Baltic birch plywood splinters

[Jerry W.]

I am new to the forum and this is my first post.

I am cutting .250 and .500 holes in Baltic birch plywood and many of the holes get splinters (see photos). One 12" X 24" plywood sheet needs needs 36 holes, about 3 of 10 sheets has splinters. What can I do to reduce this?

I am using a 3/16" 3 flute carbide end mill, 16,000 rpm, feed rate 45.0 inches/min, plunge rate 30.0.

Thanks!

Jerry

[jerry_stanek]

Are the splinters on top or bottom of your material

[billp]

Jerry,
Welcome !
Hard to tell from the picture but it looks as though your end mill has "up cut" geometry. With an up cut bit you WILL get "tear out" on the top of your material because there is nothing to back up the upper surface and the flutes are trying to "lift"as they cut.
One solution is to switch to a "down cut " bit which will do the reverse but possibly cause some tear out on the lower face of your material .
("possibly"because in some instances the surface of your table will act as a "backer"and prevent the edges from tearing out).
If you need BOTH faces to be free of tear out then the answer is a "compression bit" which has it's lower portion working as an up cut, and the balance of the shank working as a down cut. The trick here is to set up your file so that you plunge through your material just enough to engage the up cut flutes. If you'll use the search feature on the Forum you should be able to find numerous discussions about this issue.

[dlcw]

I'm not sure drilling with a compression bit is a good idea. It is intended to cut going sideways.

For the 1/4" holes I would look at a 1/4" boring bit and drill the holes out.

For the 1/2" holes you can use a 1/4" compression bit and spiral into the hole leaving a really clean cut top and bottom. The secret with a compression is you have to first plunge down into the material far enough so that the upcut flutes are below the top edge of the material before you start moving the router. Otherwise you are just using an upcut and you will get the chipout.

I've not figured out how to get Aspire or Partworks to first plunge 3/16" (assuming 1/4" upcut flutes on the bottom of the bit) then start ramping/spiraling down in to its cut. With SBLink this feature is available.

[Jerry W.]

Thanks for your suggestions.

The splinters on top.
The end mill I am using is "up cut". Where is a good plase to buy a"compression bit"?

Thanks!
Jerry

[knight_toolworks]

the part looks thin so myself I use use a downcut bit and a bit small enough to do a inside profile on the holes.
I cut a ton of bb and usually have no tearout either side with a downcut bit.

[knight_toolworks]

a compression bit can tear holes as it is an upcut at first. I did these acoustic panels that had so many holes that had to be very clean a pocket cut made them all good with a downcut but was so slow. so I drilled the face with a downcut just a shallow cut then changed to a upcut and cut through perfect both sides.

[Ajcoholic]

Jerry,
Try a down cut spiral. I also cut a fair bit of baltic and i use a 1/4" two flute spiral. Onsrud brand. No chips but i do cut on an mdf spoilboard.

AJC

[sawkerf]

I've drilled tens of thousands of holes with a 1/4" compression bit with great results however, those were limited to 3/8" deep. The few I tried to drill a full 3/4" deep resulted in a rather "crispy" spoilboard. :D

[Brian Moran]

....
I've not figured out how to get Aspire or Partworks to first plunge 3/16" (assuming 1/4" upcut flutes on the bottom of the bit) then start ramping/spiraling down in to its cut. With SBLink this feature is available.
Hi Don,

You could set the start depth to 3/16" and then subtract 3/16" from the cut depth.

Brian

[jerry_stanek]

I would try the 3/16 inch bit and use a pocket tool path

[Jerry W.]

Thanks guys for your help.

I now have the down cut end mills to try tomorrow.

Thanks!

Jerry