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Cuprousworks
08-08-2003, 01:08 AM
Maybe it's a little outside the usual Machinist realm, but here goes:

I'm trying to make use of an alligator-type pneumatic rivet squeezer that I purchased from eBay. I'm trying to use copper rivets (solid, 1/8" dia, 1/4" long, with either round head .094" or flat head .047"). I am trying to secure either 2, 3 or 4 sheets of 16 oz copper, which I am told is approximately 26 gauge, or .0216" per sheet.

The final product is craft, so the appearance of the crushed stud is important as is the structural clenching of the copper sheets. I bought the squeezer because I was seeking repeatability and good production throughput.

The squeezer came with a variety of the dies - varying in both length to close the jaw gap, and in diameter. There are also flat and concave forms. I've experimented with various die lengths to come up with the closest to the sheet thickness without pressing and deforming the sheets, but I never seem to get it quite right. Do I need to shim the dies, or should I plan on buying dies for each combination of number of sheets?

The squeezer has one fixed jaw and one moving jaw. My most successful results have been using the fixed jaw to hold the rivet head, but I still sometimes have the rivet bend or otherwise deform. Also, I've found it's very difficult to not have deformation of the copper sheets - are rivets just not appropriate for such thin material?

Any hints or advice would be appreciated.
Mike



[This message has been edited by Cuprousworks (edited 08-08-2003).]

Evan
08-08-2003, 01:35 AM
I've squeezed one hell of a lot of rivets. Use the fixed head on the rivet head.

Use a pressure regulator to control the amount of sqeeze.

Anneal the rivets before use (heat to low red, air cool) and then if necessary pickle them in an acid bath to brighten. Use H2SO4, battery acid diluted 1 part acid, 2 parts water. You can add sodium dichromate for a tarnish resistant coating of chromic acid. Wash well.

The amount of rivet protruding from the work should be equal to the rivet shank diameter and no more. With several different thicknesses of material you will need to trim the rivets to obtain a uniform appearance.

Use a setting die. Polished brass is good with a slightly rounded head where the hole is, make the die heavy, with a hole in it slightly larger than the size of the rivet shank, about 5-10 thou. Lightly tap the rivet with a plastic hammer to fully set it through the material before squeezing it. This is important, it tightens the layers and prevents dumping (the tail bending over) and distortion of the work.

Ensure the squeezer fixed head (on head of rivet) is held straight with the work. If it is even slightly tipped the side of the snap (die) will contact the work and deform it.

Don't shim the snap (head die). Leave it as close to the fixed jaw as possible.

There is some technique involved to learn but a squeezer will produce the most consistent results. Bear in mind that with soft copper it is very difficult to avoid deforming the work. If possible build a jig to hold everything in alignment.

You might want to invest in a few dozen Cleco temporary fasteners and a pair of Cleco pliers that are available from any aircraft tool supply house. There is no substitute for these for easily and temporarily holding thin sheet metal in alignment when riveting.

Hmm.. this is turning into a tutorial on sheet metal work. Best results are obtained by predrilling all holes and using the Clecos in each hole after you drill it. If you drill a hole and then rivet it you will distort the metal slightly by the compression of the rivet. Rivet holes in a pattern like tightening head bolts, not in a row but at alternating holes so the metal does not grow towards one end. IE, one in the middle of a row, one at each end of the row, one in between those etc.


One more item. Since you are obviously working close to an edge I would suggest investing in a hand held Beverly punch. Much easier and cleaner way to make holes in the kind of material you are working with. I have had one for 30 years and would not be without it.

[This message has been edited by Evan (edited 08-08-2003).]

INTERPOLATE
08-08-2003, 02:26 PM
Good post Evan.
I have a few riveting projects on my list too. Anyone have a reference for a good source of small rivets. Stainless and steel.
.062 and under. Short .187 and under.
Thanks..
DB

WJHartson
08-08-2003, 04:07 PM
I agree with Evan about punching being the best. If you have to drill the copper make sure it is clamped tightly if you stack drill the sheets. If they are not tight you will get burrs in between the sheets and the thickness of the sheet stack will vary slightly.

Clecos are handy to have and make working with sheetmetal a lot easier and more accurate results are achieved.

