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Joining Top and Back Wood


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43 minutes ago, arglebargle said:

Yes. The bench doesn't move.

The geometry of attachment points does not suggest that!

I didn't realize how much my big Ulmia bench (bolted to the floor) flexed, until I posted a video here of trimming the sides of a cello neck with a roughing gouge, and someone pointed it out.

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2 hours ago, David Burgess said:

The geometry of attachment points does not suggest that!

I didn't realize how much my big Ulmia bench (bolted to the floor) flexed, until I posted a video here of trimming the sides of a cello neck with a roughing gouge, and someone pointed it out.

I'm not sure what to tell you. Maybe we have different definitions of movement and flex? When I have a cello neck on the bench and I'm planing it, there is no motion from the bench. When I am graduating a back, there is no motion. The truss rod that runs between the two legs is reinforced with wooden boards and tightened after the legs are attached to the bench. ?:huh:

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You could try the following, all of which I've found helpful to make  invisible glue line rub joints for backs and fronts. Working back wards...

Using a metalwork vice to hold the wood when gluing, as  the short length of the metalwork vice's gripping area ensures it will not distort your piece of wood. Hold one piece in the vice, hold the other next to it, use a wide brush to get both surfaces at once and not too thick glue. A fresh batch and the consistency of maple syrup. A quick up and down glue stroke, a quick up and down rub, leave. Do not heat the wood pieces up, to give a longer working time with the glue, they will distort.

Plane your two pieces held together in the vice, until they're pretty good. then take them out of the vice and put your plane in, blade up - despite having a Bailey jointer, I find myself using another, medium length Bailey plane. With the blade set extremely fine, you can now adjust high spots in your two pieces.

There are various ways to check the fit of the joint - pressing together, twisting and looking through with a light behind. Another one if find very useful is to put one piece in the vice,  and balance the other on top with just gravity keeping it there - small gaps where it doesn't fit seem to be more obvious. When you have established where a high spot is, and made an educated guess which side the fault is with, take a see-through shaving with your plane by pressing a little harder in that area as you pull the wood over the plane blade. The plane needs to be razor sharp. The adjustment can take a few strokes to each side, if you're in luck and it goes well, or a bit longer. But bear in mind there is no faffing about clamping up, so you save time there. And the joint is almost impossible to see, as most of the glue rubs out, and hide glue shrinks and pulls in anyway.

 

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There is a very comprehensive book available from Taunton Press: The Workbench Book by Scott Landis. There is even a complete chapter dealing with the specific needs of luthiers. This book is a wealth of information on the subject of workbenches. I have a copy in my shop library and refer to it still from time to time as the need arises. This author has also written The Workshop Book which is also a gold mine of ideas for setting and configuring a workshop.

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22 hours ago, arglebargle said:

I'm not sure what to tell you. Maybe we have different definitions of movement and flex? When I have a cello neck on the bench and I'm planing it, there is no motion from the bench. When I am graduating a back, there is no motion.

There is no such thing as zero deflection when a force is applied. Maybe it would be better to move on to how much flex is acceptable?

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2 hours ago, David Burgess said:

There is no such thing as zero deflection when a force is applied. Maybe it would be better to move on to how much flex is acceptable?

I'l bite. How much?

I've worked on benches that you need to anticipate the benches motion when planing. That sucks. These legs are as close to the feeling of the bench being attached to the wall on two sides that I've found. I have two work surfaces with these legs on them. One of them has (as close to ) zero (as can reasonably be expected in a physics governed universe) motion when pushed. The other I can detect a very small motion when I really give it a shove. But I don't typically work that way. 

Anyway, I love them. They work great for me, and the checks from Lee Valley every month don't hurt either.

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4" maple top, 4"x 4" maple legs with deep rails, 2 no. 10.5" Record vices to add some extra weight :).  When I moved house I asked the removal men if I should remove the vices before they moved the top;  they gave me a pitying look, me being built on the slim side.  Their pride wouldn't let them go back but I did notice their eyeballs bulging as they carried it downstairs.

When I plane joints I clamp one corner of the plate in the vice and support the other on a piece of wood clamped to the bench and in that way there is no distortion.

 

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13 hours ago, David Burgess said:

There is no such thing as zero deflection when a force is applied. Maybe it would be better to move on to how much flex is acceptable?

 

Hi David - that's an eternal truth. Once one takes it to heart and applies it to design, life as an engineer/designer becomes a walk in the park. Getting it into the youngster's skull is the hard part.

Real life example:

1.0 Clamp your rifle to the bench and zero it.

2.0 Turn it upside down and clamp it with the cross hairs  on the point of impact in 1.0.

3.0 Anyone care to forecast the result?

 

 

 

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As a brief note, I have good flat planes up to No. 7 in metal.  Ended up truing one of my great grandfather's wood planes with a forge-welded blade, only used for joining tops & backs.  Quite quick to get to a single shaving thinner than a cigarette paper the whole length.  Minor need for adjustment.  On a shooting board.  Well worth setting something up and leaving it alone!!  

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6 hours ago, edi malinaric said:

 

Hi David - that's an eternal truth. Once one takes it to heart and applies it to design, life as an engineer/designer becomes a walk in the park. Getting it into the youngster's skull is the hard part.

Real life example:

1.0 Clamp your rifle to the bench and zero it.

2.0 Turn it upside down and clamp it with the cross hairs  on the point of impact in 1.0.

3.0 Anyone care to forecast the result?

 

 

 

my guess it would shoot low but I've never tried it

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11 minutes ago, MikeC said:

my guess it would shoot low but I've never tried it

Hi Mike - a 0.22 rifle, range 50 yards and after correcting for bullet drop the impact point was a further 1.1" low - due to the barrel deflecting under its own weight.

ref: https://www.goodreads.com/book/show/360565.Rifle_Accuracy_Facts

 

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On 3/11/2019 at 6:55 AM, edi malinaric said:

 

Hi David - that's an eternal truth. Once one takes it to heart and applies it to design, life as an engineer/designer becomes a walk in the park. Getting it into the youngster's skull is the hard part.

Real life example:

1.0 Clamp your rifle to the bench and zero it.

2.0 Turn it upside down and clamp it with the cross hairs  on the point of impact in 1.0.

3.0 Anyone care to forecast the result?

 

 

 

That's not a real life example.  No real shooter clamps a rifle on a  bench to shoot it and then turn it upside down on a bench to shoot it again.

A real shooter would shoot the rifle while holding the normal way standing free hand.  If he wanted to see what happened with the rifle upside down he would still hold it exactly the same way but would stand on his head instead of his feet.

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4 hours ago, Marty Kasprzyk said:

That's not a real life example.  No real shooter clamps a rifle on a  bench to shoot it and then turn it upside down on a bench to shoot it again.

A real shooter would shoot the rifle while holding the normal way standing free hand.  If he wanted to see what happened with the rifle upside down he would still hold it exactly the same way but would stand on his head instead of his feet.

Mea Culpa :-(

My only excuse is that I don't have one of those Afghanistani Pakol hats.

cheers edi

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  • 3 weeks later...

I found a perfect vice for a bench without a side vice, the 6” carpenter’s vice with clamp at Harbor Freight for $20.  The clamp looks too weak to hold but it more than enough does the job and my bench which is just average and the vice together when planing plates are rock solid.

16355BE3-AEF7-413D-8E86-AFA4790E31EF.jpeg

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