# Basic sheet metal work



## spike7638 (Jan 26, 2019)

Every now and then I need to do something with sheet metal -- always stainless, because this is for a sailboat. I've got some stock in the basement -- some 0.075, 0.048, 0.06, 0.03 strip in various widths/lengths. 

For today, I need to bend a 1" strip into an ell (one leg about 2", the other 1.5"), drill a couple of through-holes for #10 screws in the long leg, and drill a 5/8 hole in the short leg. 

I can do the bending on a bender at work. I can drill the holes on a milling machine. I can clean up the holes with a countersink to de-burr the rough edges if I've got the terminology right. 

My problem comes earlier: I want to use the thicker material -- 0.075 -- for which I have a 2 x 24 piece. And that material is too thick to cut on the shear at work. So what's the best way to get 1"-wide stock with a nice fairly clean edge? 

On a related note, when I work with thinner material, I can cut it with the shear, which is great...but when I try to drill a large hole in it, I often find the drill "grabbing" right at the end of the cut and mangling the edge of the hole, or otherwise messing up the material. I'm sure I'm doing something wrong here, but I don't know what. Any thoughts? And clever solutions for making holes in thin stainless stock? 

Thanks in advance.


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## mzayd3 (Jan 26, 2019)

Bandsaw to length, punch the holes


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## Submachine (Jan 27, 2019)

Bandsaw
For drilling, try some lubricant to see if that helps.  Also, what is your drill speed?


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## mmcmdl (Jan 27, 2019)

spike7638 said:


> On a related note, when I work with thinner material, I can cut it with the shear, which is great...but when I try to drill a large hole in it, I often find the drill "grabbing" right at the end of the cut and mangling the edge of the hole, or otherwise messing up the material.



Drill a small hole and use the electricians punch out dies .


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## cbellanca (Jan 27, 2019)

Cut the piece with thin cut off abrasive wheel on a hand grinder . It is not a good  idea to use a band saw on such thin material unless the tooth count provides at east 2 teeth in contact with the material.     
As far as drilling thin stock, bind it between two pieces of hard wood or some scrap aluminum. This will provide backing so the drill won't grab the thin material.


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## Janderso (Jan 27, 2019)

“Two teeth touching the material”.
I had forgotten that rule. Thanks,


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## BGHansen (Jan 27, 2019)

I do some work with stainless up to 0.050" and feel your pain.  I have a Tennsmith 37" stomp shear and am really hesitant to cut anything over 0.036" in stainless on it.  Instead, I use an 8" bench shear for cutting strips.  Photo of one is below, run a touch over $100 and are rated (at least mine from Woodward Fab) at cutting 3/16" CRS plate.  Mine cuts 0.050" stainless like butter.  It does put a little curl in the stock, but it's easily worked out by hand.  No burrs or rough edge to deal with after the fact either.  I also have a project that uses 0.100" stainless and cut that on a band saw or with 1/8" wide horizontal milling cutters. 

For holes, I'd recommend a Roper Whitney #5 Junior punch for the thinner stuff.  They're rated for up to 16-gauge mild steel, work fine on stainless under 0.040".  You'll need to drill the thicker stuff however and deburr.

Bruce




My sheet metal work bench.  DiAcro 24" brake, 6" 4-ton notcher, 8" bench shear, Roper Whitney #218 punch press


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## Winegrower (Jan 27, 2019)

For larger holes in sheet metal, I like the progressively stepped drill bits.   Start with a small maybe 1/4” hole, and then switch to the stepped bit...wham, wham...you’re done.

For really big holes, i’ve used the 4 jaw in the lathe if the overall piece fits, or clamp to a plywood backing on the mill and use a boring head.


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## tq60 (Jan 27, 2019)

Step drill is a control cut device so best for sheet stock.

Punch sets also work well but limited by material type and thickness.

