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steveperry

Bulk rib thinning method

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I have decided to eventually build 15 violins.  That's the amount of wood I have.  I'm well along in joining the plates, with only a few more to do (jointer to level bottoms, thickness to 17 or whatever on the planer so that I can see the glue lines well, jointer for roughing in the gluing surface, shooting board with one of great grandpa's wood planes all trued up and the massive cast steel blade razor edged).  The neck blocks are all to size.  Now I have a fair number of ribs roughed out and need to thin them all.  

 

I have available:

 

Planer

Jointer

Big drill press, with rib thinning sanding jig

Wagner power planer

Lots of hand planes

A Stanley scraper thing with two handles

Lots of scrapers

Double stick tape

 

There must be a proven system for most effectively taking a mix of ribs, some rough cut, some finished but thick, and turning them into ready to bend ribs.

 

Description or pointing to proven easy system would be very welcome.  I am making fixtures as I go along, so something that takes a fixture isn't necessarily a problem.

 

Thank you all very much.   

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There must be a proven system for most effectively taking a mix of ribs, some rough cut, some finished but thick, and turning them into ready to bend ribs.

 

Description or pointing to proven easy system would be very welcome.  I am making fixtures as I go along, so something that takes a fixture isn't necessarily a problem.

 

Thank you all very much.   

 

A "full size" oscillating spindle sander will do the job but it's not in your inventory. Mind you, a small one hasn't got enough power to thickness them in one pass. There is a drawback though : there will leftovers from the sanding sleeves and those will eat up scrapers, plane blades, knives.

 

Anyway, I wish best of luck with your project - great stuff !

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Remember that you have to scrape them down to remove sanding marks. Hold the ribs up to the light looking for the groove shadows.

 

I do have some great scrapers for this, but I also like using disposable single edge razor blades purchased from the local hardware store. Get one of those little plastic razor holders too.  ^_^

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Worth making an interrupted blade plane?  I have so many planes that I could simply notch one.  I have never had a full size plane done that way.  

Fortunately, I am assisted by two people generally, one has been doing the bulk work on the plates while I do the final fit.  He will have fun thicknessing ribs, I'm sure.  I can probably make a simple jig for having the Stanley No. 80 cabinet scraper do the final thicknessing!  I finally remembered what that is.  If I recall, I can put three pieces of wood together with the middle one 1.1 mm or whatever lower, use the side pieces as a stop for plane and / or scraper.  That's probably the thing to do.  

 

For the moment, it's back to trying to get the brakes bled on my Moto Guzzi.  Has ABS and who knows what to really do with that.  I've got a bubble somewhere.

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For the moment, it's back to trying to get the brakes bled on my Moto Guzzi.  Has ABS and who knows what to really do with that.  I've got a bubble somewhere.

 

Allow enough time for the pump to refill with fluid or you'll be pumping air. If the bubble is inside the ABS pump , you'll need to cycle it. That means take it to the agent. :)   ( you can't complain you don't get advice here... :)  )

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Assuming you have a fair bit of wood to remove, I'd suggest a rough grit drum to take off most of it, and finish up with the fine.  It's amazing how deep the rough grit grooves go, and it's also amazing how the fine grit heats up the wood without removing much.

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I usually have good results hand planing one edge of the stick I'm taking the ribs from then rip off a rib using a band saw. Maybe set your ripping thickness to be 1.5mm or so, test your thickness on a scrape first to make sure you can remove any saw marks when finish planning the cut side. To plane the cut side I use about 25mm of double stick tape to hold the the rib blank in place while planning. Use a caliper to test for consistent thickness.

Best,

Mike Spencer

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Think I'm set now.  I'll set up my drill press drum system, make a jig for scraping to uniform thickness, and work through them all.  Somehow a jointer or planer should work, but I just can't see how I'd do much but create slivers.  I do recall the coarse drum being very aggressive!  Fortunately, many of the ribs are jointer smooth on one side from cutting them out.

 

Thanks all.

 

And I'll bang through the whole brake line system tomorrow.  If I can get enough brake to engage the ABS, then that will pump some fresh fluid through and probably dislodge whatever might be in there.  I actually forgot about the ABS when I started bleeding the thing.  This one is just like mine: http://s.wsj.net/public/resources/images/OB-XD794_moto_E_20130420101803.jpg   1380 cc pushrod V twin, air/oil cooled, six speed, dry clutch, shaft drive.  Big bike, handles smoothly, lots of lean angle, dances through the twisties like a sport bike, rock steady on the Interstate at 85 on cruise control.  I was getting 47 mpg at 70 mph on cruise control, will do better once fully broken in.  Over 50 mpg at 55.  25 mpg riding hard in the twisties.  I suppose my partner's VStar getting 75 mpg makes up for some twisties!

