T-Tracks and ply

[Doug Mason]

I'm putting 3/8 t-tracks in 3/4 ply for some jigs (using a dado a bit more than 3/8). I then have used tiny screws to attach the t-track. I'm finding that the dado really comprimises the strenght of the ply--but I couldn't imagine using 1 inch ply. What do other people do in this situation?

[Steve Clardy]

Can you double up your ply?

[Vaughn McMillan]

For auxiliary fences and other shop fixtures, I've beefed up the plywood strength at the dado by bedding the t-track in epoxy. I used the little scews only to hold the track in place while the glue dries. (Of course, after the epoxy dries, the screws are pretty much unremovable, too.) So far, everything has stayed straight and flat.

- Vaughn

[Doug Shepard]

The few times I've been in that situation I ended up using a T-Slot router bit to slot the ply instead of buying T-Track. But the same issue pops up there as well and I ended up using 2 layers of 3/4" BB ply.

[Curt Harms]

except I used Roo clear glue instead of epoxy. The T track is ridgid enough that even cutting most of the way through the plywood, the ply seems strong enough for jig use. A 3/4" router bit, make one pass, move the fence a few thousands (not much!) make a second pass and embed the T track. I used it to make a higher bandsaw resaw fence. So far, so good.

I've been experimenting with the Roo glue. So far, it's interesting stuff. Single part glue a bit thinner than Titebond, will bond metal, stone, vinyl, melamine, wood. It's not messy like polyurethane glues, "impervious to water" about 20 minutes open time, won't gap fill like epoxy. I did try it on some prefinished plywood. The Roo glue did bond, but the joint failed after whacking with a hammer and the plywood & finish stayed intact.

Curt

[glenn bradley]

On jigs or fences where it is possible, I have backed up the dado area by laminating a 1/4" x 2" strip of oak along the track path. Where this is not possible, I epoxy. The rub is that if the track needs to be parallel to another surface or slot, you better get it right before the epoxy sets or its wrong for life.

[Tim Solley]

I too just double up on the ply. So far I haven't had a situation where it hasn't been possible. Perhaps doubling up 1/2" ply instead of 3/4" will seem like a better compromise?

Tim

[Doug Mason]

Thanks for the reply's. I am making the jigs per Jim Tolpans "Table Saw Magic" book, and overall it is working well. I am having problems w/the T-tracks and ensuring everything is square--but I'll keep working on it. I haven't gone to the better quality ply yet--but will do so soon.

One jig I made involved tapping my fence--it was easy and I can forsee alot of uses. Now I just need to get my grip-tite fence working (no fingers near the blade, ever).

[Alex Berkovsky]

I just epoxied the t-track into the dado.

[Cliff Rohrabacher]

I suspect anytime you cut throuth the layers of ply you will have seriously weakend the lumber. It's really a no brainer since ply gets it's strength from the crossing plys removing one or more would dramatically lower strength. I'm not offering a calculation but I suspect it's a log of the number of plys cut. It is surely not a direct ratio of thickness to strength.

[Vaughn McMillan]

Doug, here's a thread where I described my journey down the path you're taking:

http://sawmillcreek.org/showthread.php?t=23905

You can see in one of the pics that the dado for the blue t-track goes more than halfway through the BB ply, but with epoxy in there, it's stayed very stable. I have since switched to an Incra TSIII fence system, but I can still use the vertical sled by attaching the Tolpin auxilary fence to the outside of the Incra fence (instead of straddling the fence as was originally done).

HTH -

- Vaughn

[glenn bradley]

Go Baltic Birch for your jigs. Once I stepped up (the cost is not THAT bad) I never went back and haven't had to rebuild one that has gone south.