lathe troubles. bits,toolpost, tapered shafts!

[Thomas Harris]

The results are improving, but the bit grinding is a skill I need to work on. Some of my tools cut fine, then I'll attempt a grind on another and it does nothing but chatter and make ugly threaded rod. The lathe seems to turn .005" taper on straight turns the max. length. Maybe this is setup/ajustment, or perhaps just the wear of the lathe. It easily made some of the tools I mentioned in an earlier post, and they look and work quite well. I don't quite get the dead center part. It tends to heat up and smoke, then get lose sometimes. I oil it and predrill it slightly with a center drill. Is turning on centers and using a lathe dog more reliable on long pieces. The lathe also has no reversing gear. I would guess someone had a "incident and ran into the headstock. Is the proper leadcrew direction toward the headstock or away from the headstock? Seems like I read toward the chuck is best beause that's the most solid connection to push the tool into. I know this is nothing but a list of rambling questions, but any advice from an experienced lathe operator would be appreciated.

[vicegrip]

You , have a handfull of issues here ,,,,and no messaging options ..

If you would like some detailed attension , I'll help over the phone ....and call you back ....


not spending my week-end on the keyboard ....
type WAY too SLOW

Reguards Phil ..........262-930-0516
1000s of hours of lathe-experience at your service

[precisionworks]

There's a wealth of lathe info on the Practical Machinists BBS, click here. Try the search function first, read as much as you can, then post your question.

If you haven't already read the classic book How to Run a Lathe (from South Bend Lathe Works), that's a great place to start. Available online for under $10.

[vicegrip]

In short ....you likely have a lathe with tapered ware in the bed-ways , and one or more spindel issues ......and along with tool-grinding learning-curves ..... and trial & error getting feed / speed ballances right .....

thats a lot to sort thru .....if you're just starting out !!
a veteran lathe-hand can walk up to a lathe that belongs in the re-melt & in a few minutes get results by compensating for all the issues.

but that's a tall order for a beginner

Phil

like me sorting thru my oldest tranny's High-freq. system ....had to lean heavilly on the pro's here

[aametalmaster]

Here's a link for a free copy of HTRAL by South Bend, its old but most copies are.
http://www.wewilliams.net/SBLibrary.htm
I can also help. Here is a group i have with lots of pics of lathe work done without a lot of tools and tooling of some easy stuff i have done. http://groups.yahoo.com/group/southbend10k/ ...Bob

[Mike W]

You can get a live center for the tailstock. It has a bearing in it. You need to adjust the tailstock so it is inline with the spindle. You can use a test indicator in the spindle to sweep the taper in a tailstock and adjust the tailstock screws to zero it. If it is off, you will cut a taper.

You can turn a center out of mild steel held in the chuck and then use a lathe dog against one of the chuck jaws. Mark it so you can take it out and put it back in the same location. This saves time over taking off the chuck to use a center. Lock down the compound slide to eliminate one cause of chatter.

[Qrazy]

Also, this may sound strange, and I am not saying this is your problem, but make sure your lathe is level. I know, I have a Starret level that I have used in the past, and a level lathe is a happy lathe....

Good luck...

[vicegrip]

Above is spindle with poor fit in bearings....
under heavy ruFF cut...it rides-up in the head and leaves a good finnish.
with a fine cut it rides low in the bearings and leaves a good finnish.
BUT ....in a medium cut the spindle chops up & down in the bore ,
as it rides-up on the tool and backs down ....leaving a bad finnish

Above is where you look for heavy wear ....the tiny un-worn regions (green)
above and below
will have a measurable depth to the worn area (yellow) ....the heavyest I've seen .014"
getting worst near the chuck!!

