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View Full Version : help! mounting two new chucks! dont fit!



steve schaeffer
07-24-2003, 02:43 PM
hello all, its been a while since ive proposed a ponder, but here goes.
i finally got my sheldon lathe project done(almost)
i got the variable drive and related controls all done and it works better than expected. including a jog function and digital speed readout picked up off the spindle gear teeth with a mag sensor. cool stuff.
heres my question, i have a 2 1/4 -8 threaded spindle, and i bought a 3 jaw and a 4jaw chuck for it. both have a 2.250" register, but my spindle is around 2.280. the lathe had a back plate on it when i got it, and its register was machined to 2.315! im confused as to what i need to do to make these chucks fit my spindle. should i machine the spindle on the lathe to fit? and what clearance should i allow (.002"?)i thought these things would just bolt on but its not happening, and im not sure where to go from here. im afraid to mess something up without having asked a question first. so thanks for your input!
thanks,
steve schaeffer

kenc
07-24-2003, 03:38 PM
Steve,
I have a Sheldon also, 1957 WM56-P with mechanical variable speed drive. The stuff supplied with the lathe, a 6" 3jaw Buck, 4"
4 jaw Cushman on 5" backplate and 8" faceplate all fit my 2 1/4-8 spindle perfectly. As I recall, the spindle diameter was 2.250 OD across the threads exactly but I would have to confirm.
Now, I did buy a POS 4 jaw Taiwan made chuck from warnertool on ebay. This thing had it's threads undercut by 20thou so as supplied is useless. I will endeavour to cut the additional 30 thou once I've purchased the necessary all new belts and a missing hi-pro key.
Anyway, isn't it the threads and not the register that should be 2-1/4?
Are your chucks Taiwan/China stuff?
Ken

nheng
07-24-2003, 03:42 PM
Steve: Here's a link to a listing of lathe spindles and your numbers match the Sheldon.

http://www.lathe.com/spindles.html

I have a Bison on one of my machines which came with only 0.0005" clearance between the stock chuck and the spindle register. It should probably be kept as close as possible provided nothing else prevents it from seating on the spindle properly.

IMHO, you'll get the best runout by fitting to this area AND seating squarely when screwed all the way on. This topic can tend to get somewhat religious at times though http://bbs.homeshopmachinist.net//smile.gif

Den

steve schaeffer
07-24-2003, 05:32 PM
it looks like the spindle register diameter is 2.2704", and the chucks i have,(a bison 3jaw, and a gook 4 jaw, ) have 2.2508 register bores equals a difference of about 19 thou.

should i bore both chucks out, or turn the spindle down? how much clearance should i allow?

Evan
07-24-2003, 05:45 PM
It sound like the chucks are correct. I would leave them that way so they can be used on another machine if necessary. Don't blame me if you make a misnake, but I would fix the spindle. Clearance? Yes, just enough to accept the chucks. As is said, you can't put a 1" part in a 1" hole. Maybe try for .0002 or 3 clearance. Use a bit of fine lapping paper each time before micing the spindle. Sneak up on it. Sounds like the chucks may have .0008 clearance intended.

SGW
07-24-2003, 06:09 PM
I'd machine the chucks as necessary. A new chuck backplate, if you mess up, is a lot cheaper and easier to replace than a lathe spindle.

nheng
07-24-2003, 06:31 PM
I agree with SGW. Your chuck seems to match the "survey" numbers in the link I posted earlier. Also, the spindle may be hardened and ground or case hardened. In either case, there is a risk of permanent damage by altering it.

DR
07-24-2003, 07:02 PM
<font face="Verdana, Arial" size="2">
Originally posted by steve schaeffer:
should i machine the spindle on the lathe to fit?
steve schaeffer[/B]</font>


Whatever you do, DON'T MACHINE THE SPINDLE!!!!!!!!!

