Plate roll question
I have an old Baldwin Southwark Roll 12" Ø rolls 14' long. These things are old and I am trying to find its capacity. (min max rolling dia & thickness).
Is there a chart anyone knows about that might tell me say- if I know I can roll a 5/8" thick A-36 mild steel plate x long and x dia. what would I be able to roll in say Ar-400.
would the percentage less be based on ductility alone?
I dont think there is a universal chart anywhere, but Bertsch's chart gives you an idea-
Bertsch Plate Roll Specifications
Judging from that, I would guess that your rolls were originally rated at somewhere between 3/8" and 1/2" at full width, depending on how stoutly they are built.
A new Bertsch with 12" diameter rolls, 10' wide, is a half inch machine.
Capacity for rolls and brakes is usually based on tensile strength of the material, with A36 asssumed to be around 55ksi.
So if AR-400 is at 140ksi
then I would derate by 2/3.
Meaning you should be able to roll 1/3 the thickness in AR-400 that you can in A36.
Here is a chart of some common stainless and aluminum alloys-
Could the rating be established empirically, by measuring deflection?
or by seeing when it breaks?
There might be deflection in the actual 12" diameter roll, but my guess is that it would come after something else has already broken.
The rolls are usually turned down at the ends, and put in bushings or bearings- so it makes sense that, before a 12" cylinder would deflect significantly, the 6" diameter end shank would bend or break.
Not to mention gear trains, adjusting bolts, cross bracing, and all the other parts that make an older set of rolls work.
Many many people overwork their rolls. Its human nature, I suppose- and its easy to assume that, if it will roll 14 feet of 3/8", then it should be able to roll 4' of 3/4", right?
And, sometimes, especially with older machines, they are enough overbuilt that they do it.
But it is not without cost. Its possible to spring rolls, break teeth off gears, bend frames, and lots of other bad stuff, some of it subtly over time.
I have a friend who has a big set of Lown Rolls, that she is sure are 3/4" rolls- after all, she has rolled pieces of 3/4" plate in em. But when I did some research, I found out they were rated by Lown for 12 gage at full width. Its a testament to their construction that they havent blown apart yet, but I sure wouldnt recommend repeated rolling of 3/4" in them.
And even though these rolls seem incredibly herky with 12" diameter rolls, most likely they were only designed to roll 3/8" mild steel.
I don't mean to argue with you Ries, as you are far more knowledgeable about metal bending than I. However, I am quite curious about the capacity rating. Wouldn't the yield strength be a more meaningful comparison than tensile strength?
Originally Posted by Ries
But its pretty easy to find the tensile strength of most metals, and so they generally use it as a rule of thumb rating.
Basically, all of these machines are overbuilt- they know people will misuse them.
Its just a matter of how much they are overbuilt, and what is a handy measuring stick to use to compare apples to apples.
The relationship of the yield strength of A36 versus AR 400 is pretty similar to the relationship of the tensile strength- you still would be talking about somewhere around 1/3 of the capacity.
You also need to consider leverage. When rolling a shallow curve the plate contacts the rolls further out. Tight curve and effectively its like trying to bend something on a break with narrow V's. The difference there depending on roller spacings - diamiters would probaly make a significant diffrence in thickness capacity too.
I have an older Niagara roll rated at 5/16" over the 4ft length. We roll 3/8" AR235 & 3/8" AR400F almost exclusively. The widest parts are 24" and the tightest bends are 4ft radius in AR400 and 18" radius in AR400F.
My rollers are 9" dia but only 4ft usable width.
If you are rolling the AR400 make sure you specify the AR400F (Formable). Also, rolling with the grain will give you a different result than rolling across the grain.
All the information from Ries is accurate but maybe what I have experienced will help somewhat.
ps - 24" of 3/8" AR400F is all my rollers can handle. Anymore and I break drive gears, which in this roll are a pain to change.
Last edited by Walter A; 03-17-2011 at 09:25 AM.
Reason: added information
Thank you for the great info! I was wondering what would be the chances of getting a manual for my Southwark Philadelphia 14' x 14" roll? I have the serial #.
I found out when they bought it they guessed it was rated 5/8 x 14' capacity.
I was talking to the fab guy and they were rolling 1-1/4 plate (x 2' wide) with no problem.
Also I was wrong,the rolls are 14" Ø and have a center support. The frame is really beefy compared to modern rolls and has a 35Hp wound rotor motor with a huge gearbox.
Last edited by Tin Man; 03-21-2011 at 07:45 AM.
Reason: Added Info