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August 28, 2006

steel armature progress

by sven at 9:49 pm

sandwich plates so far

I'm about halfway through making my first all-steel armature. The design is nearly identical to the one I used for my last brass armature. The exceptions:

trick for starting a hacksaw

I've come up with a handy trick for getting the hacksaw started. I use a pair of pliers as a straight edge. Before I tried this, I was having trouble with the saw skipping.


I'm using my "sushi roll" method again: drilling all the holes in two long strips, then chopping the strips into individual joints. Now that I'm working with a mill, I very much like the precision of using its XY table.


Steel is more difficult to tap than brass. I broke two taps while threading holes... It's just the price of learning. I think I've got the hang of it now. Use lots of lubricant, only turn a little ways, then turn the tap back far enough so that you're definitely breaking off the metal chips. Squeaking is a bad sign.

the "sushi roll" strips

Here are the two strips before they get chopped up. In theory, what you're looking at is all of the sandwich plates, laid out in two straight lines...

close-up of the strips

Unfortunately, I discovered too late that my milling vise got out of alignment while I was working. You can see that some of the holes aren't perfectly centered. I had to go back and re-make the effected joints.

Incidentally, the cutting speeds I listed in my last steel armature update were incorrect. Since then, I've figured out how to do the calculations that determine RPM for a specific diameter (and shape) of cutter based on the properties of whatever metal you're choosing to work with. There isn't just one RPM for each kind of metal; it depends upon a number of factors.

posted by sven | August 28, 2006 9:49 PM | categories: stopmo