PB Cohen Creations

Making stuff and things - sometimes jewelry

Pancake Dies

I recently bought a couple of pancake dies from Potter USA, aka Kevin Potter. Kevin has a few videos on YouTube about how to use these tools to punch out shapes from sheet metal. Here's one, Using Pancake Dies (Shearing Dies) with PotterUSA hydraulic press. I have just a couple of personal tips for those of you who have never used these before.

punched star
First, it will take a bit of strength on your part to pump up the jack on your hydraulic press — particularly if the die is big (one of the ones I bought is 2.5 inches wide), and the metal is on the thicker side (I was using 18 gauge brass).

Second, at least if you're punching out a big shape in thick metal, you should wear earplugs — at least if you're punching more than a couple of pieces at a time. And particularly if your ears are already sensitive to loud noises, from all those rock concerts, or noisy pet birds. The "pop" when the die breaks through the metal is very loud. You might also warn other people in the building that you'll be making noise more similar to the sound of a gun shot than is wise to make among unsuspecting people.

Third, at least if you're punching out a big shape in thick metal, you should use some sort of spacer to move the pancake die and metal down lower — this will give the jack better leverage than it would have if the sandwich is nearer the top. In these two photos, the pancake die is represented by a light green piece of paper that's been folded in thirds. You can click on these for bigger versions.
press held lower
Do this
press held higher
DON'T do this

We have a lot of random pieces of steel around the shop we can use as spacers, but hydraulic press people have spacers and pushers and things available.
Posted on 25 November, 2011 in "Tools"
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The Toolbox, Part 1

I am taking a fabrication class at Washtenaw Community College this term. The prerequisite for the class was a whirlwind tour of all the different kinds of welding there are — more on that later. Suffice it to say, I am now capable of barely welding four-inch lengths of very specific materials under absolutely ideal conditions.

The description for the fabrication class is, in part, the following:
For advanced welders [Hahahahahahahahahahaha!] planning to use their welding skills in manufacturing, this class teaches the skills necessary to design, cut and fit pieces to be welded. Welders are trained in the use of modern machines for bending, punching, cutting and shaping.

Despite the emphasis on welding in the class description, our first project was a toolbox made out of 20 gauge steel sheet, put together with folds and bends that are used all the time in things like duct work, plus a few rivets. No welding at all. With a few minor exceptions, we followed the tool tray project in the back of what seems to be the standard book for sheet metal in the US, Sheet Metal by Leo A. Meyer. (Note that the book has been around for at least twenty years, published under slightly different titles with the various editions. I haven't seen the most recent edition.)

the tool tray
The tray looks like this (be sure to click on the image for a big picture):

I've been told that job applicants in the field of fabrication of stuff and things are often handed some sheet metal during a job interview, and are pointed to the shop: if they are able to build a well-made tool tray, they get the job.

You may have noticed that the book, and most people, call this object a tool tray, not a toolbox. In fact, Mr. Meyer has plans for building a toolbox in his book — complete with lid, hinges, latches, and tool tray that fits inside. (The tool tray I made is the first of the "Supplementary Projects" in his book; the toolbox complete with a slightly different tray design is next to last.) But the folks at the community college call it a "toolbox," so toolbox it is. Here is mine, after Paul at Cramer Tech Coating, Inc. threw it in with a real powder coating job, and gave me a very nice price. Thanks, Paul!

the toolbox the toolbox

Once again, I have made something that is difficult to photograph, this time because of the matte black finish. (You can click on these photos for larger versions.) No worries, it's beautiful in real life. The powder coating makes a beginning shop class project look like a real, professional thing.

I have to say, it's really fun to start with a flat sheet of metal and turn it into something useful. Here are some details. The box is made of three pieces of metal: two end pieces, the handle, and the bottom-and-sides. You can click on these for larger versions.
the end pieces the bottom and sides the handle

The handle is attached to the end pieces with pop rivets (also known as blind rivets). The end pieces are held in place by "Pittsburgh seams," which are formed along the bottom-and-sides. In the real world, there are machines that make these seams quickly and easily, but we had to put them together with the bench brake and whacking by hand with a mallet.