 

Anyway.  I'll have to level the rib side of all the plates once they settle in from gluing, knock them down to 17 or 18 mm.  Then check my molds, see whether I need to refine or make new.  I will most likely draw up a nice del Gesu / Amati model (Vary the corners) and get the arching concepts set, then go about making molds, blocks, rib bending guides and so on.  I probably need to make a pile of linings, too.  Think I'm almost out.  

 

Should be fun.  Having some help really makes things tick along nicely.

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You should be careful with your drill press, the massive sanding operation can mess up the quill, shaft and chuck by stressing to one side. 

 

A  drum sander with a coarse grit pass followed by a fine grit pass, and then scraping will get you there faster. And hand planing with a toothed plane before rough sanding will get you to the thickness dimension safer than a power plane, which can break or pull up wood from thin stock. 

 

And then going from toothed plane to scraper is not bad either. Tooth marks from the plane scrape out easier than coarse sanding marks. Doing it all by hand methodically with a toothed iron is tough on the body, but almost as fast.

 

Personally I dislike scraping sanding marks out. Toothed iron marks are narrow and stand proud of the surface and flatten faster. Sanding marks by contrast are deep and narrow and you have to remove tons of flat surface wood to dig them out. 

 

Might be worth check out both methods. Just for kicks. 

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I have Mr. Charlie here now, eating oatmeal.  We'll go pick a plane and notch the blade, get it toasty sharp, and move onward into bulk thinning.  I have much more rib than fiddle, so we'll likely do them all and be set for the next batch, assuming I live long enough!  Actually, with help things are moving quite smartly.  That will slow down when we get to detailed handtool work.

 

We will try:  scrape the smooth side smooth, if there is one.  Plane the rough side a bit.  Hit it on medium sanding drum in drill press (it is a massive ancient thing, and I never do more than just ghost the stock through).  Check and repeat until ready for final scraping in the scraping thickness jig we have yet to make!

 

Thank you all.

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If you have access to a good bandsaw, plane one side smooth, and resaw the other side along a fence leaving it slightly on the thick side. Plane and / or scrape off the saw marks and you're done.

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That's where we are, more or less.  All are sawed already.  After trying a variety of thinning methods, we are at 

1.  No. 80 smooth the face side.

2.  Wagner power planer with guide, featherboards etc to 1.5 mm

3.  Wagner power planer final cut to 1.25 mm

4.  No 80 cabinet scraper to 1.0 - 1.15 range.

 

That seems to work quite well.

 

We may shift to medium drum for the 1.5 to 1.25 step should issues arise.

 

I am wondering how to convert my belt sander into a thickness sander!!!

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I made a jig for rib planing using a piece of plywood with 600 grit sandpaper on it.  There are two holes at either end that are drilled with a template, and two matching holes get drilled in the end of the rib, so you can pin the rib in place using 1/8 wooden dowels.  The dowels are sacrificial, so you can plane right over them, and don't have to work around clamps.  You can also remove the rib to check thickness without undoing any clamps.  You can run this jig through a thickness sander as well.  

 

I did a little thickness sanding off the drill press on a particularly unruly rib, but I wasn't happy with the amount of work to remove sanding scratches and unevenness from the drum.  Maybe a better setup would sand more evenly, but I suspect that you'll always have some rounding at the edges.  In the end I found it faster to plane them than to fuss over getting the machine right.  If I had a scraper plane I probably would have had less issue with the unruly rib, and been done in no time.  Hasn't usually been a problem, though.

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The scraper plane is superlative for the final work.  Charlie hasn't quite gotten the hang of it and is still a little slow, but he'll get there.  

 

Turned out my Guzzi has a tricky master cylinder that traps air.  Lots of tapping with a screwdriver handle and I got all the bubbles out.  We actually changed fluid on three bikes today, but the Guzzi is the finest.  Like a Maserati Ghibli S mated with a 69 Boss 429 Mustang, had a bitchy out of control daughter who whupped up on everyone, but got sent to finishing school.  Iron fist in velvet glove.  Torques through the twisties like a sport touring bike, no need to go over 5000 rpm, but hit the straight, roll the throttle back, and hang on after 5500 rpm.  Can put the beast on cruise control at 85 mph and there's no sign of any real work being done up and down and over anything so far.  Love the wrong way V twin - amazing machine.  I'm trying to figure out how to use it for advertising - attracts people everywhere I go.  

 

Now I need to find block wood somewhere, I'm all out of willow.  Spruce will have to do. 

