is close enough for anything in this project and probably a double base. My back is sore, my arms are now 6" longer than when I woke this morning but for $25 I didn't get burned. Violin didn't arrive, tung oil didn't arrive and now no plastic, fooey. Have to think about my plaster of paris molds... Cheers, gtm
  24. quote: Originally posted by: doctahg quote: Originally posted by: gtm ... cut a thin section and put under my microscope to see what the actual penetration level is. gtm. Assuming that you have a microtome capable of cutting a very thin section without crushing, shredding, or otherwise altering the sample, I personally would find it academically interesting to view such a sample under a microscope. However, does anyone know the correct depth of oil (or any varnish) penetration for optimal sound? There seem to be so many variables - wood quality, amount applied, degree of pressure, speed of application, temperature, humidity, drying time, etc. Can it be said with any certainty how a micrometer or two difference in the finish affects the sound? Very interesting to read all these ideas! Hi doctahg, Mauricio, yuen and all: Ha,microtome I want one!!! I was going to slice across the grain with a veneer saw to take a 1/32-1/16 thick sample and look at it edge on. There is no need to see through the sample at some super resolution. My objective(?) is to have a better understanding if it's as good, equal, or better than varnish. Are we dealing with a stressed skin where the finish plays a significant roll in sound production which is desirable. Best analogy I can come up with is say that of a gear and a leaf spring where the substrate makes the difference in their properties. The gear is hardened on the outside and soft inside to absorb the shock. However, the spring is elastic and the bimetalic skin protects the substrate and adds to the function. At some point I will need to examine some of the properties of a trashed violin essentially for penetration and hardness. I agree there are so many variables, we have some known history with varnish and an unknown with tung oil which has different properties. Do I expect to take a sows ear and convert to a silk purse ... no. Do I expect a difference yes, can I identify that at least it's not harmful to sound production and an alternative finish. How many coats are needed to seal and are eye pleasing without having excess. We have been given examples of satisfactory results but little else. In email I had suggested to Mauricio using index cards and coating samples with varnish and tung oil. Once dried some observations can be established as to how each sample reacts to vibration, elastic properties, distortion, memory, etc. This may be more valid than using on a violin because of the variables. If I'm going to do this then will need to know what varnish to buy and a brand of index cards. It would be nice if I could recruit someone to do the varnish to their liking since I claim ignorance. Cheers, gtm
  25. Ive given this a bit more thought and now wondering if I should consider making a sound post and stringing it to get a sound sample before any work is done. Granted there will be a bunch of variables introduced in thinning and re-gluing the top, fitting a new sound post and stringing again for a new sound sample before oiling. Any gut feelings it this is necessary or will the thinning make such a significant difference that the results would be meaningless? ................. All the coats after the first and 2nd are quite thin. In an earlier post I had suggested 20-40 drops per sq ft for each additional coat. My postal scale only weighs in grams, not sure if that will be able to identify if there is any weight loss when rubbing and then drying. There will be some loss when sanding the first coat and maybe the 2nd, after that it's just adding coats. I don't know if it was the supplier's site that suggested 3 coats but I found 7 gave the results I wanted in my boat. I'm going to do some testing on scrap, then cut a thin section and put under my microscope to see what the actual penetration level is. I was not planning on using any sealer which may actually penetrate deeper than the oil. I'm still questioning which will have a harder surface and which will be more elastic and perhaps deaden the sound when in fact a harder more brittle surface will provide better sound. Cheers, gtm.