Jet 1642 Problem

[opus 98]

Hi, all, I need to defer to the accumulated wisdom of the forum..........
I purchased a new Jet 1642 in April, and spent many hours turning and learning on it with no problems.
About a month ago, I noticed that there was runout occuring, and whether I was using a faceplate or chuck, it didn't matter. I also did some spindle turning, and the same thing was happening.
Although the lathe is still under warranty, I went ahead an ordered a new spindle from WMH to replace the original. I also upgraded the bearings, front and rear.
To my dismay, the lathe is still not turning true. I checked the spindle at various locations along it's length with a dial indicator, and it shows a consistent run out of .003.
I even went so far as to switch the headstock from one end of the bed to the other, to no avail.
Today, I contacted a local Jet warranty repairman, and he was as mystified as I am. He will come to my shop next Tuesday to check the machine out.
Does anyone have any insights?
BTW, I built a ballast box per Dominic Greco at WoodCentral, and the lathe is very stable.
Thank you all for your comments ahead of time! This forum is fantastic.

 

[spinsdawood]

How bad was the runout before you installed the new spindle?
Jim

 

[opus 98]

Jim,
Thr runout was identical to what Im experiencing now, which makes me believe that the spndle is okay, but the alignment of the spindle from the rear to front bearings is not straight. I inspected the headstock casting very carefully, and there are no cracks anywhere in it. My first thought was that the headstock may have cracked in the region of where the front bearing is seated.
Thanks for your reply, I appreciate it.
John

 

[Rob Wallace]

Please keep us informed!

John:

I'm impressed that someone will come to your shop and look at the lathe! I've appreciated WMH service and parts operations, but this is welcome news!

Question: Are the front and rear bearings the same part? If so, (....although it would be a major PITA....) you could switch them and see if you get the same runout - this might implicate the spindle as the cause.

I also heard about another spindle fix done (I think on a Delta Lathe) where the guy rotated the outer race of the bearing (...or bearings, I can't remember) 180 degrees to try to compensate for any mis-machining of the casting in which the bearings sit. Apparently it cured the problem. You may need to do some experimentation to find a cancellation point by changing the position of the bearings to offset errors and mutually cancel the runout. In theory, this shouldn't be necessary because all bearings and machined parts are perfect (!), but in the real world, stuff happens.

Please do keep us informed of what was done to fix the problem. (I keep a file on all postings related to the Jet 1642 - three of us in our club have this machine). I'm buiding a ballast/storage box for mine over the next month or so as I can catch time to do it.

I hope you resolve the problem and that the fix is an easy one! Good luck!

Rob Wallace

 

[opus 98]

Rob,
That's a great idea, thanks. The front and rear bearings are different sizes, the front one being much larger. And I will definitely pass along any and all news regarding the fix.
Yes, I have always had very good luck with Jet tools, myself. I work in architectural woodworking for a living, and we have always had various Jet tools in our shop. And I was floored myself when the fellow said he'd come up from Denver as soon as he got cleared by Jet to do the repair.
Small world.........I'll be in Boone, Iowa over the weekend of the 8-10th of Sept to attend a family reunion for my g/f's clan!
Thanks again for the response!
John

 

[john lucas]

On my home modified lathe that I used to have I had a .005 runout that I was having trouble finding. Turned out to be the 2 bearings weren't aligned parallel. I pulled everything out and seated them again and it went away. An older machinist told me about this.

 

[opus 98]

John,
That's exactly what it seems like to me, that the spindle is somehow not running true down the long axis of the headstock, and so it is turning a kind of ellipse no matter if I am turning between centers, using a chuck, or a faceplate. When I put a spur drive in the spindle and line it up point-to-point with a live center in the tailstock, it moves 'around' the live center point. It seems very slight, but by the time you get out to 7 or 8 inches from center, it becomes a problem.
The only other thought that crosses my mind is this.....the motor (and it is quite heavy) is mounted on a hinge-type mount, and so the motor shaft, motor pulley, drive belt and spindle pulley are bearing the weight of the motor. It seems impossible, but maybe the weight is causing the spindle to bend a hair under load. Just a guess borne from running out of reasonable explanations, lol.
John

 

[Richard Baker]

John, How did you specifically observe/notice the spindle runout originally?

