[Closetguy]

I am having some small chip-out issues on the back side when through boring 3/4 melamine.

I have seen videos of Gannomat boring machines that drill from the bottom with no chip-out. The literature says something about some sort of "breaking" for clean though bore. Anyone know what that means?

I'm getting chip-out even with a new spoil-board.

5 drill aggregate running at 4000 rpm.
Using carbide through bore bits from Morris Wood Tools.
Currently using a strategy of cutting at .2 ips through the top skin
speeding up to 1 ips then slowing to .1 ips throuth the bottom skin.

this seems to have yielded the best results.
the top is always good, the bottom somtimes has chipout.

Any suggestions for a better strategy to yield better results on the back?

Thanks
Bob

[ger21]

Quality of the melamine is a big factor. The thicker and harder it is, the cleaner the holes will be. Some lower quality melamine is almost impossible to get chip free cuts.

Your feedrate seems really slow. Have you tried is at 1.5-3ipm?

Also, what kind of machine is this?

You might also want to try a different brand bit.

[Closetguy]

HI Gerry,

thanks for your response.

I am using a shopbot PRS alpha with 2 Z axis.
One has an HSD boring head on it running at 4K rpm.

I use Dixie-(Funder) Melamine.

One note is that Shopbot uses ipS not ipM so there may be some confusion on the plunge speed.

So actually, I think i am running at 6 ipm (out bottom) and 12 ipm (through top.)

If I tries any slower than 6 ipm the bits got pretty hot.

[Dropout]

Think in terms of chip load. Onsrud suggests 0.011 to 0.013 chip load for their 5mm drill bits. At 0.012 chip load a 4K rpm gives a feed rate of 48 IPM or 0.8 IPS.

We're running 72 IPM at 6K rpm and have no trouble.

[Closetguy]

I did not know that Onsrud made a through bore bit.
Last I checked they only made brad points.

Are you doing through bore?
My problem is exiting the bottom.

[Dropout]

No, we're not doing through bores. Missed that. Sorry.

[ger21]

I meant to say inch per second. Actually, I've always through bored at about 2 meters/min, which is about 1.3 ips.

[Dropout]

Onsrud has both, 72-XXX series. I use brad point.

[Closetguy]

Gerry,

What RPM are you running?
If you don't mind me asking what brand of bits are you using?

Dropout- I will check into Onsrud again. I use only their compression spirals to cut with. A little extra mony but definalty worth it.

thanks
Bob

[ger21]

Not sure about the rpm, it was at my last job. But I think it was closer to 3000.

I've used bits from Vortex, Amana, and European Tooling.

I've also found that once bits were sharpened, they never cut as good as when they were new. Probably due to the sharpener we used.

[Nat Wheatley]

Closetguy,

Have you had any further luck with this?