Ruined MT

Re: Ruined MT

Dick Coers

Shouldn't be that tough to replace. I don't see a way to put a new taper in there short of boring it out more, pressing in a sleeve, and reaming in a new taper. Replacement shaft will be cheaper. You could shorten the shaft some, losing some threads, but then getting closer to the taper that is left in there. But I don't like that idea much either. I hardly ever use the morse taper on my Oneway. If I have a chuck on it and want to use a drive spur, I have a spur designed to fit in the chuck.

Re: Ruined MT

John K Jordan

I agree, replace the spindle. It would be just as labor intensive to remove the spindle for machining as it would for replacement AND if machined, the new full taper would sit too deep in the spindle.

I use the MT a lot, both for a variety of drive centers, jacob's chucks, rubber chucky mandrels, pen mandrel, custom mounts, and my favorite, holding long, thin spindles (far better than a chuck - I cut the taper into the end of the blank).

Unless you accidentally drilled very deep most existing mandrels and things will still fit but probably not securely enough to suit me.

In a pinch you could probably get by for a while by filling the drilled section with JB Weld then reaming to size. You can buy an MT2 reamer for $25 but it would have to be reamed with precision which might be difficult holding the reamer with the tailstock on the wood lathe.

JKJ

Re: Ruined MT

Dave Paine

Wow, that is a big "oops". You have my sympathy. I would be kicking myself.

The taper is part of the spindle which is the part you would need to replace. As you said costly in time and materials.

The headstock diagram from a Powermatic 3520B from the manual. The spindle is part No 4.

A full length MT2 taper is 2.25in. I do not know if manufacturers of wood lathes make full length tapers. If yours is full length, you may get away with using the short taper with your MT2 accessories, although you may need to use a drawbar.

I think attempting to get a bushing to press fit into the 3/4in hole will not be easy since I expect the diameter of the hole may not be consistent. On my metal lathe a drilled hole is not consistent. I have to bore out or use a reamer to get a consistent dimension. It will not be easy to get the taper in a bushing to align exactly with the existing MT2 taper. If not aligned well, then MT2 accessories will not hold.

Perhaps an easier solution is to get a machinist to make an adapter to screw onto the spindle threads with MT2 taper.

What are the MT2 accessories you presently use? Can they be replaced with versions which use a chuck or a collet chuck?

Re: Ruined MT

david delo

Not as a permanent fix but is there enough meat left in the taper that you could tighten up your center with a 1/4-20 drawbar?

Re: Ruined MT

Dale Gillaspy

Yeah, I usually use a Steb style drive for between center work and I have one that will fit in my chuck jaws...just hate that I did this and I like my tools to be complete and working right, not just getting me by.

Replaced spindle.

Doug Wolf

Dale, We had to replace our clubs 3520A spindle shaft in 2010 due to demonstrators messing up the outside (1-1/4') threads and here is the result.



We took the headstock to a local Powermatic approved dealer repair shop and it has been like new ever since. The prices have probably gone up since then. Good luck.

Re: Replaced spindle.

Barry Irby

Wow! Looks like something I would do. And kick my self in the butt for it. I would rant and rave and kick myself for days. OTOH, I have what is practically a motto, any blunder that can be fixed for less than $100 is not worthy of that much outrage. Been saying something like that for thirty years, so maybe it should be $200 when adjusted for inflation. I would replace the shaft. Especially if I could get one for the price mentioned above. I am concerned this weaken the shaft and the tapers would never work right or be safe. And I want my machines to be "proper" and not kluged together and require odd fitments to keep going.

Re: Replaced spindle.

Dale Gillaspy

Yeah, I agree. I think I'll just bite the bullet and look into a new spindle.

Re: Replaced spindle.

William Duffield

The spindle, part # 3530B-204 is $124.33 from Powermatic or $133.68 from ereplacementparts.com.

https://parts.powermatic.com/SearchResults.aspx?s=3520b&PageNum=3

http://www.ereplacementparts.com/powermatic-3520b-1352001-tefc-2hp-220v-woodturning-lathe-parts-c-32549_32637_32638.html

Re: Replaced spindle.

Doug Ladendorf

I don't know how old your machine is but you may want to replace the bearings while you are at it. It's relatively cheap insurance.

Re: Replaced spindle.

Dale Gillaspy

Good point.

Re: Replaced spindle.

john lucas

And if your careful removing the bearings you will have them as back ups in case the new ones ever go bad.

Re: Bearings are likely generic

Dave Paine

Good idea to consider replacing the bearings if you decide to replace the spindle.

The bearings may be purchased from a bearing supply house.

For example in the 3520B manual they should front bearings (Qty = 2) as code

BB-6207ZZ

The bearing generic code is 6207ZZ. Dimensions and specifications are defined by "6207". Shield material is defined by "ZZ" which means two steel shields. May be stainless but depends on manufacturer.

The rear bearing is BB-6206BB. Dimensions and specifications defined by "6206". Shield material is defined by "VV" which means two non-contact shields. May be Viton or some other plastic depending on manufacturer.

The bearings will state the manufacturer. If you purchase the code and same manufacturer it will be the same as purchasing from Powermatic.

Re: Bearings are likely generic

Joe Kaufman

Received Chinese manufactured spindle bearings from Powermatic about a year ago. Did not like the grinding quality of the external surfaces so purchased NSK bearings made in Japan. The original bearings were made in Taiwan and look as good as the NSK.

Re: Bearings are likely generic

Doug Ladendorf

Agree. Japanese bearings are not terribly expensive and are good, consistent quality. Another brand I have used for several projects is Nachi.

Doug