Southworth rotative pump

Quote from: JasonbUse the **GT ones made for non ferrous.

The pip on the end of the work suggests you may be a little over ctr height which won't be helping. The effects of this get worse as diameter gets smaller

Also try to use 303 stainless as it is the free machining one

I did start with the **GT ones and then swapped over to the one in the picture. I checked what I ordered and it was silver steel not stainless steel, is that the problem? 303 stainless, okay, I'll remember that for the future!

The tie bars are made (probably from the incorrect material  ) and you can start to see what the engine/pump will eventually look like assembled

I've found that some inserts are strong in compression, but weak in tension.  So any kind of backwards motion or upwards pull can break them.  For me it's always at the end of the cut, as I withdraw the tool.

Wilf

Quote from: Sanjay F5/32” diameter, 9/16” long running at 650rpm

That seems very slow. If I calculated correctly, less than 30 ft/min surface speed.

Carbide, even on SS, needs to run much faster to get a good finish.

Gene

Quote from: internal_fire

Quote from: Sanjay F5/32” diameter, 9/16” long running at 650rpm

That seems very slow. If I calculated correctly, less than 30 ft/min surface speed.

Carbide, even on SS, needs to run much faster to get a good finish.

Gene

Thanks Gene, let me try and speed it up, 1000 rpm? - even though it was a short length sticking out of the chuck I could see the rod flexing?

Quote from: Sanjay FI’m getting pretty average results finish wise using the Ali and the yellow/bronze coloured carbides on this stainless steel

5/32” diameter, 9/16” long running at 650rpm - it’s not critical as I’m about to thread them but what’s best for stainless steel?

It looks like you are a little below centre height looking at the pip. Eyeing the tool against a dead centre in the tailstock usually gets me close enough

As the pip looks conical I thought the tool was high, a low tool usually leaves a more cylindrical pip.

Though as the cut was so poor it could just be the work deflecting and riding up on the blunt insert.

I'll post a photo later of a bit of stainless I turned yesterday, 4mm dia so similar to your 5/32" and 40mm stickout.

I set the tool heights using the ruler method, maybe the tool got blunt very quickly and therefore created the pip? The vibration, deflection and grinding noise was significant.

Thanks I look forward to seeing how this should be done, SS not used that often, but it'll be good to get it right 

For Myford lathe users, and others with lathes that have flat topped bedways, a tool setting height gauge along the lines of this gadget ( another of the Geo. H. Thomas designs ) is well worth the bit of time to make up.  Will set tool height from the bed ways or from the cross slide surface, to within a thou or two, and will also scribe a centre line, useful at times. I made it long ago, and must have used it countless times ..  Dave

Here you do, the top left was 4mm dia and 40mm stick out. The one on the right 3mm dia but I did use tailstock support for that.

All done with DCGT 0702020, about 900-1000rpm from 303 stainless.

Dave/Jason - thanks, the finish looks great I think the tailstock support and increased RPM will hopefully do the job! 

For a job like that where you are just reducing dia prior to threading rather than use tailstock support you can just expose the rod in stages so you are only turning a shortish piece each time, say 8-10mm in the case of your 4mm material. Any slight difference in cut will not show once you have cut the thread.