Stopping Unwanted Ribbons of Swarf?

[SillyOldDufferModerator @sillyoldduffer]

Posted by Hopper on 29/05/2017 09:11:15:

Posted by SillyOldDuffer on 28/05/2017 15:28:58:

Posted by Hopper on 28/05/2017 12:15:02:

…

What is that material you are turning in the pics? If it is steel, is it some kind of galvo pipe? Probably never get it to machine nicely. Pipe making does weird stuff to steel and it never ends well for doing much other than conveying liquids.

It's some sort of stainless steel pipe with a welded seam. I found in the gutter and originally thought it was galvanised. However, a short piece of it has been outside for a good twenty years without going rusty on the cut ends. It's neither good nor awful to machine and the weld doesn't interfere. I get a better finish on it with hard fast cuts than slow shallow ones. If I knew what it was, I wouldn't recommend it!

Dave

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Johnston on 29/05/2017 08:57:59:

Posted by SillyOldDuffer on 28/05/2017 21:24:06:

My lathe only has a 1500W motor. Using the calculator, I worked out that the maximum DOC I should attempt in steel with 1200 rpm feeding at 0.14mm per revolution is about 1.4mm.

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So it seems possible that the 1500W motor is not producing 1500W at the spindle. GIven it's driven by a VFD I'd sugest it is runnig below base speed?

Andrew

Correct. The top speed is 2500 rpm and I'm running the spindle at 1200rpm in these tests. I don't know what the relationship between power, torque and rpm is on this machine / VFD combination is.

Certainly there's less than 1500W at the spindle, perhaps much less. I'd guess the self-act uses a fair proportion of the available power. Also, apart from the VFD/Motor's unknown electrical efficiency, there's plenty of friction. Two belt drives, compound reduction gears in the banjo, a headstock gearbox, a drive shaft, saddle gears, and various bearings are all soaking up power.

Measuring what's available at a lathe's spindle might be an interesting dynamometer project.

Dave

[HopperParticipant @hopper]

Posted by SillyOldDuffer on 29/05/2017 10:50:06:

Posted by Hopper on 29/05/2017 09:11:15:

Posted by SillyOldDuffer on 28/05/2017 15:28:58:

Posted by Hopper on 28/05/2017 12:15:02:

…

What is that material you are turning in the pics? If it is steel, is it some kind of galvo pipe? Probably never get it to machine nicely. Pipe making does weird stuff to steel and it never ends well for doing much other than conveying liquids.

It's some sort of stainless steel pipe with a welded seam. I found in the gutter and originally thought it was galvanised. However, a short piece of it has been outside for a good twenty years without going rusty on the cut ends. It's neither good nor awful to machine and the weld doesn't interfere. I get a better finish on it with hard fast cuts than slow shallow ones. If I knew what it was, I wouldn't recommend it!

Dave

Stainless is a real pain in the neck to machine at the best of times. Work hardens as you go, make stringy swarf, and so on. A bit of welded seam pipe of unknown provenance, I reckon I would consider myself lucky if I could turn it at all with any kind of halfway useable result. The best cure I could suggest is to do your turning tests on ordinary mild steel.

[HopperParticipant @hopper]

Posted by SillyOldDuffer on 29/05/2017 11:10:42:….

Certainly there's less than 1500W at the spindle, perhaps much less. I'd guess the self-act uses a fair proportion of the available power. Also, apart from the VFD/Motor's unknown electrical efficiency, there's plenty of friction. Two belt drives, compound reduction gears in the banjo, a headstock gearbox, a drive shaft, saddle gears, and various bearings are all soaking up power.

Measuring what's available at a lathe's spindle might be an interesting dynamometer project.

Dave

1500watts! That's like two horsepower. You should be able to pull stumps out of the ground with that motor. Really, that is a lot of power, compared with a typical Myford etc with a half horsepower motor.

Here's what my 1937 Drummond lathe with a half-horsepower motor will do all day long. Flat belt drive and all. .100" deep cut at about .006" feed, on black mild steel.

[JonParticipant @jon]

They don't make them like they used to Hopper.
Cheapskate you recycling?

Heres an action shot from 2002, 1 1/2HP motor spindle running flat out 1000 RPM on powered cross feed facing off 1/2" depth of cut on 5 1/2" diameter 6082. Nothing will stop 6082 coming off in strings and work with it daily, only way break the cut up manually. The production operatives use free machining aluminium and does chip break.

[Carl Wilson 4Participant @carlwilson4]

That pipe looks like nominal bore stainless hydraulic pipe. Schedule 40.

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