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Taper pins on a Southbend lathe?

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  • Taper pins on a Southbend lathe?

    Hello,

    I am in the process of reassembling my 13x40 Southbend and I am in need of a taper pin. I had looked through the Southbend section of the PM site in order to find out anything I can about the taper pins. The only thing that I found out is that somebody got some at a hardware store. So, I tried that route and bought two taper pins that I thought would be close to the right size. (I forgot to measure it...or the two parts of it, as the one I need to replace is broken.) Anyhow, the two pins that I bought didn't fit. The one was too big and the other too small.

    So, I figure I'll just make the pin on my ancient P&W lathe. I made what I believe is the missing piece, to the taper attachment, on the P&W lathe and I only need 4 bolts. Then I'll be ready.

    Anyhow, what I really want to know is this: Are the taper pins, that Southbend used, the same as the dimensions of the pins in the Machinery's Handbook? Or, did Southbend use a proprietary taper?

    I figure that I'll just measure the size of one of the holes and use the Machinery's Handbook to determine the dimensions in order to make the pin. Does this make sense?

    Thanks,

    Brian
    There are only 10 types of people in the world: Those who understand binary and those who don't.

  • #2
    The online McMaster/Carr catalog has some info. Just do a search on tapered pins. They sell them for cheap too.

    SP

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    • #3
      You guys who can't resist wrenching on old neglected iron should assemble kits of Woodruff keys, grease fittings, roll (spring) pins, etc and naturally, buy only full length taper pins from #0 to #5. Theyre soft steel and hacksaw eazily to length. Save any parts you cut off. They come in handy later. If you cut them in a vise pad the jaws with hardwood so you don't ding up the taper.

      Select a pin with little extra length to suit your hole. Re-ream the hole a little to clean it up. Tap the pin in the hole, mark the length, cut it, dress the ends, and sock it home. File anything sticking out flush and, finally, put a prick punch mark on the small end so you know which end is which come time to remove it.

      Oh yeah, get a set of cheap taper reamers. Face it: the stuff needed to equip the home machine shop never ends. Never.

      Adding: US taper pins have a 1/4" per ft taper (1:48). I understand their metric equivalents have 1:50 taper. This may not sound like much but in the closely fitted world of machinery that difference is enough to drive a truck through. Be sure you have the right taper reamer to suit the pins you buy. the difference will no be apparent to the eye and it's hard to measure the taper reliably.
      Last edited by Forrest Addy; 01-17-2008, 04:31 AM.

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      • #4
        Measure the small hole. Measure the big hole. Measure the distance between the big hole and the small hole. Calculate the taper. Make a pin of that taper. A big nail will probably work for stock.

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        • #5
          Your above average local hardware store will have the pins

          Ace, etc...

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          • #6
            Originally posted by Bguns
            Ace, etc...
            I tried that already and they don't have the right sizes.
            There are only 10 types of people in the world: Those who understand binary and those who don't.

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            • #7
              Thanks for the information, everyone. I'll set my taper attachment to 0.250 per foot and make a new pin.

              Regards,

              Brian
              There are only 10 types of people in the world: Those who understand binary and those who don't.

              Comment


              • #8
                Here is how to make a taper pin longer than the travel on your top slide.


                Turn up a stick of material so it looks like this using a live center. Make it .020" larger in OD than the Max OD of the pin.



                Determine what offset you need based on the length of the pin blank from the center drilled end to the middle of the necked in portion near the chuck. Take a grade 8 bolt shank and chuck it offset from center by the proper amount and make a dead center.



                Chuck up the dead center in a drill chuck and proceed to turn the pin. The necked in part will serve as a rotating hinge to hold the part in the chuck securely.



                This isn't a fussy process as long as the taper is correct. You make the pin longer on each end than needed and then select the portion that has the right dimension and cut it to size. The finished product cut to length:

                n
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  Or, do as the original owner of my b-port vise did with the shear pin. Replace it with a broken off 1/8 inch drill bit. That takes "un charcutier" of a machinist to think of that solution.

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                  • #10
                    Update!

                    Ok, I made a taper pin, on the P&W lathe tonight. I set the taper attachment to half-way between the 0 and 1/2, on the scale. At that setting, the taper was too great in comparision to the old pin. So, I gradually cut less of a taper and got a pin close enough to work. It is possible that the old pin wasn't original, either, as it was poking out the opposite side pretty far. Right now, it is installed. However, I want to knock it back out and cut it a little shorter. Once that is done, I just need to get the oilers and put the back plate on and the apron will be ready for installation.

                    Evan: Nice tip for making a taper without an attachment and without offsetting the tailstock.

                    Regards,

                    Brian
                    There are only 10 types of people in the world: Those who understand binary and those who don't.

                    Comment


                    • #11
                      I like that idea, Evan - I need to make several pins for my Whipp shaper and that will do the job nicely.

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                      • #12
                        Evan,
                        I'm curious why you went to the trouble to make a offset center and then hold it in a drill chuck in a tail stock. Most drill chucks have some run out so that might throw off the desired taper from the offset center you made. Why not just turn the taper by offsetting the tail stock?
                        Am I missing something?

                        Steve

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                        • #13
                          Originally posted by S_J_H
                          Evan,
                          I'm curious why you went to the trouble to make a offset center and then hold it in a drill chuck in a tail stock. Most drill chucks have some run out so that might throw off the desired taper from the offset center you made. Why not just turn the taper by offsetting the tail stock?
                          Am I missing something?

                          Steve
                          Probably to avoid the "hassel" of re-centering the tail stock. I just PM
                          Evan to find out how to index the offset center. ????
                          ...lew...

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                          • #14
                            I'm curious why you went to the trouble to make a offset center and then hold it in a drill chuck in a tail stock.
                            I suppose if your drill chuck had a lot of runout it might be a problem. If mine was that bad I would toss it. I don't want to mess with the tailstock offset every time I need a taper pin. I keep my lathe aligned to better than .001 over the full length.

                            Also, the dead center can be used again, it need only be made once. Note that the dead center is chucked to offset the work toward the operator. Exact placement of the offset isn't necessary as long as the work is on center with the tool. The rule of small angles means the difference is very small for the first few degrees of rotation of the dead center either way.
                            Free software for calculating bolt circles and similar: Click Here

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                            • #15
                              Evan,
                              Thanks for the good explanation. I also had not seen the necked down trick before. I'll have to remember that one if I ever cut a taper manually again.

                              Steve

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