Remember that rivets when set properly expand in the body as well as deform to create the head of the rivet. This makes everthing tight.

Joe

Cuprousworks
08-08-2003, 04:52 PM
Thanks for the insights and help. I'm currently punching the 1/8" hole with an old Heinrich bench punch, so the holes seem uniform and clean. The work isn't secured in Clecos, but is held in a pretty stable jig.

I've had better luck after annealing the rivets, and I've been nipping them off to make them shorter. The 1/8" length was probably too long for my thin sheet copper, but they were the shortest that McMaster Carr carries. I've since located some shorter rivets, and I'll see how those work. I've also experimented a bit with the different snaps to get the best results. One additional question: I've been using a concave snap on the moving head to deform the rivet post. Is this the normal procedure, or should I be using a flat snap?

I'm quite sure that there's a lot of technique involved and that I might pick it up after setting a couple of pounds of rivets. I was just hoping to accelerate the learning curve, and your comments helped do just that!

Mike

[This message has been edited by Cuprousworks (edited 08-08-2003).]

Evan
08-08-2003, 05:34 PM
Mike,

It's up to you which snap you use on the tail. Use whichever one produces the best result. In aircraft work a flat would be used but I assume this is not a concern.

Glad to be of some help.

Evan

CCWKen
08-09-2003, 01:24 AM
Geez Evan, after you come over and set a few 5/16 and 3/8 steel rivets for me (Model T frame), how about a beer and a barbque?
I'm dreading this task. (replacing front and rear cross-overs.) I had to cut down some steel rivets for the door hinges on a 31 Ford. That wasn't too bad. I set them cold with an air hammer. The T frame rivets need to be set HOT.
Heck, make that two beers!

Evan
08-09-2003, 02:40 AM
Ken,

My sister lives in Texas but I'm not planning a visit any time soon. How much beer do you have?

Dave Opincarne
08-09-2003, 05:59 PM
Ken

For that use an air riveter (basicly a specialized air hammer with specialy shaped tips) and a bucking bar. If you want the next time I head to Boeing Surplus I'll look for some for you if you'd like. I've also got a copy of Boeing's tooling manual with a good section on riveting procedures if it'd help.

-Dave

CCWKen
08-10-2003, 12:32 AM
Evan: I can garantee there's no shortage of beer in Texas... Except maybe Fort Worth http://bbs.homeshopmachinist.net//wink.gif ... and a few dry counties.

Dave: Thanks for the offer. I do have a collection of .401 bits and bucking bars my uncle gave to me. He used to work for Boeing. Moved down here after retirement. He's given me a lot of pointers but says he's never set a hot rivet. I've got the procedure down and will practice but just hate to think about drilling out mistakes.

Oh ya, my "air hammer" is not stock. I've made a few mods to it. I use it a lot to form 10ga. In fact, it'll drive a spike bit through 1/4" HR in about 3 seconds!

Thrud
08-10-2003, 04:24 PM
Rivets will not deform thicker material, you might want to look at dead soft rivets, larger heads or a combination.

It is possible to build a stop system to ensure consistant riveting action. Note too that most riveters run on high air pressure and produce a significant wallop to the rivet. In this way it is less likely to de-form the rivet. In a way, the action required is similar to nail guns - fast hard blow.

I used to hand hammer copper rivets to repair and reinforce canvas tents as a boy with my dad. A proper rap of the hammer did it every time - otherwise they would bend...

Evan
08-10-2003, 07:21 PM
Thrud,

This time you have made it obvious that you have never used a rivet squeezer. They do not deliver a fast "wallop". The tool squeezes the rivet, just like it sounds. Some squeezers have a stop adjustment, some do not. Using a regulator will produce the same effect.

I have an air hammer of extrodinary power. When faced with the task of cutting eight feet of titanium just behind the engines on a C-130 I whipped out the mega-hammer, slapped in a muffler chisle and cut that sucker off in ten minutes instead of the 4 hours allowed us. Went and had a nap in the gas tank. (bladder removed)

Thrud
08-12-2003, 04:20 AM
Evan:

I missed the part about the Alligator type riveter. I should quit skimming these posts.

Hell, I prefer pop-rivets anyway (as long as it runs on 120+PSI air). http://bbs.homeshopmachinist.net//frown.gif