Recommended Lathe speed?

Good afternoon,

Could I ask please what others would recommend as the most suitable speed for turning the brass as in the photo below. Its 1" long x 3/4" dia stock turned down to 1/4" as the small end. (The sample in the photo had to be finished with file & abrasive to get it to look that nice)

Tool bit is 1/4" HSS.

Many thanks in advance

Chris.

I'd use 1200rpm, 1700rpm is nearer recommended but the gears in my headstock start to get a bit noisy. Not good when you live in a quiet rural village - even quieter at the moment.

Andrew

The calc I was taught at Long Eaton Government Training Centre in 1975 says 1600 rpm for HSS.

But I'd be unlikely to exceed half that.

My pension doesn't depend on cubic inches per minute metal removal, but the admiration of family and friends does on visual appeal and attractive finish.

A couple of pics for you to print off & keep for ref... ref.Mechanical World Year Book 1975/76

George.

Thank you for your prompt responses guys, that confirms my suspicions as a novice.

Currently my top spindle speed is 675 RPM, my lathe being a 1930's ML1.

Clearly I'm not going to be able to run my lathe with adjustments to anything like that, so I should expect slow cutting progress and rough finish? (that's what I got)

Simplest way to increase speed I think will be to reduce the motor pulley size, something else for my to do list!

Cheers

Chris.

Chris... another ref chart for you ... ref Model Engineer's Handbook by Tubal Cain 2nd edtion.

George.

You might find that has the wrong effect

1000 rpm might be safer for the old girls bearings

Thank you George & Dave, Dave do you mean I need to increase the motor pulley size rather than reduce it?

Cheers

Chris.

Not necessarily, A sharp knife tool with a little bit of top rake, good side and front clearance (say 5-10 deg, it's not an exact matter), a small nose rad and set over to a low plan trail angle, can peel it off with little effort at low speed and leave a fine finish. I use such a tool for 90% of everything, whatever the material. I gather that it's carbide tools that need high speeds for a good finish. I do use those occasionally, but not usually for finishing and hardly at all on materials like brass.

Before speeding up the old girl, As Mick B1 suggested, do try using some positive rake on a really sharp tool.

I think one problem is with all manual control of the tool so it will be imprecise and jerky. I suggest the largest radius you can get like quarter inch radius. Since it is just brass you can use a bit of silver steel if you haven't got an untouched bit of HSS. However you also need the front face, ie looking from above, to be as smooth as the proverbial babies posterior.

Brass is very forgiving, so it should be fine at slower speeds with a commensurate reduction in feedrate. The tool looks like it is quite pointed. Put a nice radius on the end.

Andrew

With a theoretical speed ratio of 1:3 from the 3/4” to the 1/4”, Andrew’s 1700 rpm is not so far off for the average diameter! As others have indicated, either get a speedier lathe or put up with what you have. Raising the lathe’s design speed will only shorten its life - and if it has wear already....

Another point in favour of a suitable speed less than maximum is that, as you know, brass chips go everywhere and I think this will be less of a problem at the lower speed (don't know if a chip shield can be used with your Turnado).

Thanks very much one and all, its great to have several options to try.

Don't worry not done it yet, I was only thinking of raising the speed to what seems to be the max recommended 800 RPM...I do respect my lathes vintage!

ega, I'm just thankful that the chips from the Turnado are just that, turning brass on my faster wood lathe produces splinters that are a real pain in every sense!

Cheers

Chris.

Good morning, Just an update after all the helpful tips earlier about lathe speed/finish on my brass turnings with the Turnado. Speed has remained the same (waiting on a new belt) but larger radius tools sorted my issue out.

I finished the batch of cone finial turnings and just made the pair of handles shown below for my tapping tool.

I was very surprised though that the finish on leaded steel was much better off the tool than on brass.

I think an Acorn nut is next, baby steps!

Thanks once again and stay safe.

Chris.

If, like me, you are under no commercial obligation to remove as much metal in the shortest possible time and are not subject to inspection or examination, then what works for you is the correct optimum speed which you can adjust to best suit the finish you want to achieve and to keep the chatter/noise down. I will, no doubt, be castigated by 'Inspector Meticulous' for expressing such an opinion, but I take the view that my workshop is 'my space'. Whilst I am working in there, there is no 'wrong way' or 'right way' of doing any job, there is only 'my way'. If I was working in a commercial environment I would, quite rightly, be required to work in the most efficient manner and to recognised industry standards, but the fact remains that this does not apply in the home workshop.

Again, and I can almost hear the brickbats heading my way, but in my personal opinion too many people seem to want emulate industrial production standards and textbook working which may be taken as a starting point and guide but adherence to which is sometimes hardly possible in the back shed . Whilst I always seek to produce my best work, I sometimes have to apply a little common sense, ingenuity and guesswork to what I do which for me 95% of the time works perfectly well. My apologies if this view offends some of the purists.

I would try to rig up a hose from a vacuum cleaner while turning brass, I think it is even worse than cast iron.

Chris,

I think we must be in the same club ! Common sense is in short supply [in more fields than one ]

There is a big difference between factory and backyard shed, so, what applies in one, does not apply in the other. Sparey made this plain in his book, Bin the tables and see what works best for you, bearing in mind the equipment you have. This then is the "right" way for you to go.

I am now heading for the shelter before the hostile fire begins !