Problems with mini lathe

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sseamen

sseamen

Member
Joined
Dec 15, 2010
Messages
115
Location
Huntsville, AL, USA
I have a Harbor Freight mini lathe I bought last April. I've used it quite a bit since then. Quite a bit to me anyway, maybe a one or two hundred pens and such. I seem to be developing a problem and I'm not sure the cause, therefore not sure how to fix it.

Some background.

I started turning pens for the Freedom Pen project. at my fourth or fifth Turn-A-Thon, one of the guys who started the same time I did noticed I was using Gorilla torque when I tightned the knurled nut and again when I advanced the tailstock live center. He pointed out that it was supposed to only be 'firmly tightened'. I checked my lit and found out that over tighteneing either or both could cause the mandrel to bow or bend, so I decided to loosen up some. Almost immediatly, I noticed that my pens were no longer exactly round. One side of the blank was exactly even with the surface of the bushing and the other side was still too large, or one side was exactly even with the surface of the bushing and the other side was now too small (below the surface of the bushing. I bought both a complete new mandrel and a replacement rod. Both the old mandrel with the replacement rod and the new mandrel seemed to fix the problem, but I noticed more chatter when I'm working at the tailstock end of the blank than when I'm towards the headstock.... sometimes. Other times it seems to be reversed.

I also noticed that the point of the live center had a groove around it, silghtly in from the tip, as if it's not turning and the mandrel is. It's a ball bearing live center so that doesn't seem likely. I replaced the live center with a new one and, in only a couple of pens, I had a groove on the new live center point.

The other day I was experimenting with turning beads from a 5" x 5/8" x 5/8" pen blank made from scrap hardwood. I drill a 1/8" hole centered in the blank. My drill is not 5" long, so I drill from each end and meet in the middle. I'm sure it's not perfectly aligned, but when I look thru the hole the light coming in from the far end appears round. If it was much out of alignment I would think the light would appear as if coming thru an oval hole. I turned beads from two different blanks. On set of beads came out with the hole centered, the other set came out with the hole way off center.

Anyone have any guesses on the cause(s) and cure(s). Since it seems to vary, I would think it's something in the lathe itself that's not aligning correctly when I move the tailstock in and out and lock it into place. I just don't have the experince to be sure.
 
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How does the points on the tailstock center line up with the headstock with the spur center installed? I've noticed on my old Excelsior lathe the tailstock has play and needs to be held against the front of the base rails when tightening to center true.
This also may be a case where a mandrel saver will work to solve the problem as it doesn't seat against the mandrel shaft but on the bushings themselves.
 
I honestly don't follow much of the above, but you might try turning on the lathe, before bringing up the tailstock. The mandrel will spin, seeking center. When you bring the tailstock up, make sure it IS centered. Hitting it off-center, repeatedly could be what is wearing your tailstock center.

FWIW
 
If you are using the factory supplied live center one step in the right direction would be to replace it with a 60* live center. John at Penturners Products sell a real nice one for around $35.00. Factory supplied centers are not 60* and the indent in the mandrel is.
 
Hey Steve -

As for the chatter it could be the bearing in the head stock or the live center, after running the lathe for a while check to see if you can wiggle the drive center or live center.

Depending on slop in the bed, One thing that helped me keep my holes straighter when drilling was making sure I always pull my tail stock over to the front rail to try to make sure is is sliding on the same z axis as much as possible.

You may want to try a Mandrel saver.

Give me a call at work tomorrow, I have a mandrel that I can take to Tx with me next week and have Kevin bring back to you.

Curtis
 
There are a few threads with advise on how to check your lathe alignment, but I'm wondering something else: if you were happy with your first 200 pens, why change? The only reason many advise not to tighten too much is because it might result in out of round pens: but since you didn't have that problem, why not stick with it?
 
Whaler said:
If you are using the factory supplied live center one step in the right direction would be to replace it with a 60* live center. John at Penturners Products sell a real nice one for around $35.00. Factory supplied centers are not 60* and the indent in the mandrel is.
Click to expand...