This is how the Pittsburgh seam is made: in these two sketches, the end pieces are being slipped in on the right, and the bottom-and-sides, with all the folds to accept the end pieces are on the left. Once the end piece is in place, that last fold from the bottom-and-side is whacked over with a mallet.
Pittsburgh seam part 1 Pittsburgh seam part 2
These sketches are taken from another book by Leo Meyer — who has apparently written all the books you'll need for learning about fabrication, plus a few more — Sheet Metal Layout. This one is out of print; I got both books at my public library.

Despite appearances, my toolbox isn't finished yet — I'm adding some embellishments. More to come.
Posted on 12 November, 2011 in "Other Fabrication"
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Liberty Local

liberty local
I'll be participating in Liberty Local On October 8-9, 2011. Ann Arbor's newest indie craft fair, Liberty Local, will showcase handmade crafts from regional artist vendors whose work embraces the indie spirit - unique, handmade and creative. Liberty Local will be held in the historic Walker Carriage Building, home of the Ann Arbor Art Center, at 117 W. Liberty Street. You can see the list of Liberty Local vendors here.


Posted on 16 September, 2011 in "Business"
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Rivets

This post isn't actually about rivets; rather, it's about matching your wire, measured in the B&S or American gauge, to the corresponding drill bit number. You need a tight fit (but not too tight), or it will be difficult (or impossible) to make the rivet.

It's the end of the semester at the Ann Arbor Art Center, so I've been seeing a lot more students during "open studio" hours trying to finish up projects, and a few people have been wanting to work on rivets. Their materials kits include, among other things, 20 gauge wire, and a #67 drill bit. Which, as far as I'm concerned, is wrong. I did a bit of research, and this is what I found:
B&S
(American)
Oppi
Untracht
(1)
Tim
McCreight
(2)
Rio
Grande
(3)
class
supplies
(4)
my
memory
(5)
1451.75152

1655.35455

1859.55660
60
206765686766
2271.57072


Notes:
1. Metal Techniques for Craftsmen, Doubleday, 1968/1975
2. Various books published 1982-1997
3. Tool Catalog, 2011
4. Recommendation of instructor and Armstrong Tools
5. 'Nuff said

I consider Untracht, McCreight and Rio Grande to be excellent sources, and Armstrong Tool & Supply Company is right up there, as well. And yet, these sources don't agree on anything.

Untracht gives a clue in his table, which includes measurements for inches, millimeters, B&S Gauge, and Stubbs Steel Wire. The only B&S wire gauge with an exact drill bit size is 20, at #67. 18 gauge, according to Untracht, is halfway between a #59 and #60; 22 gauge is halfway between a #71 and #72. 14 gauge is closer to #52 than #51 (that is, in increments of hundredths of an inch, —

No. Wait. I can't really see any coherent method to how he is listing any of these five items. No regular increments of inches or millimeters, which you think would make it easy. This suggests that he was simply trying to match up B&S, Stubbs and drill bits to whatever measurements corresponded to these three, different, industry "standards." Suffice it to say that 18 and 22 gauges are "halfway" between drill bit numbers on his table (thus my ".5" notations); 14 gauge is closer to 52 than 51 (thus my "51.7" notation), and 16 gauge is closer to 55 than 56 (my "55.3" notation). Go look at Untracht's table "Comparison of Measurements" (on page 457 in the 1975 edition of "Metal Techniques For Craftsmen") and see what you can make of it.

I should really make a bunch of holes with my drill bits and match them up to actual wire — as much as that might help, considering how various manufacturers might have minor variations in their finished products. I might just do it one day, though. I am that anal retentive. (But I am also lazy.)

Anecdotal evidence, however, suggests that I am right. I took a student's drill bit #67 and was unable to fit a 20 gauge wire in the hole. I enlarged that hole ever-so-slightly with my drill bit #66, and it fit. HA HA!

Well, I won't claim vindication until I do a more thorough experiment. But still, the differences in "knowledge" are surprising, particularly the range given for 18 gauge: 56-60?!? That's a pretty wide range, in the scheme of tiny little measurements.

