# Can a boring bar be used as a fly cutter?



## Charley Davidson (Dec 27, 2012)

Probably a dumb question but had to ask


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## OldMachinist (Dec 27, 2012)

I've never done it but don't see any reason it wouldn't work as long the tool was ground properly and rigid enough.


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## Tony Wells (Dec 27, 2012)

Since some boring heads are able to do facing work, I'd think it would be possible. It would be all in the tool profile, and probably wouldn't be quite as efficient as a dedicated fly cutter. For myself, I'd rather not use one for that, though. I don't like the hammering of the fly cutter that would bear against the dovetails of the boring head.


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## Kevin45 (Jan 4, 2013)

It can be done but I wouldn't recommend it. If something happens, you are out a boring head. We had one guy at work that had to cut some larger holes into an aluminum panel, so he made up a trepanning cutter using a boring head. When it caught, it busted the head into pieces. It's not so much that it can't be done, but if you need a flycutter, that means you have a mill, so if you have a mill, make a flycutter. Lol!!!


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## DMS (Jan 4, 2013)

I have done it. I needed a wide slot cut with a radius, and not having a rotary table, I used the boring head. I took light cuts. It was a bit hairy at times to be honest, but did work. The nice thing about a boring head is that you have fine adjustments, so you can get an accurate slot. If you were just using it to face stock, I would spend an hour and make a fly cutter. It will be more rigid, cheaper, and more satisfying.


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## rgray (Jan 14, 2013)

I took the question to mean a boring bar from lathe not a boring head. That made me think about truing the bottom of a blind hole with a boring bar with the tool bit at a 45 degree angle. That works so why not flycut.
So I tried it and it works but use speeds you would use on the lathe.
I set up a 1/2" bar with 1/8" bit with not much bit hanging out. Have to run the mill in reverse. I had been milling with a 3/8" endmill at 1800 rpm and that made alot of noise when it touched the aluminum I reduced speed to 800 rpm and it worked much better...even that would be faster than I would do it in a lathe. Maybe I'm just lazy but seems like 200rpm is my speed on the lathe.


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## MCRIPPPer (Jan 15, 2013)

fly cutters are simple. i made one with JUNK in my shop. got an old dulled/overheated drill bit with a nice 1/2 shank and larger diameter step up about 3/4 in diameter, cut off drill part, annealed it, drilled it, milled it, tapped it, and iv got a fly cutter. as a blade, i cut up an old carbide tipped circular saw blade and sharpened the carbide on a diamond wheel on my dremel. it works great. it only goes up to about 1.5 to 2 inches wide(as far as i feel comfortable hanging the cutter out of the tool) but thats plenty for what i do on my mini mill. it even put a nice finish on some semi hardened steel when i was fixing up my cheap "quick vise".


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## 8ntsane (Jan 15, 2013)

Hi Charley

I use a rather large boring bar for facing stock, its a offshore 1 inch od bar with carbide inserts.
The holder is just a shop made unit from scrap. I only use this setup for facing stock, and works quite
well. I suppose you could use a boring head with a small boring bar, but I would think the small bar would be pretty springy, and not ridged enough.

Depending on what job you have at hand, you may be forced to use a small bar with your boring head for the adjustability.


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