Whaler,
You're right about the live center. I was using the factory live tail center and switched to the Grizzly H3403. I have another live center from Woodcraft with replaceable points, one is cuppped but the other is not, I'll have to check the angle on the one that isn't cupped, but it looks like it might be around 60*. Thanks for the tip!
 
Gary Beasley said:
How does the points on the tailstock center line up with the headstock with the spur center installed? I've noticed on my old Excelsior lathe the tailstock has play and needs to be held against the front of the base rails when tightening to center true.
This also may be a case where a mandrel saver will work to solve the problem as it doesn't seat against the mandrel shaft but on the bushings themselves.
Click to expand...
Gary,
I'll check the alignment this weekend when I get home. I'll also look into the mandrel saver, couple of people mentioned that. Thanks!
 
ed4copies said:
I honestly don't follow much of the above, but you might try turning on the lathe, before bringing up the tailstock. The mandrel will spin, seeking center. When you bring the tailstock up, make sure it IS centered. Hitting it off-center, repeatedly could be what is wearing your tailstock center.

FWIW
Click to expand...
Another good tip! Thanks!
 
sseamen said:
Gary Beasley said:
How does the points on the tailstock center line up with the headstock with the spur center installed? I've noticed on my old Excelsior lathe the tailstock has play and needs to be held against the front of the base rails when tightening to center true.
This also may be a case where a mandrel saver will work to solve the problem as it doesn't seat against the mandrel shaft but on the bushings themselves.
Click to expand...
Gary,
I'll check the alignment this weekend when I get home. I'll also look into the mandrel saver, couple of people mentioned that. Thanks!
Click to expand...

I checked the alignment of the tailstock and the headstock with a center in each. When I hold the tailstock against the front rails the points of the two centers are almost exactly aligned, the point of one center just misses the other.

There is also quite a bit of play ion the rails. When I hold the tailstock against the back rails the two points miss each other by almost 1/8".

Obviously, I want to make sure the two are as closely aligned as possible, but is 'almost' good enough? Is 1/8" totally unacceptable, or just something to avoid if possible?
 
If you use a pen mandel and a live center it must be a 60 degree cone.
I had a HF lathe a small wood lathe variable speed, messed up my first mandrel cause did'nt know about the 60 degree thing. As for the other problem, I let my friends wife say it ,she owns a ----- store. ( I told him if he is going to mow yards ,He needs to buy a good mower ,not one that is made to mow one yard. His mover is less than a year old and is wore out. I figured it out, that mower in real life is ten years old, no wonder he wants me to get him another.)
 
Steve that seems like a fair amount of play in the rails. In my opinion you want it to align perfectly, although we all know perfect is subjective... .1 for Gov't work but .001 - .0001 for any real precision. After thinking about it for a while, I plan to have a friend cut me a #2 mt taper and bore it as to take a generic laser pointer. I figure with this I can use it like a bore sighter and determine if I have any variation in my rails as the tail stock is moved back, that is as long as it is able to be centered and repeatable...
 
sseamen said:
sseamen said:
Gary Beasley said:
How does the points on the tailstock center line up with the headstock with the spur center installed? I've noticed on my old Excelsior lathe the tailstock has play and needs to be held against the front of the base rails when tightening to center true.
This also may be a case where a mandrel saver will work to solve the problem as it doesn't seat against the mandrel shaft but on the bushings themselves.
Click to expand...
Gary,
I'll check the alignment this weekend when I get home. I'll also look into the mandrel saver, couple of people mentioned that. Thanks!
Click to expand...

I checked the alignment of the tailstock and the headstock with a center in each. When I hold the tailstock against the front rails the points of the two centers are almost exactly aligned, the point of one center just misses the other.

There is also quite a bit of play ion the rails. When I hold the tailstock against the back rails the two points miss each other by almost 1/8".

