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15 hours ago, Nestorvass said:

There are people who believe that a rub joint isn't sufficient enough for a strong joint.

Everything else being kept the same a properly clamped joint ( there is a "formula" for that ) is aprox 46% "stronger" than a rubbed joint. This might be overkill for violin making or, if one considers not so obvious aspects of "strong", might be something worth looking into.

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19 hours ago, Nestorvass said:

Yes you are right. It just wouldn't come apart I was practically leaning on the joint. Only the outside part started to seperate a bit. The rest was practically untouched. So I had to use the saw. I probably should have gone for the saw in the first place as I am not a huge fan of making a perfectly dried wood wet. But oh well we live and learn :rolleyes: it is my first instrument and I expect to make many more mistakes in the process from which I will learn.

The person "who never made a mistake never made a fiddle," [HS Wake, A Luthier's Scrapbook, p.16].  

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14 minutes ago, Carl Stross said:

Everything else being kept the same a properly clamped joint ( there is a "formula" for that ) is aprox 46% "stronger" than a rubbed joint. This might be overkill for violin making or, if one considers not so obvious aspects of "strong", might be something worth looking into.

Perhaps it is though 46% is a very specific number :lol: Honestly even if it is stronger with clamps i dont see the need for it. As i said in a previous post i couldnt take the thing apart after an hour of heating it and applying hot water on the joint. So why bother with clamps, which add another parameter for things that could go wrong (eg. if the clamping pressure is at an angle instead of perpandicular to the joint)?

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1 hour ago, Don Noon said:

Granite surface plates are the tool for the job.  Check against the plate with chalk, and it will show you everything you want to know... twist, ripple, concave.  With a feeler gage, you can even measure how much concave you have, if that's what you want.  Surface plates aren't terribly expensive (although shipping can be), and they are astonishingly flat.  Every shop should have one. 

I was looking to buy something like this to flatten my planes, especially my smoother. I was looking at this to be specific https://www.fine-tools.com/granit-messplatte.html . I wonder would marble/ granite tiles do the job as well since they are a bit cheaper? Probably not but I have to ask. Also what kind of chalk would you recommend? I would like one that doesnt interfere or show up in the finished joint .

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20 minutes ago, Carl Stross said:

a properly clamped joint ( there is a "formula" for that ) is aprox 46% "stronger" than a rubbed joint. 

Do you have the formula and reference for where this suspiciously specific number came from?

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2 hours ago, David Burgess said:

That's an excellent method for planing the joint, too.

That is what I tried at first but my jointer plane is extremely heavy (its visible in the picture, its on top of the tool "cabinet"). Its way heavier than a stanley no.7 not sure about the lie nielsen as their significantly sturdier than the stanleys. Anyway I found that the weight of the plane didnt allow me to feel the cut and it was also easy to flip it to cut more on one side creating a twist. So I clamped the plane like that instead. I was getting a better feel as to how much wood i was removing when i was holding the plates instead of the plane. I could sense the gaps in the plate, as well as  the thickness of the shaving etc.

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2 minutes ago, Nestorvass said:

I was looking to buy something like this to flatten my planes, especially my smoother. I was looking at this to be specific https://www.fine-tools.com/granit-messplatte.html . I wonder would marble/ granite tiles do the job as well since they are a bit cheaper? Probably not but I have to ask. Also what kind of chalk would you recommend? I would like one that doesnt interfere or show up in the finished joint .

Tiles are made flat enough to walk on or use for a countertop, which is not very.  Maybe some tiles are flat... maybe they aren't.  Surface plates are precision flattened to a specific value, usually ridiculously better than most woodworking needs... but it's nice to have something you KNOW is flat.

For chalk, I'd use whatever shows up good, and remove it with water or an eraser.

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1 minute ago, Don Noon said:

Tiles are made flat enough to walk on or use for a countertop, which is not very.  Maybe some tiles are flat... maybe they aren't.  Surface plates are precision flattened to a specific value, usually ridiculously better than most woodworking needs... but it's nice to have something you KNOW is flat.

For chalk, I'd use whatever shows up good, and remove it with water or an eraser.

I also bought a bandsaw recently from makita. It has a cast table, this is also pretty flat but the granite plate sounds better not only because it might be flatter but because its portable (well kind of... they are pretty heavy). I will try the chalk method, but  not on this joint because Greece is in lockdown right now and we can only buy online and the courier services have extreme delays (3 weeks)

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37 minutes ago, Carl Stross said:

Everything else being kept the same a properly clamped joint ( there is a "formula" for that ) is aprox 46% "stronger" than a rubbed joint.

