Bit breakage trouble

I have been reading the posts on the group about bit breakage with interest, as I have not yet run a job without breaking a bit, even changing speeds and feeds.

My project is a control panel face plate, using the two color acrylic from inventables as the material, and 1/8 and 1/16" bits for carving. Using the standard feed rates broke a 1/16" bit instantly. I am experimenting with slower feeds as I am stuck with the speed of the standard 300 Watt spindle, whatever it is. Curiously, once the bit is shortened (after the break) it seems to work rather well. Could I have an alignment problem? I have checked that the Z axis is perpendicular to the X-Y axis as best I can.

I need to use a 1/32" bit for some text, but I need to get the breakage issue straightened out first. All suggestions are welcome.

What stick-out are you using? Are you pushing the bit as far as it can go into the collet?

Well the only thing I can say is stock up on a lot of Quality 1/32 bits. I broke the one that came with the starter set just taking it out of the case. It may of been defective, but if your going to use them a lot i suggest you stock up and only use them with low depth and soft material

Low dept is how low, can you please put numbers down and we can see what is the problem point. Cut Depth = , FeedRate = , Spindle speed =
Also how many passes you’re using and what is the number for per pass.

I got the same problem as Keith. I could not cut acrylic at the default Easel settings for acrylic (25in/min, 0.020" per pass at 12K RPM, using a 1/8" single flute bit). I put back the spindle I used on my Shapeoko2 (DW660) and no issues at all. So either the spindle has a lot or runout or the RPM drops too much under light load.

I think it’s in as far as it will go. Not sure, will check. However, the breakage occurs about 1/8" past (closer to the tip) the taper. Using a 1/8" shank, 1/16" bit.

I am using a depth of cut of .002, a feed rate of 10 or 20 IPM, doesent seem to matter. Bit breaks within a minute or so. However, once the bit is broken, and I reste the home position, it seems to run OK, in that i can carve, but the finish of the cuts is not too good.

Possibilities are shrinking. You may have jerky movement on your X or Y axis. Did you circle test in air. Maybe you can see erratic movement or hear humming. Low running spindle not breaking bits. I just try .005 / 15 ipm and slow down as slow as Spindle goes, didn’t brake 1/8 bit.

I found a few issues with mine that I believe to have resolved. First make sure you have the proper power from all of the Pots. Second, I found I had lost a screw from one of the axis pulleys, (specifically the x-axis on mine). Then I upgraded the spindle to a dewalt 611. And lastly (which I actually did first) Making sure the surface was completely flat. This made the largest difference as it was cutting .002 in one spot but due to the surface it would be cutting .005 in another right by it. I also found that by starting the cut about 1/16" above the surface and letting it work its way down helped a lot. Even though it added a considerable amount of time.

1 Like