What's a decent cut for a 9x20 import?

[Ulma Doctor]

I hate 300 series stainless....

303 is very machineable , even with HSS tooling
302 and 304 not as fun to play with, as they work harden easily
416 is also very machineable with HSS
But other 400 series not so much

IMHO,
For smaller lathes 12L14, 1214,1215, 1018, 303, 416 and 1144 are adequate steels for most things , and still workable on lighter machines.

 

[RaisedByWolves]

Sounds like you have an add on boring bar . Are your numbers above reversed ?

I was going to break his balls about this.

You run the lathe in reverse and sprinkle the chips over the boring bar.

 

[durableoreo]

No way of knowing that without knowing motor torque and drive reduction.

That SB may have had a 1hp motor, ditch the calculator.

If I understand it, gearing only changes the speed of rotation, not the power.

 

[durableoreo]

So far,

• 0.020 deep x 0.005 in/rev in 4140, 520 SFM (OP)
• 0.125 in unspecified material (SB sales literature)
• 0.025 in steel? (ARC-170)
• 0.031 in free cutting steel (benmychree)
• more than 0.015 (RaisedByWolves)
• 0.030 deep x 0.030 in/rev in 4140, unspecified diameter or SFM (verbotenwhisky)
• 0.020 in aluminum on 7x16 (GrifterGuru)

 

[durableoreo]

Sounds like you have an add on boring bar . Are your numbers above reversed ?

I'm not sure I understand the question. Diameter and depth? The bore is definately 2.1" diameter and 0.813" deep.

 

[David2011]

If I understand it, gearing only changes the speed of rotation, not the power.

As with any transmission, gearing down increases power as the output speed is reduced. Reducing speed electronically also reduces power without some advanced circuitry to manage torque.

 

[mmcmdl]

I was going to break his balls about this.

You run the lathe in reverse and sprinkle the chips over the boring bar.

I'm not sure I understand the question. Diameter and depth? The bore is definately 2.1" diameter and 0.813" deep.

Ahhhh ........................... The words had me mixed up . The depth was not mentioned . I figured you had one of those un-obtainium add on bars .

 

[verbotenwhisky]

So far,

• 0.020 deep x 0.005 in/rev in 4140, 520 SFM (OP)
• 0.125 in unspecified material (SB sales literature)
• 0.025 in steel? (ARC-170)
• 0.031 in free cutting steel (benmychree)
• more than 0.015 (RaisedByWolves)
• 0.030 deep x 0.030 in/rev in 4140, unspecified diameter or SFM (verbotenwhisky)
• 0.020 in aluminum on 7x16 (GrifterGuru)

Its not just about depth and feed, its also speed/RPM and if I understood you correctly your running 1000 RPM where I run 550 to 700 Max. David2011, pointed out, rightly, the difference between gearing and electronic speed control and I am running a PM1236 geared lathe which at 550 RPM has very high torque.

 

[RaisedByWolves]

If I understand it, gearing only changes the speed of rotation, not the power.

You don't understand it.

Gearing, belts/sheaves multiply power. A reduction of RPM results in an increase of torque.

This is a 5" Prazi lathe taking a .060 cut in O-1 tool steel.

Granted the boring bar is limiting the rigidty of your setup, but if you slow things down and set your feed right there's no reason you couldn't take a .030 roughing cut.

Personally I would run that setup at 200-350rpm.

 

[David2011]

Very impressive for a 5" lathe!