Thread: Face mills and Fly cutters

Originally Posted by simonl

To me they seem to do the same thing, except most fly cutters only have one cutting edge as opposed to several with most face mills.

So, is that the only difference? Face mills allow for a faster feed rate due to multiple cutters?

Do they both produce the same finish or does one produce a better finish over the other with all other factors being equal?

Simon

Yes, they do the same job, but a facemill of the same diameter as your flycutter can be fed much faster due to the multiple teeth, and given that most facemills you now buy are carbide insert jobs, spindle rpm is much higher too.

Some people say that flycutters give a better finish than a carbide facemill, but now we're back into the HSS vs carbide surface finish argument . I'll only say that IMO, the finish I've achieved on from carbide facemills is very good, and given the eternity it takes for an HSS flycutter set at 2 or 3 inch to make a single pass over the part, I've been grabbing the facemill every time.

There is also a point of view held by some that a flycutter destroys spindle bearings, due to the interrupted nature of the cut. I'll let you make you own mind up on that one, plenty of posts on practical machinist (IIRC) about this topic.

Get the face mill

A face mill will take a 5mm+ cut a at a nice and fast feed rate where as a fly cutter takes bugger all 0.3mm maybe its not worth the cash. On the other hand fly cutters are easy to make

Yep I'm thinking a face mill. Only thing is, I have some TCT indexable inserts for my lathe and now I'm finding that I am turning away from their use and becoming more reliant on HSS again. This is because when it comes to light cuts and finish, I find that HSS is superior. Will I find the same issues with the mill?

Thanks for the replies!

Simon

Maybe.

Hi pipeclay. Maybe?

What sort of facemill should i get. So many types. 90deg. Round?

I bought mine from CTC and it works good. They have positive rake inserts and will suit your mill as well.
Ray posted a picture of the finish a face mill leaves here
https://www.woodworkforums.com/f65/face-mill-fly-cutter-142500/

As for a fly cutter they do leave a nice finish, but are slow. Just buy a face mill and make up a fly cutter while you wait and compare the 2. Some guys take out all but 1 of the inserts and report good results used as a fly cutter. With a face mill you will be able to hog out metal, but a fly cutter is only used to finish in steel. On aluminium you will be able to take bigger cuts with a fly cutter.

Another thing you want to think about is indexable end mills, and see if you can get some to suit the same inserts.
I prefer inserts on the mill over HSS, but I still use HSS end mills a lot as they leave a nice finish on the edge.

Ray posted a picture of the finish a face mill leaves here
https://www.woodworkforums.com/f65/fa...cutter-142500/

I have posted a few pictures of a piece of HSS mounted in a boring head used like a fly cutter, I only used it to cover the whole area (220mm x 300mm from memory) in one go to leave a nice finish.
https://www.woodworkforums.com/f65/50...ad-set-132912/

For a quick try you could try a smaller diameter in a boring head (from memory I think you got one with your package)

Dave

I forgot to say I bought a 63mm face mill and if yours is 2 HP machine you should have no troubles powering it.

Dave

Thanks everyone,

Hi Dave, The fly cutting you have done with your boring bar, did you use the standard cutters that came with the boring bar or did you make up some dedicated ones?

The thought had crossed my mind to use my boring bar as a fly cutter, but I never followed it up!

I'm assuming you did make another cutter as I don't think the cutters (well on mine) can protrude past the boring bar itself.

Cheers,

Simon

I just ran out to the shed (left screaming kids in the house. Wife gone to shops and left kids with me!) to do some fly cutting with my boring bar. Attached a pic. Is this how others possibly use their boring bar to do fly cutting? I see that Dave has his cutter attached radially or horizontally which would perhaps give potentially greater diameter if you had the rigidity and HP to drive it. My standard cutters would not clear the boring bar body so not an option with my standard cutters.

The results look OK as a first attempt.

Cheers,

Simon

Hello Simon,
I have a 60mm.dia facemill which takes square inserts (SCGT-32.51-FH), although I think slightly thinner ones are the correct size. They are set at an angle (15deg. from the vertical) which means that I cannot machine right up to a shoulder.
I think a facemill which takes triangular inserts mounted at 90deg. , and set with positive rake would be the best setup. Carbide is certainly useful if you need to machine hard steel or machine through welds or scale etc. I reserve worn tips for this and then use good tips when the metal has been cleaned up.
I recently made a flycutter from a piece of 100mm. dia. 4140 which I threaded to fit a threaded arbor which I purchased from CTC. It holds two 5/15 HSS cutters (if needed). I haven't used it yet but I think I will be able to machine about 150 mm at a time (slowly) if I extend the cutters out 25mm. It will also be useful for machining aluminium, wood,(shock-horror) and plastics.
I don't think it is a case of either-or, Both have their uses.

Regards,
Russell