Breaking a router or CNC bit is frustrating. I know it is because I’ve broken dozens of them. Here are three suggestions for reducing the likelihood of breaking a router bit.
Accidents happen to us all but try to reduce mistakes. There’s a process involved with changing any router bit. Add a quick checklist to your routine to double-check that not only is your setup correct but also your workflow with the setup won’t be obstructed. If you’re changing the bit height in a router or in a CNC machine, always double-check to make sure it’s correct after making a change.
Check your feeds and speeds. The correct chipload is necessary! It’s called chipload for a reason. You want to be ejecting CHIPS, NOT DUST. If you’re making dust you are not taking a large enough bite. That’s true for the majority of materials. On MDF you will never get chips as it is nothing but compressed dust to begin with. Analyze your material waste. Can you clearly see chips?
- AvidCNC did a great video on feeds and speeds. https://www.youtube.com/watch?v=5ubn8q4b8VA
- The G-Wizard program made by CNCCookbook.com will take all the guesswork out of chipload size. It’s an incredibly powerful tool that will likely have more features than you will use. It is a super handy reference tool though.
- Great video on chipload from Cuttin It Close https://www.youtube.com/watch?v=AHs-ifaB8G0
- Burning? Either slow down your RPM or increase your feed rate.
- Creating dust? Either slow down your RPM or increase your feed rate.
- Grabbing and pulling the material from you? Decrease your bite.
Bigger is better! Most of the time it is.
- ¼” bits are way more delicate than ⅜” bits.
- ⅜” bits are way more delicate than ½” bits.
- It’s almost always worth the extra time to change the collet for a larger bit. You’ll make up the time with faster material removal and decrease the unnecessary costs associated with breaking bits.
Can my spindle handle a larger bit? Most likely. Do some testing!! My previous CNC was an Axiom with a 2.2kw (I think) spindle. I had good results testing a 3/8″ bit at 100 inches per minute with a 3/8″ depth of cut. On my current CNC with a 6+ HP spindle I can cut full depth per pass in 3/4″ melamine with both a 3/8″ bit and a 1/2″ bit.
Excellent information. Appreciate you sharing your expertise especially on “burning” which I have done several times
Now I know exactly how to avoid it and that is to make a cut on a scrap piece of the same material to determine the propper speed while checking for burning. Then once chips come out with no burning, do the same thing on the good piece. A little extra work and time, but worth it to have a good cut
Thanks Jay, very good explanation of the proper techniques when using router bits. You explain things so clearly. Personally I would love to see more CNC type videos.
Getting advice from someone who has broken dozens of bits ?
Question I have a old Craftsman router and need a collet but the only one I can find is $75. Do you know of any place I can get one of these. My router # 315.269210. I would be better off buying a new one at twice that price.
Thank You Fred
First find out what type/size of collet it uses. Then try here: https://www.precisebits.com/gateways/ColletsNutsHome.htm
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