Obviously, I want to make sure the two are as closely aligned as possible, but is 'almost' good enough? Is 1/8" totally unacceptable, or just something to avoid if possible?
Click to expand...

I would definitely hold the tailstock to the front rail as a matter of practice when locking down. Is the vertical alighnment good too? You might want to slide the tailstock off the rails and see if theres any adjustment built in you can tweak or if theres anything you can do some simple mods to for improvement.
 
Alignment problem.

I had an alignment problem with my General Midi lathe when I got it. Whne you looked from the front, the head and the tail stock ligned up great, but when I looked from the top down it was ou of alignment. I just loosened the head stock screws and filed a little bit off of the front right corner where it fits into the slot, and thend lined it all up and then slowly tightened it all down so it wouldn't move and problem was solved.
I found this just the other day at (www.jlrodgers.com) under Lathe tune-up or Lathe alignment. If you PM me I'll send you a copy of it as I do not know how to attache it to this reply.
Good Luck and I hope you find success.

Sheldon
 
Turning between centers is an option too --- that allows for a lot of missed match of alignment of tail stock and head stock.

Where you are at -- Smaller is better than bigger in missed alignment.

(P.S) Spin the headstock to make sure the match point is indeed centered - Have seen a few that were not manufactured to have the center point dead centered (made a circle).
 
All good posts.

Mac, I just ordered a mandrel saver from PSI, so I don't need to worry about the cone.

Curtis, the bore sight laser idea sounds cool That would certainly ensure the tailstock was aligned with the headstock no matter how close to, or far from, the headstock it sits. Definietly something you'd want to use each time you mount a piece if it's something that really needs to be aligned. I wonder if you could mount a laser pointer behind a mandrel saver and get it accurately centered to shine thru the hole?

Gary, the horizontal and vertical are both off about the same amount. I'll take the tailstock off next weekend and see if it's 'tweakable'.

Grizzlyss, my headstok is mounted inside a casting that is part of the rails. It's not bolted to the rails and therefore I don't believe it is adjustable.

KenV, I haven't tried turning between centers yet. I may get to that, but I understand it requires different bushings. Also, when I was tunring beads (Individual, 15mm long by 10mm diameter, wooden beads, like you'd use on a necklace) I was tuirniog those between a live center (inserted in the 1/8' hole) and a 4 jaw check. After turning, the hole was not in the center of the cylinderical bead. Just judging by the rough measurements I made the other day and by the bead itself, I'm guessing I must have had the tailstock to the rear rail when I tightend it down and turend that nead.
I will try spinning the headstock to make sure the center was indeed centered.

I will also let my lathe spin (well, use it) for about an hour and see if there is any wobble in the bearings once it's gotten warm. (Curtis' tip).
 
I hate to say it but I had the same problems with the same lathe, I must of bought 10 mandrels and still had the same thing going on. I learned to shut the lathe off and turn just the blanks not the bushings 180 degrees during final turning and sanding, it seemed to help a little. Now I got a Turncrafter Commander and a thread on mandrel. No more of that stuff for me.
John
 
Grizzlyss said:
I had an alignment problem with my General Midi lathe when I got it. Whne you looked from the front, the head and the tail stock ligned up great, but when I looked from the top down it was ou of alignment. I just loosened the head stock screws and filed a little bit off of the front right corner where it fits into the slot, and thend lined it all up and then slowly tightened it all down so it wouldn't move and problem was solved.
I found this just the other day at (www.jlrodgers.com) under Lathe tune-up or Lathe alignment. If you PM me I'll send you a copy of it as I do not know how to attache it to this reply.
Good Luck and I hope you find success.

Sheldon
Click to expand...

Sheldon, Thanks for the tip! I folowed the link , did some checkeing and found the PDF you refered to. If anyone else has these problems, check http://www.jlrodgers.com/pdf/lathe_alignment.pdf. It explains both how to try and fix my alignment problem AND that this is also the probable cause of the 'groove' in my live center.
 
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