 

[opus 98]

Hi, Richard,
It was just one of those things where I turned on the lathe and started making a platter and something was wrong. Nothing out of the ordinary had happened previous to that, no huge catches or anything of that nature. My initial thought was that maybe the front bearing went bad on me, so I replaced it with an upgraded bearing. Next step was to replace the rear bearing, and finally, the spindle itself. I'm not a millwright by any means, and hunting down something measured in thousandths is beyond my experience.
John

 

[hcbph]

Hi, all, I need to defer to the accumulated wisdom of the forum..........
Although the lathe is still under warranty, I went ahead an ordered a new spindle from WMH to replace the original. I also upgraded the bearings, front and rear.
To my dismay, the lathe is still not turning true. I checked the spindle at various locations along it's length with a dial indicator, and it shows a consistent run out of .003.

Opus
You say there there was runout both before and after changing the spindle and bearings. Short of having a bad two pair of bearings or both spindles, I don't see how that can happen. Being you have the parts, have you thought about mixing them (old bearings with new spindle or reverse) and see what happens.
I know it's a pain but it may help resolve it.

Paul

 

[DeanGThomas]

Since you've deduced the runout, I'm guessing that you know the direction relative to the spindle (up, down, to, fro, or some explicit combination thereof).

My first thought was that if there was any play at all where the bearings are seated, could it be shimmed? That would not seem to make any sense, though. If they were simply out of alignment, they would stay out of alignment in the same direction, creating a permanent off-center turning situation.

If the point of the spur does indeed describe a circle around the tail center, wouldn't that indicate a permanent flex or bend in the shaft? Could that indicate that the bearings are not parallel in their seats? Could the bearings exert so much force on the shaft that it would flex?

If the motor's weight was causing the flex, wouldn't that cause the shaft to stay in a constant state of flex in the same direction rather than causing it to circle the tail stock's point.

I'm looking forward to hearing what the solution is! 🙂

 

[john lucas]

Texian I first noticed it when I replaced the bearings and I had vibration that I didn't have before. I put a dial indicator on it and it hopped about .005 every revolution. The reason I replaced the bearings was some noise and a slight eccentric wobble similar to what he's describing with the drive center making a little circle around the tailstock.
I replaced the bearings and it ran closer to center but hopped every revolution. When my friend suggested the bearing missalignment issue I took everything apart and cleaned everything. Then I was very careful to make sure the race was seated against the bottom of it's flange.

 

[opus 98]

Dean and Paul, thanks for your comments.
A machinist friend of mine came over this morning to give his assessment. We removed the spindle, checked the casting, lubed everything up with LPS and he put it back together. Dial indicators everywhere, it showed just a .0005 runout! I am baffled by it all, but grateful that evrything seems okay.
Which leads me back to my first suspicion, that it is a case of pilot error. I am a novice turner, and I think my best move right now would be to get some hand-over-hand lessons from a local pro. When I decided to pursue turning as a creative hobby, I invested in all of the best tools and sharpening equipment, but that doesn't mean much if technique is inadequate.
Thank you all so very much for your insights, you are a great bunch of guys. I'll head back into the shop now with my Raffan book in hand and see if I can do this lathe justice.
Cheers!
John

 

[Hawaii Turner]

Looseness?

Opus,
Is the shaft a light press(tap) fit into the bearings? Also, are the bearings a light press fit into the housing bores? You might want to check the bottom of the housing bores for dirt, or even machining burrs that might prevent the bearings from seating square. Check the flange of the shaft also for burrs. I would suspect the outward bearing as being the problem.
Good luck
Doug :cool2:

 

[hcbph]

John

You're going to like the Jet. I bought one a year ago last spring, plus bought the bed extension. I added a shelf up high with a couple of drawers for chisels, so I can park my metal lathe under it. So far it's done everything I've tried on it so it's a keeper. Of course my Jet is my third lathe, and only took 30 years to get.

