PDA

View Full Version : Bending Rolls



willmac
11-03-2012, 06:10 AM
I thought some of you guys might be interested in a little project I just finished. It is a set of bending rolls which I will be using to form some guards and other bits and pieces for a much longer term project - classic make the tools to make the tools situation ...

The rolls are from a Hemmingway kit, which in turn is based on a classic George Thomas design. I made a few minor modifications but it is essentially the original design. The idea is to use a rear mounted deflecting roll rather than the more typical pyramid arrangement. This is supposed to have some advantages in that the radius being rolled can continue right up to the end of the stock, rather than having flats at each end. This does work as intended, although it is necessary to reverse the stock on each pass.

The overall layout:

http://i122.photobucket.com/albums/o248/moorbrook1860/P1000987C.jpg

the rolls are intended to be held in a vice as shown. The gears provides a positive feed to the two front rolls, which pinch the work under the control of the screws at the top.

http://i122.photobucket.com/albums/o248/moorbrook1860/P1000983.jpg

Since the front rolls need to adjust to accommodate different thicknesses of stock, the gear arrangement has to allow for this.

The latches on top open so that if a complete ring is rolled, the stock can be removed with the roller. The bronze bearings have inset hardened steel pads so that the bronze doesn't get damaged by the ends of the screws. There is a similar arrangement for the bearings holding the rear deflecting roll, which has a much longer range of adjustment.

http://i122.photobucket.com/albums/o248/moorbrook1860/P1000972.jpg
View from the back:

http://i122.photobucket.com/albums/o248/moorbrook1860/P1000982.jpg

Black Forest
11-03-2012, 07:24 AM
That is a great tool! Did you make CAD drawings for the parts? I have been wanting to build a leather splitter that is crank operated. What you have there would work almost perfectly with just a small bit of modification.

Did you make the gears yourself?

Black Forest
11-03-2012, 07:59 AM
The roller that is adjusted to make the actual bend could be replaced by a blade and a containment apparatus. The driven rollers would actually pull the leather not push the leather.

.......I feel a project coming on!

willmac
11-03-2012, 08:28 AM
The drawings with the kit are copyright so I can't give you those, but the original George Thomas article is here:
http://www.metalwebnews.com/howto/rolls/BendingRolls.pdf
That has the original drawings in it. There are only minor differences between that one and the version that I made. I think it is worth the effort to add the captive tommy bars as I have done, it only takes a few minutes to make them.

I don't know what leather splitters do- can you explain?

willmac
11-03-2012, 08:36 AM
Did you make the gears yourself?

No - the gears came with the kit. They are just standard off the shelf parts - all you need is four the same size, preferably two with keyways already in. If you can't get them with keyways you would need to put them in yourself. I made the keyway in the handle with just a couple of files - it takes a while to do it that way, but cheaper than buying broaches.

BigJohnT
11-03-2012, 09:19 AM
There are only minor differences between that one and the version that I made. I think it is worth the effort to add the captive tommy bars as I have done, it only takes a few minutes to make them.

What is a tommy bar?

John

RussZHC
11-03-2012, 09:45 AM
I think I am looking at this correctly...
There is a similar arrangement for the bearings holding the rear deflecting roll, which has a much longer range of adjustment., is that the "slot" with the bronze widget partially hidden by the crank are in photo # 2 ?

Black Forest
11-03-2012, 09:49 AM
The drawings with the kit are copyright so I can't give you those, but the original George Thomas article is here:
http://www.metalwebnews.com/howto/rolls/BendingRolls.pdf
That has the original drawings in it. There are only minor differences between that one and the version that I made. I think it is worth the effort to add the captive tommy bars as I have done, it only takes a few minutes to make them.

I don't know what leather splitters do- can you explain?

Leather splitters split leather! The leather is pulled over a long blade and split to a desired thickness. Leather as it comes from the cow is not a uniform thickness so for a lot of work it must be split to a uniform thickness. On a wide piece it is quite difficult to hand pull the leather through the blade. Typically on a leather splitter with a crank the lower driven roller is serrated to give traction. The flesh side of the leather goes against the serrations so as not to mark the smooth side. A good old cranking leather splitter is a Landis Model 30 for shoe sole splitting but they are hard to come by nowadays.

bborr01
11-03-2012, 09:57 AM
Willmac,

Nice job on the roller. I made a small 19" press brake recently and a roller like that would complement it nicely.

It is now on my to do list.

Brian

PS. That would also be a great candidate for the shop made tools thread.

willmac
11-03-2012, 10:11 AM
What is a tommy bar?
John

The little bar with two ends on it that adjusts the screw. It gives a bit of extra leverage compared to knurling the top of the screw. I don't know where 'tommy' comes from; its UK terminology and maybe a bit old-fashioned.

willmac
11-03-2012, 10:18 AM
I think I am looking at this correctly..., is that the "slot" with the bronze widget partially hidden by the crank are in photo # 2 ?

