PDA

View Full Version : Educate Me About Sheet Metal Tooling



john hobdeclipe
04-14-2009, 10:46 PM
A situation is developing where I will be doing some sheet metal forming. But I know next to nothing about it, so I need some education.

All of this will be 301 or 304 Stainless Steel about .029 up to about .035 inches thick.

What I envision is the need to cut pieces to size, nothing larger than about 16 X 16 inches or so, and rather loose tolerances, say plus or minus 1/16".

Some pieces will be formed into a sort of pan, with about a 1 or 2 inch high rim, and some of these will be triangles, some squares, some perhaps a shape I haven't thought of yet.

Other pieces will be rectangles formed into an "S" curve, or a simple arc, or maybe something a bit more complex, who knows? These will need to be repeatable...I'll sometimes need several that are as close to identical as I can get them.

OK, so I know I'll need "slip rolls". And possibly a brake. I simply do not have room for a sheer (unless it's free.) But I need a way to cut these out without wearing out my bad hand with aviation snips.

These things don't have to be pretty...they are just forms for slumping and molding glass. It's the end product, the glass that has to be pretty.

So, what should I be looking for in the way of tooling to make these forms?

Is it feasible to make clean and controlled bends, either sharp or with a predetermined radius, without a proper sheet metal brake?

And when I inspect used slip rolls and brakes, what should I be looking for?

Are there brands to be wary of? I know that Tennsmith, Pexto, and Diacro make decent stuff but what about some other brands? What's good and what's not?

Thanks.

rmack898
04-15-2009, 06:47 AM
I'm not a tin knocker but I do have a nice sheet metal area in my shop and Pexto, Tennsmith, and Diarco are the tools I have. Without going into the whole import/old US iron debate, the weight of the machine is as important as the capacity of the machine and this is where old US iron will win every time. Add Cincinatti and National to your list.

If you think you will be working near a machine's maximum capacity, you need to go to the next larger size machine. If have a 16ga x 48" brake and will be bending 16ga full length than you will be much better off with a 12ga brake.

If you don't have room for a squaring sheer than a Beverly B-1 or B-3 is a real handy and impressive tool to have that takes up little space when bolted to a bench.

Evan
04-15-2009, 07:04 AM
You will need a box and pan brake and a stomp shear. Room or no room if you have much to make the shear is a must have, especially for stainless steel. Rolls and possible a beader/edge roll, maybe an edge shrinker and stretcher. Cutting .032 SS with snips is not an option. A bench shear will work but a stomp shear is how you make money and make really professional cuts.

SS has a large amount of springback. You will need to insure the brake has sufficient overtravel to handle it. Take the capacity listed for a machine and reduce it one guage for SS, perhaps two if you think it sounds inflated a bit.

If you are going to be doing any hand forming you need a couple of sand bags and a selection of planishing hammers, dollys and leather lead shot bags.

I would suggest finding a good book on the subject. I can't give any suggestions as I learned on the job.


And when I inspect used slip rolls and brakes, what should I be looking for?


Look for nicks and marks in the rolls caused by rolling wire. If you look at a shear look for nicks in the blades especially on the right end. With a brake put in a piece of metal of the rated capacity about 1 foot wide with one edge aligned with the center of the brake. Bend it 90 degrees and examine the bend to see if it is the same at both ends. If it isn't the brake has too much flex.

Liger Zero
04-15-2009, 07:16 AM
Inspect your dies carefully before you purchase them. 90% of the V-dies (used ones that is) I've looked at are either cracked or "blown out." For example if it's an 8mm die, the die will be expanded to 9-10mm due to severe usage/overloading.

Punches... Punches can take more abuse than the die, just make sure you are getting matched sets and not one long punch cut to length on a abrasive saw. There are ALWAYS issues with those with things not matching perfectly. The other issue is and again this is why a majority of punches come on the market... run at/over capacity and you can actually squish the punch out of shape make it shorter. This will be obvious if the punches are in a matched set, the abused punch will be slightly shorter or a slightly different shape than it's brothers.

JCHannum
04-15-2009, 07:26 AM
Some education on the subject will help. A lot will depend on the quantity needed and the frequency of making them. If you will only need a dozen or so and be done, versus dozens on an ongoing basis.

The brands mentioned are all good, and reasonably useable import knockoffs are available. A throatless bench shear is a step up from hand shears and will cut curves as well as straight lines.

I am usually reluctant to recommend Harbor Freight, but you might consider taking a look at their sheet metal tools, they are less of a risk than their machine tools, and if suitably de-rated could serve your needs. There are some three in one machines that incorporate a shear, brake and slip rolls.

Liger Zero
04-15-2009, 07:30 AM
I have one of those 3-in-1 units.

At best its an exercise in frustration and a "starter kit."