Does this apply to hot hide glue, or is it for other adhesives?

If for hot hide glue, what is "properly clamped"?

Source?

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12 minutes ago, Don Noon said:

 

For chalk, I'd use whatever shows up good, and remove it with water or an eraser.

Eraser debris can be problematic, if not scrupulously cleaned up. It takes just the smallest bit ending up in the joint to hold it apart. Water can change the shape of the wood.

I brush chalk away with fast strokes of a soft brush. Any remaining in the pores doesn't seem to hurt the glue bond (presuming the chalk doesn't use something like wax as a binder).

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56 minutes ago, Nestorvass said:

I also bought a bandsaw recently from makita. It has a cast table, this is also pretty flat but the granite plate sounds better not only because it might be flatter...

Your bandsaw table won’t be nearly as flat as even a proper B grade granite surface plate, it also won’t be as stable as the granite.

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45 minutes ago, David Burgess said:

Does this apply to hot hide glue, or is it for other adhesives?

If for hot hide glue, what is "properly clamped"?

Source?

Pretty much it does at least as far as I checked. The reason clamped makes for a stronger joint is pretty obvious, though who knows, there might be exceptions.  

I attached the actual research paper to a long post I made a couple of years ago. When I'll have  time I'll  find it and re-post. I remember I explained there what "strong" means and that might be of interest to some.

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21 minutes ago, Carl Stross said:

The reason clamped makes for a stronger joint is pretty obvious, though who knows, there might be exceptions.  

I attached the actual research paper to a long post I made a couple of years ago. When I'll have  time I'll  find it and re-post. I remember I explained there what "strong" means and that might be of interest to some.

It is not obvious to me why a clamped joint should be stronger.  If there's full filling of the gap with glue, and full wetting of both surfaces, why should clamping make such a big difference?  Please explain why it is obvious to you.

I was able to locate this post, with different percentage values, but no link to a research paper or source:  

 

 

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53 minutes ago, Don Noon said:

It is not obvious to me why a clamped joint should be stronger.  If there's full filling of the gap with glue, and full wetting of both surfaces, why should clamping make such a big difference?  Please explain why it is obvious to you.

I was able to locate this post, with different percentage values, but no link to a research paper or source:  

 

 

It's not that one . The one I need was in the context of some discussion about neck joints. I'll try find some time to extract it from one of my back ups as soon as I can.

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Shooting board should be enough. On my last boards I had no Gap without clamp. It was a cello. Main factor is probably how to use the shooting board. I also don t use clamps during shooting, to keep everything free and avoid the twisting. Twist avoidance is key. The twist comes from perpendicularity defect( table flatness, board flatness and plane angle). Even a very fine defect will create a twist. If you use well the shooting board you can compensate : finishing with the smalest plane thickness as possible, then alternate 180deg each shooting.

Below some pictures after shooting board. Free, without clamps.

 

20200919_071351.jpg

20200919_071821.jpg

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33 minutes ago, Carl Stross said:

It's not that one . The one I need was in the context of some discussion about neck joints. I'll try find some time to extract it from one of my back ups as soon as I can.

Good luck.  I found many posts of yours regarding neck joints, but nothing with a reference to relative strength of clamped joints.  The one I found above was the closest.

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19 minutes ago, David A.T. said:

Shooting board should be enough. On my last boards I had no Gap without clamp. It was a cello. Main factor is probably how to use the shooting board. I also don t use clamps during shooting, to keep everything free and avoid the twisting. Twist avoidance is key. The twist comes from perpendicularity defect( table flatness, board flatness and plane angle). Even a very fine defect will create a twist. If you use well the shooting board you can compensate : finishing with the smalest plane thickness as possible, then alternate 180deg each shooting.

I was thinking to make a shooting board but my wooden jointer doesnt have square sides to be used on one. The shooting board could also be very useful for squaring the blocks. Its what they where designed to do making end grain square, but I see how they could be used as a tool to make the center joint. Thank you for sharing your results they do seem very nice :)

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I don't use a shooting board for making center joints, in part because it requires flattening one side of each board to be successful, and the assumption that they will stay that way (which they often will not, particularly with cello plates). I prefer to join them, and then do the flattening in one fell swoop. Economy of motion. :)

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Just a thought...

Since wet glue causes the edge to exapnd and bend the board, you could wet the opposite edge to compensate.  That edge is usually narrower, so maybe you'd wet a little extra around on the top and bottom nearby.