Evan
07-24-2003, 07:12 PM
I belive the concensus is to NOT machine the spindle. I must concur and withdraw my earlier advice.

steve schaeffer
07-24-2003, 08:23 PM
well, i couldnt wait, and i machined the spindle. i took a thou at a time and i got it right.after looking at the chart it seems that there is no standard register size from machine to machine, however the chucks are standard size. i used a carbide tool and took the 19 thou off. i figured that the machine is very old, and i wanted to be able to use the chucks on another machine if the need arises. now i have other problems, i cant get a cut without it chattering like crazy. i have those steel leveling feet and im thinking that is my problem. im going to try putting some paper under the feet to see if it goes away. im very frustrated right now. i got the lathe for nothing, because it was missing some of the original drive pulleys. i made my own motor and jackshaft assembly, with the mounting plate, and installed a variable frequency drive. i spent a lot of time (too much) cleaning and painting everything, and making new parts as needed for it, im starting to think i put perfume on a pig. i put a 1" piece of bar stuck in the chuck, length about 3' to a live center in the tailstock. i cant even take .005" without it chattering like crazy.
im going to eat something and chill out then get back into it and see if i cant figure it out. thanks for all of your advise regarding the spindle though. i dont know if what i did was right or wrong, but the chuck is on, and my other one fits too.

steve

Evan
07-24-2003, 08:47 PM
Check for play in the crossfeed screw. Try locking the crossfeed gibs and take a cut. A three foot bar of 1" is pretty long. Did you use a center steady rest?

steve schaeffer
07-24-2003, 08:55 PM
no , i dont have a steady rest for the machine, i would like to build one in the future, but that doesnt help me now. when i get back out there im going to try turning a stub in the chuck and see if it is indeed the machine, or just the long bar that i was trying to turn. i thought id be able to dump a bar in there, turn it straight, and align my lathe with the leveling feet., but i guess it isnt going to cooperate with me.

Oso
07-25-2003, 01:02 AM
I agree, 3 foot of 1" might not chatter, but it won't turn right either. Or we might not both be calling the same thing "chatter".

You don't need a steady for that kind of turning, you need a follow rest that always is right near the cutter because it rides with the carriage.

If that is an old lathe, and given to you, check the ways for dings.

A ding will form a point for the carriage to rock on, and will drive you nutty. An old "giveaway" machine may have been functioning as a handy workbench and anvil for a while before you got it...........
Stone down any you find, level the bed, and adjust all the gibs, oiling things too..

Then you should only have "legitimate" machine or work stiffness type chatter left as a problem. That you just work around.

Most Sheldons are pretty stout, so it shouldn't be a problem unless there is a lot of wear. Then the carriage might be loose in spots and tight in others, and tippy going from one to the other.

Evan
07-25-2003, 02:48 AM
Oso,

Yeah, you are right. I really meant to say a follower rest...

I don't think of it 'cause I can't mount one on my SB9 without modifying the cross slide. It's the biggest single fault of the SB9, no T slots.

[This message has been edited by Evan (edited 07-25-2003).]

Thrud
07-25-2003, 03:01 AM
Steve

One other source of chatter is inadequate waylube on the carrage and cross slides as well as the bed. The Way lube helps to dampen vibrations. If it is inadequte you will never get rid of the chatter what ever you do. Fact of life. If your ways have been scrapped and have not been done for an approriate number of bearing points this can also cause problems with stiction (a term from hard drive technology where the polished heads would wring themselves to the platters - it was solved by controlling the surface finish on the platters).

[This message has been edited by Thrud (edited 07-25-2003).]

