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Outboard turning speeds, longish.

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Outboard turning speeds, longish.

#1

Outboard turning speeds, longish.

Ron, Neosho, Wi.

>I am rebuilding a Powermatic 90 to suit my needs. I acquired all the parts to date piecemeal, ie. the body about 50 miles from here the tailstock about a 1000, etc,.etc. It was set up with speeds ranging from 500 rpm to 4000 rpm. It also had a 3 ph motor. All this is being changed. I am installing a 1.5 hp motor (1 ph.) to compensate for the loss to a jack shaft and the variable speed pulleys that turns at 1725rpm. I need to know what would be a reasonable speed to turn stool seats outboard. They will be trued, and dished only, no major work, but in my "BIG KEESTER" line the dia. of some of them will be 17-18". This is lots of feet per sec at the outer edge. I am thinking in terms of 200-300 rpm. Turning between centers will be at about 700-1000rpm which is just fine for my needs for legs and spindles. I need to figure the pulley sizes for the motor and the jackshaft to step down the speeds and after that I can't really change much. Sooooo, you experienced turners, whadaya think? Thanks for your time and "little grey cells."

Re: Outboard turning speeds, longish.

#2

Re: Outboard turning speeds

Al Crandall

>I've got an 18" bowl on the lathe right now. When I was turning, sometimes it was running in the 600+range. While I am power sanding, it is running from 60 to 200. You will need a wide range of speeds.

Re: Outboard turning speeds, longish.

#3

Re: Outboard turning speeds, longish.

Fog Tanner

>One "rule of thumb" that Mike Mahoney talks about, that he got from another professional turner, is rpm = x/dia where x is 6000 to 9000 with 9000 being the max and diameter is in inches. That would work out to

rpm = 9000/18" or 500 rpm max. A ten in bowl would be 900 rpm = 9000/10" and so on.

A platter will have different forces than a bowl, but the surface speed at the rim can still be quite high even at slow speeds. At 500 rpm the rim of your "platter" will still be traveling 26.7 mph.

For normal size pieces I have a chart I copied from Raffin's Turning Wood. It has the max size for bowls of a given diameter and depth. For your size pieces, I have to calculate using the above formula. I always use the 9000 number and figure on the max I can work up to. I have a VS drive, so I start at 0 and work up to what feels comfortable within the limit without going into the twilight zone.

Fog

Re: Outboard turning speeds, longish.

#4

Re: Outboard turning speeds, longish.

Arch

>I don't mean this as smart-Alec, but in turning wood I suggest you forget the speed rules made for turning metals, including those of thumb.;) There are just too many variables in the equation to have speed be the given: ie.the lathe, its fixings, the wood blank, the acceleration ramp, the turner, all vary and influence reasonable turning speed perhaps as much as the size of the blank. I think that unless all variables are understood and under control it's best to start each blank spinning as slowly as possible then move up to a speed that's reasonable for the particular turner.

IOW, I suggest that you plan your set-up for the slowest speed possible that's practical. Then go to your comfort level for each blank, ignoring formulas and speed tables. Arch

Re: Outboard turning speeds, longish.

#5

Keith Tompkins

Re: Outboard turning speeds, longish.

Keith Tompkins

>Hi Ron, why not keep the three phase motor, and adapt it to variable speed? Once you use a variable speed lathe, you will be spoiled forever.

Re: Outboard turning speeds, longish.

#6

Kieth

Ron, Neosho, Wi.

>The speed is already changeable, the pulleys are variable in dia. by moving back and forth. It is less precise than a variable speed motor, no doubt, but there's only so much time I want to spend of this project. Thanks.

Re: Outboard turning speeds, longish.

#7

Re: Outboard turning speeds, longish.

Bill Hale / The Wood Spinner

>I agree with Keith " Keep the 3 phase motor ".

With the variable speed you can tweek your speed by vibration and comfort. Faster is easier.

Speed is how you feel to some extent.

The longer you turn the faster you may go.

Good turning and be safe

Bill

Re: Outboard turning speeds, longish.

#8

Re: Outboard turning speeds, longish.

George Van

>I have a Powermatic 45. Does anyone know where I can Look for a variable speed pully to replace the original?

Thanks, George

Re: Outboard turning speeds, longish.

#9

Re: Outboard turning speeds, longish.

Steven Wilson

>You would need between 50 rpm and 1500 rpm. If you're rebuilding a PM90 or PM45 the only sane modification is to scrap the reeves drive and go with a fixed pully (or three) setup and a VFD controlling a 3 phase motor.

Re: Outboard turning speeds, longish.

#10

Re: Outboard turning speeds, longish.

George Van

>Thanks Steve,

I have a 3-phase motor that is like new that came with the PM45.

Can you steer me toward a source for a VFD? I would like to pursue this further.

George

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