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3 hours ago, David Burgess said:

I don't use a shooting board for making center joints, in part because it requires flattening one side of each board to be successful, and the assumption that they will stay that way (which they often will not, particularly with cello plates). I prefer to join them, and then do the flattening in one fell swoop. Economy of motion. :)

That's how I do it. No faffing about by flattening the battens twice. 

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On 1/12/2021 at 3:32 PM, Don Noon said:

I don't think it swells in the center... the damp edge expands in all directions, including longitudinally.  The rest of the plate doesn't expand, so it has to bend slightly, making the joint line convex.  Spruce is far more stable along the grain with humidity and moisture, so you don't get it as badly if at all.  I imagine that highly figured, flatsawn maple (where the flame squiggles laterally) would be the worst, on several accounts.

Perhaps the cross-grain shrinkage is faster towards the ends of the join, due to the exposed end grain making the glue dry out faster, causing the ends to open up.

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15 hours ago, Nestorvass said:

Yes planes have a tendency to make surfaces slightly convex. So to counteract that more pressure should be added in the middle. The way Christopher Schwarz describes it who is not a luthier but an authority in fine woodworking, is imagine the wood is icecream you short of push the plane down as you go into the middle like you would a spoon if the wood was  ice cream. Silly metaphor but  quite intuitive. Also what is a number 4 block plane? Theres a number 4 bench plane and a block plane which is another plane held with the palm. Also what is the point of using a low angle block plane and put a high angle microbevel when you can use a normal angle block plane with more acute bevel?  Unless you have another blade with a more accute angle to use for trimming end grain such as the blocks, i dont see a reason to own a low angle plane at all. On the contrary most of the planing work on violin is on maple and ebony which are wood species very prone to tear out, which benefit for a very high angle block plane

I should have been more specific about what I mean. I'm not saying that planing the edge results in convexity although it can look that way when testing with a straight edge. What I have found is that the plane tends to cut deeper at the end of the stroke, perhaps 3 or 4 cm from the end at most. And going by your pics that seems to be exactly what has happened.

I don't think varying downward pressure affects the depth of cut at all. With a sharp blade the depth of cut will always equal the projection of the blade.

The increased depth of cut at the end of the stroke seems to be caused by the toe of the plane passing over the end of the board thereby losing some forward support.

I refer to my low angle block plane as a number 4 because it is the same length as a number 4 bench plane or smooth plane if you like. And as I have said it has a significantly lower centre of gravity.

As far as blade angle is concerned I think that a low angle block blade bed is 12 deg. With an edge sharpened at 25 deg. the cutting angle is 37 deg. OK for end grain work but a bit low for general work.

It's not hard to sharpen a higher angle bevel. I have blades sharpened at 25 deg. and others much higher to suit the job.

The acuteness of the honed angle does not affect the planing ability of a low angle block plane. A blade sharpened at 33 deg. for a bevel-up block will cut just as easily a bevel-down blade sharpened at 45 deg.

 

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8 hours ago, David Burgess said:

I don't use a shooting board for making center joints, in part because it requires flattening one side of each board to be successful, and the assumption that they will stay that way (which they often will not, particularly with cello plates). I prefer to join them, and then do the flattening in one fell swoop. Economy of motion. :)

Exact. That's clear. It is time consuming. To flatten the cello parts before and after is a very big amount of (annoying) time. 

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On 1/13/2021 at 8:59 PM, Nestorvass said:

I was thinking to make a shooting board but my wooden jointer doesnt have square sides to be used on one. The shooting board could also be very useful for squaring the blocks. Its what they where designed to do making end grain square, but I see how they could be used as a tool to make the center joint. Thank you for sharing your results they do seem very nice :)

here is how I do.

The plates are first flattenned to try to get the lowest defect as possible - it is very long to do, in particular for mapple.

then I use  2 flat piece of wood (the bottom one is hard wood) , and the low angle plane at 90°. I alternate 180° each pass through. nothing clamped, just free hand. to alternate 180° let compensate the twisting due to shooting board imperfection. even a 0.1 mm on the shooting board will create a gap. slowly done .very fine piece of wood should get out the plane

I don't know how to correct the issue you had. But I had same issuer in the past due to twisting (due to shooting defect). Personnally I would have restart the process. The gluing operation is one of the shortest one in the whole process.

 

 

 

 

Edited by David A.T.
Removed my pictures - they were out of propose as discussion now switched to cnc.
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