Sheet metal bending and cutting?

I have a Harbor Freight 30" 3-in-one sheet metal machine. Also have a Tennsmith 37" stomp shear and a Diacro 24" box & pan brake. Bought the HF machine first. If I'd have bought the Tennsmith shear and Diacro brale first, I wouldn't own the HF machine if that tells you anything.

The HF's work fine for what it is, but you'd be really hard pressed to shear 0.100" aluminum. Kudo's on one hand to HF; I broke one of the cast link arms that goes from the eccentric at the crank handle/slip roll down to the shear bar trying to bend a 12" length of 16-gauge steel (think they're rated at 20-gauge max). Called HF and got a replacement casting for around $12 back in the day.

My Tennsmith maxes at 0.0625" for mild steel and 0.100" for aluminum. I've cut 12" lengths of 0.050" 303 stainless and 1/8" aluminum around 20" long with little problem. If the HF is rated for 20-gauge (think that's around 0.036" in steel), you're probably at around 0.050" max in aluminum.

On one hand, you might be able to push the shearing a little more than the braking. When you shear on a 3-in-one machine, the link (one that I broke) between the eccentric at the crank and the shear bar/brake "V" is in compression. Can take a ton of load. When you brake, the link from the top to the shear bar/brake "V" is in tension. There's a pair of these links on the sides of the machine, they're shaped like a comma. The bottom of the comma has a bolt that runs through it to the shear bar/brake bar. When braking, this joint is in tension and in my case I snapped the bottom of the casting off. Also, the 3-in-one is hand operated, the stomp shear is my body weight. You can only pull/push so hard with one hand, get a lot more impulse from a hop on the Tennsmith shear.

Another "nuance" with the HF is a lack of table size as designed. Guys have a work-around here. The support table for the shear is about 3 or 4" wide. It can be a challenge to set a 20" deep piece of sheet metal in place, get it aligned with the blade, and not have it move on you. Guys have extension tables to overcome this. My Tennsmith has a 14" table in front of the shear bar. One hand is ALWAYS tied to the 3-in-one machine to turn the crank. You have one free hand to hold the material in place. Always two hands free with a stomp shear.

The press brake is a challenge also. Imagine a "V" block 30" long and resting a 24" wide by 24" deep piece of sheet metal on top. While balancing the piece of sheet metal, rotate the crank to bring the press blade just down to the work, then double-check alignment before bending. Same work-around here, make an auxiliary table to support the work. Also, only one hand available to stabilize the work as the other is turning the crank.

I bought my HF 3-in-one for $500 in around 1991 (going price back then). Bought the Tennsmith shear used for $700, Diacro brake for $400. Think those two run around $2000 and $4000 new; another case of you get what you pay for and should expect more for over 10X the cost.

If you are only going to do an occasional job, might not be worth buying the equipment (did I actually type DO NOT BUY A TOOL?!?!). I've had metal cut at a local duct work shop and they didn't charge me anything. Albeit, I buy my 20 and 24 gauge sheet metal from them.

Depending on your length of cut, you may consider an 8" bench shear. They are under $150 and could easily cut 0.100" aluminum. Mine is from Woodward Fab (Chinese generic) and is rated at 3/16" steel. I cut 1/8" steel all of the time. They work like a guillotine shear for paper with no stop fence. Let's you make a cut, advance, and cut again. Maybe more like a pair of scissors where one of the blades is fixed to a base and a long handle on the other one. I've comfortably cut a 15" length of 1/8" steel and held a line well within 0.015" inch.

Bruce
 
Last edited:
Not in the same class of work, but I do occasional sheet metal work. Some on an old truck, some on the roof of my shop, some electrical enclosures, some etc. I have tried several methods, from clamped up 2X4s to hand powered press brakes. Had a friend (co-worker) that built a homebrew airplane with nothing but a few 2X6s and lots of patience. Most of my work these days is with rolls of "flashing tin".

I started out serious braking with a HF 3 in 1 shear, brake, slip roll machine. Back a few years when they didn't cost that much. The same machine from W W Grainger was 4X the cost and very little better finish. The brake "fingers" were independant so I could get into corners easy. But in the long run, the machine was too heavy and too big for most of my work. A 30 inch version. When the smaller (12") version came out, I gave the big one to a local "maker space". It took 2 goodly sized men to move it and a pickup truck to transport it.

The big issue was that it would only do full width work up to 16 Ga aluminium. That's 0.062 more or less. 11 Ga is roughly 2mm, 0.080". 10 Ga is around 0.100". That's some "heavy" weight metal and not easily bent in a home shop. When working heavy weight material, I cut it with an old "Skil Saw" with bad bearings and a backward blade. And good ear plugs! But even that is limited to 16 Ga and lighter. Anything heavier is with a jig saw and metal cutting blade

I tried a power shear. . . from Milwaukee. Like a hand drill with a "scissors" instead of a chuck. Did more damage to the tool than I did to the sheet metal. Now-a-days I just use a hacksaw or jigsaw, and file the rough edges. For "true" corners, I use Home Depot alum shapes and appropriate fasteners to a straight sheet. Pop rivets, sheet metal screws, or machine screws. A little overhang on the corners conceals the internal angle frame.

