The thread is tapered on them to prevent the bolt going through and push up on the deck.
Why would you want through threads t nuts (unless you are using them for an entirely different purpose)?I'm guessing you already know that some are and some are not. You can buy both through threaded and part threaded T-nuts. I have some of each. I prefer the through threaded but that dictates extra care in use.
By accident, I found that the clamp kit I use with the mill/drill actually works well with my drill press. The T-nuts register in the slots in the drill press table. If the nuts were through-threaded (they're not), it would mean that there would not be studs sticking up and potentially getting in the way. OTOH, a 1/2" nut and a fender washer works quite well too.Why would you want through threads t nuts (unless you are using them for an entirely different purpose)?
Why would you want through threads t nuts (unless you are using them for an entirely different purpose)?
Thanks @Susquatch for that excellent discussion. Sometimes I can be too terse, and I really appreciate someone that can tell the whole story.
I have one thing to add to the discourse: when you have an unstaked T nut, lubricated or not, and you use a bridge clamp (as illustrated), sometime the screw jams in the nut, and only turns in the t nut. This is caused by a little too much angle on the bridge clamp, and is far too common. This causes the 'terrible stud' to turn as instead, causing the stated problem.
Where possible (such as mounting my vises or index head) I *always* use Grd 8 custom length bolts, with custom washers. It is only a momentary sacrifice, but the bolts and washers stay forever with the vise, and there is no jury rigging. You always have the percect mount at hand, and is a lot faster than hunting down a flange nut and correct stud from the kit.
@Susquatch does better math than me, I just know that unsupported t-nuts and a cast iron t-slot is a recipe for disaster.
Plus we all tend to think fasteners need way more torque than reality. If you need 150 ft-lbs of torque on your 3/8" t-nuts to stop your workpiece from moving, you're not using enough fasteners.
T-nuts and strap clamps can truly be your friends, just takes a little lateral thinking. To drastically eliminate the tension load on the cast iron t-slot, use a short clamp against the table and a bottom clamp nut. Also means the threaded rod doesn't flop all over the place and disturb your support arrangement when you loosen the top clamp nut.
View attachment 25453
So this inspired me to make some t-nuts. I had some bar stock that I'd brought down to size breaking in my little power hammer a while back, and I figured this was just the use for near-dimension stock.
Not the prettiest toy soldiers, and, frankly unnecessary given I have a stap set... But I hit *almost* all my dimensions, including fixing a couple of close calls in the backlash department.
In the strap clamp horror stories though, this seems like the most over-worked length stop possible, but I had no way to hold a stop inboard of my vise jaws to take the little blocks to final length:
In retrospect I should have made 4 t-nuts 1.25" long instead of 5 at 1".
Still need to get some acetone and some blueing compound.
I have used carriage bolts with flats ground on each side of the cap head so it will fit the slot and also keep the bolt from turning when tightening.
When you make your own t nuts, make a couple with the threaded hole offset. they will come in handy for tight setups.