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## spike7638 (Jan 27, 2019)

Wow...you go to sleep one night and the next morning magic has happened. Thanks, everyone, for these tips. 

Winegrower I even have one of those step-drills, but somehow I've never used it on anything but aluminum, so it wasn't in my mind. 
BGHansen: For shearing...I think that in the shop at work there's actually one of those bench shears tucked away in a corner, and I'd always sorta wondered what that thing might be. With your closer-up picture, it's obvious. 
cbellanca: The 2-tooth rule is a great one... I'd never heard that, but I can think of a whole lot of mistakes I'd have avoided if I HAD! And using the cutoff tool is a great notion. 

Thanks again, folks!


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## GL (Jan 27, 2019)

Old timer at work trick for drilling in thin material is to put a shop rag between the bit and the material.  This gets rid of the triangular hole that sometimes shows up.  Not sure of the mechanics, but it works - maybe damps out chatter.  For small holes the clamp between wood works great too.


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## T Bredehoft (Jan 27, 2019)

5/8 hole in sheet metal, sandwich the metal between to pieces of scrap wood/plywood. drill in one pass.


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## spike7638 (Jan 27, 2019)

I'm going to be really naive here, but I've done that before...  

"Sandwich the metal between two pieces of ply/alu and then drill" is advice I've often heard/used, at least for non-precision things. But if I'm trying to drill nicely spaced holes in a piece, I tend to want to set it up on a milling machine, in a vise. At that point, I no longer have the piece itself to reference my hole placement, and ... I must just be missing something here. How on earth does one really do this in practice, and get the holes where you want them within a small tolerance (like, say, .06 inches, which is close enough for most of what I do)?


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## kd4gij (Jan 27, 2019)

I use step drills for sheet all the time.


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## tjb (Jan 27, 2019)

GL said:


> Old timer at work trick for drilling in thin material is to put a shop rag between the bit and the material.  This gets rid of the triangular hole that sometimes shows up.  Not sure of the mechanics, but it works - maybe damps out chatter.  For small holes the clamp between wood works great too.


Here's a video of this technique.

Regards,
Terry


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## spike7638 (Feb 3, 2019)

OK -- I'll try the "bit of cloth" trick if it turns out to be necessary. 

But going back to the "clamp between pieces of aluminum" thing... when I'm drilling, do I use the light thin lubricant for aluminum (I'll be going through 1/2" of that) or the oily lubricant used for stainless? 

Also: I'm hoping to make a disk-shaped part in this thin stainless, with a few holes drilled in the middle of it. About 3.25" diameter. I think I can manage the holes and slots in the middle, but making the piece "disk shaped" in the end is what's worrying me. If I were doing this in wood, I'd use something like a trammel cutter. Is there a similar tool I can use on thin stainless clamped between two sheets of 1/4 aluminum? I'm not using a CNC machine, so just milling it won't work. I could bandsaw it, with the two pieces clamped together, but it'd be tough to get a really nice circle. It doesn't have to be perfect, but my bandsaw skills are...limited, and it seems as if a milling machine is perfectly set up to help me do something circular like this.


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## Asm109 (Feb 3, 2019)

Dykem the part, use a compass to scribe a nice circle.  Bandsaw outside the line. Finish on a disc sander bringin it up to the scribed line.
Frequent dunks in water to avoid overheating.  Burned dykem is hell to clean off.


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## Ulma Doctor (Feb 3, 2019)

a trick to drill thin sheet metal is to clamp a sacrificial piece of thicker material on top of the intended boring victim.
then drill like you don't even care, the holes will come out just fine if you incrementally increase the drill bit size as you go.

as far as cutting 1" strips,
you can make a sacrificial fence from just about any substantial and straight piece of angle iron or flat iron bar.
simply clamp the sacrificial fence to the work and space the fence to 1" plus the thickness of the cut off blade.
use an angle grinder or die grinder to cut the strip free
clean up the edge after cutting with a sander or grinder and you are done.

