Bolts for T-Slot on cast iron tops - what size?

[Patrick McCarthy]

I want to make an outboard fence for my Powermatic 2700 shaper. I want to invert 2 bolts in the T-slot and use 2 thread-through knobs to tighten down the plywood on top of the cast iron table. Simple, eh?
I went to the McMaster Carr catalog, thinking i would get hex head bolts to slide into the T slot . . and was delighted to see "T-slot bolts". Seemed like an elegant solution, and an obvious choice. Went to a specialty bolt shop in town but they had nothing suitable. Went back tot he McMaster Carr site and struggled a bit with the diagrams and ordered some small ones (91523A628 with 3/8"-16 thread, 1 1/2" long)yesterday and was amazed they arrived today (yes, i was impressed) but they are too big. Back to the diagrams but not finding something to fit.

I assume most T slot on table saws and shaper and WWing tools is relatively standard, but i am perplexed as it seems i am hunting for a unicorn. Clearly i am missing something obvious. . . . or dumber than i care to admit . .

So, rather than re-inventing the wheel, might i ask what you gents have used in similar situations?

Humbled, but not deterred. Thank you, Patrick

[Doug Garson]

Assuming the tee head is too big not the threaded part, try filing it down to fit.

[Aaron Inami]

It's $10, but you can get the Milescraft t-slot kit for Milescraft/Kreg clamps. The t-slot bolt should fit right into your standard Powermatic miter slot:

https://www.amazon.com/gp/product/B09KYBY6PN/

Probably expensive just for the t-slot bolt, but it's custom sized for the normal tablesaw/machinery t-slots.

[Wes Grass]

Buy a couple extra files...

;-)

Those are for 't-slots' on a Bridgeport mill, or similar.

Assuming a typical woodworking machine, there's a teeny little undercut on a standard 3/8x3/4 slot for a miter gauge that needs a washer underneath ... a washer thinner then you'd likely find at your local hardware store ...

Drives me to drink ...

Like I need any encouragement. Working on a Mason jar of moonshine from a 'friend of a friend'.

Seriously. Has a charred stick of Oak in it. Reminds me of the Eddie Murphy/Arsenio Hall bit about the 'bum' with his 'facilities', a pickle jar ...

LOL!!!!!!!

[Jamie Buxton]

What fits the slots on my drill press are toilet hold-down bolts. For instance https://www.amazon.com/LASCO-04-3645...104947034&th=1 You can get them at any hardware store, or home center.

[Bill Dufour]

Maybe a wood working tee nut insert with the prongs bent flat. I assume the asia machines use metric tee nuts<br>
maybe 5/16 will work.
1+1/2" LONG not a standard tee slot nut to me. much too long. We need dimensions. neck width, bottom width, bottom thickness, top thickness, total thickness.
Bill D.
https://www.temu.com/ul/kuiper/un9.h...0aAv2JEALw_wcB

[Clint Baxter]

Lit’s of options out there for T-slot nuts. Here is one from Infinity tools, https://www.infinitytools.com/t-slot...yABEgLs5_D_BwE, for instance.

Clint

[Phillip Mitchell]

I have done this with the Kreg Automaxx hold down clamps in the slot on my sliding table saw. I sourced the T slot nuts *and matching thread pitch short stubby bolts* from McMaster. For my table saw, I was able to get all the dimensions right except the thickness of the top of the inverted T. It was about 1/16” too thick to fit in the slot so I ground them down with an angle grinder in about 5-10 minutes and they fit great. I will see if i can dig up some photos.

You say they don’t fit, but it which dimension(s) and how far off is it?

I use an outboard fence on my shaper, but it does not have a t slot so I tapped the table in a location that works generally well for the outboard fence to bolt to with slotted holes. It also is the same bolt hole location that works for a bolt on sliding tenoning table so 2 birds, one stone.

[Jim Becker]

If you have a saw with a tee type miter slot, you'll note there isn't a lot of height to the "tee" part. You may need to fabricate what you want by welding a thick washer to the head of a bolt so you have the larger diameter at the end of the bolt. And don't assume there is any "standard"...things are likely to vary with this kind of thing. There will be a similarity, but "this saw" might be slightly different than "that saw" and tha tmight come into play with your choice of thick washer.

[Rege Sullivan]

Not sure what the size is but I made a couple of jigs that bolted to the slots using elevator bolts that are available at a local hardware store nearby.

[Bill Dufour]

I have made one or two from carriage bolts by grinding off some of the head here and there.
Bill D.

[Doug Walls]

try filing it down to fit.

Most of the stock t-slot nuts are case hardened, so they are best modified by grinding them down. I had to do that to some t-nuts for a Powermatic drill press table.

[Patrick McCarthy]

Gentlemen,

Thank you all for the insight. Seems like i am looking for a unicorn.
Jamie, Toilet hold-downs do well on the T tracks in my Woodpecker's drill press table, but the slots on the machine top are way different. The toilet bolts are 3/4 long and my slot, at the surface is 3/4. Also, since i will have the power feeder pushing against the outboard fence i was hoping for something sturdier.
Phillip, the outboard fence on your shaper is where i was headed initially, and intended to do the holes in a pattern that would fit the Panhans or Rangate sliding table (which i do not have, but a guy can dream) but changed paths when i focused upon the T-slot. The problem with my T-slot vis-a-vis yours is that the height of the bottom (widest part of slot) is 5/32 or 4mm . . . but i could keep grinding . .

Dimensions are imperial/metric: Starting from the bottom up -
width of widest part - base - of T is just under an inch: 15/16ths or 23.25mm
Overall depth of slot from bottom to surface top is 13/32nds or 10mm
height of bottom or base of T is 5/32nds or 4mm
height of top of T or shoulders of 3/4 slot are 1/4 or 6mm
width of slot are surface of table is 3/4 or 19mm

[Phillip Mitchell]

I am not finding any T slot nuts on McMaster that would fit those slot dimensions without a good bit of grinding down in thickness/height on both top and bottom sides. You could do that, but may be able to find a simpler solution that works? 13/32th of overall slot depth is not very much to work with. I think I would rather drill and tap the table in 2 places (if you have that kit already on hand…) than go on a wild goose hunt for obscure t slot nuts that may not exist, but if you could find something close or right on….

You could also look for a shorter hex head bolt that is at least 13/16 wide at the head (to fit in 15/16 slot but not come out of upper 3/4 slot if centered) and grind the thickness of the head down until it fits in that 5/32 height of the bottom slot…or an even smaller diameter hex head bolt + 7/8” OD washer and grind that bolt head thickness down to fit slot height.

[Patrick McCarthy]

Phillip,
I think i will return to original plan and do what you did. I will be in Joe Calhoon's shop for another Alpine class this week, so will try to remember to get the spacing for the Panhans/Rangate sled and use those measurements for my spacing.

I sincerely appreciate the help guys. Thank you again, Patrick