Forming a clock depression

[radman5506]

I recently tried using my 1/2" straight bit to cut a depression in the back of a piece of pine the put in a clock. I had set the path offsets @ 3/8" . Cut Passes set to depth of 1/4" total depth of 3/4". I started the project and walked away to do something else. I came back within a few minutes and smelled a burning smell coming from the machine. I stopped the project and opened the machine. I found first pass had been completed and second pass was almost done. The saw dust behind the cutter was packed as it always is behind a dado cut but was smoldering in about four places. I use a dust collector. Question is was I trying to cut too deep or too wide too fast. Any thoughts would be appreciated.

[mtylerfl]

Friction causes heat (I'm stating the obvious, I know). Somehow enough heat (friction) was created to lead to the smoldering.

- Is the bit sharp and clean?

- Was the Pine dry? Pitchy pine creates a lot more friction for a bit.

- Was the board tending to warp or cup (closing) on the kerf of the bit? Might be hard to tell if this was happening, but something to try to check for.

- What quality setting was selected when you uploaded to the card? Draft and/or Normal might run the bit feed rate too fast for this bit.

- I would think the 0.25" Max Pass depth should be fine, normally. However, I would reduce that to 0.125" if the problem repeats itself at your original setting.

- Now that you've seen this happen, you will need to stay near the machine and observe whilst cutting a pocket like this - just to be sure you can intervene quickly, if necessary in the future.

[lawrence]

I must be getting the hang of this carvewright thing because I came up with my answer and then read Michael's and my suggestions were the same as his for 4 out of his 6 suggestions :) (1,3,5,6)

My only additional suggestion is that with pine I find that my dust collection really doesn't keep up with the heavy chunks (and esp those in dados/grooves) so I find that I have to "help" the chips with
compressed air through the top groove- this knocks them out and keeps the channel clean. A clean channel is a less friction prone channel, which reduces heat and increases bit durability...

Lawrence

[Digitalwoodshop]

Is the bit a Plunge Bit as in it has a cutter on the bottom?

I do .1 deep cuts with the 3/8 bit shown for letters. I would think that a Up Spiral Bit might be better for deeper cuts...

AL

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_solid.html

[radman5506]

Thanks so much for the replies. The wood was select pine from HD and is not warped or cupped that I could see, the bit is the 1/2" straight bit from LHR. As far as sharpness is there a test that be done to determine sharpness before use. I know looking at a knife edge to see if light glints on the edge works for knives. Is there something similar for router type bits?

[Digitalwoodshop]

I cut this Slot Board a long time ago with the LHR 3/8 bit and it worked fine....

Could be the Pitch Content of the wood....

This would be a good time to mention that I recommend everyone install a Smoke Detector above the CW...

AND I was reading on Wood Web where a Wood Shop had a fire on Sunday and the last cutting was on Friday close of business using a dust collection system. It was a Smoldering Ember in the dust Collector that finally Flamed on Sunday.... so with that said.. CLEAN OUT YOUR DUST COLLECTOR TODAY.... Since you mentioned having smoking embers and a dust collector...

AL