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I have a very old 1" belt sander (uses a 24" belt, sits upright with no safety shields over any of the pulleys etc).  Probably 50 years old.  I keep a very worn out fine belt just for burnishing ribs, taking off that last 25th mm or so.  As its an upright the belt runs perpendular to the rib wood, and as long as I don't pause anywhere, and keep the wood moving back and forth, it does great.  Very little to scrape, and because you're scraping with the grain, the sanding marks (which I cannot see with my eyes anyway) are perpendicular to your scrape stroke.  I think any fine lines you might miss are running the same direction as the curl.  You have to scrape finish even if I can't see sanding marks because it really does pull up all the dust trapped in the pores and cut off any loose particles  (but you knew that).

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One warning about scraping is pulling chips out of the flame regions. These can look pretty bad.

 

And yes, those deep sanding marks are another thing to watch for. Some makers don't see them until they varnish. As I mentioned above, hold your ribs up to see light reflections. Get rid of the sanding marks before you assemble the garland.

 

Mike

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IMHO the best way to avoid deep sanding marks is not to use a sander on your ribs. I process several sets of cello ribs at a time and it's a lot of square centimeters to work with. I feel like I have a fairly efficient system. A good toothed blade (with irregular teeth) is essential.

If you can cut the ribs yourself you can get a lot closer to measurement, unfortunately a lot of the commercial ribs rock is cut very thick.

After planing and scraping the outside of the ribs to a finished surface, I drill depth marking holes in the ribs on the drill press- like you would for rough graduating a plate. My system is pretty dialed, so I drill to two tenths over my measurement and plane until the holes are gone. After that a light scraping is usually enough to finish the thickness. I was astonished the first time I used the depth holes at how much time I saved by not picking up the calipers to check the thickness every 30 seconds.

M

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I am wondering how to convert my belt sander into a thickness sander!!!

First I run my ribs over a nice old Rockwell 4" sharpened to perfection,, then I cut them so one side is all but finished, so I don't use this much any more, but two belt sanders have bit the dust,,

but the jig still lives on.

(I don't understand the difference in size of the pics, they were take at the same time,?)

post-48078-0-48686800-1435703041_thumb.jpgpost-48078-0-12313900-1435703113_thumb.jpgpost-48078-0-99917600-1435703086_thumb.jpgpost-48078-0-74455300-1435703123_thumb.jpgpost-48078-0-20117900-1435703133_thumb.jpgpost-48078-0-79055400-1435703144_thumb.jpgpost-48078-0-04482900-1435703154_thumb.jpgpost-48078-0-52527400-1435703163_thumb.jpgpost-48078-0-21755500-1435703174_thumb.jpgpost-48078-0-22841400-1435703182_thumb.jpgpost-48078-0-57621000-1435703188_thumb.jpgpost-48078-0-23582600-1435703198_thumb.jpgpost-48078-0-93478700-1435703206_thumb.jpgpost-48078-0-69503900-1435703216_thumb.jpgpost-48078-0-57739100-1435703224_thumb.jpgpost-48078-0-87228900-1435703241_thumb.jpgpost-48078-0-72637800-1435703254_thumb.jpgpost-48078-0-49203900-1435703264_thumb.jpg

The table has to be flat,,

I welded struts underneath the table to strengthen it ,( it flexed a lot,,) then I leveled it.

I placed a graphite pad over the table,,it greatly reduces friction.

I placed the unit on the sander (sander covered in saran wrap) I placed epoxy over the contact

area to create a perfect fit to the sander.

You need to grind down the joint area of the belt so it won't have a bump.

220 won't leave noticeable sanding marks,, 320 is better,, fine as frog hair.

It is very precision.

The three screw adjustment makes for very easy adjustments.

Once it is set just a turn of the center screw is all it takes.

Just noticed my fingernails,,,YUCK!

I just got back from weiser,,,

if you don't understand you don't need to,, it was HOT !

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OMG, Evan. That is the coolest fixture I have seen in some time. 

 

I use a lab jack on its side against an oscillating sanding cylinder. 

 

post-6615-0-85867500-1436015232_thumb.jpg

 

I then scrape with single edge razor blades to remove sanding marks.

 

 

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OMG, Evan. That is the coolest fixture I have seen in some time. 

Must have been some time since I posted this photo of my rib sanding fixture, so here it is again:

post-25192-0-83709700-1436018195_thumb.jpg

 

I might not use it next time, though, as it isn't real fast, and I think I can get away with just using my hand-sharpened bandsaw blade to go to very near final thickness, and then a scraper to smooth the outside surface.  The inside rib surface can just be the sawed finish (it's really very good).

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Mine's Craftsman, same as Delta, same as Grizzly.  And probably others.  Same machine, different nameplate, as far as I know.  There might be some minor differences in the housings.

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