As to speed, you can turn brass faster.

On our sizes of lathe, typical speeds and depth of cut really sharp trumps correct to book angle every time. In practice it seems to be harder for a neophyte to get a really sharp edge with shallower angles. Especially if finishing off by hand honing. Until you get the feel its dreadfully easy to take the sharpness off by tilting the abrasive stick or diamond hone a fraction at the end of the stroke. A degree or so on 55° probably won't make a huge difference. But on 2° most of the edge will be gone. Easier to hold against 55° than 2° too.

Book angles are derived from industrial and toolroom practice to give a good balance between tool life, rate of cut, ease of cut and protection from things like built up edges, mile long swarf rats nests and so on. For small lathe users generally whatever works works. But don't get caught faffing around with mini cuts. Should be able to take material off at something approaching book rate for the motor power. Although those of use with industrial size lathes usually don't exploit the power because its such a pain handling scarf that thick coming off that fast.

You should use the correct speed for the materials in question. Brass in particular is a proper speed demon and you probably won't be able to go fast enough with small diameters. But, as you have found, it responds well to a sharp tool.

Clive.

Edited By Clive Foster on 13/08/2018 17:18:40

X2 Larry!

What Clive said, and Larry too. And I discovered ages ago that whatever angle you quote from a book, there's another book which gives a different angle.

George

Andrew

Squeak, squeak. A piece of cheese would be really nice. Squeak, squeak.

Can do the hefty cuts'n red hot swarf thing. Have done it. But rarely need to. Generally on my work the gain from saving a couple or three passes isn't worth the candle when I can come straight down to size on normal cuts without having to bother with fine finishing cuts. Or correct for really hot work measuring oversize. Given the chance 50 thou / 1 mm is a finishing cut to me.

Clive

PS Shouldn't that have been "Squeak for yourself" not "Speak for yourself"

Edited By Clive Foster on 13/08/2018 20:09:17

I use Sparey's standard knife tool geometry for both steel and brass/bronze. Works for me on these small (Myford/Drummond) lathes.

I like hot chips,but not when they,re heading for me at a rate of knots.

I like cheese too,much easier to cope with !

While these removal rates are impressive,and may be required in industrial situations,I doubt if they would show up often in the hobby world.

Sparey mentioned in his book,while talking about HSS, that Armstrong Whitworth removed swarf 1 1/4" wide x 1/4" thick at a rate of 32ft per minute ! Makes no mention of how hot it was,but I doubt if anyone was standing in the line of fire. Perhaps had they used carbide tools,they might have been to produce 2 x 1/2" flat BMS.

There are times when I produce deep cuts,mostly when I dont want them ! Has anyone else been there,done that ?

Mostly, chipped CCMT0604 bits are used with the unused 100 degree corners for roughing. (Andrew would like the blue stuff coming off). Hundred thou cuts can make it chatter.

The original tips are used in a Boring bar. So the angles are already chosen. For most of the other straightforward turning, the Diamond (Tangential ) tool is used. Freshly sharpened, (Boasting!) it will take a cut of 0.0005 inch, or much greater. With a 1/4 toolbit have never exceeded a 0.050" cut.

The HSS parting tool, ( Secondhand when I got it, at least thirty years ago, and still nowhere near worn out)   is inverted in the rear toolpost has zero top rake, and gives few problems.

On the RF25 Mill/Drill with HSS cutters, rarely exceed 0.050" depth of cut.

So am looking for fresh types of cheese.

Howard

Edited By Howard Lewis on 14/08/2018 14:16:14