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Dunc
09-09-2016, 11:01 PM
I need to make some t-nuts for a t-slotted drill press table. I watched the Tubalcain 2 part series (#102 & #103) and got a few good tips. The only topic not covered is how long should it be. I have noted (internet but no specific sites I can post) that
milling the opposite sides of carriage bolts to fit the t-slots is discouraged since it concentrates the forces onto too small an area.

Is there a formula to suggest a suitable length... for example, if the table slot is "x" wide then the length should be "y" times that dimension... or any other suggestions?

1-800miner
09-09-2016, 11:07 PM
Just a guess: I say four or five diameters. I have some on the front porch, just too lazy to get up.
I can give you a real answer tomorrow.

PStechPaul
09-09-2016, 11:43 PM
These images might help:

http://enginuitysystems.com/pix/tools/T-Nut_Dimensions.png

http://enginuitysystems.com/pix/tools/T-Bolt_Dimensions_800.png

http://enginuitysystems.com/pix/tools/T-Slot_Dimensions.png

oldtiffie
09-10-2016, 01:57 AM

Ed ke6bnl
09-10-2016, 08:45 AM
I just made some for my new to me rotary table, and I suggest you make one long strip tee nut and then cut them to size when done, much quicker, I made it long enough for 12 Tee Nuts.

justanengineer
09-10-2016, 09:12 AM
Is there a formula to suggest a suitable length... for example, if the table slot is "x" wide then the length should be "y" times that dimension... or any other suggestions?

Paul's already shared them, but all of the common standards are in Machinery's Handbook plus a ton of other useful data. There's everything from "machine not cutting" checklists to design standards in there, searching the index is usually faster, easier, and more likely to be correct than the internet.

Dunc
09-10-2016, 11:41 AM
Yeah, my copy of MH sits & gathers dust. I "know" it has the answers to everything but I can never remember to look until I get a gentle reminder.
Thanks for the replies

old mart
09-11-2016, 03:25 PM
I have made some, and measured the slot dimensions first to make them the closest fit possible. If I was going for bolts, I would either reduce larger ones, or make them out of solid.

JohnMartin
09-11-2016, 04:25 PM
Short, long and extra-long.

Short for when two t-nuts have to butt up together or when one has to come close to, say, a vise or fixture key.

Long for normal use.

Extra-long for when you want a t-nut to extend out past the edge of the table. Two or more holes. Often find a need for this on the rotary table, to fix a work stop to the mill table, etc. If you're extending it out past the table, this is the time I'd be very careful of the table slots.

I wouldn't worry about the short nuts breaking out table slots. It's always better, though, to have the fixture or workpiece against the table, so that the action of the t-nut is more to compress the table ledge than to lift it. More t-slots are broken out by bottoming out the stud or screw than by anything else.

When making t-nuts, I make them in long strips, and keep some strips for something that might come along in the future. Once you're set up to make them, it doesn't take long to make more than you need.