i use this method all the time, as i don't have a sheer


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## tq60 (Feb 3, 2019)

spike7638 said:


> OK -- I'll try the "bit of cloth" trick if it turns out to be necessary.
> 
> But going back to the "clamp between pieces of aluminum" thing... when I'm drilling, do I use the light thin lubricant for aluminum (I'll be going through 1/2" of that) or the oily lubricant used for stainless?
> 
> Also: I'm hoping to make a disk-shaped part in this thin stainless, with a few holes drilled in the middle of it. About 3.25" diameter. I think I can manage the holes and slots in the middle, but making the piece "disk shaped" in the end is what's worrying me. If I were doing this in wood, I'd use something like a trammel cutter. Is there a similar tool I can use on thin stainless clamped between two sheets of 1/4 aluminum? I'm not using a CNC machine, so just milling it won't work. I could bandsaw it, with the two pieces clamped together, but it'd be tough to get a really nice circle. It doesn't have to be perfect, but my bandsaw skills are...limited, and it seems as if a milling machine is perfectly set up to help me do something circular like this.


Visit harbor freight and get s hole saw kit.

Make hole in plywood first (3 inch) next clam plywood over work an position on drill press and remove pilot bit as plywood is guide.

Drill press as slow as it can go and short light pecks.

If a mill with back gear then slow constant heavy pressure

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## GL (Feb 3, 2019)

Circle on a mill, do the sandwich thing and use a hole saw.  If you don't want the center pilot hole in the part, choke up on the pilot drill so it engages the sacrificial top, but doesn't hit the part.  On a lathe, build the stack on an arbor, could be a bolt, and turn the outside down to size.  Trammel cutters on a mill can work with a sharp pointed tool.  Go slow, there's a lot swinging around and they look kind of scary.  Boring head with a custom ground cutter would work similarly.  This is better for hole making than circle making since holding the middle is harder than holding the outside.


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## spike7638 (Feb 3, 2019)

Asm109 said:


> Dykem the part, use a compass to scribe a nice circle.  Bandsaw outside the line. Finish on a disc sander bringin it up to the scribed line.
> Frequent dunks in water to avoid overheating.  Burned dykem is hell to clean off.


If I bandsaw/sand the aluminum/stainless/aluminum sandwich, the dykem will all be on the aluminum, so it won't be a big deal if it burns.  This sounds like a good solution, as the OD isn't a critical measurement -- I just want it to not look ragged and ugly. 



tq60 said:


> Visit harbor freight and get s hole saw kit.
> 
> Make hole in plywood first (3 inch) next clam plywood over work an position on drill press and remove pilot bit as plywood is guide.
> 
> ...


I've got hole saws, but nothing with a 3.25" ID, alas. The "slow light pecks" is useful to learn -- thanks. I'll probably use that somewhere soon. 



GL said:


> Circle on a mill, do the sandwich thing and use a hole saw.  If you don't want the center pilot hole in the part, choke up on the pilot drill so it engages the sacrificial top, but doesn't hit the part.  On a lathe, build the stack on an arbor, could be a bolt, and turn the outside down to size.  Trammel cutters on a mill can work with a sharp pointed tool.  Go slow, there's a lot swinging around and they look kind of scary.  Boring head with a custom ground cutter would work similarly.  This is better for hole making than circle making since holding the middle is harder than holding the outside.


 
Right --- the "holding the middle" thing was what worried me (not to mention using a trammel cutter at all, which always scares me a bit). I'm not yet at the point where I can custom grind a cutter, so that boring head idea won't go. The "stack on the lathe with an arbor" idea is a nice one...but I'll probably do the bandsaw-and-sander approach, as it's not essential that it be perfect, and I've already got to drill a much larger hole in the center of the piece, making the whole "arbor" thing tougher. 

It amazes me how many ways you experienced folks come up with to answer my questions, when I can't think of even one. I'm much obliged.


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