First time fly cutting

[754]

I use one similar to right hand one in wooden block, but has 3 setscrews. I took a 1/2 shrank brazed carbide, thinned 1/2 'of the shank so it would fit the slot and catch 2 set screws. Then I ground a round profile on the tip , a small chipbreaker giving a bit if positive rake.
now keep in kind fly cutter. NoT a face mill .. light cuts , low removal.. flatten things.
so it cuts a 6 inch swath on a B,port type mill on regular steel or aluminum.... does a nice job...
so much for too much stickout.........light cuts, use positive rake for easier cutting, less beating up of machine..

I also have shorter tools for it. And I also use my boring head, sticking out the side hole ... probably 8 inch swath..

[BaronJ]

I use one similar to right hand one in wooden block, but has 3 setscrews. I took a 1/2 shrank brazed carbide, thinned 1/2 'of the shank so it would fit the slot and catch 2 set screws. Then I ground a round profile on the tip , a small chipbreaker giving a bit if positive rake.
now keep in mind fly cutter. Not a face mill .. light cuts , low removal.. flatten things.
so it cuts a 6 inch swath on a B,port type mill on regular steel or aluminium.... does a nice job...
so much for too much stickout.........light cuts, use positive rake for easier cutting, less beating up of machine..

I also have shorter tools for it. And I also use my boring head, sticking out the side hole ... probably 8 inch swath..

The major problem with that kind of fly cutter is that as you extend its reach it becomes more out of balance, which gets worse as the rotational speed is increased.

Another issue not often realised is that the out of tram of the mill causes the cut to be hollow along the centre of rotation ! So the large plate that the OP was trying to flatten will have very shallow scallops across the surface.

[challenger]

I have a set like the picture that I rarely use. If I do, I keep the surface speed way down to prevent damaging the cutter. Revs are about 150 and I get decent results.
I haven't used them in a few years and now use the multi insert carbide face mills.

I just bought something similar on the bay.

FYI, I've been running this mill way too fast. Here are the current rpms/hz:


Do these seem reasonable?

[754]

Same as a faceplate or 4 jaw, out a balance, add counter weight opposite. Speed is usually down a bit to prevent hammering..
it's not much more out of balance than the first one shown.

[Ringo]

Two points:

1. If you want to finish the entire surface of that sheet of metal, I think your mill does not have enough throat for the job. You will never reach the center. So, you may want to use a different technique to finish it.

2. I can't see the fly cutter very well, but from the looks of the path that you have already cut I think you could work on the sharpening of that tool bit. You need to get the angles correct for the way it sits in the holder. And, of course, make sure they are dead sharp.

OK, three points:

3. Use a coolant or at least some oil while cutting. It will cool those flying chips down for less pain when they land on your arm or go down your shirt. And it will improve the surface finish.

And here's another shop made fly cutter. I like a two cutter design because it is balanced better.


This one was made to fit on the spindle of my SB-9 lathe but it could have had a shank for use on the mill. In this photo you can see that the tops of the two HSS tools are on the center line of the cutter. That way I can cut the angles for the tip in the same manner as I would for a lathe tool. One exception to this is the added relief on the outer edge of the tool. It is a bit difficult to see, but that outer edge has a second facet to allow more clearance at the bottom side of the bit.

It is very well balanced so it can run at higher speeds.

geez, that is a good looking cutter, perhaps a dandy to make up in 3-flute or 4-flute style in the home shop.

[redlee]

geez, that is a good looking cutter, perhaps a dandy to make up in 3-flute or 4-flute style in the home shop.

It is, but with 2 cutters its a PITA to get both on the same plane.
Set screws tend to dimple steel and it can be a pain.

[dian]

they dont have to be.

[754]

I agree they dont have to be, and that design....add a pusher adjusting setscrew.. so easy..

[BCRider]

It is, but with 2 cutters its a PITA to get both on the same plane.
Set screws tend to dimple steel and it can be a pain.

My old mill drill and new knee mill both had a big head with four brazed carbide cutters. I'd happily send the head unit for it out to anyone willing to pay the shipping. And yes, as soon as we go away from a single cutter we run into the need for some manner of indexable holder so we can grind both tips to the same shape. And that turns it into a very annoying tool to use.

The whole point of a single tip fly cutter after all is that it gives us a way to easily make a large diameter surfacing tool without needing fancy tool and cutter grinding setups.

[redlee]

they dont have to be.

If the 2 cutters are not the same then one does all the work, so ....... stick with one and no setup required.

[john b]

All you need to set up a two bit fly cutter is feeler gauges. Each it has to cut on a different diameter. Bring the fly cutter down until it is touching part, place .005" or less shim under one of the cutting bits and make sure that it ois cutti a larger dia than the other bit. Now you have a rougher and finished cutter that is better balanced.

[genea]

Before you go any farther get rid of the weld bead either with a more appropriate cutter or by grinding. The interrupted cut isn't doing your fly cutter any favors no matter what geometry you end up with.

And, it's not much of an exaggeration to say that I have cold chisels with better cutting edges than the one I see in your first picture.

[754]

If the 2 cutters are not the same then one does all the work, so ....... stick with one and no setup required.

Apparently you have not heard of a wiper insert on a face mill ?
the fact that 2 cutters are hitting the work , should be lower impact on the spindle... if unable to set it up, use a single tool.

[PStechPaul]

The cutters should be the same height. The tool is constantly moving so each cutter will be cutting fresh metal, twice per revolution. AFAIK, face mills, and multi-flute end cutting mills used to smooth a surface, have equal height cutting edges.

[dian]

not really. there are facemills with rougher and finishing inserts. besides you never get anything absolutely equal anyway. you just have to adjust the feed.