Lathe backplate/chuck allignment

[mark roberts]

I recently got a harrison 140 and wanted to put a new chuck on it that I won at an auction. I got a new backplate and mounted it on the lathe, machined to size and left a small tenon of 4mm to align the chuck. The tenon was a very snug fit. The chuck is a new Tos svitavy 4jaw self centering. They look quite good quality. After I installed the chuck and put a clock on it I got 7thou runout.
I would of thought it would be better considering the close fit?
Should I do the tenon a bit smaller and then just dial in the chuck to run true before fully tighten the bolts.

 

[Scalarocco]

Try doing runout tests on various sizes of bar, just to rule out any possible error in the machining of the scroll. If the error is the same regardless then you could do as you suggest and dial it in after machining the spigot.

 

[Agroshield]

Send the chuck back and buy an independent 4-jaw. SC 4-jaws are the Austin Allegro of the chuck world.

 

[Brad93]

Have you clocked the backplate.

L00 taper notorious for lack of repeatability if there are any dings to mating tapers

 

[brightspark]

if it was fitted and machined in situe it should be spot on if u have taken it off put it back on minus the chuck and clock its accuracy for repeatabilty as above post

 

[mark roberts]

Send the chuck back and buy an independent 4-jaw. SC 4-jaws are the Austin Allegro of the chuck world.

I bought a bunch of stuff that was poorly photographed on bidspotter, there was a 4 jaw independant also. I noticed it has big holes machined in the back is this for mounting onto a backplate, it came with a backplate bolted to it.

Have you clocked the backplate.

L00 taper notorious for lack of repeatability if there are any dings to mating tapers

I stoned the taper on the spindle and made sure everything was clean, I used a new tip and powered feed to get a really good finish. I then clocked it and it had no runout. I wonder if its because I then had to take it off the machine to bolt on the chuck and once it was refitted it introduced the error? Either that or my spigot wasn't as accurate as I thought.

I also went to lube up everything and some numpty has used grease. Ive took the cross slide to bits to remove the grease but didn't fancy taking the saddle to bits. If I keep putting oil in will that purge the grease.

 

[Agroshield]

...there was a 4 jaw independant also. I noticed it has big holes machined in the back is this for mounting onto a backplate, it came with a backplate bolted to it.

...If I keep putting oil in will that purge the grease.

To get the best out of the SC chuck you have, your idea of making the spigot smaller and then dialling in the chuck before tightening the bolts is a good one. Have a read up on 'griptru' or 'set tru' three jaw chucks as that might give some ideas.

Once it is dialled in at a particular diameter, test it on some bigger and smaller diameters (without changing how you have dialled it in). That will tell you a bit about whether it is the chuck itself that is not so good or if the problem was with the mounting. It is worth clocking the outside body of the chuck just to get a feel of how true it runs, but what you see is not conclusive of anything. It is possible but a little unlikely that the recess in the back of the chuck is not true to the jaws

For the 4-jaw independent, can you post a picture?

The traditional method of flushing a lathe headstock was to fill it with paraffin (kerosene), run it for a bit and then drain it. I think heating oil is a close relative of kerosene. The saddle is the horizontal bit that slides on the ways. The apron is the bit at the front which hangs down and has the handwheel and levers on it. In any case, a light oil will flush the grease out better and it will be easier to wipe up the residue. If it is possible to remove the oiling points, you might be able to squirt some carb cleaner in as that is a good solvent.

 

[ukracer]

@doubleboost has videos on fitting taper chucks.

He will probably see this thread and drop a link in when he has time...

 

[Seadog]

Mister Crispin recently did a video on refurbishing an L0 spindle.

 

[Brad93]

Mister Crispin recently did a video on refurbishing an L0 spindle.

that was a short taper spindle, camlock style.

L00 would be very difficult to repair in situ

 

[Sergei Slovenija]

Mister Crispin recently did a video on refurbishing an L0 spindle.

where to see it?

 

[Seadog]

Search Mr Crispin on YouTube. As Brad said, it was a camlock, not L00.

 

[doubleboost]

 

[ukracer]

Told you he would be around.

 

[mark roberts]

For the 4-jaw independent, can you post a picture?

Heres a pic

 

[Agroshield]

Heres a pic

The big holes are for lightness and to reduce inertia when it is spinning. That has been machined from solid and is as it left the factory. Older ones were cast and would have had four recesses in them between the bits that secure the jaw screws.

 

[Brad93]

have you reclocked the backplate after removing from machine and refitting?

 

[Hopefuldave]

Did you stone any dings (however small and insignificant they look) off the mating surfaces? Really doesn't take much to get loads of runout!

Dave H. (the other one)