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.
Jason-
Do ALL of your table fixtures and accessories have the same .003 clearance? Like across the board? Or are they different for each size of fixture? EG- 5/8” vs 3/4….?
.002-.003 is the target for all the pins.
FWIW, I put hands on some actual Fireball fixtures this evening after work, and all of the pins that I put a mic on were .749" or just a fuzz bigger. Except for the pin on the pusher block that I bought, which was .746". It’s likely that the difference I am seeing between the -.003" that Jason specified and what I measured, is maybe the difference after coating.
Given that, if somebody wanted to machine their own pins, and has access to 19mm drill rod, that would be a great starting point at .748", and would save some machining. Unfortunately for me, a few years ago McMaster decided that ALL shipments to Alaska have to ship by the most expensive method possible, and Grainger (which has a warehouse in Anchorage) only carries inch sizes.
The ones I have made so far, are just from some bar stock that I had on hand, to the -.003" that Jason specified. I’ll probably increase that a little on subsequent pieces. They seem to fit OK into the Fireball blocks, although slightly more loosely than the actual Fireball pins. The 1-2-3 blocks I bought have .500" holes with the correct 2" spacing on one side, so I machined the pins down to around .502" on one end, and press fit them into the blocks. Obviously not anywhere near as versatile as the official fence blocks, but they’ll increase the number of fixture blocks that I have, and free up the FB ones for use in places where I need the additional features.
If you order normal A108 cold rolled round bar, the tolerance is +0 -.002 and it works perfectly. I have no idea what the availability looks like in Alaska, but I can usually get it same day from Amazon if Alro is closed.
I have been using 12L14 for the 1-2-3 block pins. It’s not my favorite stuff to use these days, but it machines nicely enough, and I have an assortment that I bought when I first got my lathe, because youtube said it was the stuff to get for machining. The 19mm drill rod would be kind of a waste for these anyway, other than time savings and the size is perfect.
Removing these posts/images because even though I used BBcode to hotlink to my images directly off my server, for some reason the forum software is uploading them and serving them off the forum server. This is unacceptable, and I will not be posting any further images at this site.
Just came back in from the shop and it occurred to me that an explanation is probably in order. When I post images to a web forum, I do not upload them to the forum server. Rather, I upload them to my own server, and then insert code into my forum posts linking to the image files, and the image is displayed inline in the post and generally the reader doesn’t notice any difference. This allows me to retain some small measure of control over my files.
On a couple of occasions in the past, I have found it advantageous to be able to turn “off” images in my posts without having to edit individual posts. Based on what I have observed at the Fireball forum thus far, I think the odds that I would want or need to do this here are remote, but I have seen some crazy s— happen at a handful of forums over the years. So that’s just how I handle pictures that I might want to post wherever I happen to be doing so.
Additionally, in the past I have had project posts and pictures literally stolen from the forum where I posted them, and uploaded to some other person’s website, with the reader given the impression that I had submitted them for publication to that other website. With the images originally having been hosted at my server (and only my server), I have a better chance at being able to get a takedown notice to stick, at least where the images are concerned. If I upload them directly to some forum, then it can be argued that any dispute is between the thief and the owner of the forum, which makes doing anything about the IP theft even more difficult than it would otherwise have been.
Anyway, I thought I should elaborate on why I removed my posts and pictures here. It’s not because I have any issue with Fireball or the forum; it’s just about how I have chosen to operate when it comes to posting pictures. Whether the automatic uploading that I observed is a conscious choice on the part of site management, or if it’s just a default setting, I have no issue with the site management, and I intend to keep posting here. Just without pictures.