# powermatic 90 lathe speed , pulleys



## ibewjon (Oct 2, 2010)

I recently purchased a powermatic 90 lathe. I cannot get the speeds listed in the manual, so I am wondering if the machine has the correct motor pulley and belt. What diameter should the motor pulley be, and how long should the motor belt be? This info is not listed in the owners manual I have. I cannot get the speeds listed on the tag on the machine. And if anyone has the size for the reeves drive belt, please post that also. Thanks, Jon [ the motor is 1725 rpm 1 hp.]


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## mhermann (Jun 7, 2013)

The motor you describe is the same rpm and horsepower the lathe originally came with. Those lathes also came with a reeves drive that consists of two spring-loaded expanding pulleys, one on the motor and one on the spindle. Rotating the speed control lever on the front of the lathe will expand and compress those pulleys to get you your variable speed. If your lathe has step pulleys in place of these, then that would be the reason why you can't get the required speeds.

The belt that came with this setup is a flat-ish belt. I dont have the number handy.

Hope this helps.
-Mike


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## mhermann (Jun 7, 2013)

The stock belt number is 1422V360 which is a 36" belt. I found replacements online pretty easily. This belt won't do you any good though unless you have the stock pulleys.

-Mike


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## ibewjon (Oct 2, 2010)

thanks for the reply, however i forgot to post that mine has the intermediate shaft between the motor and spindle pulley. these reeves drive pulleys are original, but i do not know if the belt is stretched or worn. the pulley that i am questioning is the motor pulley, the 1/2" pulley on the mid shaft appears to be original. My motor is mounted in the base cabinet on a hinged plate. Any ideas? jon


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## wormil (Nov 19, 2011)

How far off are the speeds and how are you measuring them?


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## ibewjon (Oct 2, 2010)

for speed measurements, i am using a friends' penn state digital tach, maybe not exact, but i only need close. with a 2 3/4 inch motor pulley, which came on the machine, the lowest speed was 750 rpm. i changed to a 1 3/4 inch pulley, and got the speed down to 450, but the highest speed is now down to 1240. [i know that speeds change on both ends when changing a pulley]. i saw a picture of a 90 with a factory sticker that gives speeds for various diameters, from 200 for 12" rough, to 3000 for some finishing. the book i downloaded shows speeds for the machine from 500 - 4000 rpm, however i do not know that it is for my machine. my serial # is 390111, the 3 should be for 1973, the 90 is the model, and 111 is the machine. the book says it is for # 1000 and up, so my 111 may need a different book. i wish that powermatic would have given part sizes instead of just part #s is their books. is there any help anyone can give me with this?


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## rick1955 (Jun 26, 2014)

Why do you not call Powermatic???? I know they don't make that model anymore but someone there should be able to trouble shoot your problem.


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## ibewjon (Oct 2, 2010)

just figured i would get a better answer here than india, or wherever the call center is, but i can try it. thanks


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## Wildwood (Jul 22, 2012)

Hard to answer your question because some models shipped with a 1800 RPM and guess some came with 1725 Rpm or switched later. Know lathe speeds normally shown on the speed shift lever.

Can only guess motor mount is hinged to make belt change simple, and you have something called a jack pulley in that reeves drive motor set up. One other advantage turners like about these lathes is installing a foot clutch to change speed or stop lathe without using the shift lever or on off switch.

Del Stubbs, demonstrated & explained foot clutch set up & operation on a General reeves drive lathe in his Bowl Turning video.

Back when your lathe was made could bring the old belt into any store selling belts for a replacement. That may or may not be true today.

Today common for folks to remove the reeves drive and modify lath into EVS adding new motors, inverter/controllers set ups.


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## ibewjon (Oct 2, 2010)

there are no speeds marked on this model. the belt is easy to find, but i do not know if it is stretched. even powermatic can not tell me the size of the pulley, but they did send me a manual from a newer model, and three speed ranges were available, but no pulley size is listed. changing to a vfd is no problem because i have been an ibew electrician for almost 40 years, i was just hoping not to have to spend money for a drive, i would rather buy tools. i will find the answer somewhere. thanks for the help. jon


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## rick1955 (Jun 26, 2014)

> just figured i would get a better answer here than india, or wherever the call center is, but i can try it. thanks
> 
> - ibewjon


Whatever would make you assume their tech help is in India?


> ?


always start with the manufacturer for tech help…
Technical Service
1.800.274.6846 - 8:00 a.m. to 5:00 p.m. (CST, Monday - Friday)


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## mhermann (Jun 7, 2013)

If you want tech support, go over to owwm.org and post your question there. There are four or five active guys who have worked over multiple 90s and would be happy to answer your questions, plus there are easily a dozen more guys like me who own and use them. That's where I get my info for old machines, and that's where I would go to get my problem solved. Be sure to have a couple of pictures handy also.

