Tuning a Lathe

Chip Charnley

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136
OK, first a little background...

I am finally back in woodworking after a 25 year hiatus that ended roughly 2 years ago when LOML and I built a new house and she let me design most of the basement as a shop. Bought a lot of tools in a 6 month period including an old Delta Rockwell VS lathe. The lathe became available at a great price so I grabbed it as I knew, eventually, I would go down that slope again.

Well, I finally did last week doing a few quick pens for a special occasion. What became apparent is that the lathe is not spinning things smoothly. Now I'm not talking the type of wobble that happens with out of balance pieces of wood before you have trued them up a bit. This is when you are done to the final wood removal. It's not a huge wobble (I think you would call it runout but I'm still learning the technical terms ;) ) but things were not turning true and, with pens, there's not a lot of reason for wobble other than the mandrel not being true (which is not the case). Thankfully things are close enough that sandpaper still produced a quality finish to the pens despite the tearout from the tools 'bouncing' on the surface.

Which all leads to my question. I have a mag base and dial caliper for measuring/adjusting TS, jointer, etc. But how would I go about using it to test a lathe? Or should I even bother and just jump right to disassembly and replacement of the bearings which I suspect are the culprit? Or am I just being overly sensitive? The 'wobble' is very small but it is noticeable.

I'm reasonably comfortable with most WW tools but I never did a lot of lathe work before now and I can't say I feel very comfortable at the moment.

Thanks in advance for any advice.
 
Chip, welcome back to the abyss of turning. :wave: I had the same problem on my homemade lathe and the problem was the bearings. I still haven't had time to replace them, but when I check them out, one was shot and the other will go soon. How old is the lathe? A replacement of bearings may be a good idea either way?
 
Hey Chip, welcome back to the dark side! :D :wave:

Put the mag base on the ways of the lathe, and then arrange things to the dial indicator touches the side of the spindle, in a place without threads, set the dial indicator to zero, and then turn the lathe by hand.

Could you post the model of the lathe, and a pic?

I do not know, but there may be a way to snug up your bearings somehow... :dunno:

Your lathe should not have run out that you can notice like you are saying, I would imagine a bit, on the dial indicator might be within specs, but not what you are talking about, that doe sound like a lot.

I'm sure you can get it running true again.

Cheers!
 
Chip, are you only seeing the wobble on pens? Even with a perfectly straight mandrel, if you overtighten the tailstock it can flex the mandrel enough to cause some wobble. (DAMHIKT) Just something else you might check before performing major surgery.
 
Chip, are you only seeing the wobble on pens? Even with a perfectly straight mandrel, if you overtighten the tailstock it can flex the mandrel enough to cause some wobble. (DAMHIKT) Just something else you might check before performing major surgery.

Yeh, I considered this but I don't think that's it. I did 10 pens (got eight good ones. *I* screwed up one in assembly and one chipped out really bad at the end)> The point is I experienced this on all of them and, at least on the last 6, I was beign careful about the tailstock.
 
Welcome Chip,

What Stu and Vaughn said, and, is your mandrel one with a morse taper shank? It is possible there is something inside your taper bore in the lathe spindle that is seating the mandrel shank off center. Take a good look inside and if you have a round wire brush (the kind you use for cleaning copper fittings for soldering), run that inside to see if it helps. Also take an indicator readings along the mandrel shaft with the tail stock tightened as it would be for turning. See if you get any runout there.

Also a possibility of a bent pulley, or "lumpy" belt bouncing enough to flex the spindle shaft which would be amplified further out from the headstock.

Just MNSHO. Your instructions Mr. Charnley, if you should choose to take this assignment, are to return a full report complete with pictures.

Aloha, Tony
 
Using just some pens as your test for the lathe can't be definitive. The mandrel, even if true, can, and will, flex. IMHO, you can't get a perfect pen using a full length mandrel. Try turning someting 1" in diameter, or thicker on centers and test again. Do the centers meet?
 
Chip, do you have a chuck that can be fitted to the lathe?
If so get a length of reasonably straight steel bar stock or metal pipe about 1" dia and clamp it in the chuck.
Put you mag base on the bed and place the dial caliper against the bar some way from the chuck and pull and push the chuck*, if the bearings are worn or loose in the case of a plain tapered sleeve bearing you will see movement on you gage.

*A length of 3x3 timber levered between bed and chuck maybe.
 
Thanks for all the input guys. I WILL make use of it but I didn't get a chance last night and I am off on 10 days vacation out of state after work today (well, 18 hours at home over Tue night but ...:rolleyes:)

:D:thumb:

I'll let you know what I figure out in around 2 weeks.

Oh, by the way, I did run an initial 6"D bowl blank through the lathe too and that seemed to be a problem as well
 
Well, I finally got back to this last night. I am pretty sure it's the lathe. I used a dial indicator against the MT for the pen mandrel, a cup MT, and a screw-on face plate (the latter I had less faith that it was perfectly round but figured it was a data point). In ALL cases, during one complete revolution of the lathe, the dial indicator made a complete revolution and then returned to zero! :eek:

So tonight I start tearing the thing down. I'll get the model number as well and post it. Anyone got any suggestions on where to get new bearings for a Delta Rockwell Lathe (at least I am assuming it's the bearings)?
 
Well Chip, I'm sorry to hear that you have this problem, but, now that you know what the problem is, or at least that there IS a problem, you can go about fixing it!

The bearings should have a number on them, just order them through your bearing house.

Good luck, take pics! :wave:
 
those old lathes used off the shelf industrial bearings so any bearing house should be able to fix you up. just clean up your old ones and carry `em in and let the guys there tell you what you need. most bearing houses will overkill on the load and rpm ratings.
 
Chip,

Sounds to me more like you have a bent spindle. I don't think bearings are going to be able to cause that much runout (a full revolution of an indicator could be .100" {.125" = 1/8 inch} depending on what indicator you have.) without having a great deal of slop in them. I haven't read anything in your posts about the bearings being real loose. I'm going to stay with a bent spindle as your problem from all you have stated. (That's my story, and I'm sticking to it.)

Aloha, Tony
 
Chip,

Sounds to me more like you have a bent spindle. I don't think bearings are going to be able to cause that much runout (a full revolution of an indicator could be .100" {.125" = 1/8 inch} depending on what indicator you have.) without having a great deal of slop in them. I haven't read anything in your posts about the bearings being real loose. I'm going to stay with a bent spindle as your problem from all you have stated. (That's my story, and I'm sticking to it.)

Aloha, Tony

That's been a theory advanced by a couple other people as well. Hard to believe someone managed to bend something that sturdy but time will tell. I agree that there doesn't appear to be any slop in the bearings but, in either case, I need to get the thing torn down. First order of business however, looks to require a spanner wrench that I don't have so need to improvise and alternative. Once I get her apart, the first order of business will be to roll the spindle on my table saw to look for light under the spindle. :D

Perhaps by the end of the week. LOML wants me to make wooden bookmarks for her tonight to give out at her book show this weekend.
 
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