View Full Version : Using end mills as boring bars???

04-03-2004, 11:55 AM
I sometimes need to bore small (1/4" or less) holes accurately on the lathe, and I don't have a small boring bar. What's wrong with using a end mill smaller than the hole as a substitute? It would be mounted so one of the teeth does the cutting.

The first problem I see is the chips might clog on the other teeth, but there won't be a lot of material being removed. I realize that the hole cannot be flat on the bottom, but that's probably not important. Has anybody done this?


Spin Doctor
04-03-2004, 11:58 AM
This what you always save the endmills that have one side of the cutter broken off for. Under .250" sounds like light cuts to me

04-03-2004, 12:42 PM
Whatever works!

If you have a busted end mill, you can grind off the bad side to give more clearance, leaving one tooth to do the boring with.

04-03-2004, 02:45 PM
Theres nothing wrong with doing this, I have used good endmills for boring bars in lathe toolholders for years, I also have a set of bushings to use down to an 1/8" shank endmill in my Criterion boring head, have used endmills for years as a boring bars on the mill in the Criterion and it works very well. It leaves a good finish and besides it is a cheap alternative to buying a certain size boring bar that you might only use a few times a years.

04-03-2004, 10:37 PM
A busted endmill is merely a round toolbit thats trying to be free http://bbs.homeshopmachinist.net//biggrin.gif

04-03-2004, 11:37 PM
I use end mills all the time like chucking reamers up to 5/8" thats in the tailstock, when I go with a endmill in my toolpost holder, I advance slow, because sometimes the cutter will dig into the work and pull itself in and stall my lathe, (small 7x10 mini lathe) but endmills make great boring bars in my opinion.

04-04-2004, 12:52 AM
Did that just a day ago. I used a 3/8 endmill to make a hole in a knob since my drill bit wasn't handy. This is not a plunging type, so I drilled a smaller hole first.