The pillar-drill thread finally prompted me to get some T-nuts (the sort that slide in a slot, not the spiky ones) so I can fix my little vice/clamp properly to the pillar-drill's table.
I was surprised to find the nuts weren't tapped all the way through. The supplier said they are all like that, so the bolts have to be exactly the right length. Is that true? It means the bolts have to be pretty-much exactly the right length.
You're not supposed to use a bolt, you use a stud with a nut and washer on top. Nothing to stop you tapping them all the way through. The reason they're made that way is so that you don't distort the slots on a milling machine table where the slot is not open below the T-nut.
Well they can't stick out the bottom anyway as they would hit the base of the T slot.
However I think you want T bolts. usually they are shaped like a T and you can push them through the top of the T slot, rotate them about a quarter turn and they stay there while you put the job and a nut on.
They are deliberately made like that. It's to stop the bolt going straight through the nut, hitting the bottom of the T-slot and putting excessive upward load on the slot when it's not supported from above - believe it or not it's not unknown for a heavy-handed soul to break a piece out of the T-slot.
As others have said, you use them with a bit of studding screwed in as far as it will go then a nut and washer on top - that way you can't damage the T-slot.
Thanks all. I saw T-bolts but thought that would leave the threaded-end sticking up into the work area unless they too were just the right length.
For this application there is no bottom to the slot so nuts work better. Anyway, problem solved as I shortened the bolts I had - with an angle grinder.
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