material hold down systems....ideas?

[mobus1]

Hello folks. I just joined the forum.
I am planning on building a cnc router setup to do work on acyrlic.
I am fortunate to have come across linear rail/bearing and slides of several types. I have amost all the components i need. One question i have been wondering about in work piece clamp dow techniques.
i have not found much detailed info on hold down methods. I was considering a vacuum hold down system, but that doesn't seem workable. I would like the option to route out complex shapes like letters, not just rectangular pieces.
I'm sure it's silly beginers question, but bear with me here.

[BobF]

One of the least discussed methods is also the easiest. Screw the work to the spoil board. Drill some holes in the work piece in the waste area, I countersink the holes, and use deck screws to hold to the spoil board.
I have glued hardwood underneath the MDF spoilboard in strategic areas.

[cmittle]

I haven't built a table yet, but I'd like to try something like this. There is a matrix of holes in the base material and this could be inserted in one as the case dictates. You would turn the bolt and pull the wedge up into the upper piece driving it apart and wedging it into the hole. The square part obviously should be a little closer to the green piece but I think it projects my idea. I've seen something similar to it on a fixture table. I don't know exactly how to make the angled part without a lathe, but I'm guessing some sandpaper and spare time.

[Geof]

cmittle; Your idea will work but it has a potential problem. The wedge has to bend the other part to spread it so when you loosen things it does not loosen completely so it is difficult to extract. I made some fittings almost identical to your design and discovered this the hard way. An alternate system is to just have matching flat angles on the two pieces so they get pushed sideways against the side of the hole when the bolt is tightened. When the bolt is loosened and tapped down everything becomes loose. If this description is not clear enough I can get some pictures.

[joecnc2006]

here is the one i just posted.

post #629

http://www.cnczone.com/forums/showth...345#post414345

Joe

[wyldesyde007]

Throwing my hat into the ring also

http://www.cnczone.com/forums/showth...153#post415153

this was my solution very easy to do without much cost and you don't have to worry about wrecking your Tslot if you bit got plunged into it.