steve schaeffer
07-25-2003, 04:58 AM
thanks for the posts. while you were typing ive been working, haha. it 3 am, and ive made some progress! i found that the way sheldon's cross feed screw is assembled, wear occurs between the spacer and the bushing, allowing for slop, i took care of it with a little turn of the end of the micrometer dial to allow the handle to tighten up the assembly, also a new woodruff key., then i shimmed my gib on the cross slide, and had to break out the file to knock down a high spot towards the end of the cross feed way. (probably the anvil theory?) i dont have a scraper nor do i know how to do it, so i blued it up and used a file instead. next i found the taperlock drive pulley was loose, bouncing a little on its hub, fixed that, then back to the apron and bed ways, i found that the guides/gibs that go under the bedways to sandwich the assembly was too loose, especially on the v-way, which i felt was important to keeping things running in a straight line.tightened that up, oiled everything again, and started cutting on an 8" long x 3/4" shaft, supported on end with a live center. took cuts of as much as .035" with no chatter and good surface finish. i set up to cut a thread when i got to .500" to see if that all works, and got into the depth of thread about .040", and the shear pin broke on the lead screw. (i had a piece of 1/8 aluminum welding rod in there, so its no wonder, i hadn't made it for some brass pins before the store closed) however for the amount of thread i did get cut, it looked pretty good and the repeatability was also good. im starting to feel a little better, ha. im just glad to finally cut something. i put a lot of work into the thing, making the drive and control panel, and im pretty happy with how it functions. the only thing that i was worried about really as far as that went was how the apron clutch would work, as i did not install a lever clutch on the main drive. it works great so i dont have to worry about it now. i do have a problem with the wormgear that is driven by the lead screw, it is worn pretty badly, and i dont think i can make that because i dont have a lead capable dividing head. any ideas? or would anyone be willing to make me one? ive never made a gear yet either. maybe there is a way i can do it?
thrud, how did you lock your chuck to your threaded spindle? is that something i can do to my chuck? i would like to be able to run in reverse if possible.
ok, time for me to go to bed! long night. thanks for all your input, this project has been killing me today.

i really appreciate it.

steve schaeffer

metal mite
07-25-2003, 09:00 AM
Steve,

What radius are you using on your tool?
A small radius (1/64 max) with a moderate speed and feed should let you cut .1-.125 per side, or more on mild steel.

On a light lathe I use a tool with about a .005- .010 chamfer, sometimes lightly stoned to a radius for aluminum.

Put a nice lip, like an icecream spoon for steel, and aluminum, (exagerated) on the tool and stone a flat of .001 or so across the top.
Use a flat top tool for cast iron and brass.


Use a 0 to a couple degree positive lead angle (tool nearly square to machined surface).
The more lead angle, the longer the effective cut per material depth of cut.

The chips should curl off making clean c's and 6's (shape).

Thad Sheldon should be a good machine provided the bearings, or ways and slides aren't fried.

Too light a feed will also cause chatter.
I would use .005 min feed and adjust the rpm, and depth, to max. conditions.

Sometimes the back gearing on a machine can transfer vibration to the work. Use belt drive if possible.

I have seen a "tool and die man" try to use a 3/8 dia button tool on a new Roberts CNC lathe and pronounce the machine junk cause the noise scared the birds off the roof.

Worked fine for me as described above.

mite

Oso
07-25-2003, 10:23 AM
For a burr file, take a 6" or so not-new file and rub it on a medium grit stone until the points of the teeth are flatted somewhat.

Then it won't cut except for things that stick up. Just like a thread cleanup file.

firbikrhd1
07-25-2003, 10:33 PM
I second the post mentioning the correct radius on the lathe tool bit. The other night I was turning something for the first time in quite while and kept getting chatter. I checked gibs, ways all kinds of stuff and the bit "seemed" sharp. I was using a tangental lathe lool which usually gives me excellent results. Well, I finally took the bit out and low and behold the radius was ever so slightly chipped away from some project last time I used it I guess. So little was the chipped area in fact that I needed a magnifyer to see it well. I took it to the grind stone with the jig and it cuts smooth as glass again and like a hot knife through butter. Sharp tools with correct radius make all the difference in the world!

Herb W
07-26-2003, 12:40 AM
<font face="Verdana, Arial" size="2">Originally posted by Evan:


Yeah, you are right. I really meant to say a follower rest...

I don't think of it 'cause I can't mount one on my SB9 without modifying the cross slide. It's the biggest single fault of the SB9, no T slots. </font>

Evan,
SB did make a follow rest for the 9" 'workshop' series lathes (if that's what you have). It bolts to the verical surface, RH end of the saddle.

http://www.zetagraphics.com/shop/sbparts/941A.pdf

Evan
07-26-2003, 12:45 AM
Thanks, I think I'll have to make one of those.