Hello, new user in Anchorage AK. I have some of the Fireball squares and clamps and have been generally happy with them. I recently purchased the 54"x30" “Pro” fixture table plate, and while I am waiting for my order to ride the barge up to me, I would in the meantime like to start machining some of my own fixtures and clamp adapters for use with it. What I have not been able to find online, is the dimension/tolerance of the 3/4" nominal pins. I am assuming unless I learn otherwise, that I can count on the holes in my plate to stick to the .750" nominal size, so I need to know how far under that diameter I should shoot for in my pins for ease of insertion and secure holding/clamping. If somebody could be so kind as to put a caliper or mic on some of their fixture pins for me, that would be awesome.
Funny, I just joined here to ask a very similar question! It seems the holes on my 24x36 Pro fixture table are either dead on 3/4 or just under. I was curious if others had checked their tables to see the tolerances of the Pro table tops.
I actually have old 5/8 fixtures. I bought a length of 3/4" x 0.065 wall HREW to make bushings, but the tube measures .7530 OD; it doesn’t fit.
I bought some 3/4" OD x 5"/8" ID bushings and they measure 0.7510 OD; they don’t fit.
I put my calipers on several holes, and it is hard to find the dead center to get a perfect reading, but I cannot get them to read 0.75 anywhere. The closest I can get is 0.7495.
Bottom line, I have yet to buy something that says it is 3/4" OD and have it fit without modification. But everything I have purchased has also measured just slightly over 0.75".
Regarding the fixture pins themselves, they consistently measure between 0.7465 and 0.747 using my Mitutoyo calipers.
I hope that helps!
Pins are to be unsized .003.
Everything has a tolerance. If the holes were within .0005 I would say thats plenty close for a fixture table. In fact I would say that’s incredibly close.
Nice Job Fireball tool.
Thank you for all of the replies; Jason that was exactly what I needed thanks.
Yeah steel tubing is almost never dead on its nominal size. FWIW I have found that aluminum tends to be a lot closer but obviously that’s not helpful here. Eventually after playing games long enough trying to make things fit together that weren’t intended to, you will get to where I was a few years ago, and buy a lathe and mill. 8^).
Fireball’s fixtures actually seem to be a decent deal for the most part when taking into account the time it would take to machine my own. For now the first projects I need my table for won’t involve much fixturing, so the only immediate need I have for fixtures is to build the table frame itself. 1-2-3 blocks are relatively cheap, and if you get the right ones, the hole spacing is correct too. eventually I’ll have some FB fence blocks and other fixtures, but to get the table built this will get me going, and bulk up the quantity of fence blocks that I have, so I can reserve the FB ones for where I need to use them as a base for their other fixtures.
Oh, I wasn’t meaning to imply I was disappointed! I am very excited to get my table properly setup. Ordering fixtures is addicting, and for a hobbyist I have to really think about what I need v want. 
I am disappointed my simple “conversion” solution for my 5/8th fixtures is not as simple as I had hoped.
Haha, I promise I was not looking at small lathes! Machining parts is fascinating to me, and I would love to be able to do small stuff. Maybe someday… I need a better shop.
I was originally looking at getting a small lathe and mill, and then I made the mistake of talking to my friend who is a self employed machinist and gunsmith. And he pointed out at length that while you can do small work on a big lathe, it’s difficult to do big work on a small lathe. Which is how I ended up with a 12x36 lathe, and later, because he had been right about the lathe, a 1965 Bridgeport mill. I’ve actually made some of the money back that I spent on them, because occasionally my employer pays me to recreate tooling that is no longer available for their out of production aircraft.