Final Fitting of
Powermatic's Model 90 Lathe

Part 2: --Finishing Details and Adding a VFD

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Two glaring omissions on my lathe are the speed control knob and the spinner handle on the tailstock's feed wheel. I'm actually sort of glad they're MIA, because its the perfect excuse to show off and customize the lathe. I don't have anything against Powermatic's orange ball that's OEM for the variable speed dial... likewise for the feeble-colored plastic spinning crank on the tailstock. I do like the look and feel of wood, so..... why not turn these things in some beautiful hardwood.

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I don't own a metal lathe...... yet, but access to one in our school's metal shop. The lathe was used to turn, bore, thread, and part-off two brass spacers that mount on either side of the handwheel. These operations could be done on a wood lathe, but are a lot more fun when done using a legitimate machine for the application.

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The brass spacers were bored to specs. The one on the handle end was to be threaded for the 1/4X20 carriage bolt, so a 13/64 bit was used. The tap was then chucked in the tailstock and the tailstock unclamped, so it "floated" on the ways/bed. Turning the chuck by hand pulled the tap and tailstock into the workpiece as it slowly rotated.

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The finished pieces were parted off, cleaned up on a belt grinder, and ready to go. The spacer on the tailstock-side of the handwheel was a plain 1/4 hole for the carriage bolt handle to pass through. Because of a tricky angle on the backside of the handwheel, the spacer has a corresponding angle ground on one end.


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The square corners of the carriage bolt were ground off, so the rosewood "sleeve" could turn easily on this shaft. The carriage bolt was then measured to allow for an acorn nut to be applied on the inside end.

The finish I prefer for these parts is Waterlox.... a VERY durable tung oil product. It takes about 10 days for 10 applications, but is well worth the effort.

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The headstock only required the addition of a 1-1/2" ball to be turned and added to the stalk at the end of the variable speed dial. The stalk is threaded with 5/8"X18 tpi., so a tap was run into the 9/16" bored hole in the rosewood knob.

Beautiful fit...... no glue required!


VFD Installation

The use of a Variable Frequency Drive (VFD) has solved several problems:

  • Phase Conversion
  • Step-down of variable speed range
  • Replacement of magnetic controls
  • Additional programmability

The unit selected is a Hitachi Model 100-4L and was purchased from Dealers Electric, out of New York City. Priced anywhere from $125 to $145, these units are a real value when compared to the costs associated with achieving the above solutions using other methods.

The unit needs to be mounted in some type of enclosure to protect it from debris, impact, and curious hands, yet must allow for heat to be dissipated. I chose to use a piece of aluminum to form into the "L" shape that makes up the back and top of the cabinet. I also picked up an entry door kick plate from my Home Depot's clearance rack to use as the cabinet for another VFD I'll be putting into service. Two pieces of 3/8" brass rod were bored and tapped on a lathe and bent into an "L" shape to provide the enclosure with a "front" and "bottom". I'll develop a swinging door on one of these bars to block sawdust from entering the electronics area. It does not need to be completely sealed, but if most of the cloud of chips and dust can be kept out, I'm sure things will run longer.




The top of the enclosure has a double-pole switch to shut off input current in an emergency, and when the unit is not in use. The output line will eventually have a twist-lock cord-end so that this VFD can also run a three-phase State OS sander that sits nearby.




A tool rack for lathe tools, calipers, chucks, wrenches, and the plethora of other paraphernalia used in wood turning is needed someday.




Faceplates, toolrests, toolrest bases, and chucks have been collected over the last four years to round out the list of tooling. Still not here yet is an outboard toolrest stand that I have yet to find.

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