It's Only 1 O'clock And I Finished Something Picture

For anybody who cares. The 5/8 holes are down the center on 2 inch centers starting one inch from the cross. The bar has a shelf machined in it perpendicular to the row of holes, and one edge of the cross was machined flat and straight to but up against the lip created by machining the shelf. With the machined edges butt up snug against each other the two parts were vise gripped together. 4 alignment pin holes were drilled and reamed with a .001 under reamer. Pins were set using the quill on the mill. They were a very light press fit, but I had a slight over size lead in to help start them straight, and I covered them with green cylindrical surface locker. (sleeve and bearing locker.) Then three holes were drilled and tapped through both pieces, and clearance drilled half way, and three machine screws cinched down with red high strength loctite. I hope I got it square, because it will take a torch to get it apart.

For anybody who cares. The 5/8 holes are down the center on 2 inch centers starting one inch from the cross. The bar has a shelf machined in it perpendicular to the row of holes, and one edge of the cross was machined flat and straight to but up against the lip created by machining the shelf. With the machined edges butt up snug against each other the two parts were vise gripped together. 4 alignment pin holes were drilled and reamed with a .001 under reamer. Pins were set using the quill on the mill. They were a very light press fit, but I had a slight over size lead in to help start them straight, and I covered them with green cylindrical surface locker. (sleeve and bearing locker.) Then three holes were drilled and tapped through both pieces, and clearance drilled half way, and three machine screws cinched down with red high strength loctite. I hope I got it square, because it will take a torch to get it apart.

I do care, because I have similar problems accurately laying out and drilling hole patterns much larger than my milling machine. The tractor bucket loader required matching parallel bearing holes at the ends of the 4' lifting arms, the gantry crane and sawmill matching holes in the 8' track sections.

That mill has an X travel of 36 inches. The bar is 51 inches long (a little over). Both vises average .0005 - .0009 of parallel to the machine over about 20 inches. Good enough for a welding fixture. I just cut half the holes, moved the bar, indicated in on one of the holes, reset zero and cut the rest of the holes.

I found all the holes cut with the annular cutter have a taper, and the holes cut in my aluminum spacer blocks are slightly smaller than the ones get in the steel T-square bar. None of my pins fit even though the measurements said they should. LOL. I'm taking some extra care with the pins, because if I make them well I can use them as work stops on the welding table when I am done cutting holes in it.

I have one more pin to make (for now) and one more cutting guide. The other cutting guide is a single hole guide to locate the first hole on the corner of the plate.

I thought I was done with the T-square, but I think I'm going to have to run a reamer through all the holes.

I turn one or more grooves in the heads of locating pins to make them easier to remove if a snug fit. Either a threading or parting tool works. I used to knurl them, grooves don't deform the edges and they fit a collet better if the pin needs trimming. Grooves near the ends make the bushings that hold screws in collets easier to extract.

That's a good idea. I will certainly make more of these pins along with spacer blocks to be able to quickly build setups.

The current 4 pins have head 1 inch heads. On the 2 x 2 grid that gives me all the odd number inch measurements for setting up a fixture. I figure it I make some 2 inch blocks to set under the pin heads that will give me all the even number increments. As a counter to your idea of a groove, I also considered drilling and tapping the pins. Since I make them on the lathe, it wouldn't be any big deal to pop a 1/4-20 hole in the top when I turn them aroung to clean up the heads, and it would leave the ability to keep them low profile, or make taller ones as needed.

Eventually I'll probably need about a dozen pins and a dozen blocks. I'm not sure sure about hold downs since my table top is only 1/4 inch thick. I'm not sure that is enough racking action to get a good bind without damaging the table top. I'm not crazy about putting a nut or a bolt on the bottom. I'll probably just keep using Vise grip style welding clamps with swivel pads. (The hard pad ones always seem to be less well built and twist.)

The current 4 pins have head 1 inch heads. On the 2 x 2 grid that gives me all the odd number inch measurements for setting up a fixture. I figure it I make some 2 inch blocks to set under the pin heads that will give me all the even number increments. As a counter to your idea of a groove, I also considered drilling and tapping the pins. Since I make them on the lathe, it wouldn't be any big deal to pop a 1/4-20 hole in the top when I turn them aroung to clean up the heads, and it would leave the ability to keep them low profile, or make taller ones as needed.

Eventually I'll probably need about a dozen pins and a dozen blocks. I'm not sure sure about hold downs since my table top is only 1/4 inch thick. I'm not sure that is enough racking action to get a good bind without damaging the table top. I'm not crazy about putting a nut or a bolt on the bottom. I'll probably just keep using Vise grip style welding clamps with swivel pads. (The hard pad ones always seem to be less well built and twist.)

I looked up standard welding table hole patterns and confused a photo of