Thread: Advice needed with wonky lathe

Is the spindle shaft running true? Check the insert for the chuck and locking grub screw are tight.
have you over tightened the the jaws to the timber? That's all I can think of at the moment

Originally Posted by chuck1

Is the spindle shaft running true? Check the insert for the chuck and locking grub screw are tight.
have you over tightened the the jaws to the timber? That's all I can think of at the moment

i think it will be the insert, that is often is the problem.borrow another one and try it .....bob

I've tried two different chucks and have the same problem with both. One has an insert and this is in tight while the other doesn't have an insert but has the tread directly in the body of the chuck. Both have the same wobble and in the same spot relative to the shaft.

My thoughts are it is damage to the thread on the shaft but I can't see anything obvious.

If you dont have a dial indicator to check run out on the spindle use a marker and color the but face of the flange on the spindle. turn on the lathe and carefully move a piece of very fine sandpaper backed up with a block against the face just a couple rounds. listen to the sound as it contacts the face. smooth and consistent or loud soft.run it 300-500 rpm.if the sound varies you should be able to see the scrub. bearings will always run concentric they cant help it. do the bearings get overly warm? bent spindle? the only thread you could have damaged that could give you that much trouble would be the lead thread. use a thread file and dress it up. it is possible for the centers to line up and still the head could be skewed across the bed. chuck up a tappered shank drill in the headstock taper and check the end of the drill bit for alignment. it moves the target point further from the lathe. then rotate the spindle by hand and see if it still remains true.

I don't know the technical term, but I think it is about register. That is where the back of the chuck or the insert "registers" on the flat part of the shaft (just behind the threads, in your last photo.

Is it possible that you did some damage to this flat part when you "forced" things to pieces? As far as I know, there is always a poofteenth of give in threads, so the back of the chuck has to meet the shaft squarely or it will be out.

You could ask over on the Metalworkers side of the forum. What those blokes do not know about tolerances and runout is not worth talking about.

Cheers,
Alister.

I'm with Big A and Oreos. Get a nail brush or tooth brush and get the registers and inside and outside threads of the spindle and chucks shiny clean.

Look at the flats of the spindle and chucks with a strong light and maybe even a magnifying glass to see if there is a nick that made a raised place. If so, use a stone or some 150 to 220 grit sandpaper backed by some hard flat wood to stone down the bump.

The threads just hold the chuck on, where the flat parts meet is what makes the face of the chucks at right angles to a line between the center of the spindle to the center of the tail stock.

It is a good habit to clean and lightly oil the threads and flats on the spindle and chuck anytime they are assembled.

Also good to clean and oil the Morse Taper male and female fittings from time to time. I oil up a drive center and rotate it around in the spindle and tail stock every once in a while. I am always surprised how much rusty oil comes out. I then wipe out the inside with a cloth.

I have a bottle brush that I put in the MT and rotate around before inserting a drive or tail center. The centers are wiped off before inserting.

A little chip or some sawdust can make things run cattywampus.

Wood Hacker,

I had another look at your photo of the spindle. The register looks a bit rough. Did you hit that part with anything harder than a brass hammer or wood block when you were removing and replacing the spindle?

Driving the spindle into the bearings or driving bearings into the carrier can damage them.

I just realised that it is possible to enlarge a photo on here. When I blew the photo up, I could see what looked like a nick on the top other side of the register and some galling at the bottom.

This could be the problem.

Cheers,
Alister.

just a bit of advise. brass can also damage faces and threads if used improperly. an aluminum drive is much more safe but still can cause damage if used improperly.

Originally Posted by Big A

I just realised that it is possible to enlarge a photo on here. When I blew the photo up, I could see what looked like a nick on the top other side of the register and some galling at the bottom.

This could be the problem.

Cheers,
Alister.

See sketch below, black is spindle, blue is tool rest, red is hard stick of 12 X 12mm timber with 120 - 150 grit sand paper over the slant facing the spindle register.

Run lathe as fast as it will go. Slower, the bumps will push the stick out of the way more. Feed in very slowly, you should hear a fast snick, snick, snick. Start toward the center and work out. A slight dish is better than the opposite. Do a couple swipes and stop lathe and have a look. Put on fresh sandpaper and again. When it is smooth all around you will hear a hisss.

If the register is a rim with a recess, don't be concerned with roughness below the rim. Get the rim smooth.

Just barely touch the sandpaper to the rotating spindle, this will knock off the high places.

Thanks for all the suggestions guys. I had a bit more of a play this morning before reading todays replies and this is the result.

1. I used a thread file to clean up the spindle thread. Chucks go on and off a lot smoother now but no change in the wobble.
2. I used a marker pen to colour in the register and then lightly held a block of wood with 320 grit paper wrapped around it against the register. As you can see from the pic the whole register is a bit rough but is definietly removing the pen on one side. Where it is removing it is right where the biggest gap is when rotating the block against the tool rest which makes sense.

I only used a wooden block when driving the shaft in and out but my guess is that the pressure was not being evenly applied and it has "pushed" one side of the register back slightly.

I'm going to try Pauls suggestion to smooth out the register and see what happens.

I'm presuming that you used the same block of wood in both chucks so may be when you turned the block in spindle mode with the right sized spgit did you also make sure the face of the block that goes against the jaws was also true . If it is the register that has been bent you may need to take the shaft back out and have it fixed by a good machinist, just my thoughts. And have you checked the thread is running true and hasn't bent with the register.

Well I'm pleased to report that after trying Pauls suggestion my chuck is now running true (or at least as true as it has ever been). It took a bit of time and patience to get it to flat but the register is now all shiny and scratch and dent free.

Thanks to everyone for the helpful advice.

Old thread, but a related new question.

I have one of those old Hyco lathes. I have a little problem with wobble on the left hand side, but some of the comments
in this thread have given me ideas what to do. I acquired the lathe from a friend who made a living by turning kauri bowls for many years,
but eventually he burned out on it and went on to make stretchers for his painter sister and fine furniture. So I ended up with the lathe
for 100 bucks. I haven't done a great deal with it, turned a few bowls, and did a bit of turning between centres for a few mallets and bits
for my wife's looms, but I am far from well-versed with it.

Now my drive/fan belt has gone old, brittle, and shiny and I really really want to replace it. Last bowl blank I tried to rough out, it started
slipping like crazy without my applying much force at all.
I am not sure how to drive the shaft out of the bearings. Obviously you need to loosen grub screws in the pulley, but what else needs
to be removed/loosened, and do you drive it towards the bed of the lathe or do you drive it towards the headstock end? I'd rather know
beforehand so I don't trash the seating of any bearings and for all I know the shaft may be stepped in there.

thanks in advance, -Peter