Yes that is correct. The bronze bearing is similar to the one for the top roller, just a bit smaller. The screws are 'timed' so that when the deflecting roller is in its fully up position, the tommy bars are aligned. This means that you can get the deflecting roll parallel by counting turns on each side and making sure the tommy bars line up. The top adjusters are done the same way.

dp
11-03-2012, 11:01 AM
Where would one find beefy gears like those off the shelf?

wierdscience
11-03-2012, 11:16 AM
Very nice set of rolls Willmac!

wierdscience
11-03-2012, 11:25 AM
Rolled pinion stock,just bore the shaft hole and part off the width you want.

http://www.grobinc.com/coldrolled/std_spur_gears.htm

Boston gear,McMaster and several others also carry it.

Black Forest
11-03-2012, 11:25 AM
Where would one find beefy gears like those off the shelf?

Here:http://www.maedler.de/Product/1643/1618/1034/1066/1070.aspx

Mcgyver
11-03-2012, 12:01 PM
Nice job Bill, built a similar one myself....what I think is called a pinch roller vs a pyramid. they are the preferred style imo.


The little bar with two ends on it that adjusts the screw. It gives a bit of extra leverage compared to knurling the top of the screw. I don't know where 'tommy' comes from; its UK terminology and maybe a bit old-fashioned.

that's what I've always call them....I do them with with peened on collars, feels kind of traditional

willmac
11-03-2012, 12:07 PM
Nice job Bill, built a similar one myself....what I think is called a pinch roller vs a pyramid. they are the preferred style imo.
that's what I've always call them....I do them with with peened on collars, feels kind of traditional

No-one ever asked me before what it was so I have to admit that I don't know where the word comes from. I have made peened on collars before. That works well for a bigger bar. I made these with Loctite. It works just as well, but is a lot easier to make. I have made quite a few like this and never had an end come off.

BigJohnT
11-03-2012, 12:17 PM
Nice job Bill, built a similar one myself....what I think is called a pinch roller vs a pyramid. they are the preferred style imo.



that's what I've always call them....I do them with with peened on collars, feels kind of traditional

Do you turn down the end a bit to get a shoulder then put a chamfer on the collar then peen the end over to fill the chamfer?

John

Mcgyver
11-03-2012, 12:24 PM
thats' it, I'll post a new thread some pics

Jaakko Fagerlund
11-03-2012, 01:41 PM
The little bar with two ends on it that adjusts the screw. It gives a bit of extra leverage compared to knurling the top of the screw. I don't know where 'tommy' comes from; its UK terminology and maybe a bit old-fashioned.
Probably the same with Tommy gun - gives you that little leverage in tight spots :D

MarkBall2
11-03-2012, 01:57 PM
I like this. Most of my projects I build from pictures to get the idea, then just build it.

Pherdie
11-03-2012, 02:07 PM
Nice execution of a Hemingway project, Willmac.

I sure am glad Hemingway is as far away as they are from me, otherwise I would have bought most of what they have to offer!!!!

willmac
11-03-2012, 02:30 PM
Nice execution of a Hemingway project, Willmac.
I sure am glad Hemingway is as far away as they are from me, otherwise I would have bought most of what they have to offer!!!!

I have built quite a few of their tool projects and I have been happy with the results. In most cases they are tools that you can't readily buy, or if you can the quality is suspect. The prices usually include materials and drawings; you pay for the convenience factor, but I think that is reasonable. If you are put off by the distance, give Kirk Burwell a call - he may be prepared to sell drawings only.

willmac
11-03-2012, 02:45 PM
What is a tommy bar?
John

Getting a bit OT here.

John - you set me wondering where this word came from. I did a bit of lazy on-line research and found a plausible explanation.

British soldiers were often given the name 'Tommy Atkinson' as a bit of a shorthand like the US 'John Doe'. That got shortened to Tommy or Tommies. Even the German army used to refer to Tommies in both first and second world war.

Artillery shells had a fuse which was fitted and perhaps adjusted with a box wrench with a captive bar. This became known as a Tommy bar, and then by extension to any arrangement like this on any tool.

That is probably why the terminology is common in UK, Canada, Australia etc, but not in US.

Seems to make sense to me.

customcutter
11-03-2012, 03:20 PM
Very nice work. I like it.

Ken

BigJohnT
11-03-2012, 03:48 PM
Getting a bit OT here.

John - you set me wondering where this word came from. I did a bit of lazy on-line research and found a plausible explanation.

