1/4 baltic birch tear out

[jim shula]

I have to make 1000 pieces of 1/4 Baltic birch about 6" wide by 11" long. Each piece has two 1/4" holes within about 1/8" of the top.

I've been doing the cutting in two passes. The first 1/8" with a dwoncut bit and the second 1/8" with an upcut bit. I do the holes first with an upcut, then the profile with the upcut. Then I switch bits and do the holes with a downcut then the profile with a downcut. When I do the final profile pass, I get tear out in the small section of plywood between the top of the hole and the top of the piece.

Is there any way to avoid this?

[Kyle Stapleton]

Post some pictures.
What are you using for a hold down?
Feeds, speeds depth of cut?
Are you using tabs? (2d or 3d)

The more info the better.

[genek]

I have to make 1000 pieces of 1/4 Baltic birch about 6" wide by 11" long. Each piece has two 1/4" holes within about 1/8" of the top.

I've been doing the cutting in two passes. The first 1/8" with a dwoncut bit and the second 1/8" with an upcut bit. I do the holes first with an upcut, then the profile with the upcut. Then I switch bits and do the holes with a downcut then the profile with a downcut. When I do the final profile pass, I get tear out in the small section of plywood between the top of the hole and the top of the piece.

Is there any way to avoid this?

Can you spray lacquer on the Baltic birch. this helps with the tear outs.

[kubotaman]

Just a quick suggestion. Possibly you can apply a small piece of blue painters tape to the area that you have the problem with. I have done that for a lot of years when having problems with veneer on the table saw.

[jim shula]

I'm using vacuum hold down with no tabs. I've been playing around with feed and speed, but basicly 12-15k rpm with 2.5-3.0 ips feed. I'll try to get a picture after lunch.

[bleeth]

With the distance from the edge of the hole to the edge of the board only about 1/8" I think you only have a shot at having no tearout by using a 1/4" brad point bit for drilling only and making sure that spoilboard beneath is clean where the bit goes through. You may even need a block positioned at the end to stop any blowout
Since you are using a drill bit now slow your spin down to emulate a drill press as close as possible. Play with feed and speed a bit.
Counting on the slight thickness of veneer at the edge to be naturally so well bonded that it doesn't tear out at all in birch (even Baltic) is a bit optimistic.
I would cut all my parts and then set up a positioning fence to drill all at once after changing bits.
I would make no guarantees of perfection on this to the client.

[Sk8MFG]

A compression bit may help.


I use one for near all my plywood and laminated wood cutting.

[scottp55]

Jim,
Is the inside of the hole clean with zero tearout?
On your profile cutout, have you tried a "last pass"? If no last pass option, perhaps an offset of about .015" and then no offset with slightly lower feed and increased speed as you're only doing a skin cut?
Have you tried a spiral ramp on both cuts yet?
Perhaps leave only a skin cut for the upcut to do?
scott

[dubliner]

Pressure foot from Widgetworks perhaps?

[jim shula]

I think I've got it figured out now. I'm using an .125 end mill to drill the 1/4" holes, then doing the profile cut in two passes. First with a downspiral .25 bit to about .2 deep, then with an up spiral bit to full depth.