Face mill decission

[Chris MateParticipant @chrismate31303]

Hi, I am so happy with a 40mm Walter shoulder mill with 6 inserts, that I want a face mill of the same nature maybe 7-8 inserts, however the inserts will not be the same between face and shoulder mill.

Thinking about it, why should I not just buy another larger 70-80mm shoulder mill(Called shell mill by some I think) instead, if It could use the same inserts than the 40mm, to limit the amount of different inserts to cope with-?
I tried the 40mm shoulder mill as a face mill on large flat aluminium plate, and it seems good, just too many passes.

Edited By Chris Mate on 17/09/2022 00:44:08

[Chris MateParticipant @chrismate31303]

Larger shoulder mill or face mill(Inserts)

[David George 1Participant @davidgeorge1]

What mill are you wanting using the large face mill on and what material are you cutting on it as it us easy to overload a small mill. It is possible to use a fly cutter to get a nice finnish with less load.

David

[Martin ConnellyParticipant @martinconnelly55370]

Something to consider is how fast you want to remove material. An 8 insert face mill removes material 8 times faster than a fly cutter. If time is not an issue a sturdy fly cutter set to Ø80 will do the same job as an Ø80 shoulder mill but just take 8 times longer. You did not say why you want to reduce the number of passes so maybe it is to save time.

Another consideration though is that the larger the shoulder mill or fly cutter diameter being used the more it will magnify any slight errors in tram. Any tram error will lead to some scalloping in the surface. This is hardly noticeable with small diameters but becomes evident at large diameters.

Martin C

[JasonBModerator @jasonb]

The face mill will remove metal a lot faster than in martin's example as the carbide allows for a higher surface speed than the typical HSS flycutter so you can multiply that 8 times faster by a factor of three so in total that is 24 times faster

It will also tend to have more than one insert cutting at any one time so will be a lot smoother running than a flycutter and is better balanced at my top speed of 2000rpm.

I use an 80mm six insert shell one on aluminium and that works fine on the X3 and SX2.7

[Martin ConnellyParticipant @martinconnelly55370]

Jason, you are assuming I am talking about HSS flycutters, I often (can't say always) use carbide inserts in mine.

Martin C

[old martParticipant @oldmart]

Be careful, getting one is one thing, but are the inserts proprietry? If so the prices and availability will be high and difficult.

[Chris MateParticipant @chrismate31303]

Thanks for advice, its 2HP motor, it came with cheap 80mm 4x brased inserts facemill, mainly aliminium.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris Mate on 19/09/2022 23:31:03:

Thanks for advice, its 2HP motor, it came with cheap 80mm 4x brased inserts facemill, mainly aliminium.

Not just a matter of rpm and cutting points, the machine has to have the power and rigidity needed to push several cutters through metal. Reductio ad absurdum, a 100 toothed face cutter would stall most machines!

Adding more cutting points to an underpowered weedy mill won't cut metal faster if the operator has to back off to avoid overheating the motor, bending the frame, or thrashing the drive train and bearings.

A 2HP motor is a good start though. Rule of thumb, 1 HP will remove about 1 cubic inch of mild-steel per minute, and if the machine can sustain that, more teeth should help especially as Aluminium is easier to cut than steel.

Can you report back? On your mill does a 6 or 8 toothed face-mill remove metal faster than a 4 toothed? It may be it removes metal at the same speed but gets a better finish or does something else useful. Or results might be inferior, or equivalent. Hard to predict I think.

Dave

[JasonBModerator @jasonb]

fairly easy to predict, an 8 insert cutter will remove metal at twice the rate of a 4 insert one of the same diameter for the same given chip load and give the same finish.

You could feed at the same rate as the 4 insert one and get a finer finish in the same time using the 8 insert as the chip load would be halved.

We seldom push our cutters to the max as far as DOC and chip load goes so the 2HP motored machine will be OK, the SX2.7 is happy cutting with an 80mm one and that is only 1HP

[VicParticipant @vic]

For what I do it’s hard to justify the ongoing costs of inserts. I’d be interested to know what sort of depth of cut you can get on a modest machine with a face mill – mine is 1.5HP. I often use HSS in my flycutter but I do make use of round carbide inserts for some jobs.

[JasonBModerator @jasonb]

Depends somewhat on the width of the part but if it's most of the 80mm then I'll take 1mm DOC on aluminium with the 80mm one running and feeding fast and the SX2.7 and X3 don't miss a beat but have used upto 6mm Ap (vertical depth of cut)

So far I'm still on the same inserts and same cutting edge as when Ketan sent them to me to review and no sign of them going off yet and that was almost 3 years ago

This video I did to go with the review in MEW gives some idea of feeds, speeds and DOC, probably push them a bit harder now that I have got used to what they can do.

[JellyParticipant @jelly]

Posted by old mart on 17/09/2022 18:46:38:

Be careful, getting one is one thing, but are the inserts proprietry? If so the prices and availability will be high and difficult.

Prices can indeed be very high!

I bought a mixed lot of insertable tooling in an auction some time ago… Everything else took more or less standard inserts, but I recently went to order a set of 10 inserts for the face mill (a Sandvik Coromill 360), and it's £274 per set!

Unless anyone has a set of ten 360L-1906M-MH or 360L-2807M-MH inserts they have no use for kicking about, I think I'll have to go part-ex the face mill for something more affordable.

