T Track & plywood

[dubliner]

I've used T track in thick material when I made a router table & jigs but I hadn't really thought about it when it came to making a hold down table for a BT 32. I drilled & pocketed the attachment holes ( thanks for the file Brady ) and dadoes for the 8020 track, but at 1/2 inch it only leaves 1/4" material to adhere to & there is very little room inside the recess for screw heads. Can I epoxy them in place or Liquid nails or??

[acb]

I drilled and tapped the back of the tracks for a 10-24 screw every eight inches or so, then came in from the bottom of the board with 1/2" flat heads. I had the same anxiety about the thin material but they seem to be holding just fine!

(I think the bevel of the flathead screws transforms some of any upward force into compression sideways through the MDF, which it handles well. But that's just my theory.)

[Gary Campbell]

Neville...
I am not sure how this applies to the BT, but I drilled, countersunk, tapped and bolted my T track down using #8 SS flathead machine screws.

Here is a pic showing the hold down screw near the "ovals" cut to allow nuts, t bolts and carriage bolts to slide into the track.

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Here is one showing a weld nut slid into the track. We use these for nylon cap screws that thread in from the top.

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Gary

[dana_swift]

Wouldn't it be nicer if the BT tables had more drilled and tapped (I suggest screw size #8) holes so the rails could just be bolted to the extra holes.

A lot of us have had that problem. Here is how I did it:


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My spoil board consists of two sheets of 3/4 MDF. The C-Rails channels only go through the first sheet, so I use 1/2" sheet metal screws to hold the C-Rail down to the lower sheet. This method costs 3/4" for the extra MDF which really hurts on a BT with a limited Z travel. I put vacuum fixtures on top of the spoilboard so the problem gets worse.. Tapping the table and mounting the C-Rails would give us back that precious 3/4". The spoilboard is mounted to the table using 1/4x20 bolts hidden in the pocket you see on the left. The remaining table holes are drilled through the spoilboard to be available to mount fixtures, securing them to the table.

Also in the picture you can see just left of the C-Rail channel where there is the outline of one of the gears I cut this weekend. That has been an interesting thing to develop. They are standard 20 degree involute spur gears, in this case the distance between teeth is 1.125. The spoilboard needs to be resurfaced! Later this week..

Hope that helps

D

[knight_toolworks]

I dumped the aluminum track it was a hassle to anchor it got damaged it added up in price and so forth. so I just t slotted mdf and it works well.



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[chiloquinruss]

Steve - you slotted the spoilboard, do you have any issues with pull out? Is the slotted sheet glued to the bottom board or screwed for easier swap out? I have seen inserts for making a reinforced slot wall have you ever tried that as well? Thanks. Russ

[knight_toolworks]

no pullout with the pictured clamps. any7thing else that puts more pressure without support over the screw I would use a larger head i think. this is just screwed down as needed.

[sheridan]

I tried just cutting my own T-Tracks directly in the mdf but ran into a problem. When the clamp (the shopfox ones like Steve used) tightens down, it pulls up a slight bit and can pull the material up. Here are some pictures. Note on one that there is a very small gap on the bottom. I'm back to using the tracks and two pieces of mdf screwed down . . . unless someone comes up with something better!

Phil


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[Gary Campbell]

Neville...
If you really want the T track to hold things down well, drill and tap it into the aluminum. Ours is bolted about every 8" with a #8 machine screw and we have tried some nasty things with it. That 8020 extrusion is very tough, not at all like the woodworking supply versions, which are much ligher duty. You can drill a shallow pilot hole in the track and the table with your BT so that they all line up. I like to use the tap drill & tap combo from McMaster in my air screw gun to tap holes, but a battery drill would work fine.
Gary

[knight_toolworks]

I just checked and I see a bit of a gap. I am going to try a longer piece of metal in the t track its easy to do.