British soldiers were often given the name 'Tommy Atkinson' as a bit of a shorthand like the US 'John Doe'. That got shortened to Tommy or Tommies. Even the German army used to refer to Tommies in both first and second world war.

Artillery shells had a fuse which was fitted and perhaps adjusted with a box wrench with a captive bar. This became known as a Tommy bar, and then by extension to any arrangement like this on any tool.

That is probably why the terminology is common in UK, Canada, Australia etc, but not in US.

Seems to make sense to me.

Makes more sense to me now... thanks for looking that up.

John

lockstocknbarrel
11-04-2012, 07:02 AM
Very professional Bill, if I could only workout how to post attachments then I would show the CAD drawing..............................
DUH...!!!!
Is it because I am still a snotty nosed Junior................
Would love to put up some posts but struggling to post attachments.
Kindest Regards
Beagles
Thanks John,
Drew these myself, metric measurements.
http://bbs.homeshopmachinist.net/attachment.php?attachmentid=57&d=1352031780

John Stevenson
11-04-2012, 07:20 AM
Very professional Bill, if I could only workout how to post attachments then I would show the CAD drawing..............................
DUH...!!!!
Is it because I am still a snotty nosed Junior................
Would love to put up some posts but struggling to post attachments.
Kindest Regards
Beagles

You cannot post attachments on this site, only link to photos etc hosted elsewhere.
See the third sticky post down from the top in this section for info on how to do it.

Also be careful that with any drawings you post you have the right to do so and not breach any copyright agreements.

BigJohnT
11-04-2012, 08:15 AM
Drew these myself, metric measurements.


That does look like a Solidworks drawing... it was interesting in translating the original article to a SW model. He had some tricky ways of laying out the slot and if you didn't read the text you could not figure it out from the drawing.

John

MarkBall2
11-04-2012, 09:26 AM
I would love to have a print of the end plates shown (PDF as I have no idea how to do CAD). Metric or inch works for me. I have 2 round bars waiting for a project like this. One is 2.5" diameter & 12 feet long, the other, is 2" x 8 feet long (I've been slicing a bit off here & there). This would be a perfect use for these round bars.



http://bbs.homeshopmachinist.net/attachment.php?attachmentid=57&d=1352031780



You cannot post attachments on this site, only link to photos etc hosted elsewhere.
See the third sticky post down from the top in this section for info on how to do it.

Also be careful that with any drawings you post you have the right to do so and not breach any copyright agreements.

Also if I may be so bold with a suggestion.......... is there is a "simple" way to put an "Add Attachments" button to the BBS, then the pictures/drawings will always be here & not lost if the original poster moves or deletes the picture/drawing. A couple other forums I belong to do this & even when a software/site crash occurs, the back-up always has the photos & such.

J Tiers
11-04-2012, 10:05 AM
The idea is to use a rear mounted deflecting roll rather than the more typical pyramid arrangement. This is supposed to have some advantages in that the radius being rolled can continue right up to the end of the stock, rather than having flats at each end. This does work as intended, although it is necessary to reverse the stock on each pass.



So, how do you arrange three rolls not in a triangle shape, to bend right down to the end of the sheet?

it seems that there will NEVER be any bending on the last bit, approximately a roller diameter, since as soon as it leaves the double roll, all leverage on it stops... same as it is fed in, before it hits the other roll.

BigJohnT
11-04-2012, 10:11 AM
So, how do you arrange three rolls not in a triangle shape, to bend right down to the end of the sheet?

it seems that there will NEVER be any bending on the last bit, approximately a roller diameter, since as soon as it leaves the double roll, all leverage on it stops... same as it is fed in, before it hits the other roll.

That's what I get with my Griz pinch roller on my 3 in 1 machine a flat at the ends unless you roll to the same diameter as the rolls... seems the smaller you roll the less flat you end up with. I do need to fit some Tommy Bars to the bending roll.

John

John Stevenson
11-04-2012, 10:19 AM
I would love to have a print of the end plates shown (PDF as I have no idea how to do CAD). Metric or inch works for me.

Mark,
See the link in post #4

Jerry,
same applies link explains better how the end follows the curve.

Now playing Devils advocate and going against the great Mr Thomas.

When I first saw the picture posted by the OP I couldn't visualise how the third roller worked or the need for 4 gears.
looking at the drawings cleared this up and in the Soildworks renderings by Beagles the adjustment is clearly visable in the downward facing slot.

Now to my mind this isn't that easy to work given it is downward facing.
If the design was altered a tad and the slot made open at the top and the opposite hand then the adjustment screws would be on top with the top roller screws.

Being tommy bar operated both would be assessable. I know they would clash but you only use the top roller screw to insert full rings and if the 3rd roller screw was longer this would be well clear for the constant use it would be needed for when rolling a tube or ring.