This should not be taken as a recommendation of methods. I am an old man and appearace is a low priority in my shop. I build what I need, not what I want, most times.

.
 
I've been "making do" with a HF 39103 (the 18" version of that brake) and a plate shear (described in thread https://www.hobby-machinist.com/threads/improving-a-plate-shear.78519/ ). +1 on posts that said that such a brake is in no way suitable for 0.100" aluminum. Sounds like you're working with relatively small pieces, so the 18" brake would probably be OK. Note that you need a couple of good C-clamps or Kant Twists, to clamp down the pinch(?) bar that holds the "fixed" part of the stock. And sometimes, despite reefing down on the claamps, the bar will shift away from the bend. I've drilled my bar and the "table" beneath it, to take dowel pins. There are a couple sets of holes, to allow for different stock thicknesses.

If you' stay under 6" width, you might want to look at a vise brake (Grizzly P/n H3243 thru H3245) They actually have configurable "fingers," so you can do small "box" work. Might even be stout enough to bend 0.100" aluminum! I have a couple, and they do work well (for their size).
 
Thanks for the comments and suggestions from everyone. Sounds like I have some pretty good options for bending. As far as getting clean cuts go, that will continue to be an experiment.

One thing I don't think I mentioned is that, apart from cost, a major factor for us is that we've got a very small shop, so anything with any footprint to speak of will be a problem. Although some of those larger shears and 3-in-1 machines probably do a good job, I doubt we have the space for them. Probably still looking at doing rough cuts in some way and then cleaning up on the mill.
 
Frank O said:
Thanks for the comments and suggestions from everyone. Sounds like I have some pretty good options for bending. As far as getting clean cuts go, that will continue to be an experiment.

One thing I don't think I mentioned is that, apart from cost, a major factor for us is that we've got a very small shop, so anything with any footprint to speak of will be a problem. Although some of those larger shears and 3-in-1 machines probably do a good job, I doubt we have the space for them. Probably still looking at doing rough cuts in some way and then cleaning up on the mill.
Click to expand...


I have cleaned up sheet meal edges by clamping the edges between 2 angles or bars and sanding with a flap wheel.
 
Thanks for the additional comments and suggestions.

Picked up a 3' x 5' sheet of .050 5052 aluminum from Industrial Metal Supply today. I can see that's got a little thickness to it.

brino said:
For cutting also check out this thread:
https://www.hobby-machinist.com/threads/cutting-thick-sheet-metal.83671/

It covers the many ways people are doing it.
Click to expand...


Looks like good ideas there. I ended up ordering an 8" bench shear today of the type BGHansen mentioned.

For roughing out, I was wondering how far I can get with some of my existing saws. Somewhere I think I have one or two metal blades for my table saw, which for a lot of materials is a quick way to cut straight lines -- just wouldn't want to run into issues keeping it under control due to flexing of the metal sheet.

Working with a band saw seems like it might be a little more low-key. I have one of those Harbor Freight 4 x 6 tilting band saws that we usually use to chop end pieces from metal, though I guess you can tilt it upright and use it like a regular band saw. I have a Milwaukee handheld M12 band saw that's great for slicing off Unistrut, but I'm not too sure how useful it'd be with metal sheet. And finally I have a little Delta 9" benchtop band saw which might be okay for some work, but I know the blades I have are not for metal, so I'd have to hunt around for an appropriate blade.

If anybody has ideas (or warnings) about any of those ideas, it would be great to hear.
 
I would have suggested cutting .050 Al on the table saw (if I had known you had a table saw). Be certain that the blade is designed for nonferrous metal.

After you've set the saw fence for a cut, double face tape a sheet of plywood to your saw table. Run the blade up through the plywood creating a zero clearance insert, and more importantly, the plywood will raise the aluminum up so there's no chance of binding while trying to sneak under your fence. Use a large enough piece of plywood to serve as an out-feed table, as required. I also apply a waxy stick lubricant to the blade periodically. After a proper sheet metal sheer, the table saw (with a proper set-up) is my second choice.
 
Table or ras work well for Aluminum.

Skill saw for larger chunks, do use a chunk of plywood clamped in place for a fence.

For bending thicker stuff back cutting works.

Aluminum does not like sharp corners and nut be bent with a radius that depends on thickness.

Thicker stuff will overwhelm any "affordable" finger brake.

Back cutting is simple, you adjust table saw or radial armsaw to only cut part way through material with a narrow blade.

Either cut normal or if you want fancy tilt blade 45 degrees and it will be miter and bend exact.

Now the bend is easy and radius small.

Your brake is just 2x4 and clamps

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
You must log in or register to reply here.
Back
Top