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Shamisen Appreciator
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2,094 Posts
Discussion Starter · #1 ·
Cut and Paste from my blog that I hardly update and no one reads. I'm sure that relevant details are missing as it was written hastily so if you have questions, ask them here and I'll do my best to answer them. Since it's here, Don can respond too if he wishes.

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This is a very long overdue post. Late last year, I heard that Don was going to make a tube bender similar to something he made years ago and discontinued. A few months ago, he sent me one to test. If you're looking for a summary, here it is...if you have tubes that need bending, this bender will get it done beautifully. Repeatability is excellent, quality of the bend is excellent, setup is super easy and for S-bends, keeping the bends in phase is dead simple. Only one of those comments holds true for the JD2 bender I've been using for the past four years.

The Details:

I've only used two other benders before, a JD2 Model 3 and a fork blade bender available through Nova. It was possible to use the fork blade bender on 5/8" x 0.032 and that's it. Ti tubing of larger diameters wouldn't bend without severe rippling. I have dies for my JD2 bender for 3/4" and 7/8" tube diameters with the CLR of the dies ranging from 3.5" to 5.5". Unfortunately, I've never had great luck with the bender. 3/4" tubing will bend well on the 5.5" CLR die but will ripple on the 3.5" die. A 3.5" CLR is out of the question with a 7/8" tube and the 5.5" CLR die was spotty at best. I have a huge scrap pile of rippled tubes. I think the biggest problem with the JD2 bender is three-fold. 1. the "clamp" doesn't securely hold the tube in place. 2. there's a significant amount of friction on the follower die which often forces the tube to slip through the "clamp". 3. The trailing wiper on the follower die doesn't sit over the area of greatest stress on the bending tube, it's ahead of it, allowing the tube to deform and ripple because it's unsupported in a critical area.

The Anvil bender uses a rolling die for each tube diameter and is profiled perfectly. Once everything is setup, the tube is fully encapsulated at the area of greatest stress and it's impossible for the tube to deform out of round because of how closely the follower fits over the tube. My guess is that there's about 0.003" of room and that's it. Don suggested that because the tube is formed through the bend process, I should mount the bender so I can pull horizontally. I mounted it to my mill, which is the heaviest piece of equipment in my shop and proceeded to pull it off of it's blocks. It takes a tremendous amount of force to bend a 7/8" x 0.035" tube. I machined a base for the bender and re-mounted it on my mill so I can use my body weight to pull the bend downward. For my uses, this is a perfect setup.

Don sent the bender with 3/4" and 7/8" dies with a 11 3/8" CLR which is perfect for mellow S-bends. I'm told that he will be making dies in 2" increments from 5 3/8" through 11 3/8" for three tube diameters; 5/8", 3/4" and 7/8". The dies are cross drilled for pins that act as bending stops. I bent about 20 tubes to the same stop and found that in my sample there was less than 0.005" deviation in the bend offset over the length of the tubes. I also made a "phase gauge" for indicating the edge of the tube when making S-bends and I found that I could keep the two bends in phase to less than 0.008" across the length of the tube when flat on my surface plate. This is EXTREMELY important and was making me crazy with my JD2.

I only had one recommendation for improvement. The tube stop block fit so tightly that it was impossible to load the tube in the bender to make closely stacked S-bends. I milled the stop pin holes about 0.030" longer and solved the problem. I think Don is considering making a similar change for the final design. I believe he also intends to include a "phase gauge" though it only takes a few minutes to make a very effective one on your own.

I'm going to post this up on the Framebuilder forum on MTBR and will link to it here once I do. If you have questions about it, please ask them on that forum and I'll do my best to answer.
 

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Shamisen Appreciator
Joined
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2,094 Posts
Discussion Starter · #3 ·


Just one at the mo. I'm waiting on another order of 7/8" and 3/4" tubing to come in and then I'll take the time to snap more to post.
 

