View Full Version : Fly cutters

11-06-2004, 04:58 PM
I am fairly new to machining and am slowly building up the tooling for my vertical mill. I'm saving my pennies for a decient boring head. I've seen some fly cutter sets about and was wondering if I could use these for crude boring operations, and also what other operations do they lend themselves to?

Michael Az
11-06-2004, 05:41 PM
Yes, a flycutter could be used to enlarge a crude hole. Their main purpose is to machine a larger surface. Last week I had a 12" square plate that I needed to use on my welding table. It was warped about 1/16". So I used a flycutter to resurface the top of it. Only took three passes. You can't take too deep of a cut with them.

[This message has been edited by Michael Az (edited 11-06-2004).]

11-06-2004, 05:50 PM
Sure, you ought to be able to use a flycutter to enlarge a hole. The thing you won't have, that a boring head gives you, is fine adjustment on the diameter, but with sufficient care you ought to be able to come pretty close to a desired size.

Incidentally, I've got one of the Travers Tool "precision import" 2" diameter boring heads, and while a Criterion boring head may indeed be slightly better I sure can't see anything wrong with the one from Travers for less than half the price.

Oh -- another thing. When you get a boring head, get the proper shank to fit your milling machine taper. I started off with a straight shank, to be held in a collet, but because of the length of lever arm that a boring head creates it's not rigid enough.

charlie coghill
11-06-2004, 10:57 PM
Friday I wanted to mount three gages that required a two inch hole. The closest hole saw that I had was 1.750". I used the hole saw to cut the three holes and a fly cutter to open the holes to the 1.750 dia. This was in 16 gage plate with the metal clamped to a piece of 1 inch plywood.
You do need to watch the tool bit clearances.

G.A. Ewen
11-06-2004, 11:16 PM
My first boring head was a small one with only one hole in the center to mount the tool. This was my solution to bore a hole larger that its capacity.


The face of the tubing was also done with the fly cutter.

[This message has been edited by G.A. Ewen (edited 11-06-2004).]

11-07-2004, 06:50 AM

A small flycutter in a endmill holder in the spindle of my 11" Logan, milling a sight base. I did this a few days ago and it was my first ever to use them. I couldn't figure out how you were supposed to get the right diameter. I'm sure there is an accepted way.

What I did was with the flycutter base in the holder, and while running I ran the tailstock up with a centerdrill and put a tiny pip in the tool holder channel at center. This was the smallest cutting head and it takes 1/4" bits. I had a bit I'd ground, so determined the rough length and cut it off.

The radius had to be 1.110" (rifle barrel dia). I put the cutting face of the tool in the head to bisect the 'pip' I had put in the tool channel. This was my zero. I had a tool in the toolholder of the compound so it brought it up to touch the non-cutting end of the flycutter bit and I retracted the cross slide .555" which pushed the flycutter bit out that much. Then I tightened the setscrews in the head to hold the 1/4" bit.

Since the sightbase was 5/8" wide I clamped it in the toolholder as if it was the vice and commenced flycutting! Worked like a champ.


11-07-2004, 10:07 AM
Good job! As my mentor and former supervisor said, "You are limited only by your ingenuity".

11-08-2004, 09:48 AM
Many Thanks
Think i'll treat myself and see how I get on.

11-08-2004, 10:45 PM
Very good Buckshot, will remember that trick, will be useful for other things too.