Another GHT Bending Rolls

[GWRdriver]

Hello All,

Quite some time ago I began building a set of bending rolls based on the George H. Thomas design, as it appeared in ME many years ago, and a couple of circumstances developed which let me consider rolls with an increased sheet capacity, although not necessarily with an increase in gauge capacity.  In checking my orphaned materials bins I found a piece of 1" steel plate just large enough to make the end plates and couple of lengths of alloy steel bar sufficient for the main rolls.  Based on those finds I enlarged the GHT design in CAD, maintaining it's original details and proportions, to make full use of the material.  This produced main rolls 1.500" diameter and 12" long.

The 1" thick steel for the end plates was perhaps overkill, but in the end this allowed for larger and longer bearings (which were and are plain bronze) which I assumed would have greater bearing capacity.  I briefly gave some thought to rolling bearings of some kind but decided that there wasn't enough (or any) benefit to justify the additional work in preparing the roll ends.

Since the bar stock for the main rolls was only just long enough to make 12" long rolls, I made the bearing shafts separately from 4140 steel and these were pressed and Loctited into the main roll bodies.  Once cured the roll assemblies were finish turned between centers.  All the other components were milled from CRS (aka BMS.)

Even though I roughed out the end plates first and had them deep annealed before final machining, there was still some closing of the bearing block slots when the connective tendons were finally cut away.  This eventually required fitted stepped cap blocks acting a spacers, and then quite a bit of hand fitting, to get smooth movement of the bearing blocks.

In maintaining the proportions of the GHT gear train, I correctly assumed I would have trouble finding commercially available gears which were anywhere close to what I needed, so I had to cut my own.  This gear cutting was a 1st-time experience for me, so I found the correct cutter, and I made sure to have extra "mistake" material on hand.    To my relief all went very well and I came away with a perfect pinion of gear material.  Individual gears were then sliced off the pinion and finish machined.  The gear train has but one very minor tight spot which will disappear when it gets a bit of run-in.

The base was made from a scrap section of structural steel channel acquired from a friend.  What wasn't needed was band-sawed and milled away leaving a mounting platform for the rolls and a "tail" for holding in a vise (or bolting to a bench) while it's being used.  The frame assembly is held together with alloy cap screws and the adjusting screws are made by me in stainless.

The next step will be disassembly, taking the sharp edges off the plates and caps, and preparing it all for paint, except of course for the rolls.  The Push roll (the smaller one) has been lapped with a course compound and has a "frosted" surface, and in order to give them a better grip I may do the same to the main rolls.

All in all it's been a very satisfying project.

Cheers,
Harry

[awake]

Looks great!

[Don1966]

Awesome. Results....


 
Don

[Kim]

Very nice! When do you get to use them?

Kim

[nj111]

Beautifully made and very useful!

[Saxalby]

Nice work on the rolls.
Getting to old to lift the big rolls I made for the work on my Atkinson lorry, so as I no longer make big models I scaled down and made
a, one hand liftable, set of 4 inch rolls.

[GWRdriver]

Nicely done Saxalby, and no doubt very useful in that size.  I've given some thought to making a set of very short rolls for this one which I could groove as-needed to roll T's and angles, but I'd need to have a lot of T's or angles to roll to go to that trouble.
I like the addition of the vice jaw "stop" and will probably add a similar bar to my base, for the same reason.
And these rolls are about as heavy as I want to lift these days!

Kim, I don't know when my next need will appear . . . probably first up will be something associated with building or wrapping a boiler.

[PJPickard]

One scaled up and one down, both are great. Harry I have wanted to make GHT's rolls for decades, but always wanted them a tad bigger. I like what you did, maybe this will get me off the peg and do it!

[GWRdriver]

I made a test of the rolls today, which turned out to be quite a bit more than just a test, and several things were learned.  First, make sure all driving shaft and gear keys have been installed before commencing any testing! 

Secondly, the crank handle grip is hardwood, drilled through, pressed between flanged ball bearings, on a metal shaft.  The outboard bearing soon broke out so the wood grip arrangement must go.  A metal tube, with perhaps a cushioned rubber grip, will make a solution.  Otherwise things went surprisingly well and an actual project piece, rather than a test piece, was produced. 

I needed a 5" square of 16ga black (hot-rolled) mild steel sheet rolled to a 3.25" radius so I put the rolls to use, tested or not.  The job took quite a bit of time, and many cycles, but eventually they did the job.  So from that I can declare that 16ga black mild steel is probably the practical limit for these rolls, at least without taking an extended length of time.  They might curl thicker steel, say down to 12ga, but that would strain everything, including the operator.  Copper and brass should be a piece of cake.