Advice needed with wonky lathe

[wood hacker]

Hi All

I'm hoping that that brains trust here can offer some advice to help fix a wonky lathe. A while ago I needed to replace the belt on my old Hyco lathe, which requires taking the whole spindle shaft out. The shaft was difficult to remove and required a bit of force to get it out. Knowing that damage to this could bugger the lathe I did everything I could think of to protect the shaft and threads during this operation. I replaced the bearings at the same time and reassembled the whole thing. Centres lined up nicely (pics from above and the side) and away I went again.

Since changing the belt I had only been turning between centres and have had no issues. However I have now come to do some bowl turning and have struck a major problem. When the scroll chuck is screwed onto the shaft there is a noticable wobble. This certainly wasn't the case before changing the belt. I have tried both my scroll chucks and they both exhibit the same wobble.

In the pics attached the wood cylinder has been turned between centres and then mounted in the scroll chuck. The tool rest was placed against one side and photographed and then rotated 180° and again photographed. As you can see there is a noticible gap. At the size of this piece its about 1mm but as the size gets larger the wobble gets more and more pronounced.

So throwing it open for ideas. What could be the cause and more importantly how to I fix it.

cheers
WH

[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

[robyn2839]

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

[wood hacker]

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.

[oreos40]

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.

[Big A]

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.

[Paul39]

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.

[Paul39]

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.

[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.

[oreos40]

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.

[Paul39]

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.

[wood hacker]

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.

[ian thorn]

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.

[wood hacker]

Well I'm pleased to report that after trying Pauls suggestion my chuck is now running true :hpydans: (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.

[P.W.H.]

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

[Paul39]

Peter,

If the bearings sound good, you might want to use one of these:

1/2" Power Twist Plus Link V-Belt - Rockler Woodworking Tools (http://www.rockler.com/1-2-power-twist-plus-link-v-belt?utm_source=google&utm_medium=cpc&utm_term=&utm_content=pla&utm_campaign=PL&sid=V9146&gclid=CIr-tYOCr8sCFUwvgQodqPQFYQ)

They are reputed to run smoother than a regular V belt and can be installed without removing the spindle.

You might first try rubbing your existing belt with a rag soaked with rubbing alcohol, giving the running surfaces a rub with 220 grit sand paper, and increasing the tension on the belt.

If a belt has gotten stiff and set from sitting for years, often a 10 minute run at medium speed will warm it enough to make it run smoothly.

It is best not to drive the spindle out. Banging on the shaft may damage the bearings by making dents in the running part with the balls or rollers. Better to pull or press out with a long bolt or timber and long clamps.

Be sure to check for one grub screw under the first one in each hole. When the area on the shaft appears where the grub screw has bitten, sand off the raised ridge. Use lots of penetrating oil on everything.

[P.W.H.]

Things turned out to be more wonky that I was aware of. I had a look at the shaft opposite the bed of the lathe,
and that runs true, no wobble in it at all. However ...
... up against the bearing there's a recess milled into the shaft that holds a split bush that presses against the bearing.
over the top of that sits yet another bush that holds the split bush in and comprises a register of sorts.

373573373574373575

But, as you can see, that register is nowhere near the faceplate. The faceplate sits up against nothing. That is, what my
friend had done was to put a grindstone in there with a couple of washers (and fat paper disks on the grindstone) so
of course it would be somewhat loony to expect that to be wobble free ... which apparently it was for him, but certainly
not for me.
Even the face of the outer bush is not wobble free as it were. I am at a loss as to how to actually get a register here that
the faceplate (or a chuck) can ride against. There's a huge gap between the bearing and the thread on the spindle.

This is how he had it set up when I got the lathe:

373576

Sadly, the register on the other side of the shaft, facing the bed, is no better. It's seriously scarred and looks like it's actually
been attacked with a cold chisel. The MT drive centre is fine, but I can't get a chuck on there either, I think, without taking the
whole thing to an engineer and getting it rebuilt. It does not look like that face can be undone from the shaft at all.

I was very much hoping to be able to mount a chuck on this thing. The lathes bed and housing is in very good nick, very solid,
very heavy, bearings are good, even though it does not have a variable speed motor.
I don't think I do enough turning to warrant replacing it with a midi lathe.

<sigh>

[wood hacker]

Hi PWH

Not sure of the relative ages of our two lathes or if something is missing from your one but mine has a slightly different arrangement on the outboard end. As you can see from the pic mine has an extended collar that fits over the split bush and goes all the way back to the threads to provide a surface to register against.

Not much help for your problem though I'm afraid.

cheers
WH

[P.W.H.]

Well yes, actually, that gives me a clue. Presumably my mate has dropped a piece so he could do his thing
with the grindstone. I guess if I go and see an engineer with a metal lathe, something might be done about
this.

thanks -P.

[wood hacker]

Let me know if you need any more details pics to show the engineer.

cheers
WH

[Mobyturns]

The insert / chuck design on Nova chucks uses the nose of the spindle thread to register the chuck, so you could true up the spindle nose & use Nova chucks.

[P.W.H.]

That is excellent news, indeed. Thank you for the heads-up.

[Mobyturns]

That is excellent news, indeed. Thank you for the heads-up.

Peter my response was a little tongue in cheek :- as a lot of turners use their Nova chucks in that manner and then wonder why they get problems with vibration.

All chucks need to "register" the chuck (or insert) to the spindle to maintain accurate running, so it is important that we protect both the spindle thread and the "registration surface" which is generally a machined flat surface on a wood lathe spindle.

It is true that the inserts on Nova chucks register the nose of the insert thread to the inside face of chuck body at the bottom of the insert thread in the chuck body. Vicmarc inserts register the two flats on the rear face of the chuck body to the boss on the insert. However the rear of both Vicmarc and Nova inserts should reach and be nipped to the "register" on the lathe spindle.

Problems arise when the spindle nose thread is longer than the depth of thread in the insert which means the nose of the spindle binds to the bottom of the insert/chuck thread before the registration surfaces actually meet. Nova inserts and more so their direct threaded chucks have a relatively short thread which means they are quite often used incorrectly - which is what I was having a little dig about.

Nova / Teknatool actually advise turners to check this in their manuals and if necessary have an accurate spacer machined so that the chuck registers to the spindle register via the spacer.

[P.W.H.]

Right, and a good dig it was, too :-) Thanks for taking the time :U

We'll just have to see. My wife made the pertinent comment "And what are you going to do with all those bowls?"
and she's not at all off the mark: there are a LOT of woodturners in these parts and I would be doing it casually at
best, I have more passion for designing and building furniture - my attempts at turning are more in the way of my
usual "I want to get a handle on how that works" diversions.

So I'll give this a little rest ... getting a sleeve machined that can be a good register for a chuck should not be too
much of a problem on the bed side of the lathe. The outboard side is a mite suspect.

-P.