Flames, insults, flying bricks ?????????

willmac
11-04-2012, 11:22 AM
That could work, but it might limit the size of the rings that you can roll. In the George Thomas design the minimum radius is the same as the top roll, because the work, as it is being formed comes out upwards, clear of the rest of the tool. If the deflecting roll was at the top, then the work would bend downwards and would hit the bottom of the tool or the vice.

Having the deflecting roller adjustment underneath doesn't seem to be a big problem when I use the tool. It has to held in a vice so the handles are easily reached.

Maybe better, and building on what you have in mind is to have the adjuster pulling up on the deflecting roller rather than pushing it up? That would certainly work. but the bearing arrangement would need a bit of work. The clashing problems could be overcome easily if you didn't have captive tommy bars.

The original version apparently didn't have gears and suffered from occasional lack of traction. The gears were added to overcome this. The design is a compromise because the centre distances of the gears vary - it only works because the speeds are slow and this type of gearing is not too sensitive to centre distance errors.

This is like a lot of George Thomas designs, and I have a made a few of them. It has a lot of parts that are fiddly to make, but they are mostly well thought out.

willmac
11-04-2012, 11:29 AM
Very professional Bill, if I could only workout how to post attachments then I would show the CAD drawing..............................
Drew these myself, metric measurements.
http://bbs.homeshopmachinist.net/attachment.php?attachmentid=57&d=1352031780

That looks about right to me. You need to add some holes for the idler gear shafts. If you are going to make one of these, start out with two bits of rectangular plate pin them together so they can't move then drill and bore the holes and mill the slots in one hit. It is important that both sides are exactly the same and features are exactly square. Then you can cut away all the bits you don't need from the outside, including where you pinned them together.

The rolls need to be turned as straight as you can. Not that easy on an old worn out lathe.

J Tiers
11-04-2012, 12:13 PM
The link does explain the theory..... I suspect the bending is a little less at the end, due to the imperfect grip of two points on the metal (the metal should slip a little as it is only held by friction and its own hardness), but it should be good enough for practical use.

If it were not, we'd see plans for something to correct those problems.

I recently turned down a small set of bending rolls constructed on that theory...... selling for $2, but I hadn't any idea how they were to be used, the things was small, about 9" long with thin rolls, and the rolls were badly pitted.

willmac
11-04-2012, 01:48 PM
The bending stress on the rolls is significant so I would regard the 1 1/8 diameter main rolls is about the minimum for the span of about 10 inches. The finish on the rolls does need to be good otherwise it will transfer onto the material when bending something like brass.

For 2 dollars though --- it might have been worth cleaning up.

J Tiers
11-04-2012, 03:03 PM
The rolls were about 3/4", and would have needed to be turned down further. It was ancient, lightweight, and didn't even have a base, the frames were made each with a stud and wing nut to go in holes on a workbench.

If I had understood then how it was to be worked, I might have done it, but I have lots of projects already, including a lathe to finish reconditioning, a mill to finish reconditioning, a heat-treating oven to refurbish (recently bought for $27.50), plus some plumbing and organizational stuff, and "farm chores" outside.

if he hasn't scrapped it yet, the FIL has a set of rolls that he doesn't want. big ones, 18" x about 3" diameter. need some work, but the bones are (were?) all there.

Mcgyver
11-04-2012, 03:20 PM
one handy use of a set of pinch rollers is flattening sheet metal, you know those dings and bumps you find on a thin gauge piece when you pull it of stock....can't to that on pyramid rollers. set the rollers for a tight squeeze on the metal and get the deflecting roller out of the way. Keep passing the metal through the rollers, varying each time the angle and you can restore a piece of sheet metal nicely. I've probably used mine far more that than rolling cylindrical pieces

wierdscience
11-04-2012, 03:54 PM
One pinch roll technique is pre-bending the end of the workpiece,that eliminates some of the problems-

http://youtu.be/ekicY_oNE7I?t=55s

What I want to build in a small set of rolls is a four roll machine or double pinch.

http://youtu.be/6KGfsAbE-EY

willmac
11-04-2012, 06:03 PM
Some good skills in that first clip - interesting - thanks.

John Stevenson
11-04-2012, 07:33 PM
I have one of these cheap ring rollers and it's not bad but takes a fair bit of winding to bend 2" x 1/4" strip.
One project i have on the books is to convert this to be powered by something like a 2Hp 3 phase motor with reduction gearbox giving something like 20 to 30 revs final speed.

Rolling a ring up from 1/4" black steel strip is a cheap way to make bearing rings for motors. If you cut, roll and weld about 8 or 10 at a time it's very cost and time effective.