Face mill size

I've been thinking of getting a face mill for some time, as squaring up stock with a 10mm end mill gets a bit tedious. I'm intending on buying some lathe tooling from Glanze, and am tempted by their MT3 face mill with 3 x TPAN inserts.

What size is appropriate? I assume that bigger is better in that you need less passes to cover a surface, but at some point the mill can't cope.

My mill is a Sieg SX3 (1kW motor). Will this cope with the 50mm face mill, or should I go for something smaller?

Personally I would go for a smaller face mill perhaps a 25mm one and a fly cutter to finnish larger areas. Don't stress the mill too much.

David

Thanks David, I have a (cheap) fly cutter with hss and brazed carbide cutters, and it works wonderfully cutting acetal, but as soon as I've tried it on stainless I chip the cutter. This might have more to do with me or the quality of the tool rather than fly-cutters in general, but it lead me to look at other options for face-milling stainless.

I'm pondering how the size of face mill affects the load on the machine. I presume that it's a function of the number of teeth in contact with the work, and the speed of which you are pushing them. Does this change with a larger face mill? The number of teeth is the same, and you can slow down the mill so that the surface speed of cutter is the same.

On the the hand, with a larger face mill, the teeth are further away from axis of rotation, and this might result in more sideways loading on the bearings. Is this the stress you are referring to?

Jed

A larger face mill means more contact with the work, and thus you are trying to remove more metal. Simple as that.

Hi Jed,

I have a 30mm diameter Glanze with 3 inserts and it works well on my milling machine that is slightly smaller than your SX3. I also have a 63mm facemill and both facemills work OK on my milling machine, depth of cut is of course limited when using the largest so your SX3 should not have any problems with a 50mm facemill. Just remember to use quality inserts.

Thor

I have a similar sized mill but not the same make as yours. I use the face mill cutter to rough out you can use a higher RPM with a tipped face mill, but watch the swarf, and I have a home made fly cutter which is donkeys years old with a solid piece of carbide to give me a nice Finnish cut.

Fly cutter

Have you got a bench grinder as a green grit wheel will sharpen carbide tooling and you need a small radius to avoid the tip shattering.

David

Edited By David George 1 on 22/07/2019 11:36:52

This sort of question makes my head hurt because there are so many factors but:

• More teeth allow more metal to be removed per pass, BUT
• The motor has to be powerful enough to drive all the teeth through the metal, AND
• The mill has to be rigid enough to take the extra stress. Although it might damage the bearings, more likely it will vibrate and spoil the finish or worse, dig-ins, worn gears etc. ALSO
• The speed of the teeth over the surface depends on face mill diameter and it increases relative to spindle speed. This requires the motor to produce more torque, which could be a problem if the cutting speed requires the motor to operate at a poor rpm/torque combination.

On a hobby mill, I think lack of rigidity will be the most obvious restriction but you would also have to keep an eye on the temperature of the motor. One major difference between a hobby machine and it's industrial equivalent is how long the motor can deliver full power without overheating. Bottom line, working a hobby machine hard for too long risks wrecking the motor, even if the cutter is removing metal correctly.

Fly cutters are pretty safe because there's only one tooth and it's hard to overdo them. With a modicum of care I don't see why a small diameter 3 toothed cutter shouldn't be used on a hobby mill, but the more teeth and bigger the diameter, the more likely it will be too big for the machine. My little car could tow a trailer to the tip and back, but it would be a rotten choice pulling a big caravan on a family holiday around Europe!

Dave

I have a Sieg SX2P mill and the largest cutter I use is a 50mm dia. face mill that has 4 APKT 1604 inserts. I don't use the full diameter of the cutter, a maximum for 30mm, usually a lot less with a modest depth of cut. I do keep a check on the temperature of the motor for my own peace of mind, but it has never got beyond the warm stage.

Sandvik Coromant in their Training Handbook recommend a 2/3rds rule for cutter engagement.

**LINK**

It's a slow download but informative.

As regards machining stainless steel, depending on the grade of stainless, the inserts should machine it without a problem. I have used my cutter on an unknown grade of stainless and I did not have a problem.

As the others have said, don't overload the machine and you should be OK.

Neil

I've got a 40MM 3-tip TPAN one from Glanze that works OK on my X3.

Also got a 50mm 4-top one that takes ADKT inserts, OK once decent inserts were fitted though it does not quite cut square upto and edge if you need that option.

TPAN is very old technology, the numerous adverts for 50mm shell mills using four APKT16 are a better bet. Inserts for steel and aluminium are available from the cheapest Chinese, to premium makes. The Chinese inserts are pretty good these days.

Here is one of many on ebay UK. 1630941344584

Thanks for the replies chaps, there's some great info and food for thought in there.

Neil's point is a good one - there's no requirement to engage the full face of the cutter, so even if the mill is struggling in some situations, the depth of cut and degree of engagement can be backed off.

I'll look in detail at the APKT insert mills, the inserts certainly appear to be a lot more sophisticated than the TPAN ones.

I'll also persist with the fly cutter, given the favourable opinions. David - I assume your reference to a "small radius" means taking off the sharp point of the cutter, which I guess reduces the chances of it chipping. I do have a bench grinder of unknown provenance - the previous owner of my house left it behind when he moved, but I have hardly used it. It runs smoothly and quietly, but the guides and guards are shot and will need some work.

What is the best source of carbide to mount in the fly cutter? Can you buy "blanks", or is it easy enough to grind down the ends of broken end mills or drills?

With one of those 50mm shell mills, you can get away with removing 2 or even 3 of the tips and still use it. A 1kw motor is nearly 1 1/2 hp, which will cope with 80mm shell mills, you don't have to take huge cuts every time.

Edited By old mart on 23/07/2019 15:11:38