[Anonymous]

See this link for what can be achieved on a medium size milling machine with a face mill:

Face Milling

The tests were done with depths of cut at the maximum recommended and a chip load set by the maximum the milling machine could achieve. Finishes were excellent on aluminium and steel at around one micron Ra.

On the Bridgeport I run a 50mm, 5 insert, face mill. On low carbon steel normally run at 800rpm and ~400mm/min feed and maximum DOC of 1mm without stalling the mill. Converting to imperial that equates to about 1.3 cubic inches per minute. That is about right as the Bridgeport has a 1.5hp motor, but with a varispeed head, which I suspect isn't overly efficient.

Andrew

[BufferParticipant @buffer]

SOD makes a good point when people are talking about moving metal 8 times faster or 24 times faster. I couldn’t possibly do that. I bought a 5 insert cutter from arc just like the one in the picture above and I can’t drive it fast at all in a Tom Senior M1. The vertical head will slow right down if I try to crank the depth of cut up a bit or the feed speed. Maybe my motor isn’t working as well as it should or I don’t have it set on the right pulleys for the variable speed 3 phase gizmo to get the best out of the motor or the motor just isn’t big enough. I can’t see what power it is at the moment as I’m in bed for an early start tomorrow. I have the pulleys set on the middle size for the motor and the spindle. Does anyone have any ideas?  It does give a lovely finish though so it was worth getting.

 

Edited By Buffer on 20/09/2022 21:36:07

Edited By Buffer on 20/09/2022 21:37:17

[JasonBModerator @jasonb]

Buffer, most of that increase is due to the number of teeth not the rpm, only the 3 x faster is due to being able to run carbide faster than HSS which many (but not all) use as the tool bit in a flycutter.

Without knowing what you are cranking up from in terms of DOC and feed or material it is hard to say what you should be running at.

I'm not sure what you bought as Andrew says 5insert 50mm but ARC only do the 5 insert in 63mm dia but taking the 5 insert as 63mm gives a circumference of just shy of 200mm.

If we said mild steel can be cut at 100m/min then dividing that by 0.2 gives a speed of 500rpm.

I would set the belting to give as close to that as you can with the motor running at normal speed eg 50hz

TS is a lighter machine than Andrews and more like my X3 so try 0.5mm DOC on mild steel and a lower chip load so feed of 100mm/min to start with and increase feed if machine is happy.

[Anonymous]

It's always good to start at the beginning. So the first thing to assess is the motor. What type of motor is it, and what nominal horsepower? How is the motor driven – VFD, static converter or something else?

Andrew

[JasonBModerator @jasonb]

I assumed by "variable speed 3 phase gizmo" it was a VFD but best to get it confirmed.

[BufferParticipant @buffer]

Hi guys I’m still at work so can’t check anything except a quick peek at this. Yes it’s one of those little Mitsubishi boxes on the wall with a pendant controlling a 220v three phase motor. I’ll check all the details when I get back home.
thanks

[BufferParticipant @buffer]

I've had a look and it's a pretty pathetic 370w motor which I think is 1/2 hp. It's a dual voltage three phase motor and it's being driven by a Newton tesla inverter with a control pendant. I suppose that's why it's slowing down. The motor for the horizontal part of the mill is 750w but I don't use that.

It's interesting saying set the pulleys to run as close to normal speed at 50hz. I'm not sure how I can do that as I can only run it with the inverter and the pendant varies the speed so its hard to know what the normal speed should be.

Thanks for all the advice though it's definitely appreciated

[JasonBModerator @jasonb]

A quick look on Lathes.co.uk seems to suggest the S type head which has the separate motor had four speeds from 500 to 2800 approx.

So to give the motor the best mechanical advantage it would be best to select the slowest belt ratio eg smallest motor pulley and biggest on the spindle. Not sure how the pendant is set up or if the VFD has a read out but assuming the motor is the same speed as original then running it at 50hz should more or less give the 500rpm.

Edited By JasonB on 21/09/2022 18:23:52

[BufferParticipant @buffer]

OK thanks for that. I'm on days off now so will give it a go tomorrow and might try the same depth of cut with different pulley settings and see how much difference it makes. Thanks again for your time.

[Martin ConnellyParticipant @martinconnelly55370]

Buffer, if you haven't done so already make sure the dual voltage motor is set up for 230V (delta) for the best performance from the inverter if the inverter is like most VFDs and running off 230V mains and outputting 230V 3 phase.

Martin C

[Anonymous]

I'd be surprised if the VFD didn't have a display that could be used to display frequency or rpm. For constant power from the motor the output frequency should be 50Hz or higher. I assume that the VFD was set up by Newton Tesla so that the motor parameters and values are correct for the motor? It would be much better to leave the VFD on 50Hz and change the belt drive to change speed.

Unfortunately a 1/2hp motor probably doesn't really have the grunt to make proper use of a 5-insert face mill. I'd stick with ordinary endmills.

Andrew

[Chris MateParticipant @chrismate31303]

I think a good measure would be to measure the amps(220V) the motor draws as its loading up. I have done that in my lathe experimenting with oil thickness and it was interesting as well as higher speeds through a gearbox, this can easily be seen. As the speed gets higher it draws more current just to pull the gearbox with no load applied externally like cutting. For example in my lathe gearbox 90 oil will burn out the motor quickly in higer gears.

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