Thread: Taper turning

Nah, lost interest now....

I had the same idea as Dave, with a drill motor mounted on top of the slide.

Just made an adaptor to drive my compound handwheel with a drill. It works, but none of my drills go slow enough. Not with any control anyway. You would need a 2 speed one I think. Stuart, what are you using and how well does it work?

Hi RC,
The friction drive is a great idea.

Hi Bryan,
I said "cordless drill", both of mine have trigger speed control and will go very slowly.

Stuart

Stuart, I guess I meant, what kind of cordless drill goes that slow? Both mine are variable too, but at the speeds needed are too touchy and gutless.

Edit: Those power feeds like RC's are pretty cool but I can't find them under about $300.

Hi Bryan,
Its just a old 12V Makita. As the hex bolt on my compound doesnt do any preloading I can just put a 1/4 drive allen key in that.

Stuart

Does anyone know what's inside one of those commercial power feeds? In particular, what type of motor and what sort of gearing, if any?

I've done some calcs and if I wanted my compound to have the same range of feeds as my carriage I would need to turn the screw between .2 and 90 rpm, with the first half of that range being more useful. I think that's well out of the comfort range of most drills, without a lot of bulky gearing.

How about a spit motor and a good old Aussie 4 speed. Funnily enough I ran a lathe with an MG gearbox at a place I worked years ago lol

Phil

Hi Brayn,
Are you sure those numbers are right?
My compound is 2mm a rev so .2rpm on that would be 0.4mm a minute. Even at my slowest speed of 75rpm thats 0.00533mm per rev.(of course your lathe will likely turn slower an your compound have less tpi)

Two $20 cordless drills and put the gearboxes together?

Stuart

Stuart, no I'm not sure - I'm crap at maths. My carriage feeds go from .0007" - .012" / rev. That's about .02 - .3 mm. I worked it out in imperial, like this:

feed/rev * spindle rpm / pitch = feed rpm
.001 * 45 / .2 = .225
.012 * 1500 / .2 = 90

Hi Bryan,
Yeah your math is wrong.(thats a big statment coming from me lol)
Whats the pitch on your compound screw?

Stuart

5 tpi.

Hi Bryan,
Nevermind me, I missunderstood your post 10.
Your maths is correct.
Sorry for the confusion

Stuart

No probs Stu, thanks for checking it.

I think Ray Behner in the PM thread said he used a servo motor, so I'm wondering if that's what the commercial drives use.

Hi Bryan,
I think he is just referring to the brand of the power feed, they often call the import ones Servo clones. I am pretty sure they are just a standard motor inside geared down a lot and they have a simple clutch set up.
Here is a parts diagram for one of the Servo brand ones. They are geared down twice with the motor running onto a large plastic gear at the bottom and 2 bevel gears at the top.
http://servoproductsco.com/specs/150_6293_full.pdf

For the drill gearbox I was thinking of having a gear behind the compound hand wheel slightly bigger, and making up a simple slide mechanism so it could be disengaged when not needed. The gearing their would knock it down at a guess around 15 to 20-1 on the final gearbox output which should be enough for a 2 speed gearbox, though I haven't done any calculations.
I also found having the drill directly onto the compound bolt too fast, maybe Stuarts power grid is lower down that way, LOL

Dave