Burnt bits

[wegner81]

I am starting to experiment with 2.5 D and 3D carving. I have noticed a little char on the bottom of my bits. Am I doing something wrong?
I do not run my machine hard. I noticed on the rough out on carving that the bit will stop for just a second and there will be a small burn mark in the wood. Today I was using some alder which is fairly soft,but still had some burn marks.
I noticed also that my brand new .25 down cut bit had some slight burn on the bottom of it.
Thanks for any input
Kevin

[carlcnc]

Kevin
dn cut bits will burn if you are pocketing,any time they can't eject chips out the bottom.
on your ballnose,maybe lower spindle rpm or increase feed rate. I usually do the latter.
Carl

[rcnewcomb]

What are the RPMs and feedrates?
What is your stepover?
What brand and type of bit?
Do you notice the burn with a ballnose bit or just the downspiral?
Are you using a roughing pass?
During the pauses are you noticing if the computer is loading up additional instructions (look for a progress bar)

[drodda]

Whoa, Randall Maybe it's time to cut back on the coffee. The caffeine is effecting your typing?

-D

[myxpykalix]

You might try sharper bits from www.centuriontools.com (http://www.centuriontools.com)

(no comments from you Dave R) lol

[wegner81]

Thanks guys for all the suggestion. I dont change the feed rate of the file I am running very often. I usually run what is recomended in the sotfware for that bit. Carls point about the down cut bit makes perfect sense. I should of thought of that as a woodworker, but have mortised hinges and run dados for cabs for years and the bits would eventually gets some burn marks. thinking about it, my bot has probably cut more pockets alreay than I ever did. This may be one of those hit yourself in the head moments, when you say I should of thought of that.
Thanks.
I always I appreciate everyones input into someone elses problems. Maybe we should have congress join the forum Ha Ha

[rcnewcomb]

quote:Whoa, Randall Maybe it's time to cut back on the coffee.
mysistergavemetwobagsofcoffeefromherfavoritecoffee shopanditsreallygoodsoIhavebeendrinkingalotofitlat ely. latertodayI'mgoingtoorganizealltheplasticbagsandtw istytiesbecauseIseemtohaveallthistimeonmyhands.

[tkovacs]

Randall - that literally made me LAUGH OUT LOUD!

Thanks!

Terry

[beacon14]

When pocketing with the downspiral are you plunging straight down into the material or using a ramped entry? The former will be more likely to burn the bit, some bits are designed to plunge cut but others not so well. Also as the bit plunges it's stuck in one place in the material with no way to clear chips or heat.

I do a fair bit of pocketing with downspirals and I have not noticed any unusual burning.

You say you are not pushing the machine hard. Slower feed speeds are actually more likely to burn as the bit is not moving quickly enough through the material or generating large enough chips to dissapate the heat. You should be throwing warm if not hot chips, not dust, from your cuts.

[woodworx]

i laughed so hard too!