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Thread: Small Lathe Extended Point Live Center

  1. #1
    Supporting Member rossbotics's Avatar
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    Small Lathe Extended Point Live Center

    While turning a part in my small lathe the other day I found myself having to grind a tool bit in all kinds of configurations just to clear the live center, which I have had to do many times before, so I decided to make a small extended point live center and end that aggravation.

    I had on hand a #2 Morse taper shank with a #3 Jacobs taper that went to an old drill chuck that had been discarded, I started out by installing the #2 shank in the spindle of the small lathe and machined a 5/8”-18 thread and a 1/8”wide by .660” diameter land on the Jacobs taper end for locating the bearing housing, I took a piece of 1.250” round 4140 pre-hard steel for making the bearing housing and machined the same threads and land in the housing as I did on the #2 shank, I used a couple drops of red loctite on the threads and screwed them together tightly and let cure, I installed the shank and housing back into the spindle of the machine and bored it for a light press fit to accept two 5200 double row angular contact bearings, I then machined an extended point center in one setting without turning it around from a piece of 5/8” round 4140 pre-hard steel, the very end of the 60° center point was then further hardened.

    Below you will find a few photos of the machining process along with the assembled live center.

    As always thanks for looking and happy machining
    Doug

    Small Lathe Extended Point Live Center-1.jpg Small Lathe Extended Point Live Center-2.jpg Small Lathe Extended Point Live Center-3.jpg

    Small Lathe Extended Point Live Center-4.jpg Small Lathe Extended Point Live Center-5.jpg Small Lathe Extended Point Live Center-6.jpg
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    Last edited by rossbotics; Nov 21, 2018 at 04:37 AM.
    Comments are always welcome
    Doug

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  2. The Following 16 Users Say Thank You to rossbotics For This Useful Post:

    bigtrev8xl (Mar 22, 2019), David Johnson (Jan 11, 2019), Eaglewood (Aug 29, 2022), Home-PC (May 14, 2021), jjr2001 (Oct 6, 2018), Jon (Oct 1, 2018), LMMasterMariner (Sep 30, 2018), MountainMan (Oct 8, 2018), Okapi (Mar 21, 2019), old_toolmaker (Oct 1, 2018), Paul Jones (Mar 25, 2019), PJs (Oct 1, 2018), Scotsman Hosie (May 3, 2019), Seedtick (Oct 1, 2018), threesixesinarow (Sep 30, 2018), workshop_derek (May 13, 2021)

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    Supporting Member LMMasterMariner's Avatar
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    Nice job as always. It's very, very useful live center. Since I started with carbide inserts cutting tools I had problems with regular live center when turning small diameter shafts, barrels, etc. I found it very cheap (USD 18) in China, accuracy 0.003 mm, so I bought it 2 years ago. No more problems.

    Best regards
    LMMasterMariner
    Attached Thumbnails Attached Thumbnails Small Lathe Extended Point Live Center-live-center-mt3-60_40-deg.jpg   Small Lathe Extended Point Live Center-20170504_162213.jpg   Small Lathe Extended Point Live Center-20180305_122818.jpg  
    Download plans for lathes.

  4. The Following 2 Users Say Thank You to LMMasterMariner For This Useful Post:

    Home-PC (Aug 30, 2022), Paul Jones (Mar 25, 2019)

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    rossbotics,

    That is a very well executed and nicely done extended ball bearing center, Doug. I have also experienced that same issue more times than I can remember on my 7 x 16 mini lathe. This is especially true when using carbide insert tooling. I am going to put this on my to do list. Thanks for posting this!!
    Dick


    Links to some of my plans:

    https://www.homemadetools.net/forum/...965#post105972 OFF-SET TAILSTOCK CENTER PLANS
    http://www.homemadetools.net/forum/s...995#post112113 SMALL TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/l...994#post112111 LARGE TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/m...383#post110340 MINI-LATHE CARRIAGE LOCK PLANS
    http://www.homemadetools.net/forum/s...191#post106483 SMALL QC TOOL POST PLANS
    http://www.homemadetools.net/forum/q...849#post119345 QUICK CHANGE LATHE TURRET
    http://www.homemadetools.net/forum/m...949#post119893 MINI LATHE COMPOUND PIVOT MODIFICATION

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    Supporting Member rossbotics's Avatar
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    Thanks LMMasterMariner
    Can't complain about that price !

    Doug

    Quote Originally Posted by LMMasterMariner View Post
    Nice job as always. It's very, very useful live center. Since I started with carbide inserts cutting tools I had problems with regular live center when turning small diameter shafts, barrels, etc. I found it very cheap (USD 18) in China, accuracy 0.003 mm, so I bought it 2 years ago. No more problems.

    Best regards
    LMMasterMariner
    Comments are always welcome
    Doug

    Subscribe to my you tube channel

    https://www.youtube.com/channel/UCDD..._as=subscriber



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    PJs (Oct 1, 2018)

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    PJs
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    Great build and write up Doug. It solves a source of needs & creative frustration in many ways, especially with that shallow taper prior to the point. Thanks also for all the details on materials and ops!!

