Edges Burning

[ase3558]

I am doing a project for a client and have been cutting a bunch of 3/4" Baltic Birch ply. Got half way through the first sheet and noticed the edges were starting to burn. I stepped away for a bit and came back and smelled burning. Some sawdust in one of the cuts caught on fire and got sucked down by my vacuum table and put a big hole in it. Thinking the bit got dull and got really hot but it was a brand new bit.
I was using a Rockler brand 1/4" upcut bit going at 12000 rpm and 3 ips and doing .125 depth of cuts...I have no idea what to do. Any help?

[dlcw]

Spindle speed is to fast and feed rate is to slow. I run 10K rpm at 6ips, .5" depth of cut. Have never had any burning on any plywood or composites

[ase3558]

Ok thanks. Ill try that

[ase3558]

going 0.5 depth of cut wont put too much strain on the 1/4" bit?

[ssflyer]

I run that all the time - sometimes full depth on 3/4" material, but it depends on your machine - what model do you have, and do you have a spindle or router?

[ase3558]

PRS 96x48 with a router attached. Would making shallow cuts be buidling up heat because only 1/8 of the bit is being used?

[Ger21]

I don't have a shopbot, but what you're doing shouldn't be generating enough heat to start a fire.

Are you sure the bit is not very dull, or even chipped at the end? Is it spinning the right way?

[ase3558]

It was a brand new bit when I started the cut. Unless that one sheet dulled it half way through.

[Burkhardt]

I agree with Gerry. While you can probably cut faster, this setting is not really slow. I do something similar all the time without problem and the bits last a long time. Something else must be wrong. I would say direction if it was a spindle but with a router that is almost impossible.

[steve_g]

Austin...
Here’s the possibilities as I see them...
1. The bit hit something embedded in the goods... that’s not unheard of especially if it was Chinese goods.
2. The bit was of poor quality. You don’t hear the folks on this forum singing the praises of Rockler bits...
3. I had a third point but old age has caught up with me... Oh well, closely examine the bit and see if it isn’t chipped, broken or horribly dull.
SG

[ase3558]

I got a Freud bit at first and it broke almost immediately. I looked at the bit and it doesnt look like there are any chips and it feels sharp. Im really at a lose. I thought it might be the direction so I went from climb to conventional and no help.

[Ger21]

I meant spinning in the wrong direction, not climb vs conventional.
Something doesn't add up.
A 1/4" upcut spiral should not be breaking (or burning) with the rpm and feedrate you say you were using.

[Brady Watson]

My guess would be that your Rockler bit is high speed steel (HSS) and not solid carbide. Forget HSS for CNC work. You pretty much need to run solid carbide. There is no economy in the HSS stuff. Look for Onsrud bits or get 2-flute solid carbide end mills.

-B

[ase3558]

yeah the rockler bits are hss. how would i check if the router is going in the wrong direction?

[Burkhardt]

yeah the rockler bits are hss. how would i check if the router is going in the wrong direction?

A router practically can not spin the wrong direction unless you swap the wiring inside or the assembler at the factory was stoned.

That is more a theoretical issue for high speed spindles where you can change direction at will.

[Mayo]

If your bit was really an upcut bit, there shouldn't be much sawdust in the cut - especially if you're only at 1/8" depth of cut.

Maybe the bit was a down cutting bit?

Did you happen to pause and then resume the file at the point of the burning?

[ase3558]

So I went through all the post and tried everything. Went faster and deeper and it lost its x y zero position. I saw the whole gantry jolt. Like the rotor was getting stuck and the gantry kept moving. So I decided to just cut 1/2" MDF templates for my router table and do it that way. The bit dulled halfway through the sheet. When I pulled the sheet the bit was black and all the cuts were furry. I was listening when it was cutting and I heard the sound going up and down like the router was slowing down and then speeding up. All I can think of is that the router is dying and losing torque and thats why these bits are dying so quick. Does that sound possible?

[Kyle Stapleton]

HHS bit and blades suck do not use them.
I'm sure they have or had there place but I can't think of where I would use them.

[hh_woodworking]

If you are using the P/C router with variable speed, the speed controller maybe going out, or the bearing are going bad, or maybe brushes are getting bad also. I have had the controller control go out before.