fly cutter wear

I am having problems using a flycutter on my mill . I get rapid wear on the bottom edge of the cutter , Cutting easy machine mid steel , slow revs and slow feed

Where an I going wrong ?

Regards Phil

Are you running in reverse?

Tony

not enough clearance?

Serious wear on that, might be rubbed to death. Have you tried faster feed?

Cutter should be parallel to the holder base. Are all three screws tight?

Grind that flat completely off.

I have ground that flat off several times , but cutter will only last a few cuts , maybe it's a bit soft . great on alloy or brass

Can you vouch for the quality of the tool steel? There is some absolute rubbish out there. And when you say slow how slow?

Hard to tell from the photo Philip but it may be rubbing.

Move the cutter 'tip' up (down) to the work surface and look closely at the contact point - it should just be the tip of the tool touching and there should be clearance at the back. It's a bit harder to imagine - but the same rules apply to a fly-cutting tool as to any single point cutting tool - be that lathe, mill or shaper.

You need a defined cutting edge and some clearance - get those right first and then worry about rakes & speeds.

Regards,

IanT

Hi Guys,

I designed and made my own fly cutters, because I found that that style of fly cutter was not very rigid and tended to flex. This is what I came up with,

20 mm diameter shaft with a 75 mm steel disc and a piece of 1/4" square HSS. The cutter is double ended so you can have to cutting profiles, one on each end. I can take a 1 mm DOC in steel with this. I run this between 250 and 500 rpm depending upon depth of cut and how good a finish I want.

HSS is HSS it shouldn't be 'a bit soft' unless you have some old school tool steel that needs hardening and tempering.

Try a file on it, it if you can take anything off then its far too soft. Steel cutting steel always needs oil.

Edited By old mart on 24/09/2020 20:30:16

It's very easy to run a fly cutter too fast.

If that's a 4" radius it ideally needs to run at around 100rpm in mild steel, that's less than two cuts per second so feed has to be VERY slow.

Also what depth of cut are you using, if just cleaning up black bar with a light skim the scale will wear the small amount of cutting edge in contact quite quickly.

Flycutters of the stye shown by John Baron work very well with small carbide inserts. Either find an insert that doesn't need a complex seat geometry, round button perhaps, or simply sacrifice a small lathe tool.

Lets you work faster and gets round the sharpness issue. At a price! Depth of cut with a button is rather limited.

A late friend did this many years ago using simple square inserts on short bars, set into slots in the cutter rim rather than Johns simple hole, so he could surface cylinder heads and blocks on his Bridgeport. 6 or 8 inches diameter I think. 3 or 4 carriers et to slightly different depths for a staggered cut. No complaints that I recall from the racing boys who used the blocks and heads.

Black steel anything or a cast iron surface murders cutters. You have to get under the skin and take a proper cut.

Clive

Hi Clive, Guys,

I did try with a carbide insert but I found that they chipped very easily, usually when they hit the edge of the work. probably not suitable for too large a DOC.

Square HSS was the best to use and much easier to clamp. I think that getting the tool radius right and a shallow back rake, about 5 degrees giving more support to the cutting edge is about right.

You need a milling rated insert for interrupted cuts

This is my example of HSS fly cutting on steel, about 55mm diameter at 166rpm, 0.1mm depth of cut. As Neil says low speed, low feed. The temptation to go too fast is always there.

Edited By Martin Connelly on 25/09/2020 11:13:40

I have borrowed a rev counter , the slowest speed my mill will run is 250 , which looks a bit fast compared with Martin's video So maybe thats my problem

Phik

Hi Guys,

this picture is intended to show a fly cut surface with a HSS cutter at 250 rpm and 0.5 mm DOC on EN1.

The actual work piece is a part for my grinding spindle support assembly.

The pin standing next to the block will be a split collet that fits into the hole and clamps against a 20 mm post.

Although I actually tracked down and purchased the carbide inserts for my late friend, after 15 or so years I no longer have any idea what we actually bought. Unfortunately he is no longer here to ask.

I got advice from a reliable seller, possibly Greenwood Tools. The suggested inserts were, by my recollection, very reasonably priced and performed very well indeed giving a good finish and decent lifetime. I want to think that they were of a type intended primarily for lathe use when interrupted cutting was expected rather than true milling inserts but no longer know.

Certainly carbide of appropriate specification works well and need not be expensive. It will also cope with the rather high bottom speed of Philips machine.

That said I'm not completely happy with the idea of a flycutter of any size wizzing round at 250 rpm in a, relatively, lightly built model engineers mill.

Clive

I use TNMG inserts on my flycutter and the finish it leaves is excellent (by my standard) Never had any issues with chipping the insert and copes well with interrupted cuts. I think the OP could use an insert lathe tool on his flycutter and have a go.