Is it okay to cut deeper than the flute length of the bit?

[hipstomp]

Hi all, I'm cutting into some thick chunks of Black Walnut, using a 1/4" upcut bit (Onsrud 52-910). The flute length is 7/8".

Assuming I take 1/4" deep passes, is it okay to eventually plunge the bit past 7/8", to say 1.25 inches? I'm concerned about the non-fluted part of the bit rubbing against the material and potentially creating heat, which I understand can break bits. Any advice appreciated.

thanks,

- Nick

[knight_toolworks]

yes as long as you are only cutting with the flutes. so the steps need to fit the flute cut length. but a 1/4" is pretty small for that depth of cut in solid wood.

[hipstomp]

Thanks Steve. I thought the rule of thumb was a pass depth matching the diameter of the bit; you reckon I can go deeper with each pass without stressing/breaking the bit?

- Nick

[Xray]

I try to avoid doing that but have done it many times, in wood and plexiglass, with no ill effects so far.

[adrianm]

I regularly cut three or four times the bit diameter. It's just a matter of adjusting the feed rate/rpm's to suit so you don't overload anything.

The Onsrud chipload tables show the reductions they recommend for cutting deeper.

The only issue I've had with cutting deeper than the flutes is that, with the spiral bits, there is a fractional difference in width so the uncut part is a true 1/4". It can lead to marks in softer materials but I've never had a problem with heat buildup.

[hipstomp]

Thanks for the input, guys. I've yet to work up the stones to cut such deep passes; even at just 1/4" depth, I'm getting a horrible squealing noise from the bit that I'm trying to figure out.

- Nick

[adrianm]

Squealing with a spiral bit can mean that you're feeding too slowly.

Not sure who said it but I always remember someone on here saying that a noisy bit is a hungry bit and needs to be fed.

I slow the rpm's or up the feed rate until it's quiet on the fastest (longest) section of the cut.

[Bob Eustace]

Fred at Centurion has 1 1/4 cut length for around $25.00. You do get a slight noise but cut quality is good.

[scottp55]

Nicholas, do a test cut and reach over to VFD while watching the cut, lower RPM slowly and listen to the cut and see if it comes out of it.
THEN look at the number on the display and change your database. I was amazed a few times at the rpm the bit cut best at. THEN you can amp up feed/speed together and gradually work up your depth of pass . A lot depends on what you want for finish quality and how you're holding down too.
Hope this helped.
scott

[steve_g]

Nicholas…
It’s true that you can cut 2 and 3X the bit diameter with proper speed compensation. BUT when you’re cutting past the flute length of the bit, you may experience issues with getting the chips out of the kerf. Watch to see if this is an issue and adjust accordingly…
SG