Surface milling

[Garry ColesParticipant @garrycoles69390]

Hi,

I thought I would mention about a cost saving exercise that I have done.

I have a 50mm dia surface face milling tool which has 4 carbide inserts. These inserts (APMT 1604) are quite expensive (£ 3.50-4.50) each so I experimented with using only 2 of them in apposing positions for balance. It seems to do the milling job the same as with 4 inserts but with a little bit more noise and using a slower feed rate. The finished surface is about the same. I can't see a reason not to do this as a fly cutter has only 1 cutting tool.

Hope this tip is of use of use someone.

Garry

[Garry ColesParticipant @garrycoles69390]

[JasonBModerator @jasonb]

The slower feed rate will mean that each tip cuts the metal more times for the same given spindle speed so you may only be using two inserts but they are cutting twice as much so will wear faster.

For example using some simple numbers. 1000rpm and feed of 400mm/min with a 4 insert cutter gives a chip load of 0.1mm so to cut a 400mm long piece of work each tip cuts 1000 times at 0.1mm each cut.

1000rpm and feed of 200mm/min with just two inserts also gives the same chip load of 0.1mm but to cut that same 400mm piece of work each tip cuts 2000 times at 0.1mm each cut so twice the wear on the two inserts.

[larry phelan 1Participant @larryphelan1]

Perhaps the whole idea of having four cutters is to get the job done faster ?

[Garry ColesParticipant @garrycoles69390]

Okay Jason, I hadn't thought of it that way, perhaps I should go back to using the 4 inserts again.

[Rod RenshawParticipant @rodrenshaw28584]

Jason's post makes perfect sense, but Garry's idea might be useful if for some reason you find yourself with only a few usable tips until the shops open.

Rod

[CirclipParticipant @circlip]

And don't even think of using a fly cutter.

Regards Ian.

[VicParticipant @vic]

Posted by Circlip on 13/11/2020 10:41:37:

And don't even think of using a fly cutter.

Regards Ian.

I use mine a lot, not least because of the great finish and far cheaper to run than buying inserts.

Not so good if you’re a production machinist, although I have seen several guys on YouTube who cut metal for a living using them.

I do actually use an insert in mine for some jobs and you can buy insert type fly cutters.

Flycutter

[JasonBModerator @jasonb]

Yep, I still use my flycutters quite a bit, any specific reason they should not be used Ian?

[Jeff DaymanParticipant @jeffdayman43397]

I have used flycutters for over 30 years now when an excellent finish is needed. This follows from my working with and observing professional diemakers and mouldmakers' practices. If properly set up with correct feeds and speeds superb results are possible on many materials, and an HSS single point tool is cheap as chips. Not arguing with anyone, just stating my experience with flycutters.

Regarding facing heads with multiple inserts, what I have observed over the same period is that they work great in very heavily built toolroom milling machines, but not in lighter home shop machines like my Rong Fu mill. They just shake the hell out of my mill and produce a rubbish finish. The machine is just not rigid enough for them (a flycutter in same mill works beautifully.) I recall the huge Cincinatti roughing mill in the first toolroom I worked in. One job was a long block for a progressive die that needed a 4" wide 1" deep rabbet cut on one side. Toolmaker did the cut with a 6 insert 6" diameter face mill in two Z direction passes, 1/2" deep cuts and about .015" cut per rev per insert. Blue hot chips hitting the tray sounded like machine gun fire. The cuts had an excellent finish. I felt the frame of the machine for vibration, thinking there would be a lot. It was barely detectable. That machine weighed tons and was extremely rigid, which is the name of the game for heavy material removal and cuts.

Your mileage may vary, of course. Just my $0.02 worth.

[Nigel McBurney 1Participant @nigelmcburney1]

I have a couple of industrial quality indexable tip milling cutters,I use them very often with a single insert tip,I use hss flycutters which will produce better finishes ,they are far cheaper and easier to change rake and profile by hand grinding,I even have some expensive artificial diamond insert tips which I used for flycutting ali cylinder heads, they were a gift,its just horses for courses, Though why spend lots of cash on inserts when HSS very often gives better results on the lighter machines used with our hobby. When I started with a ML7& and vertical slide,in the 1960s I did not buy milling cutters ,for all flat faces I used an assortment of home made fly cutters and used worn out hss centre drills as tool bits, and scrounged slot and endmills where slots and grooves were needed,as you progress in engineering, contacts are useful for supplies, and now when I am getting too old,i get more messages "" got a load of tools/ cutters etc do you want them for free" .Redundancy is also beneficial at times lots of usefull stuff can be aquired.

[JasonBModerator @jasonb]

Hobby machines will never be able to drive these insert cutters like a big commercial machine will but if you treat then like a 6 cutter flycutter then they perform well, I doubt Jeff's toolmaker would have taken 1/2" deep cuts with a flycutter in the same machine but if you take say 1mm DOC in aluminium and say 0.5mm in Steel you can get a good finish.

Best thing is as they are carbide inserts you can easily run the spindle at 3 times the speed of the HSS flycutter and feed at 6 times the rate so get the job done 9 times faster than with a flycutter. Does help to have power feed as I can't turn the handle fast enough to keep up when cutting aluminium with the 80mm 6 insert head.

[CirclipParticipant @circlip]

Gary posts what he thinks is a frugal observation to save a couple of inserts which for a MODEL INGINEER seems a good saving on the pocket and then receives a "Tecky" explanation of what he's doing wrong and even though it's a balanced assembly with two cutting faces , I remark, tongue in cheek, the "Folly" of using a single cutting face?

In "Small" Engineering firms, the weapon of choice for removing big lumps would have been a shaper and despite the headlong rush for us Muddlers to try to emulate the latest industrial operations in a shed, I've never seen a multi inserted shaper tool.

As far as production machinists? perhaps we should rename the web site "Model and Production Engineering"

Regards Ian.

[VicParticipant @vic]

Posted by Circlip on 13/11/2020 17:55:48:

Gary posts what he thinks is a frugal observation to save a couple of inserts which for a MODEL INGINEER seems a good saving on the pocket and then receives a "Tecky" explanation of what he's doing wrong and even though it's a balanced assembly with two cutting faces.

Regards Ian.

Yes quite. I had to log out to read that as there are a couple on my ignore member list.

[JasonBModerator @jasonb]

Not sure where I said Gary was doing it wrong, I simply pointed out that it may be a false economy as you will be wearing the few inserts used faster so in the long term will probably not save any money. If you figure in the fact the machine is running longer using more electric, you need to heat and light the workshop for longer and if ordering in batches of two postage will add up it could be seen as even more of a false economy.

Gary also mentions noise, this is partly due to the fact the two inserts are unlikely to both be engaged in the cut which gives intermittent loading on the mills drive train which is probably more likely if there are gears in the head rather than belts but the quill splines will still know about it. With more inserts in the head the machine will run smoother as there is likely to always be at least one insert doing some work

[larry phelan 1Participant @larryphelan1]

Quite right Circlip !

I am a Model and Production Engineer. I produce loads of stuff, but sad to say, no one wants it!

There seems to be no market for junk these days !

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