Lathe Taper Attachment

Discussion in 'Machine Modifications' started by Stan, Dec 6, 2009.

  1. Dec 6, 2009 #1

    Stan

    Stan

    Stan

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    More than a year ago I had to abandon a project because I couldn't cut a a tapered thread on my Logan lathe. I watched and bid on several taper attachments but they all sold for way may than I thought they were worth, considering all were incomplete or no model number available.

    For a Logan lathe you need an extended cross slide with a slot in it as well as the guide bar. Not wanting to distort the cast iron cross slide I made a lap joint and silver brazed a steel extension to the cast iron. After milling the general shape I ground the bottom surface of the slotted area to be level with the top of the cross slide.
    http://i272.photobucket.com/albums/jj165/sdmcw/TaperAttachment6.jpg[/img]][​IMG]

    The piece with the slot in my large radius thread was then ground to be parallel with the bottom of the cross slide.
    http://i272.photobucket.com/albums/jj165/sdmcw/TaperAttachment5.jpg[/img]][​IMG]

    The guide bar is a piece of 4140 left over from another project and the traveler is a Thompson linear ball bearing in an aluminum housing with end plates that hold oil saturated felt wipers. Here are top and bottom vies of the completed assembly. In the bottom view you can see the holes in the traveler which are 8-32 set screws. These screws press on the backing plates behind the ball races. There are six rows of balls so I put adjusting screws on three with the opposite rows confined by the aluminum body.
    http://i272.photobucket.com/albums/jj165/sdmcw/TaperAttachment9.jpg[/img]][​IMG]

    http://i272.photobucket.com/albums/jj165/sdmcw/TaperAttachment8.jpg[/img]][​IMG]

    Here is the taper attachment mounted on the lathe.
    [​IMG]][IMG]http://i272.photobucket.com/albums/jj165/sdmcw/TaperAttachment10.jpg[/img]

    As soon as it was installed I couldn't resist trying it out. I put a piece of 6061 in the chuck and cut a long 11 1/2 TPI on 3/4"/foot taper. I am not proud of the thread, I just wanted to see if it would work.
    http://i272.photobucket.com/albums/jj165/sdmcw/TaperAttachment11.jpg[/img]][​IMG]
     
  2. Dec 6, 2009 #2

    Powder keg

    Powder keg

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    Nice and simple. I like it. Something like that would work good on my little South Bend.

    Thanks.
     
  3. Dec 6, 2009 #3

    Pete.

    Pete.

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    I like how you built it to index with a screw - most use a nut an bolt (taper adj mechanism). How do yopu disconnect the cross slide screw when cutting the taper?
    I have a logan 9" and have been considering something similar to you rig.
    Pete
     
  4. Dec 7, 2009 #4

    Stan

    Stan

    Stan

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    Good questions Pete. I deliberately made the screw 16 TPI (.o62" per turn) which would give 1/8"/ft taper on a 12" guide bar. Since I have an 18" bar I get 3/32"/ft taper. My method is to find zero taper with dial indicator on the work piece and then just count turns to get the desired taper. Just like setting your cross feed for a depth of cut and close enough for most work. If it must be precise you are down to the sine bar and gauge blocks. I put a pointer on the end of the bar in case I ever get around to making a calibrated plate.

    To disconnect the cross feed screw, you remove one slot head screw that is immediately behind the compound. BTW on the first thread, it about drove me crazy trying to use the opposite hands to disconnect the half nuts and back off the compound instead of the cross feed.
     
  5. Dec 8, 2009 #5

    Deanofid

    Deanofid

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    That's really a nicely done job, Stan!
    You can show us a picture of the whole lathe, if you want..

    Dean
     
  6. Dec 8, 2009 #6

    Stan

    Stan

    Stan

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    My lathe is almost always dirty, cuttings piled up, bits and pieces sitting on any available flat spots, that it would never pass muster on this board. Last week after doing some grinding on the lathe, I had to do a major clean up and oiling. By the time I was finished I was too dirty to pick up a camera. Before I cleaned my hands, it was dirty again. I will have to put a picture on the schedule as I have had this lathe for a couple of years now. It is a Logan 1825 which replaced a Logan 820.
     
  7. Dec 12, 2009 #7

    phlegmatic

    phlegmatic

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    way to go Stan! Itll be a future project for me this!!! thx :bow:
     

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