What gauges/drill bits do you use for rivets?
Posted on 07 April, 2011 in "Tools"
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Can I Save It?

ring
I made this ring a little while ago, with a sterling silver band, a hand-sawn flower-like shape of copper, and my favorite texture these days, courtesy of a waffle-head hammer.

You can go ahead and click on this photo for a bigger version, but don't get too excited, since although everything is soldered together, it isn't nearly finished yet. Below are photos of the back of the ring, which show Soldering Gone Wrong: the solder everywhere, and the shank is a little melty. Go ahead: click and take a look at extreme closeups. So sad. So wrong.
ring ring ring
I decided to share these photos for two reasons. First, to show that there are many stages during fabrication where metal looks pretty awful. Sometimes, like this time, it takes a certain amount of faith to keep going, rather than throwing something into the scrap pile. And second, so we can all find out if this can be fixed. Inquiring Minds Want To Know.

After more time than one would like, using sandpaper, small files, and various abrasive tools on the flex shaft, I managed to clean it up. I threw it in the tumbler for a while with stainless steel shot, and it turned out like this. And THIS is where I remind everyone that small shiny, domed objects are beyond my photography skills. If you're not distracted by the reflection of my black camera, you're tricked by the reflection of the silver band. Here they are anyway: click click click.
shiny ring shiny ring

No worries: an application of liver of sulfer takes care of that shine. How do you think it turned out? Sure, it isn't perfect, and I ended up filing off half of my logo, but I think I can sell it now.
finished ring finished ring finished ring
Posted on 29 March, 2011 in "Jewelry Fabrication"
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A Is For AAGH!

Remember the "U" ring I made last year?
U ring U ring
I'm thinking about trying the whole alphabet. I have a few ideas, and I started with "A" — not because I feel the need to go in any sort of order, but because the design of the "A" is similar to the "U." Unfortunately, it didn't work out so well. It almost looks good, right? It isn't finished — polished or patinated.
A ring
I tried soldering the shank onto the hollow form "A" twice. The first time, I set everything up very carefully, took my time, was completely relaxed, heated everything, saw the solder start to flow, and realized that the "top" leg of the shank, marked with the red arrow in the drawing below, had raised off of the "A." Click on this drawing for a better look for the soldering set up.
soldering set up
The "A" was resting on two different heating blocks, so that the side getting the ring shank soldered onto it was more or less level. I held both the "A" and the shank steady with third hands (a steel cross-locking tweezer attached to a weighted base — they look like sticks on top of triangles in my drawing).

When I realized that "top" part of the shank wasn't on the "A" that first time, I made sure the solder on the "lower" part of the shank was still flowing, and I knocked those pieces apart. Then I cleaned everything up, and set the whole thing up again to solder.

The same way.

In retrospect, of course, I wouldn't have done it the same way, since exactly the same thing happened. I'm guessing it must have something to do with how well (or, rather: how poorly) the tweezers grip when they're heated. Or something. This second attempt, when I saw the "top" part of the shank lifting off the "A" I tried to gently nudge it back down. As far as that goes, it worked: now both parts of that shank are solidly soldered onto the "A." You saw that in that photo up above.

Unfortunately, it doesn't do me much good. You can see why if you look at these two photos:
so sad so very sad
Go ahead, take a close look: click, click, click, click, embiggen, scrutinize, pout.

In my attempt to nudge that top leg of the shank down, I pushed too hard, and unseated the strip of silver from the copper. So sad. It isn't going to fall apart or anything, but it's awfully ugly.

I think I soldered the "U" ring flat — the way it looks in the two photos above. I would have raised the shank slightly to center it on the "U," probably by placing it on top of a piece or two of sheet metal. Too bad I don't quite remember.

I think I can salvage the silver shank and the two copper "A" pieces — although I'll probably have to trim the latter. But, I don't think I'll try that right away. For now, I'll just leave it a sad little ring, solid yet ugly.
Posted on 05 March, 2011 in "Jewelry Fabrication"
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