Holding down dimensioned lumber

[denver]

Hello,

I've used something like what was discussed here: http://www.talkshopbot.com/forum/show.cgi?tpc=29&post=44775#POST44775 in the past with good results.

However, that was always for projects where I was cutting parts out of the material, so it didn't matter if it wasn't always completely flat to the table. I may be getting a job to make some custom trim, so instead of cutting parts out of a board, I'll be carving a profile into it. In this case it's going to be very important to make sure that the material is held as flat as possible. Holding the material by clamping from the sides isn't going to be adequate unless all the 8' long boards are perfectly flat. So I've been trying to think of alternatives that might work.

One idea I had was to make a variation of the above system, but instead of a lot of holes and side clamps, I would use 2' lengths of T-Track in the Y direction, evenly spaced. Then I could use something like this along each edge of the board:
http://www.rockler.com/product.cfm?page=5739

Assuming this is a good approach, I have some questions:
1 - The T-Track I have is 1/2" deep. If I cut that into 3/4" sheet material, that only leaves 1/4" for the screws. Is that adequate?

2 - I was thinking of using 3/4" MDF. Is there something that would be better?

3 - When I cut a 4' length of T-Track in half, I end up with two screw holes in each piece. That doesn't seem like enough. How many would you recommend?

4 - Any alternative ideas would also be welcome.

Thanks,

Denver

[mrdovey]

Denver...

I made two pallets, the first 24" x 48" and the second 24" x 96", and installed T-track sections aligned with the y-axis and about a foot apart.

I used T-track that's 3/8" deep and 3/4" wide - and I glued the aluminum tracks in place. (Next time around I'll glue the T-track in stopped dados.)

I screwed a 1" x 4" fence parallel to the x-axis to ensure alignment of work - and I use a bunch of the Rockler hold-down clamps (along with some C-clamps) to secure the pallet to the table.

I found some cam clamps in the Grizzly Industrial catalog that I use in the T-slots with Baltic birch cauls. The clamps cost around $12 each and really do a good job. My cauls measure about 3" x 6" x 3/4" and perform two functions:

(1) They provide a good 3" safety zone between the cutting tool and the clamp (it's a stress reducer).

(2) They prevent the clamp from marring my workpiece.

The Grizzly clamps are shown here (http://www.grizzly.com/products/Shop-Fox-Cam-Clamp/H5740).

If you're interested, I'll shoot some photos of one of my pallets set up for use.

...Morris

[mrdovey]

Hmm - they aren't great photos, but there're a few at the bottom of this page (http://www.iedu.com/DeSoto/Projects/Bevel/).

[denver]

Thanks Morris. I was considering two pallets, each 2'x4'. That's how I did the system with the holes & side acting clamps. That way I can use just one for shorter pieces, or both end-to-end for longer ones. That also fits well with my four zone vacuum system.

Now I have more questions:

What material did you use for your pallets?

What kind of glue did you use?

Why would you use stopped dadoes if you were doing this again?

The Grizzly clamps look very interesting. I think I understand what you've described, but yes, I would like to see photos.

Thanks again,

Denver

[mrdovey]

Pallets are 3/4" plywood - nothing special.

I used Titebond III - because it was handy at the moment :-)

Installing the T-track against the end of a stopped dado will (I think) do a better job of holding it in place than would a couple of woodscrews. These clamps are capable of exerting a lot of force and several times I've popped the track loose.


We cross-posted, but let me know if you want better photos.

[denver]

That all sounds good. I like your angle setup. The photos are fine. I just had to look carefully for a while to understand what I was seeing.

Thanks again,

Denver

[wayne_walker]

Morris,

Would it be possible to forward the photos of your pallet setup to me?

Do you clamp your pallet to your spoil board or use vacuum?

Thanks in advance!!

Wayne

[sawdust535]

I just posted this on another thread, if this helps.
I have a BT32, but this can work with any size table. I attached an oversized T-Track table with hold down to attach materials that don't need to be cut thru the total thickness. If I need to cut thru, I use the T-Tracks to hold down a spoiler (usually MDF) and use fasteners (screws, carpet tape etc.) to hold down the material to be cut. Just need to make the material slightly oversized to make room for the screws. The table has guides that are 1/2" high and precisely aligned along the x and y axis to form a 90 degree corner. The table is oversized to hold a 24 x 32 spoilboard with the hold-downs, which are made from 1/2" baltic birch P/W. Easier on the bit if your toolpath is off. The table is 3/4" plywood, which holds the screws better than MDF. You are right about the lack of screw holes. Space them 3" to 4" apart or the hold-downs with pull the tracks up when you tighten them.
I posted the photos in Assembly and Maintenance today.

[mrdovey]

Wayne...

There's a link above to some photos, and I'll see if I can take some better when I get out to the shop.

I use C-, F-, and hold-down clamps to secure the pallet. Vacuum would've worked, but I was in a rush when I threw the pallets together.

...Morris

[robert_cheal]

Here is something I use with my T-track. The fender washer lips over onto the wood and the block is the thickness of the material being cut.



4854

[mrdovey]

I shot a few pix this morning and posted them to a new web page (http://www.iedu.com/DeSoto/Projects/Pallet/).

[robert_cheal]

After reading through the above posts about the the T-track pulling up. I ended up holding the T-track down with machine screws and a T-nut on the under side. I also put 5/16" T-nuts in a 8" grid across the whole table so I can bolt down pallets etc.

4855

Robert

[jay_p]

Denver,

I have been using a setup just about like the one that Morris is showing for a couple of years now and it works very well. I have the very same clamps though I bought them through a local hardware store. They are designed so that as you rotate the cam, the clamping face forces the clamped object down against the jig.

Jay

[denver]

Thanks everyone. All great ideas. I'm going to make a couple pallets with t-track that I can hold down with vacuum. Haven't decided on what kind of clamps yet, but the ones suggested by Morris and Jay certainly look interesting.

Thanks again,

Denver

[wayne_walker]

Morris,

Thanks for the photos. I have not done any dimentional lumber yet, but it looks like it would work very well.

Thanks again,

Wayne

[blackhawk]

Morris - I am interested in seeing your pictures also. I cannot get your links to work in the above posts. Can you post them again?