No clue, huh? How about if you see the business end:
Well, if you know that the bar is an inch wide (very exactly: 1.000) and half an inch tall (ditto: 0.500), you at least have a sense of scale. Yes, they are letters, and yes, they are both reversed and upside-down. So, if you hold your monitor upside down in front of a mirror, you'll see it says, "GSG". It's a Grant Street Garage stamp!
This came about after Kelly read my post on my custom-machined phone holder. He said, "You should make some more, stamp them with your Grant Street Garage stamp, and sell them to fellow BMW enthusiasts." I replied, "No stamp." So, unbeknownst to me, Kelly set out to correct that. Cool!
I had never used a metal stamp, but I've read about them, and therefore I knew that they can be a bear to align. Sure enough, my first impatient tests yielded stamps that were crooked, incomplete, doubled, and otherwise less than optimal. But, from my reading I also knew what to do: make a fixture to precisely hold and locate the stamp.
I found a scruffy block of aluminum in my modest collection, and set to work making it square and shiny:
Once done, I did some calculations and started milling a slot that I wanted to be precisely the right size to hold the stamp. As always, it takes a lot of passes - this time, I had to make multiple passes to full depth, and then precisely move the carriage to complete the slot to the correct width at the exact same depth:
When done, I had a centered slot that fit very nicely. Well done, I thought, a good learning experience.
Little did I know, the learning experience was just beginning. I decided to make a clear plastic cover for the open side, and carefully laid out, drilled and countersunk four holes in the plastic to hold it in place. Then, I "spotted" the holes on the workpiece, and started drilling. No in-process photos, but this final close-up shows the mess:
The two screws on the left are just fine. The two matching holes on the right have, respectively, a broken drill bit and a broken screw in them. I now have a much more visceral understanding of what they mean when they say aluminum is "grabby." The broken screw was particularly stupid - an experiment in using a self-tapping screw in aluminum. Note to self: don't experiment on nearly-completed workpieces. Stupid, stupid, stupid!
By coincidence, Phil Oles and I had just recently had a conversation about mistakes. He said that once he worked for an entire week making a cylinder for an engine, and the last hole was drilled and tapped in the wrong place. He said he could have done the "journeyman" fix and plugged the hole and re-drilled, but he elected to remake the entire cylinder.
Well, a "journeyman" is defined as "an individual who has completed an apprenticeship and is fully educated in a trade or craft, but not yet a master." I will probably die of old age before I reach journeyman status in metalworking - I am much more at the bodger stage. For now I just drilled and tapped a third hole. I didn't have another piece of aluminum to start over anyway. To try to partially redeem myself, I did carefully set up and scribe a centerline on the cover with my digital height gauge.
To use this, you need a very sturdy place to clamp it. I chose the spot on my workbench right above a leg. The test piece was a chunk of brass - I used a fly cutter in my mill to make a nice shiny surface for the test:
I inserted the stamp, and made one sharp blow with a two-pound drilling hammer. The result:
Dang, that looks good! Thanks, Kelly! Work in the shop will probably come to a halt as I stamp everything in sight...
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