How to slow down power feed?

[Wongster]

Hi guys,

I often find that my Proxxon PD400 is feeding a little faster that I desire. For larger diameter stock especially, the slowest setting of 0.07mm/rev left thread like finish. Is there a way to slow it down?

There are 2 settings provided by swapping a piece of gear in the box. The 0.07mm/rev is set by putting in a 20 teeth small gear and the 0.14mm/rev 40 teeth.

Regards,
Wong

[EdK]

Wong,

What gears do you have in the Z1, Z2 and L positions?

Ed

[Wongster]

Ed,

Z1 = 20/60
Z2 = 70/25
L = -/75

For the faster speed of 0.14mm/rev, Z1 = 40/60.

Regards,
Wong

[EdK]

Wong,

That looks right. Can you post a picture of the finish you're getting on the work piece?

Ed

[Wongster]

Ed,

I tried turning the 2MT arbor's business end this morning to take a pic as the unintended thread looking surface finish was filed & sanded off.



This one is not as bad. Lots of smoke while turning. Hope no one alert the fire department... :) The piece measured 25.3mm in dia. The tool use is HSS. Spindle speed 660rpm with feed set at 0.07mm/rev.

This is first cut. 0.1mm feed (0.2mm of diameter). Much nicer.




Regards,
Wong

[EdK]

Wong,

What is that you're trying to turn in the last picture? If that's one of those MT blank arbors that have the "blank" end supposedly softened then I suspect that's your problem. I bought a couple of those and couldn't get a decent finish turning them. Be sure to use plenty of cutting oil and a slight radius on the cutting tool tip and take light cuts.

Ed

[Wongster]

Ed,

You are right. It's the 2MT arbor with a supposedly soft end from the Hemingay kit. I'll swap in the indexable tool with has a radius tip. Lots of smoke with lots of oil.... Freaked wife out.

Regards,
Wong

[Bogstandard]

Wong,

What you have to realise with those types of arbors is that they are made completely from some sort of tool steel, purely because the morse taper has to be hardened then usually ground.

Material like that, even when soft, doesn't turn very well at all.

I get around it by using a tipped tool, at high speed with a very fine cut, finished off with either an emery strip or a toolpost grinder.

It is not your machines' or your fault, it is the material itself.


John

[Wongster]

Ed, this is the result of using the carbide insert tool with a little radius:





Much better than earlier. Still turning at spindle speed of 660 rpm with 0.1mm depth per pass.

The cutting oil I'm using left stain on my spindle flange...



John,

Thanks for your input. What's a "tipped tool"?

Now that I swapped in my carbide insert tool, I'm thinking of putting up the speed to the next notch at 1400 rpm and go at 0.1mm per pass. The 1" "soft" section is now at 0.75", I'll be turning down from here to the major diameter of 5/16" BSF for length of 5/16". Will the speed of 1400 rpm be too fast for this material? Not that finish is important here, I'm using this to test out what should be the right speed with the auto-feed of 0.07mm/rev.

Regards,
Wong

[DaveH]

Wong,

"tipped tool" = "carbide insert tool" = "insert tool"

Wong do you have a 1000 rpm, if you do try that first.

The staining is from the smoke of the cutting oil. Just out of interest what is the name of the cutting oil.

The staining may come off with some 'thinners' but mind the paint.

DaveH