Making holes in aluminum sheetmetal

This will probably be boringly obvious to most readers, but I'll post it in the hope that it might be useful to a few because it worked so well for me.

I wanted to cut some .700 dia holes in .062 aluminum. After trying some other approaches I tried making a shop- expedient trepanning tool.

I turned a bit of 3/4" barstock down to .700" OD, drilled it out 5/8" and milled slots in the result. No rotary table, just V-blocks in the vise and X-Y movements. Each slot was made so the cutting edge thus formed was square, OD of 1/4" endmill moving radially from the center of the workpiece. I then hand-ground a bit of relief, rake and bevel (so it penetrates OD before ID) with a Dremel running an abrasive cutoff disc.

Material was 12Lsomething free-machining steel. I love that stuff! I case-hardened it with Kasenite which seems to work OK on 12Lxx, A sharp new file skates on the hardened part. This precision process consists of heating with an O/A torch until orange, plunging into the can of Kasenite, heating again to a glowing glob of orange for a couple of minutes with the garage door open so the smoke had somewhere to go, and then plunging into a margarine tub of water. After quenching, I poured a wee dram of Menard's finest muriatic acid ($1.98 a gallon on sale) into the margarine tub to pickle off the oxides for a few minutes.

I don't think I spend an hour making this tool. This quick-a-minnit tool works far better than any holesaw I've ever used. It goes thru 1/16" al in a few seconds at 135 RPM with only mild pull on the quill and a drop of cutting fluid on the workpiece, cutting a nice curly chip and leaving a clean and nearly burr-free hole. I made a slot for poking the slugs out of the center, but wouldn't have had to. They about fall out when picked with a scribe.

Photo sent to the dropbox as "holecutter".

Reply to
Don Foreman
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Sweet. Makes me want to try at the holecutting business again ;) Too bad I have to find hardenable stock and file it to hell, since I don't have a mill or Kasenit! >:(

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

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Reply to
Tim Williams

Nice report, Don! I went all the way through your explanation to the next to last step; quenching the layer of Kasenite. I would have neglected to do that before I read your post. It is (should have been) obvious that a final quench will add an extra bit of "treatment" to a case hardening job. Thanks for the information.

Bob Swinney

Reply to
Bob Swinney

I personally like using wood type spade bits-Have them up to 2" and have bored over two inch thick material for years.Works great in sheet or solid billet. Just hang on or clamp it down! I sometimes make a small pilot ole in thicker material.

Reply to
Castvee8

Get yourself one of those $50 indexers, clamp it at an upward angle in a vertical mill, and you can cut the teeth and the relief at the same time, with a little imagination. Index, cut, index, cut. I had always thought I had an exclusive on these things. (pout)

RJ

Reply to
Backlash

Kasenit is cheap. You could start with pipe if you can find an appropriate size. If you don't have a forge for heating, etc., check out Ron Reil's page. You can make one for bopkas. Once you have the forge, used (broken) automotive coil springs are good for making many tools where HSS or carbide isn't needed.

Do you have a lathe? If so, you can pick up an import "spin index" for under $50 and start collecting 5C collets.

Ted

Reply to
Ted Edwards

Absolutely necessary! Case hardening is simply diffusing carbon into the outer regions of the steel. You now have to treat it as high carbon steel.

Ted

Reply to
Ted Edwards

I bought one with my 3-in-1 about ten years ago. One of the most used accessories.

I made a block the same shape as the rectangular base of my spin index and of such a height that the axis of the spin index is "exactly" the same height of the table as the lathe axis. This alows me to remove the compound from the table and mount the spin index on the block. I can then put the cutter in the lathe chuck, orient the spin index conveniently and use the x-y feed to do the cutting.

You can see it in use in this mode at

Ted

Reply to
Ted Edwards

Doubt they have it at Ace though.

I've got a bit of water pipe, should make good cutters...

Currently I'm making do with bits of firebrick and one torch or another. I've got some refractory curing downstairs for a 3" i.d. 8" long 2" wall forge, should work nice... I'll try 'er tomorrow...

I've got a big bar, a broken torsion bar.. wonder how the hell I'll cut that up and use it. Hehehe.

The start of a wood lathe, but if you want to send me 50-100lbs of aluminum scrap and the Gingery Lathe booklet I'll get back to 'ya. :)

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

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Reply to
Tim Williams

Ted, that's a damn good idea of using the indexer on the lathe!

RJ

Reply to
Backlash

. I can

Nice posting, photo, and description...

Paul in AJ AZ

Reply to
Pep674

Hey Ted,

Very neat idea. When I first looked at 3.jpg, I thought that the riser piece looked like some type of non-metallic material, and I was a bit surprised that a "slippery" material would be used. But then I looked at the aluminum chips in the photo, saw they were the identical color as the riser, and assumed that the riser must also be aluminum. Not so when I read the .txt lines! Has this been a problem at all?

I have pretty much the same generic indexer too, and I had a few times when I either couldn't tighten the 5C enough to grip the work, or more often could not get it to release. The knurled screw towards the back of the housing seemed designed to just apply a tension or braking action, rather than grip and lock the shaft firmly. The only thing that seemed to have a large enough radius to grip was the index wheel itself, and if you apply too much pressure, it slips too. So, I marked the shaft from through the center of the tension screw, took it apart and made a depression with a 3/8" drill to create a "detent" hole which is really quite shallow, reassembled and put a brass 1/4-20 knurled head screw with rounded off end in through the tension knob. Now, to tighten and release the 5C collet, I just rotate to that detent and run the brass screw in. No problem now. And when the screw is retracted a few turns, the original tension screw works exactly as it did before, because it "runs" outboard of the detent mark. Oh, and I did put a locate scribe mark outboard and at the collet end so I could find it easy to do the "lock". Hmmmm... it was a while ago I did this, so another Oh, and I made the detent in such a position that the handle for the spindex was generally going to rotate "down" to tighten it, so there is less chance of the whole spindex moving when you tighten it. Of course, there is a slight variation with different collets and the material in it, but you'll note that most clamping occurs in a relatively close range, about 1/4 turn or less.

One other little tip, is that all around the shop I keep a whole bunch of that "typing correction fluid" in those little bottles with the built-in brush, or much better and handier yet, the "pen type". I try to always carry one of those in my shirt pocket with the clip-on screwdriver and the pencil. Great for marking and writing on dark surfaces. Anyway, that applies to the index wheel, in that I can mark the spaces off before-hand, and it wipes off easily with just the slightest bit of acetone on a rag.

Take care.

Brian Lawson, Bothwell, Ontario.

ps...convention on a lathe has it that the cross-feed is X and there is no Y (unless you are using a milling attachment) but the carriage feed is Z. Compound would be either not described, or called W. Rotation of the compound in its "hole" would be I. Or is it K? I forget. I don't know what the spindex motion would be!?! All this is arguable of course, and a whole other thread!! XXXXXXXXXXXXXXXXXXXXXX On Wed, 14 Jan 2004 19:01:50 -0500, "Backlash" wrote:

Reply to
Brian Lawson

No. I had a piece of Aluminum that I could have used but it would have taken much more work. The piece of UHMW was jaust right except for milling the thickness down a bit. I, too, was concerned about its slipperyness but it hasn't been a problem.

I've never used mine except for an integer number of degrees. Then the locking pin prevents rotation. I set the knurled screw to prevent the collet and holder from moving in or out. It seems quite adequate for that.

Ted

Reply to
Ted Edwards

Welding store.

Reply to
Don Foreman

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