Even 0.001" out of perpendicular is still enough to cut on the "backstroke", if the head is angled "backwards" relatively to the table travel, and to produce a concave result up to 0.001" deep.

I do use fly-cutting, sometimes, but don't really like doing so as it hammers the machine very heavily. It is all right for very fine finishing work but not bulk metal removal, except perhaps on a hefty great industrial machine with power-feeds, and made to handle such arduous duty.

My preference is to use fluted cutters… and re-sharpen them!

What mill do you have? On the smaller benchtop mills you are only likely to take off say 1mm on the non ferrous metals and up to 0.5mm on steel depending on diameter of the swept circle.

Correct geometry of the cutter also plays a part, often those not use dto grinding a tool will end up with little or no clearance so the edge of teh tool rubs rather than cuts and it will tend to get pushed away particularly by harder material rather than cut.

I used to flycut quite a lot but now tend to reach for an insert shell or face mill. Apart from not needing sharpening as much as HSS you can run them faster and feed 4-6 times faster than a single point tool which makes it easier to keep a constant feed.

Bit of flycutting on the SX2.7, EN3 steel

It is possible to tram a mill so that leading and trailing edges cut equally which gives an almost holographic effect but it is very hard to get right.

So if you do find one one side cuts deeper than the other you can make use of that by feeding so that the trailing edge takes a fine finish cut after the leading edge has removed the bulk.

Though as Ramon says this can leave a very minute concave surface which is why I mostly use the flycutter or insert head to get rough sawn blocks down to a usable and square size then where a very flat surface is needed change to a SHARP milling cutter and make a series of passes, typical would be this Stuart cylinder where it was roughed out with inserts which will not get blunted by any skin or chilled areas, then finished with a 6mm 3-flute cutter which will have less work to do and keep replacement costs down

Although I showed quite a large flycutter in the earlier video my usual weapons of choice are from a set of three which I think have heads of approx 20, 30 and 40mm. the 30 get used the most with 6mm HSS shown here being used as a single point tool to cut moulded profiles and fillets. You can spin these faster than a large one without over speeding the cutting tip so feed as also faster

Edited By JasonB on 18/11/2022 09:22:27

Well done Bernard , you read my thoughts and beat me to it ! Noel.

Well what's a milling machine if it isn't a shaper Bernie the only difference is the cutters rotate

Lovely finish on that example Andrew – is that copper or phosphor bronze?

Nice set up in that last pic too but you have to admit you have a very sturdy machine there with plenty of power to boot for a good cut like that

Tug

Edited By Ramon Wilson on 18/11/2022 11:34:15