-Mike


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## Bill7255 (Feb 23, 2012)

I have a PM 90. When I got it it had a 3 phase motor which I changed to single phase. From what I remember their were two speed versions. 1000-4000, and 500-2000. They had different speed handles. Mine is the 500-2000 version. If there is something you want me to look at on mine let me know. I am sure it still has the original belts. Post a picture of yours.


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## ibewjon (Oct 2, 2010)

from what i have been able to locate, powermatic shipped lathes with different speed ranges, so it looks like none had the entire speed range, but each had different portions of the range available. at least now i know that mine will not make the entire span, and i will set it up for the low range, and if i ever want the higher speeds, i will change the motor pulley. thanks for all the help and advice.


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## ibewjon (Oct 2, 2010)

with the speed problem solved, i was wondering if anyone has heard of having a machine shop cut the drop bed into a 90 lathe that did not have one. it looks like a slot could be cut, even if not the full 2 1/2 inch depth that was in the original. it looks like it could be cut as deep as the reinforcing ribs that are cast into the bed. or is this a bad idea? would it be better to get riser blocks made, and higher tool rests to match?


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## Bill7255 (Feb 23, 2012)

I am no expert on these lathes, however I did some research when I acquired my PM 90. It would be helpful if you posted a picture. From my research only the first year(s) of these lathes did not have the cutout. If it were me I would not want to modify the lathe casting, keeping it original. Riser blocks is what I would do to gain the height. Does your lathe have a SN plate?


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## Wildwood (Jul 22, 2012)

JMHO, use the lathe as is, and save your money for bigger lathe several years down the road. If that day never comes okay too!

You will never recoup time & money spent on any of the modifications mentioned.

Good luck with whatever you do or don't with it!


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## ibewjon (Oct 2, 2010)

without going out to the shop to look,i think from the sn it was made in 1973. i will go with the riser if i want more size, and i have a machinist friend who will make the parts for free, just likes to work metal like we work wood. thanks for the advice. jon


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## REO (Sep 20, 2012)

I would get risers made instead of cutting the bed. cutting cast is a bad idea. it creates points of stress that can lead to cracks and fractures.


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## mhermann (Jun 7, 2013)

It's a little funny that you want to turn your 90 into a gap-bed. Many like to actually full in that gap with something so they can scootch their banjo up closer to the headstock. My advice also leans toward getting some risers made. If you have a friend who's willing to knock a couple out for you, then that's the berries.

If you do have them made, two inches thick is the max thickness they can be. Any thicker and you will have to have a custom banjo and tool rest.

That lathe was also originally made as a spindle lathe. If you plan on swinging the full 16" that it will be capable of after adding the risers, you will need more weight in the base. You can also expect shorter spindle bearing life if you are more than a recreational turner. Just be ginger with the lathe if you go big. Mine likes to rock a bit when I put something on that's approaching 12" and is a little out of balance.

As usual, good luck!
-Mike


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## ibewjon (Oct 2, 2010)

its funny that you mention 2", that is the size i was thinking about. i had never planned to turn that big, but i want to be prepared for when i retire and have more time. and my machinist will be retiring, and i may not have a good source for the risers. i have the lathe bolted to the concrete garage floor with 6- 1/2" stud anchors 6"" long through commercial anti-vibration pads, so it is very steady and will not take a walk on me. i have already had to make a custom post for a tool rest because of the 1 and 1/8 th inch post size. tools this solid just are not made today, that is why i look for the old ones, and for a hobby turner, older is cheaper. thanks for the advice, jon


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## restored (Sep 2, 2012)

I also have the #90. Have been trying to figure out for 3 years the best way to make this lathe safe. What I have learned from Powermatic, which is in Tenn, not Bombay, is this machine was made with a reeves drive with 2 different speed ratio's, 1000 to 4000RPM's and 250 to 2500RPM's. I may have the last high of 2500 incorrect. I was also told from one of the tech's that a number of machines were made with a low of 500RPMs, but that these are rare and not many made. My machine is the 1000 RPM low speed, model making it an adventure just turning it on. The original motor was a 1 hp 3 phase. I made the mistake of converting to a 1.5 HP single phase. I wish I would have purchased the 3 phase motor and added a VSD control to lower the speeds for both safety and more efficient cutting and finishing. Letting the tool do the cutting instead of the speed of the machine. I would guess that your machine has already been improvised if the motor is in the cabinet. I know most of the #45's are like this, due to space. When I replaced my motor I had to remove the capacitors and mount them in the cabinet, to be able to fit the motor back into the housing. I think if your motor is already in the cabinet half your work is done. Using your tack and step pulley's, along with your reeves drive, you should be able to tinker with the pulleys with a low med and high range controlled with the reeves drive. Someone has had to make the modifications to change the belt location, and length I would guess, after looking at mine numerous times. I have also seen a few of these machines with the reeves drive face plates on ebay, marked only with dots. You will need you tach to determine the speeds. There are some very clever people out there, my guess is that the reeves on your 90 probably came off a different make machine and was fitted to work. Powermatic has done this themselves with many parts being the same part being used on a entirely different machine. THis info may not help, except to say, for the most part, without spending a ton of money it seems like you only have a day of trail and error, to attain the the speeds your looking for. When you add a riser block this may end up changing the belt size, which may affect the torque, of which I think that this is your most important issue that has not been mentioned. Many of the new machines with the various kinds of VSD, VFD controls, can make the head stock spin as slow or fast as you want, but often the torque of the motor is compromised. Something I can say in making the mistake of installing a single phase motor with an etra half horse, I have no problems with. I could pull my truck into the shop with this motor. Don't know if this helped, but if your motor is in the cabinet, you have many options, to attain the speeds who desire. What I do know is the reeves drive does not compromise the torque of the motor, you are not playing with the different flow of electricity to control your speeds. If I could put my hands on a low end 250 RPM reeves drive, this is what I would do. Everything else on the lathe is perfect. I did change to a one way banjo, as the original powermatic was just a pain to lock to the bed and the tool rest to the banjo with the short levers, and the need to find the exact spot for the proper pressure.