Paul

 

[Richard Baker]

Something Was Wrong?

John Lucas, Was trying to ask John Garrity for the specific observation of the kind that you stated (vibration), that indicated to him that "something was wrong". And/but thanks for your response, as may well be helpful in future. Have a Jet 1642 about 8 months old that typically runs several hours a day, several days a week, so am interested in potential problem that might occur. When turning a piece between centers I usually crank the tail center at in at low speed until I hear a very slight knocking (bearing knock?) in the head stock, and immediately back off a bit before turning up the speed. This is NOT to seat the spur center in the piece. That's done off-lathe by Forstner drilling a shallow 1" hole, making two cuts with 1" chisel and hammer at 90 to each other and 45 to the grain, and seating the spur center in chisel cuts with light hammer blows. This does "mushroom" the back end of the spur center slightly, and I check it regularly and grind off edges of the mushroom when they threaten to exceed shape of the MT2. For ref., this usually gives sufficient grip that a big hogging roughing catch will stop the spindle and cause the belt to slip and squeal. Am using only the motor weight to apply belt tension, per the mfg. instruction book.

 

[DeanGThomas]

[Seating the spur center is] done off-lathe...seating the spur center in chisel cuts with light hammer blows. This does "mushroom" the back end of the spur center slightly...

Most instruction suggests rapping the spur, but everything I've read explicitly recommends AGAINST using a hammer for that very reason. Hard wood mallet, brass mallet, dead-blow mallet, chunk of timber, but not anything steel. Might be worth turning yourself a nice, hard little knocker for just such a purpose! :cool2:

 

[john lucas]

Ditto what Dean just said. Metal against metal is a no/no unless your a blacksmith or using a cold chisel. I deadblow hammer works well. I usually either pick that up or my wooden mallet, whichever is handy.

 

[Richard Baker]

Soft Hammer

OK guys. I'll put away my little ball peen hammer and get out the lead one and the plastic one. Maybe a sturdy mallet from that chunk of live oak I've been hauling around for years.

Has anyone else experienced the "bearing knock" that I mentioned, especially on a Jet 1642? Haven't put the dial indicator on it, but have no visible spindle runout when compared point-to-point with stationary tailstock point. There's a little side-to-side slop in the tailstock to bed. Obviously must be a few thou. clearance in order to slide the tailstock.

This thread has made me paranoid, so of course I had a new vibration at about 950 rpm this morning. Turned out to be the natural frequency of the workpiece. Was about to part off a small finger-spin top from end of 2x2 about 6" long in the chuck. Was making a bunch of tops for sister-in-law's Sunday School class of little kids.

 

[Jake Debski]

Has anyone else experienced the "bearing knock" that I mentioned, especially on a Jet 1642? Haven't put the dial indicator on it, but have no visible spindle runout when compared point-to-point with stationary tailstock point. There's a little side-to-side slop in the tailstock to bed. Obviously must be a few thou. clearance in order to slide the tailstock.

Texian,

I don't know if it is the same "knock" but our chapter has three Jet minis that knock until you either back off slightly on the tailstock hand-wheel or tighten the tailstock quill lock. I always thought it was because the spindle and tailstock were a few thousands out of perfect alignment or the quill itself had enough play to allow it to "jump" in the bore until tightened. I'm more inclined to think the latter because it mostly occurs with peices that were centered(drilled or spur driven in) off the lathe thus not truly centered and are turning on an ellipse until trued. Have never taken the time to examine the machines to see if I'm right or not.

 

[Richard Baker]

Wrong (again) about vibration

Jake, Thanks for your response. I had not tried the tailstock quill lock in the order that you described. I was wrong about that "workpiece vibration" I mentioned earlier. After some checking, found that it is indeed the spindle and/or bearings. In high speed range, which I have never used, it also vibrates from about 1800 rpm all the way up. Until recently had never turned anything small enough to turn at 900, so the problem may have always been there. When told of the "bearing knock" the WMH Tool Group tech. said "Aha!", or words to that effect, and is sending service personnel to change the bearings, under warranty. Will keep you posted.