# Woodworking router bit as an end mill?



## Larry42 (Nov 27, 2019)

My woodworking shop has a CNC router so lots of used router bits. I was wondering if I could sharpen them to work as end mills. Unfortunately most of them are compression spirals or down spirals. Less than ideal for metal. I found a 1/2" carbide, Marathon coated two flute down spiral and decided to sharpen the end only to give it a try. I used my Shars single point tool grinder and a diamond wheel. I'm far from an expert at setting it up but managed to get the chipped end of the bit to clean up. Put it on the Jet mill and a chunk of aluminum in the vice. First tries were running at 500rpm and moderate freed rate. It cut but not ideal. By increments, I increased both the rpm and feed rate until I got to 4,000rpm. WD40 and a faster feed than I normally use. .200" DOC. Chips flew all over but the resulting surface was reasonably good.  I added it to my end mills that I had sharpened yesterday. Once the tool grinder is set up, I can sharpen end mills at a pretty fast clip, ends only. 2, 3, or 4 flute but no more flutes than that. HSS or carbide with the proper wheel. Lathe tools are easy to sharpen.


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## GrayTech (Nov 27, 2019)

No reason why down spiral mills wont work for side milling. Not good geometry for end milling though.


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## homebrewed (Nov 28, 2019)

I've used some of my carbide router bits on my table-top mill to shape aluminum.  In particular I recall a project where I was making a sine table and milled the vees (for the rolls) with a 45 degree router bit.  I have not tried to machine steel with them.


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## Eddyde (Nov 28, 2019)

They'll work on steel as well, just go slow and use plenty of lube/coolant.


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## Larry42 (Nov 28, 2019)

Even though the down spiral configuration is a lot less than ideal, the resulting surface was reasonably OK when end milling. I'm sure I could improve the angles I chose as a first try. I've got lots of the 3/8" compression bits to try/ experiment with. The end is up spiral for a short distance. The shop doesn't have bits re-sharpened. So about every 3 days or less another bit goes into the used pile. Ultimately they are sent as scrap. I end up with some carbide inserts and molder knives also. Been thinking of making a lathe tool to hold the used woodworking inserts. I think I can regrind them on the tool grinder. They would have a sharp cutting edge as opposed to the "normal" eased edge of the inserts designed to cut metal. That should be better in some ways. It would reduce the forces required to start the cut and also allow very thin cuts to more easily be done. I know the life of the edge will be less but so what for an old hobby guy. The nose radius could be done on the tool grinder or hand honed.  Another project for the list. 
How many of you have single lip tool grinders? Deckle knock offs.


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## MikeInOr (Nov 28, 2019)

Not knowing the geometry of down cutting spiral router bits... could you grind the ends so they effectively remove the chips if you run them in a reverse rotation?


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