[Newbie] Face Mill Vs Fly Cutter

[kingmt01]

Personally I'd rather use the fly cutters. I actually pulled my arbor out of my face mill & built a slot cutter to fit it. However If I have to cut a weld off I put the face mill in with the brazed carbid.

 

[rick9345]

I wouldn't call that a home shop, more like a job shop. I still stand by my view through, bearings are meant to be replaced, you can baby them and try to squeeze every last hour of run time out of them, or you can just use them in a sensible fashion and replace them when they go bad.

What I was trying to say is how many actually put that kind hours(hobby/home) at full capacity of their machines! As you say when something in the shop gets bad,repair the problem.

 

[Heavycrimp]

The stress to bearings (and actually to a greater degree power transmission components like gears,etc) in not determined by how irritating an operation sounds but the combination of cutter diameter, feed rate and spindle RPM. If you have a 4 insert face mill or a fly cutter of the same diameter taking the same chip load, you are making identical stresses. With a face cutter, you will be doing it four times more often but both are interrupted cuts. I use both but use face mills more often because they are more efficient at removing cubic inches per minute. Face mills with inserts that include a wiping face can give beautiful surfaces but cost like the dickens. I have used some Japanese cutters with high positive rake that could take a .125 deep cut on 2" wide 6061 aluminum on a Bridgeport running flat out and a Servo power feed running in rapid traverse. They still left a very nice surface finish. The noise however, was deafening.

 

[samthedog]

I think each plays their role. Indexable face mills of decent quality are often out of reach for the tight home machinist, especially when you may need a stable of different inserts for different materials. A fly cutter can be modified quite quickly and will cost a fraction of the face mill. I have both and have even used a boring head as a fly cutter before. I think the strain on the spindle bearings is less of a concern than the strain on the leadscrew, leadscrew nut and the ways. The interrupted cut puts quite a bit of torque on the machine and I would be more concerned about the non-hardened surfaces.

With all that said, many of us have machines that have come from workshops where they have seen heavy-handed, industrial use day in and day out. Many of these machines although a bit rough, are ok mechanically. Will you ever be pushing a home machine as long and hard as an industrial machine through occasional fly cutting? Probably not.

Paul.

 

[TommyD]

A face mill is a gentler cut, except for the interrupted cut, a multi cutter mill always has a tooth in contact with the work as another tooth enters the cut. A flycutter is a constant interrupted cut, a single tooth doing the cutting.

Personally I use both but take a smaller chip and slow my feed rate using a flycutter. I have better things to do/make than change out beaten on bearings.

 

[Dan_S]

A face mill is a gentler cut, except for the interrupted cut, a multi cutter mill always has a tooth in contact with the work as another tooth enters the cut. A flycutter is a constant interrupted cut, a single tooth doing the cutting.
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That's not always the case, If the facemill is to wide for the work, it will only have one cutter engaged in the work, and act just like a fly cutter.

 

[TommyD]

True, there are exceptions to everything but with a multi cutter bit the feed rate for the cutter diameter determines chip size and the chip, therefore, would be smaller lessening the impact of the next cutter on the material and bearings. I've seen some monkeys speed through a cut with a flycutter that is taking some very large chips, all brown and hot and flying all over the place. I've also seen them dancing around when one of these chips land on their hand.

 

[Andre]

Some machinists and rebuilders have told me that a fly cutter is much harder on the bearings due to the incessant: WHOMP WHOMP of fly cutter. I'm guessing this is all anecdotal. Perhaps not as big a deal if you aren't taking heavy cuts.

You can grind your flycutter with a very small corner radius and heavy relief to minimize any hammering action on spindle. The angular contact bearings in milling machines are immensely strong, they shouldn't be hurt. More delicate milling heads like the early B-ports, such as my M-head, have radial deep groove ball bearings simply preloaded with spacers. These can be damaged with heavy interrupted cuts, but mine are shot anyway so just fill them with oil and take light cuts!

 

[Heavycrimp]

Regardless of diameter vs. width of work, a face mill ALWAYS is taking an interrupted cut. Were this not the case, each tooth/insert would be generating a continuous chip. I will restate that it is all about chip load no matter what whether using a fly cutter or face mill. I can take a cut with a face mill that will break a Bridgeport that will never make the racket that a fly cutter will at a much lighter load. Your ears are an excellent tool for detecting when things are going wrong but can be fooled. I still use both for a variety of reasons. It's like any task, pick the tool that is best suited for the job within the constraints of economy with which one has to operate and know how to use it properly.

 

[John Hasler]

Regardless of diameter vs. width of work, a face mill ALWAYS is taking an interrupted cut.

Sure, but it may still always have one or several teeth engaged, so the peak to peak variation in torque is usually lower and rarely goes to zero.