    On bigger lathes the OA length of a center like this is not a problem but on "peanuts (7x10-14) and micro's" every inch of travel counts. I've often thought of different ways of shortening the whole assembly, perhaps using thrust bearings or combo of thrust and angular contact. Holding the point solidly by its shank is the issue. In your case you have 2 5200's rated at ~7k N (~1600 lbf) each and More than adequate, but at 14mm width gives a probable 1.5" OA on the housing plus the point. Also a big part of the issue for peanuts is the difference between the MT2 shank and socket when seated has about a 1/4-3/8" gap. If one could turn a taper that fit further in to minimize that then shorten the live center part it would give valuable travel back.

    Sorry for all this blah, ba, blah, just to ask your thoughts on reducing OA length and using needle thrust bearings with much higher dynamic rating, but I think its a good topic for others and your wisdom is Always appreciated.

    PJ
    ‘‘Always do right. This will gratify some people and astonish the rest.’’
    Mark Twain

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    Supporting Member rossbotics's Avatar
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    Thanks old_toolmaker
    It really made a difference

    Doug

    Quote Originally Posted by old_toolmaker View Post
    rossbotics,

    That is a very well executed and nicely done extended ball bearing center, Doug. I have also experienced that same issue more times than I can remember on my 7 x 16 mini lathe. This is especially true when using carbide insert tooling. I am going to put this on my to do list. Thanks for posting this!!
    Comments are always welcome
    Doug

    Subscribe to my you tube channel

    https://www.youtube.com/channel/UCDD..._as=subscriber



    Tool Plans for Sale by rossbotics






  10. #7
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    Thanks PJs for your compliment.
    Your right about every inch counting on small lathes, like you say you could make the live center with just one double row angular contact bearing and a thrust bearing at the bottom of the bore on the live center housing, that would shorten it up a bit, you could get real critical and probably shorten the entire center up by 3/4" or so, but I really wasn't over concerned about the O.A. length beings I have another lathe with a much larger capacity (14" X 48")

    Have a Good One
    Doug


    Quote Originally Posted by PJs View Post
    Great build and write up Doug. It solves a source of needs & creative frustration in many ways, especially with that shallow taper prior to the point. Thanks also for all the details on materials and ops!!

    On bigger lathes the OA length of a center like this is not a problem but on "peanuts (7x10-14) and micro's" every inch of travel counts. I've often thought of different ways of shortening the whole assembly, perhaps using thrust bearings or combo of thrust and angular contact. Holding the point solidly by its shank is the issue. In your case you have 2 5200's rated at ~7k N (~1600 lbf) each and More than adequate, but at 14mm width gives a probable 1.5" OA on the housing plus the point. Also a big part of the issue for peanuts is the difference between the MT2 shank and socket when seated has about a 1/4-3/8" gap. If one could turn a taper that fit further in to minimize that then shorten the live center part it would give valuable travel back.

    Sorry for all this blah, ba, blah, just to ask your thoughts on reducing OA length and using needle thrust bearings with much higher dynamic rating, but I think its a good topic for others and your wisdom is Always appreciated.

    PJ
    Comments are always welcome
    Doug

    Subscribe to my you tube channel

    https://www.youtube.com/channel/UCDD..._as=subscriber



    Tool Plans for Sale by rossbotics






  11. The Following User Says Thank You to rossbotics For This Useful Post:

    PJs (Oct 3, 2018)

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    Thanks rossbotics! We've added your Extended Point Live Center to our Machining category,
    as well as to your builder page: rossbotics's Homemade Tools. Your receipt:




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    rossbotics (Oct 4, 2018)

  14. #9
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    rossbotics,

    I was back looking at your pictures once again and noticed you have milled one corner off the leading edge of your compound. What a great way of providing more clearance!
    Dick


    Links to some of my plans:

    https://www.homemadetools.net/forum/...965#post105972 OFF-SET TAILSTOCK CENTER PLANS
    http://www.homemadetools.net/forum/s...995#post112113 SMALL TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/l...994#post112111 LARGE TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/m...383#post110340 MINI-LATHE CARRIAGE LOCK PLANS
    http://www.homemadetools.net/forum/s...191#post106483 SMALL QC TOOL POST PLANS
    http://www.homemadetools.net/forum/q...849#post119345 QUICK CHANGE LATHE TURRET
    http://www.homemadetools.net/forum/m...949#post119893 MINI LATHE COMPOUND PIVOT MODIFICATION

  15. The Following User Says Thank You to old_toolmaker For This Useful Post:

    rossbotics (Oct 8, 2018)

  16. #10
    Supporting Member rossbotics's Avatar
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    old_toolmaker,

    yes I machined that off to give some more clearance working close to the chuck, seams to work fine, it didn't interfere with the working mechanics of the compound.
    Comments are always welcome
    Doug

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    Tool Plans for Sale by rossbotics






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