Unless you want to spend hours and hours modifying and adjusting it save your pennies and get a proper standalone brake and shear.

Dawai
04-15-2009, 07:32 AM
Do things like this daily..

Plasma cutter w/plywood or sheetmetal die to trace around making repeated copies.

Break can be made from angle iron and some welded on bolts and clamps on the edge of a table.. ok? relax.. it ain't that complicated.

Liger Zero
04-15-2009, 07:41 AM
Do things like this daily..

Plasma cutter w/plywood or sheetmetal die to trace around making repeated copies.

Break can be made from angle iron and some welded on bolts and clamps on the edge of a table.. ok? relax.. it ain't that complicated.

BAH! If it ain't an Amada it ain't welcome in my shop! :D

But yes, if the volumes are low and the tolerance generous you can rig up a special purpose bender. I've bent parts to shape over a retired 1-2-3 block (actually a 1-2-2.375 block due to an unfortunate milling accident) and a hammer.

Just be patient and double check your bend-lines.

Once Stainless is bent it cannot be unbent.

davidh
04-15-2009, 07:54 AM
i must agree with david coffer.

from experience, i would much rather use my plasma than my shear. clean cuts almost every time, and it takes up much less space than a shear.

i have a couple hardwood universal type strips i use as guides for straight cutting and some of the guides i have sawed different size hole in for circle burning. and you can buy rail guides for long straight cuts, acircle cutters for circles too. . . .

davidh

Liger Zero
04-15-2009, 08:02 AM
Only drawback to the plasma cutter is you need some skill to work that safely... a shear can be operated by a helper-monkey.

smiller6912
04-15-2009, 08:11 AM
How about a 3-in-1 sheet metal tool.
http://www.baileighindustrial.com/benders/shear-brake-roll.php
Hey, just an idea.
Also, when you get started, get yourself a good "bend allowance" chart and learn to use it.

Seastar
04-15-2009, 08:30 AM
+A1 for the plasma cutter approach.
You can make odd shaped forms out of plywood with a saber/jig saw and trace the shape with the plasma cutter.
I will probably be flamed for this, but I bought one of these for one of my shops and, so far, it works very well.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95136

I built a small brake from angle iron and some hinges that clamps to a workbench and works for light bends.

I also have one of these for heavy bends.
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_21896_21896
It works pretty well if you have a shop press but is slow.
Usual disclamers!
Bill

Dawai
04-15-2009, 08:37 AM
http://www.metalmeet.com/photopost/data/3846/medium/Tipping_wheel_on_eframe.JPG

Tas die tipping wheel.. able to cut a crease in metal, then take a block of steel or hammer and tap it, supporting next to the crease.. it folds metal at the crease making a 90.. then shrinking it back requires more hammer work.

Known as pizza cutter, a sharp edge rolling over a urethane caster.. I put the chain drive up there cause I am anal retentive. (can't help it, I am nuts) A bead roller frame will do the same thing with a cut wheel from a hard washer over rubber or urethane..

http://photos-g.ak.fbcdn.net/photos-ak-snc1/v2584/204/30/1298124187/n1298124187_30086790_1761353.jpg
I free handed these numbers with the plasma cutter from 12" high blocks, then took the tipping wheel around the edges, took 20 minutes.. THEN I had breakfast.. which took a hour.

THe leaves on the roses? I tipped in the vein lines after free-handing them from stainless with the plasma cutter..

Too bad you are not next door. You could buy breakfast.


http://www.metalmeet.com/photopost/data/500/medium/MVC-783S.JPG
Joe Andrews, tipping in "flames" into a panel making them 3d.. NEAT.. then you paint them and make the kids go crazyier than normal.. I am planning the HOOD on the civic truck like this. JUST AS SOON AS I GET THE WORKBENCH CLEARED OFF. Ha, maybe never.. today I am hunting a hydraulic line for the wrecker.. have to go to Chattanooga after it.

john hobdeclipe
04-15-2009, 10:22 PM
Thanks for the info. So now I have another question or two.

As far a quantity, I don't expect to make more than a dozen or so of these a year for my own use, although it's always possible that I may be asked to make more.

First; How well do these kind of shears work? It looks like a handy alternative to me, and doesn't take up any floor space, and would make it easy to work with a 4' X 8' sheet. This particular model is advertised as handling up to 18G stainless.
http://www.auldooly.com/imagehost/6805.jpg

Second; The plasma cutter sounds like a good, versatile alternative. Any recommendations as to good brands / models for a beginner?

Third; David Cofer & Seastar, could you post pix of your homemade brakes and bending rigs?

I'll be going to an auction this weekend, and there is some sheet metal stuff there. Hopefully I'll be the only one there, and I can steal everything I need for a few dollars.

David Cofer, Im sending you a PM in just a few minutes.

Thanks.