This is caused primarilly by the bad & all too common practice of using abrasive strips to acheive sise
and leaving the ways exposed to the grit / debris!!
The worse the ware the more the sise is sanded-in ....exaserbating the dammage!
The drive-way (groove) will be wider than normal in the region of most useage..
as much as another 50% !!

using the steady-rest & a morse drill extension (which is manufactured accurately)
you can extend the spindle out to fresh bed & lead-screw ....
and machine the end to receive a threaded chuch or shrink a collar on-to the end for other chuck styles ........

there is a retired fellow in Milwaukee who salvaged a H'school lathe in this manner
that was destined to the scrapyard ......he can do the finnest work imaginable on it
and has single-pointed threads smaller than 2-56 on it !!

unless you have the cash to get a bed (regrind) not possible where the head is not removeable

a bronze split collar can be custom made to choke-up on the spindle-extension
an oiler would be needed

[aametalmaster]

Nice pics grip and good explainations....Bob

[Thomas Harris]

I tweaked the tail stock and got within .001". I am ok with that. The only question I have is should I move the tailstockwith each piece chucked? Is this part of a normal setup? Basically what I am doing is putting some side pressure on the workpiece to force the uncentered holes into perfect alignment. Should I be using a steadyrest when I drill the tailstock hole? I am getting some dial calipers soon and this will eliminate lots of guessing. I have a good micrometer and vernier claiper already. Oh, by the way, my leadscrew does not have ways cut in it. It relies solely on the bed ways to keep it in alignment. Remeber, this is just a baby lathe with a 6 swing and 18 length.

[Mike W]

I don't understand "moving the tailstock with each piece chucked"? I normally drill the center hole with the end of the work close to the chuck. If I want it to be more precise, I use a 4 jaw. If your spindle hole is too small for the work to pass through, you can use the steadyrest when you drill the center hole.

[vicegrip]

I tweaked the tail stock and got within .001". I am ok with that. The only question I have is should I move the tailstockwith each piece chucked? Is this part of a normal setup? Basically what I am doing is putting some side pressure on the workpiece to force the uncentered holes into perfect alignment. Should I be using a steadyrest when I drill the tailstock hole? I am getting some dial calipers soon and this will eliminate lots of guessing. I have a good micrometer and vernier claiper already. Oh, by the way, my leadscrew does not have ways cut in it. It relies solely on the bed ways to keep it in alignment. Remeber, this is just a baby lathe with a 6 swing and 18 length.

I ended up typing anyway ...LoL
your taper is from the "ware" condition in your bed-ways (2nd pic)
and your cariage is moving toward or away from spindle-axis , as you move toward your chuck ....using your tailstock is crowding the workpeice , till it lines up with the skewed cariage travel....

using a sharp center-drill & redrilling lightly (watch for scant shavings) will give you a good center ...have the flutes"edges" top and bottum (helps)
unless yout tail-stock has a rocking-horse condition ( second most common ware problem).....inwhich case the drill will be below center .....

this can really compound starting to learn Lathe-work

[vicegrip]

your taper is from the "ware" condition in your bed-ways (2nd pic)
and your cariage is moving toward or away from spindle-axis ,................................................. ....inwhich case the drill will be below center .....

this can really compound starting to learn Lathe-work

The above asumes too much , My bad
Take a lenght of stock and hang out 4 diameters in lenght
say 1" X 4" long

Firmly chuck this peice , (if jaws are worn , use a few wraps of paper
under the outer 1/2" of the jaws)!
!! chuck only , NO tail center !!

now grind a sharp bit with exagerated Pos rake , and take a few fine passes ,
untill no more comes off .

Now mic at inner and outter ends , the difference is the taper in your ways .
If none than it's not the desciption in post # 12

[Mike W]

Visegrip, this is a 6 by 18. The ways are probably pristine.

[vicegrip]

Visegrip, this is a 6 by 18. The ways are probably pristine.

I realise that could be the case , however his original thread seems to describe a lathe that has seen considerable use if not abuse .....and although atlas built great design features .....they were not intended for tough service .....ways were not flame hardened ...I don't think!

If it has cross-screw slop , and spindle hop (chatter) it likely has advanced ware overall

I don't envy learning lathe-work on a worn machine .....If I'm incorect about this lathes condition the reasoning is still sound and may help someone who searches the topic .

On PMMB a question like this will yeild three pages of dribblings by a handfull of authorities , most of whom didn't even fully read the initial question.

So I'm attempting some ground-work for understanding used turning machinery
I bought a worn-out lathe about a year-and-half into becomeing a machinist so long ago
and was very frustrated why I couldn't get results any-where near that which I got at work
eventually sold the chucks and scrapped the thing

Phil