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Non Dual Bliss
Joined
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6,240 Posts
smudge said:
Cut and Paste from my blog that I hardly update and no one reads. I'm sure that relevant details are missing as it was written hastily so if you have questions, ask them here and I'll do my best to answer them. Since it's here, Don can respond too if he wishes.

------------------------------------------------------------------------------------------------

This is a very long overdue post. Late last year, I heard that Don was going to make a tube bender similar to something he made years ago and discontinued. A few months ago, he sent me one to test. If you're looking for a summary, here it is...if you have tubes that need bending, this bender will get it done beautifully. Repeatability is excellent, quality of the bend is excellent, setup is super easy and for S-bends, keeping the bends in phase is dead simple. Only one of those comments holds true for the JD2 bender I've been using for the past four years.

The Details:

I've only used two other benders before, a JD2 Model 3 and a fork blade bender available through Nova. It was possible to use the fork blade bender on 5/8" x 0.032 and that's it. Ti tubing of larger diameters wouldn't bend without severe rippling. I have dies for my JD2 bender for 3/4" and 7/8" tube diameters with the CLR of the dies ranging from 3.5" to 5.5". Unfortunately, I've never had great luck with the bender. 3/4" tubing will bend well on the 5.5" CLR die but will ripple on the 3.5" die. A 3.5" CLR is out of the question with a 7/8" tube and the 5.5" CLR die was spotty at best. I have a huge scrap pile of rippled tubes. I think the biggest problem with the JD2 bender is three-fold. 1. the "clamp" doesn't securely hold the tube in place. 2. there's a significant amount of friction on the follower die which often forces the tube to slip through the "clamp". 3. The trailing wiper on the follower die doesn't sit over the area of greatest stress on the bending tube, it's ahead of it, allowing the tube to deform and ripple because it's unsupported in a critical area.

The Anvil bender uses a rolling die for each tube diameter and is profiled perfectly. Once everything is setup, the tube is fully encapsulated at the area of greatest stress and it's impossible for the tube to deform out of round because of how closely the follower fits over the tube. My guess is that there's about 0.003" of room and that's it. Don suggested that because the tube is formed through the bend process, I should mount the bender so I can pull horizontally. I mounted it to my mill, which is the heaviest piece of equipment in my shop and proceeded to pull it off of it's blocks. It takes a tremendous amount of force to bend a 7/8" x 0.035" tube. I machined a base for the bender and re-mounted it on my mill so I can use my body weight to pull the bend downward. For my uses, this is a perfect setup.

Don sent the bender with 3/4" and 7/8" dies with a 11 3/8" CLR which is perfect for mellow S-bends. I'm told that he will be making dies in 2" increments from 5 3/8" through 11 3/8" for three tube diameters; 5/8", 3/4" and 7/8". The dies are cross drilled for pins that act as bending stops. I bent about 20 tubes to the same stop and found that in my sample there was less than 0.005" deviation in the bend offset over the length of the tubes. I also made a "phase gauge" for indicating the edge of the tube when making S-bends and I found that I could keep the two bends in phase to less than 0.008" across the length of the tube when flat on my surface plate. This is EXTREMELY important and was making me crazy with my JD2.

I only had one recommendation for improvement. The tube stop block fit so tightly that it was impossible to load the tube in the bender to make closely stacked S-bends. I milled the stop pin holes about 0.030" longer and solved the problem. I think Don is considering making a similar change for the final design. I believe he also intends to include a "phase gauge" though it only takes a few minutes to make a very effective one on your own.

I'm going to post this up on the Framebuilder forum on MTBR and will link to it here once I do. If you have questions about it, please ask them on that forum and I'll do my best to answer.
Thanks Sean. The bender does form the tube so the effort can be very high on a 7/8" tube. 3/4 is usually a one handed affair. Could make the handle longer too. We're putting set screws on the tube stop so that it's adjustable on the pin and the button release pins on the main pivot and the roller will be replaced with trunnions on the production version.

If folks want to see more pics of the prototype Sean is using, you can find them here.
 
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