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help! mounting two new chucks! dont fit!

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  • help! mounting two new chucks! dont fit!

    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
    extreme tractor racing

  • #2
    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

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    • #3
      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

      Den

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      • #4
        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?
        extreme tractor racing

        Comment


        • #5
          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.
          Free software for calculating bolt circles and similar: Click Here

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          • #6
            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.
            ----------
            Try to make a living, not a killing. -- Utah Phillips
            Don't believe everything you know. -- Bumper sticker
            Everybody is ignorant, only on different subjects. -- Will Rogers
            There are lots of people who mistake their imagination for their memory. - Josh Billings
            Law of Logical Argument - Anything is possible if you don't know what you are talking about.
            Don't own anything you have to feed or paint. - Hood River Blackie

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            • #7
              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.

              Comment


              • #8
                <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!!!!!!!!!

                Comment


                • #9
                  I belive the concensus is to NOT machine the spindle. I must concur and withdraw my earlier advice.
                  Free software for calculating bolt circles and similar: Click Here

                  Comment


                  • #10
                    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
                    extreme tractor racing

                    Comment


                    • #11
                      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?
                      Free software for calculating bolt circles and similar: Click Here

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                      • #12
                        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.
                        extreme tractor racing

                        Comment


                        • #13
                          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.

                          Comment


                          • #14
                            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).]
                            Free software for calculating bolt circles and similar: Click Here

                            Comment


                            • #15
                              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).]

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