Spindle adapter

[Mike Lutes]

Hi folks
I need some feedback on an idea I've had. Forgive my ignorance as I've been forced to earn my living as a Millwright for 35 years .
I'm still checking out my recently acquired old ( single tumbler )14.5" SB lathe
It's in pretty good working condition but the inside of the spindle has a couple small helical gouges where something dramatic must have happened sometime in its life. It came with a collet drawbar but no spindle adapter or collets

Today I set up my taper attachment by indicating the length of the internal spindle taper, then cut a male taper to make an "adapter" that should run true in the headstock.
It doesn't go in as far as it should and it wobbles a little.
I checked the fit with blue and think that whatever spun and gouged in the spindle also slightly distorted the hole and left a burr by the gouge.

I'm thinking if the spindle is not too hard then I should be able to
use a boring bar with the same setup on my taper attachment and clean up the distortion ?
If the spindle is too hard to turn with a 1/2"bar with 1/4" hss bit then perhaps a brass Lapp turned to that taper would eventually work ?

Perhaps this is a common problem ?
Mike

 

[Bob Korves]

I would first try to lightly stone the internal spindle taper to remove any burs, and then reassess the spindle condition. If the taper definitely needs to be re-cut, I would grind it with a tool post grinder or similar. That is a fussy job if you care to have it correct.

 

[Mike Lutes]

Thanks, I'll see if I can work a stone in there. I understand uniformity and surface finish are important I don't currently have a tool post grinder but my dad has one rigged for his Colchester. I'll check out how I might mount it if required.
Mike

 

[Tony Wells]

When you set your taper attachment to match the bore, it is imperative to have the indicator tip as close to centerline height as possible. Any error in height will be reflected as a mismatch in the taper. Be sure you are as close as possible.

 

[Bob Korves]

Thanks, I'll see if I can work a stone in there. I understand uniformity and surface finish are important I don't currently have a tool post grinder but my dad has one rigged for his Colchester. I'll check out how I might mount it if required.
Mike

An extremely accurate angle and concentricity of the taper is the important thing. A pretty surface finish is way down the list at number two... Indicating an existing taper can give you a perfect copy of an imperfect taper. Either use a new, high quality taper you think you can trust to set the angle, or use some sort of sine setup with gage blocks. Either way, this is not a quick, bang it out job, it is difficult and fussy to get a good result, at least from what I have seen and by my own efforts. It is certainly well worth doing, and it is a great learning experience.

 

[T Bredehoft]

Instead of boring or grinding, you might consider finding a taper reamer. No worries about center height. But still, take it very easy.

 

[Mike Lutes]

I'm beginning to get my head around the complexity involved and I appreciate the advice and feedback
It's been a long time since I've done a project like this but "one time at band camp" I turned, carburized, hardened then finish ground to within 2 tenths 2 #3 morse taper ring and plug gauges. ( dropped 3" it took 6 tons to push them apart) But that was a lifetime ago and as I remember setting up the cylindrical grinder to finish the ring gauge took me a few days despite having all the toys at my disposal.
Now Im limited to my meger but growing assortment of precision tools for my hobby shop and the general mechanics tools I've been unable to do without

When I set up the taper attachment I used a centre in my 4 jaw and centered a fairly new #2 to a 3 morse taper sleeve between it and the tailstock centre ( it was easy to set the dial tip on centre ) then I set the TA till the indicator read 00 across the sleeve. Then I switched to an internal indicator setup with 2" of reach, I set my mag base on the machined surface of the crossscrew cover and was able to set the indicator tip height by eye with the tailstock centre then turn the base and indicate up to 2" deep in 2 undamaged areas. TIR of less than .001" . I should also have rotated the spindle but I didn't

I think SB spec was .602" per foot I do have a rusty 5" sine bar that I made at band camp but no gauge blocks or even .0001 indicators so with my current setup if I set very slow feed ( this lathe has increadable slow feeds possible , very light cut and a sharp tool on centre ( should be easier than setting up a grinding wheel ? ) is the spindle too hard to attempt to true it with other than a grinder ?

I never actually looked for a reamer but I suspect it would not be a common tool . The taper is reportedly close to a # 4.5 in overall size but with a TPF nearly equal to a #3 it would be an oddball
I don't need to maintain the exact taper that SB specified because I don't have the SB adapter anyway but I'd like to get it as close as I can so I'll try to suppress my 35 years of brain fogging work.

Mike

 

[Mike Lutes]

I tried stoning today and made little progress as the spindle material is hard as flint. As recommended some kind of a grinding fixture will be required. So this project is on the shelf for a while.

Meanwhile today's examinations discovered a drive related problem that is going to require millwright type grunt work.
It looks like the underdrive needs to come apart to repair a misaligned bottom steppulley shaft (the drive belt runs off about 50% of the time on startups now ). I think you could throw a cat threw the fit between the shaft and bearing on the nondrive end. Its obviously pooched and it looks like both ends may be Babbitt. They predate anti friction bearings anyway.
Im looking around for info and I'll start another thread if I get in trouble but it looks like with patients, a bit of planning, and a couple skinned knuckles everything should come apart and out the hole in the side or end of the base ?
The only related u tube video I could find was a total lathe rebuild reassembly and the guy just set the base over the assembled unit. I hope I don't have to go that far but time will tell.
Cheers
Mike