using t nuts

[copperhead4321]

has anyone used the threaded t nuts that have spurs that insert into the bottom of your board for clamping? you predrill a clearance hole for size of tnut then you can use a screw to draw the 3 spurs into the mdf from the bottom of board. I thought about trying this but wanted to check to see if there have been any issues with this plan?

[JohnnyCNC]

Jim,

At work we have an old CNC machine that doesn't have vacuum. We drilled holes for 5/16" bolts every 8" and put blind nuts under the spoilboard. We did this across the table and back the table. Next we drilled 1/4" holes half way between every two of the 5/16" holes so that we could insert index pins to hold the material and for perfect placement if we had to do work on both sides of the piece. This gives us the ability go use plenty of clamping, but I think if I'd had it to do over, I might have done a 5/16" every 6" and a hole for index pins every 3".

About your question, the idea works. It's better than screwing to the spoilboard.

JohnnyCNC

[mezalick]

The Shark had them before they went to the t slot.
It worked okay

[Gripus]

I did a 3" grid of them on my Techno and they worked great. The really nice thing about them is you can make your own cam clamps out of wood so hitting them with a bit doesn't hurt anything. You can also make a number of different sized hold downs too fit any application.

Joe

[Brad Knight]

That's exactly what I did. I did 3/4" x .05" pockets for the back piece if the t-nut and then drilled 5/16" holes- then just tapped the t- nuts in with a hammer flipped and screwed it down to the original board. Then drilled holes in a few pieces of scrap- ran bolts and washers through into the t-nuts for hold downs.

Worst case - you can still drill into your spoil board for odd pieces.

The biggest problem is if you do a piece the full size of your table, then you can either screw into your spoil board or drill holes in your piece to align it with your table..

But for everything I've done so far, I've just kept my drill with th socket for my bolts and it's worked well.