Advice for holding and cutting thin plywood

[atwooddon]

Last year I built a small CNC machine I use to cut small parts for my RC airplanes. It works OK, but I am having a problem holding/cutting 1/16" aircraft ply. My cut area is about 9"x7" and I have been mounting the ply with 4-5 screws into the spoil board. Using a 1/16" carbide 2 flute bit (up cut) I get some lifting in areas between the screws. Would a down cut bit help with that problem? Also, when I am cutting across the top grain, the cut is clean, however, when cutting with the grain, the cut is fuzzy on the top edge. I have tried convention and climb cutting, both have the same problem.

Any advice for holding the ply to the spoil board better and using a different bit to make a clean edge?

Thanks in advance for any help. I can't believe the amount of information on this site and the knowledge I have gained just by reading. You guys are great!!!

Don

[lgalla]

Don check to days posts.There is a post in woodworking tooling forum on bits and cutting thin ply.
As for hold down,try double sided tape or carpet tape.Some are extreme adhesives and may hold too well.

[Big-tex]

Down spiral will help with fuzz at top but yo may end up with fuzz on bottom if not tight to spoil board. Try test cuts and you will see.

Double sided tape works well. Sometimes I use 3M known as carpet tape.

[atwooddon]

thanks guys, I went thru the thread in Woodworking Tools and we have the same issue. I think I will probably try the carpet tape and the down cut bit. Any recommendations where to buy that type bit?

thanks again
Don

[Big-tex]

Try americancarbide

[Boots]

Ballew Saw & Tool also have this bit. I use them often on thin materials. They do work better at not lifting the material. You might also consider some spray adhesive that is not perminent. Some times I do not cut all the way thru the material. Then run the blank through a sander to remove the bottomside until the parts fall out. This works well for really small parts.

[ger21]

A good 2 sided tape is golf club grip tape. It's thinner than carpet tape, and holds very well. If you have a Golfsmith store in your area, you can pick some up there.

[IQChallenged]

Any advice for holding the ply.....

You might use a variation of this...
http://projectcnc.wordpress.com/page...d-downsclamps/

[stevespo]

I've been cutting a lot of 1/4" and 1/8" baltic birch. I had some pretty poor luck with my standard upcut and downcut router bits. Too much tearout on the top and fuzz on the bottom.

I purchased an Onsrud 57-240 (.125", downcut, 2 flute) which has a bit of a "fishtail" (points) on the cutting tips. This has been cutting really cleanly on both sides in the 1/8" material.

For the 1/4" ply, the Onsrud 60-102 is fantastic. This is a "double compression" bit with up/downcut, but it really needs 1/4" material to be most effective. Cuts cleanly in one pass, and at fairly high speeds (120 IPM+), too. This is also .125" diameter.

For holding parts down, I use a lot of this tape. It's got very good holding power, fairly thin, but still releases well. Plus, it's cheap! Depending on the size of the part, I often use tabs to hold the smaller parts to the waste material.

Inexpensive double-sided tape

Steve