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## wormil (Nov 19, 2011)

Why do believe lengthening the belt would negatively affect torque?


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## ibewjon (Oct 2, 2010)

Thanks for the ideas. I had no problem getting a new belt from motion industries.. my speeds with the new belt range from a low of 500 to a high of 1250, so my speeds are safe. My 90 was machine number 111 made in 1973. My speed control has the depressed face with threaded holes to place a bolt for a speed limit, probably for school use. Older models had a speed control dial with raised lines in the face. It has always had the intermediate shaft with the motor in the cabinet. The older models had no mid shaft, and the motor was in the bed. A 3 phase motor and vfd is on the future but list. Jon S


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## MrUnix (May 18, 2012)

> Why do believe lengthening the belt would negatively affect torque?
> - Rick M.


Don't worry.. it won't 

Go to any belt calculator (such as this one) and change the center distance between pulleys all you like. The torque values will remain unchanged.

Cheers,
Brad


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## wormil (Nov 19, 2011)

> Don t worry.. it won t
> - MrUnix


I wasn't and I already know; I was just wondering why he believed that. Sometimes it's fun to read the explanations.


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## gdstutts (Nov 27, 2009)

Looking for assistance in filling out the info below:
From my research on OWWM the PM 90 manual obtained there for models with a jack shaft listed three RPM speed ranges:
Slow 215 - 1375
Standard 320 - 2100
High 460 - 3000

For each speed range the parts list has two sheaves, one for the motor and one for the jack shaft. I have attempted to cross the PM part No. to standard specs but I have been unable to ID some of them. The items I was able to cross have their commercial part# following the PM #. Here is my list:

Motor:
Slow - 6087027 (AK25×5/8)
Std. - 6807101
High - 6807035

Jack Shaft sheaves:
Slow - 6087049 (AK74 X 7/8)
Std. and High - 6087040

The belts listed are:
Slow - 4L340
Std. - 4L310
High - 4L330


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## TajBuilder (Aug 6, 2008)

There are a number of resources on the Powermatic 90 at OWWM.org and the sister site VintageMachinery.org. The Powermatic 90 was made from 1955 to 1997. Prior to October 1972, the motor was mounted in the lathe bed and the speed range was about 1000 to 4000 RPM. After 1972, the motor was moved to the cabinet and a jackshaft was added. The above post lists the available speed options that depend on the drive pulley configuration. However, the reeves drive and belt are interchangeable for all model years.

Most Powermatic 90's were shipped with 3 phase motors and a safety micro-switch in the head stock that prevented students from starting the lathe with the speed dial in any position other than full stop. Most users today add a VFD that allows you to operate the lathe on standard 220v. This allows you to control the speed of the motor giving you a speed range from zero to the reeves drive maximum. The VFD can also be programmed to gradually accelerate and decelerate which eliminates the need for the safety micro-switch and the need to return the speed dial to the full stop position.

Gap beds were offered as an option during the entire production run but many turners, myself included, prefer the standard bed because its easier to position the banjo underneath your turning. The gap bed was popular in schools so the tool rest banjo could be removed without removing the heavy tailstock

In my opinion, the optimum height for riser blocks is 3" which gives you 18" of swing. The banjo only has 15" of swing but the extra height allows you to position it underneath your turning. If you add 3" risers, you need to add 6" to the length of the reeves drive belt.

For more on the history of the lathe including how to interpret the serial number, check out the Powermatic 90 Time Study at OWWM.org.

The 1982 Powermatic Price List on the Vintage Machinery site has a cross-reference for both old and new part numbers as well as a common description of the part in question.


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