Lathe speed for different operations

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Lathe speed for different operations

Postby KimBull » Tue May 12, 2015 8:03 pm

My Boxford AUD is now firmly installed and I've started to 'play' with it and have turned a keyless chanter which now needs fine tuning. Drilling the bore true through blanks has achieved mixed results. I know I need to practice, but also wondered if lathe speed is important for the various operations involved in making a set of pipes. Does it matter, and if anyone finds that it might, what speeds do you recommend for the different pipe making tasks?
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Re: Lathe speed for different operations

Postby andymay » Tue May 12, 2015 10:02 pm

Hi Kim,

I used to use a lathe with a choice of 3 fixed speeds and managed ok, but i think the important thing to get a feel for is the relationship between feed - rate of advancing the tool - and spindle speed. If everything is getting hot then (either the tool is blunt or) something's probably going too fast. Heat build-up is generally a bad thing, especially with boring i think. Oiling the bit can help. But boring holes with parrot-nose or D bits is precisely that - boring! I think getting a good accurate first inch or so of the bore is paramount to having any chance of coming out true. Any wander will only be amplified as the bore gets longer!

Now i have a lathe with a big speed knob, which has no numbers on it! But i can tell you i turn faster for wood than brass, slower still for steel, and super-fast for finishing/surface cuts on wood.

Also worth keeping in mind that the surface speed when cutting a large cylinder is faster than with a smaller one for the same spindle speed. And the absolute centre of the piece is i guess almost stationary in theory. I maybe back the speed off a touch for turning something large.

Hopefully someone with more of a head for numbers can chip in with some actual speeds here!!!

Cheers
A
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Re: Lathe speed for different operations

Postby Francis Wood » Wed May 13, 2015 10:17 pm

Hello Kim,

I can't really improve on Andy's advice. And beyond, that there are disadvantages in specifying rpm figures because so much depends on local conditions. My usual advice on this question is probably less than helpful. 'Slower than you think!' is much too vague.

There are just so many variables, one of these being the operator's skill. Then there's the sharpness and shape of the tools to take into account. The shape and rigidity of the workpiece is another factor - an NSP chanter is a pretty whippy thing when it's going round fast, steadied or not. The setup of the lathe in terms of accuracy and lack of vibration will also affect optimal speeds for any given task.

A bit of trial and error will be needed. Ideal speeds will be determined somewhere between the two extremes of 'no cutting' on the one hand and the production of smoke on the other. Start slow, and experiment with faster speeds rather than the other way round.

It's also worth bearing in mind the kind of machines which were originally used to create these instruments. Great success was achieved with modest means and limited speed. A typical early 19C lathe is visible here and this (probably without the 3 jaw chuck), is close to what would have been used in the Reid workshop. That's not to suggest that we shouldn't improve our facilities to reflect current technologies:

http://www.laclasseloeuvre.culturecommu ... s-a-vents/

Have a look, too, at the virtual tour of this wonderful French museum which contains so much of interest for anyone reproducing wind instruments of the 18th and early 19th centuries:

http://www.hdmedia.fr/visite-virtuelle/ ... -vent.html

Francis
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Re: Lathe speed for different operations

Postby KimBull » Mon May 18, 2015 8:29 am

Hi Francis and Andy, thanks for the advice. It's really useful to know (and re-assuring) that a strategy of 'slow and experiment' is fine! I've now roughed out a 7 key blank too, so things are progressing nicely!

Love the little virtual museum Francis, but just ended up on a page with text (in French) via the first link, so couldn't see the early lathe you refer to which is a shame.
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Re: Lathe speed for different operations

Postby pipemakermike » Sun May 31, 2015 1:19 pm

The only thing that is important and then only if you are trying to save time or are producing a lot of parts is the surface speed where the tool is working. All the charts I have used have this at the root. For us, we can cope with a wide range of speeds as we are not in a hurry<G>. A more important thing is to use sharp tools with an appropriate shape at the cutting edge.
The top rake of the tool (the angle of the top face of the tool) is important. For aluminium and wood I use a greater angle (30°) than I use for steel (20°) and for brass the top of the tool should be flat. here are a couple of pictures.

cutting tool rake2.jpg
cutting tool rake2.jpg (58.21 KiB) Viewed 2487 times
cutting tool rake1.jpg
cutting tool rake1.jpg (90.54 KiB) Viewed 2487 times
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Re: Lathe speed for different operations

Postby KimBull » Sat Jun 06, 2015 10:57 am

Thanks Mike, that's very useful.

I seem to have more success boring true with higher speeds (nearer 1000rpm) rather than lower (c150rpm), but this does generate a lot more heat and even slightly charred swarf. I haven't made enough to know whether there's a correlation between lathe speed and accuracy yet, or to bore enough at all the speeds in between to check results.

Leaving cutting speed aside, has anyone noticed a correlation between lathe speed and bore accuracy? (Even a 'no' would be useful as I can then focus on other areas).

In Mikes plans about 600rpm is recommended for boring.

Thanks for all your help.
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