Myford ML7 for turning Aluminium

[Curtis RutterParticipant @curtisrutter61973]

been looking at a myford ml7 lathe. Doing some research seems that you need high rpm for turning aluminium. The myford ML7 doesn't seem to go above 8/900 rpm, will it be any good for turning aluminium?

[Curtis RutterParticipant @curtisrutter61973]

[mick70Participant @mick70]

i regularly turn it on the myford at the club.

never had a prob.

[Neil WyattModerator @neilwyatt]

It's just a case of matching feeds and cuts to the material.

Neil

[Michael Bird 1Participant @michaelbird1]

Well I have a Myford ML7 and it turns aluminium really well and gives a fantastic finish.

[Brian OldfordParticipant @brianoldford70365]

Some aluminium alloys will want to weld themselves to the tool tip. If this occurs try a very light lubricant such as paraffin.

[JAParticipant @ja]

I never cut anything at speeds above 800rpm including brass and aluminium. I use home ground high speed steel tools and neat cutting oil when required. The biggest problem with aluminium is the stuff used for castings. Otherwise I don't have problems with ordinary engineering materials other than PTFE.

JA

[Curtis RutterParticipant @curtisrutter61973]

Thanks all. Good to hear, will continue bidding on the one on eBay and fingers crossed I'll be the owner of one soon!

[Curtis RutterParticipant @curtisrutter61973]

Posted by Neil Wyatt on 04/11/2016 18:44:59:

It's just a case of matching feeds and cuts to the material.

Neil

Sorry but complete newbie! By feed do you mean how much and what distance and speed you move the cutting arm into the material?

[Neil LickfoldParticipant @neillickfold44316]

You don't need high surface speeds to get a good finish with ali.

I only run my Myford in the low range of the motor to the top pulley. I think my fastest speed is in the 600-700 rpm range. Sharp tools is really important and then finding a lubricant that reduces or prevents the ali sticking to the turning tools. Lately I have been using Rice bran oil and seems to be really good. Just make sure you clean up afterwards though. I cheat these days and use the Ali/ plastic turning inserts for most things even on bearing steels.

Have fun and learn what you can. With Ali and plastics and woods, you can not have the tool too sharp, but at the same time, don't make the angles too steep on the top rake if you are grinding your own HSS tools. Honing or polishing the top surface with a Cratex or some other polishing tool before you grind the side clearances is a good thing to do as well. But I now mostly use the nice carbides but that was if you are grinding your own tools.

Neil

[MikeParticipant @mike89748]

I've done a lot of aluminium turning on an ML7R and a Super 7, and I've never used very high speeds – as Neil says, in the 600-700 rpm range. I've always used HSS tools ground with a lot more top rake than you would use for steel, although not so steep as to make the tool tip fragile. and with paraffin as a lubricant. Although it's never happened to me, I've always thought there might be a fire risk with paraffin, so I like Neil's idea of using rice bran oil, which I see has quite a high smoke point and, I would hope, not such a nasty smell as paraffin.

[Neil WyattModerator @neilwyatt]

Posted by Curtis Rutter on 04/11/2016 21:54:06:

Posted by Neil Wyatt on 04/11/2016 18:44:59:

It's just a case of matching feeds and cuts to the material.

Neil

Sorry but complete newbie! By feed do you mean how much and what distance and speed you move the cutting arm into the material?

Feed is the rate the tool moves at and 'cut' is shorthand for the depth of cut.

Neil

[Ian S CParticipant @iansc]

The real reason for the very high speeds is for use in industry where speed is money. If you have a suitable lathe, and like the aluminium swarfe flying all over, go for it.

Ian S C

[SillyOldDufferModerator @sillyoldduffer]

Earlier this week I turned some Aluminium down at 360 rpm because the lathe happened to be set up for threading and I couldn't be bothered to change a belt. Even at that low speed there was no problem at all.

Some materials are sensitive to speed, tool shape and tool material. I find HSS tooling at moderate speeds gives good results provided it's sharp. Most of the speed cutting advice about is aimed at maximising factory efficiency and is faster than needed for ordinary work. It's best to experiment. Likewise depth of cut. After a bit of practice you get a feel for what's reasonable. I would suggest starting with light cuts (say 0.1mm / 2 thou) and working up. Apart from brass and cast-iron lubrication is good: I mostly use CT90 Tapping and Cutting fluid because I'm lazy. Others are more sophisticated!

The only problem with a maximum speed of 900 rpm is that carbide inserts won't shine at that speed. Carbide is capable of outperforming HSS by a mile but needs to be driven fast to do it. Much depends on what you want the lathe for but many people on this forum do excellent work entirely with HSS and prefer it.

Dave

[Curtis RutterParticipant @curtisrutter61973]

It's mainly a starter lathe to see how I get on and to make parts for my race bike such as wheel spacers and fairing mounts & foot pegs. Once I get the hang of it I like the idea of model engine making.

[LynneParticipant @lynne]

Curtis, I have sent you a private message . Lynne

[Neil LickfoldParticipant @neillickfold44316]

If for what ever reason the part does not shine, you can use white or grey fine scotch brite to polish the parts while making almost negligible change in size. There is also wiper inserts for turning as well, these effectively burnish the part as it is being cut to both improve surface finish and allows higher than normal feed rates. Depending on the part profile etc, you can make simple wood Vee blocks, and use double sided tape to hold various grit paper to polish and keep the part round. Like starting with 400 grit then 800 etc to 1200 or 2000 paper. The grey scotch brite is like about 800 paper or so ,the white is like 1500-2000 paper or so.

Neil

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