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Post by Roger on Feb 3, 2020 9:42:41 GMT
I have been very lucky with neighbours in the 14 years we've been here. Never had trouble with or from any of them. My machines aren't too intrusive from outside the new workshop unless I'm really hammering something with an interrupted cut etc. The compressor is probably the worst otherwise and it's just a murmur from outside (although a right clattering from the inside). A pedant would tell you that you're using completely the wrong insert for Brass, all the wrong angles and the edge being too easily chipped... but... what works is all that matters! I'm no machinist (obv) and don't even pretend to be one on YouTube, but I think the shiny Alu ones are "correct" for brass etc, given the info in the chart I downloaded. It has these letters on it which calls them ISO colour codes and it gives: P (blue) = Steel other than rustproof austenitic M (yellow) = Stainless & austenitic K (red) = Cast iron N (light blue on my packets, green on the chart) = Alu, non-ferris, non-metal S (orange on my packets, brown on the chart) = High temp alloys or other hard stuff eg nickel, cobalt, titanium alloys H (grey) = Hardened steel, hardened or chilled cast iron. N looks like the only one for brass etc. My steel ones are marked as cutting conditions "P" and my shiny alu ones are marked cutting conditions "N". That's interesting because all of the 'Old school' books will definitely show a very shallow top rake for Brass to encourage the brittle material to shear, whereas for Aluminium they will show you a steep top rake to peel off the material. They're very different cutting actions. However, that's from a bygone age, even though it's what you'll find in all the ME literature. Just because it's obsolete, doesn't stop ME from carrying on using it, witness ME threads and BA sizes! In years gone by, they didn't have Free Cutting materials that break up into chips, so the picture today is somewhat different. If Aluminium alloys will chip, then I guess there's no reason why you can't have less top rake, and that would make the insert more versatile. Who knows, the main thing is not to be driven by dogma, but to try things for yourself and find what works. ME is still in the dark ages because people as still using the old ME methods in ancient texts without questioning them. Things have moved on a lot on the past 50 years since most of them were written. |
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Post by David on Feb 3, 2020 10:10:06 GMT
The inserts look to have pretty severe top rake to me. I assumed the sharpness and smoothness were what made them work for brass, but that they'd be too delicate for steel. Still, I have no idea except that they work and N seems to be marked for anything softer than mild steel.
All the brass rod I have must be free-cutting because it certainly comes off in chips, rarely strings. I only have one or two bits of aluminium but it didn't seem to be free-cutting in the same sense. It was soft but gummy. The inserts have to be razor sharp to get a decent finish.
The trick is finding inserts marked anything other than "P" on eBay. I've not yet found "N" or "K" which I'd like. I had to get the "N" ones from Tormach.
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Post by Roger on Feb 3, 2020 13:34:19 GMT
The inserts look to have pretty severe top rake to me. I assumed the sharpness and smoothness were what made them work for brass, but that they'd be too delicate for steel. Still, I have no idea except that they work and N seems to be marked for anything softer than mild steel. All the brass rod I have must be free-cutting because it certainly comes off in chips, rarely strings. I only have one or two bits of aluminium but it didn't seem to be free-cutting in the same sense. It was soft but gummy. The inserts have to be razor sharp to get a decent finish. The trick is finding inserts marked anything other than "P" on eBay. I've not yet found "N" or "K" which I'd like. I had to get the "N" ones from Tormach. I use those Aluminium inserts for PB102 and Stainless Steel, they produce a superb finish. It's almost impossible to get Brass to come off in strings, regardless of any angles because it's so Brittle. It sounds like the Aluminium you had was pure Aluminium, not Aluminium alloy which is what we normally just call Aluminium when it comes to bar stock. If you search eBay for 'Polished Aluminium Insert' you might find some. That does return results for the UK site. You could always do that on the UK site and then find out what the order code is for a direct search on your local eBay. I try to use the most vague key words for searching so as to find as many as possible though. |
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jasonb
Elder Statesman
Posts: 1,188
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Post by jasonb on Feb 3, 2020 18:51:25 GMT
I also use the **GT inserts on brass and bronze as well as the usual Aluminium they are suggested for, also work well on wood. Likewise high helix angle milling cutters sold for aluminium are also good for the other non ferrous metals
As for not getting brass swarf to come off in anything other than chips have a look at the end of this video
I've not found the insert milling cutter that I mentioned earlier (25mm) to be much noisier than a solid cutter even when maxed out a 5000rpm. Some of the very cheap milling inserts can be rather blunt and cause noise and vibration but the mid range and name brand ones that I have used don't seem to suffer or make the mill suffer.
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Post by Roger on Feb 3, 2020 19:42:13 GMT
As for not getting brass swarf to come off in anything other than chips have a look at the end of this video I didn't say it wasn't possible, I've done it myself. However, the expectation is that it's going to be chips almost all of the time unless you happen upon the sweet spot where this happens. It would be very misleading to suggest that it was otherwise. |
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Post by David on Feb 3, 2020 21:45:38 GMT
I can get brass to come off in spirals sometimes. But I thought the point of free-cutting materials was to form small chips to take the heat away immediately so strings were not what was wanted.
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Post by Roger on Feb 3, 2020 22:43:26 GMT
I can get brass to come off in spirals sometimes. But I thought the point of free-cutting materials was to form small chips to take the heat away immediately so strings were not what was wanted. That's what they're aiming for. Free cutting materials don't usually make long stringers, and even if Brass does, they're so brittle they will probably never wrap firmly enough around the job to cause issues. A lot of inserts have chip breakers ground into them to help break up the swarf into chips as it comes off. You have to remember that commercially, they remove material at much greater rates than we do, and they can optimise their feeds and speed to guarantee you break up the chips. In a commercial environment, you'll call in the Insert suppliers and get them to find the best one for the job. For the most part, we use what will do the job, and sometimes that means you won't get the ideal result. |
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