1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. PLEASE: Read the FORUM RULES BEFORE registering!

    Dismiss Notice

Metric Transposing Gears

Discussion in 'SOUTH BEND LATHE WORKS' started by DoogieB, Oct 27, 2014.

  1. DoogieB

    DoogieB Active User H-M Supporter-Premium

    Likes Received:
    202
    Trophy Points:
    43
    City:
    Carlisle
    State:
    Pennsylvania

    -Return to Top-

    When I was lathe shopping last year, I had a list of features I wanted in a lathe: cross feed, tumbler reverse, QCGB and the option of cutting metric threads with change gears. The SB 10K I ended-up purchasing met all those needs well (and I really like it) but I was left scrounging around for the metric gears. South Bend manufactured a set specifically for these lathes (the 9A & 10K) back in the day but they are hard to find. Tools4Cheap sells a set made overseas, but they have been out-of-stock for most of the year. About a month ago I got the email saying they were back in stock, so I bit the bullet and made the purchase. Here's what $200 gets you:

    metric_1.jpg

    It's a box-O-gears! The transposing gear is 2 large cast gears (127T/120T) pinned together. The rest of the gears are steel and everything is nicely cut and fits well. The only clean-up needed was to grind the pin down in the transposing gear a bit with a Dremel as it was a bit proud. From the pictures I've seen, these look identical to the original SB set, except here you get another 40T gear.

    metric_2.jpg

    You'll need a spacer between the 56T gear and the gearbox to clear the 127T gear in the transposing set. You could use one of the small gears and some washers, but I made a simple aluminium spacer with clearance for the key cut with a file.

    The next pic is what the gear cover on my lathe looks like and there's enough room inside to close it with the metric gears installed. The cover was hitting the thin shield at the gear box which is usually about a 1/2" inside the gear cover. The shield is adjustable, but the gear cover was closed enough so you didn't have to worry about getting your fingers caught in that buzzsaw of gears so I left it as is. After all, the metric gears are only installed temporary until the threads are cut and then it's back to the factory setup.

    Next is what the stock gear setup looks like. Judging from the goop and filth on the gears, I don't think mine was ever touched in 40 years, the awesome advantage of the QCGB.

    The last pic is what the lathe looks like with the transposing gear and a 48T stud gear. I was cutting a 1.50 pitch thread for a M10 bolt, but you could also cut a few other pitches with changes to the QCGB with this same stud gear. With this gear set, you can cut all the standard metric thread pitches and then some.

    I couldn't find a really nice metric chart to print for in the shop, so I made one. You can download it here:

    http://doug.freeshell.org/files/machinery/metric_chart.pdf

    If you want to get your freak-on about cutting metric threads and have a few extra change gears laying around, you can grab this large chart for almost every conceivable combination of gears for various threads:

    http://bnordgren.org/files/metchart2.pdf

    If you are cutting metric threads with a inch lead screw, you often here "Don't move the half-nut lever until you are done". This isn't exactly true, you can pull the lever, you just have to catch the same thread on the lead screw when you are winding-backwards in reverse to the beginning of the thread you are cutting. I've read about this technique, but it didn't really make sense until I saw this video were Tom demonstrates how it works:



    It's a really handy technique when you are cutting threads to a shoulder, which seems to be about 99% of the time. Worked great for me the first time.

    While I try to stick to using SAE threads, I still have to dabble in the metric world occasionally and this will only become more common in the future. Yes, these gears are expensive to have in a box and only break them out a few times a year, but they are there if needed. Besides, if I wanted to not spend money, I would have taken-up knitting instead!
     
    Last edited: Jul 16, 2015
  2. pete1972

    pete1972 Iron Registered Member

    Likes Received:
    0
    Trophy Points:
    1

    -Return to Top-

    very nice quality for 200. i just picked up a 1937 9 and for the life of me can't figure out why i have so many gears.
     
  3. wildo

    wildo Active Member Active Member

    Likes Received:
    345
    Trophy Points:
    63
    City:
    Indianapolis
    State:
    Indiana

    -Return to Top-

    This is an old thread, but Tools4Cheap doesn't appear to exist any longer. Does anyone happen to know what a "full set" of metric transposing gears includes? I happened across a set and am wonder if I have a full set or not. Thanks!
     
  4. DoogieB

    DoogieB Active User H-M Supporter-Premium

    Likes Received:
    202
    Trophy Points:
    43
    City:
    Carlisle
    State:
    Pennsylvania

    -Return to Top-

    The chart that was posted lists all the stud gears you need.
     
  5. wildo

    wildo Active Member Active Member

    Likes Received:
    345
    Trophy Points:
    63
    City:
    Indianapolis
    State:
    Indiana

    -Return to Top-

    Ah, I missed that. So a complete set then would be:

    127/100 combo
    56T (Probably already on the lathe in most situations)
    48T
    44T
    40T
    36T
    32T
    28T
    26T
    Included spacer if you're really lucky.

    ___
    Looks like I scored a nearly complete set- just missing the 40T! That's exciting!
    IMG_7649_zpsdf5oof68.jpg
     
  6. DoogieB

    DoogieB Active User H-M Supporter-Premium

    Likes Received:
    202
    Trophy Points:
    43
    City:
    Carlisle
    State:
    Pennsylvania

    -Return to Top-

    The 40T gear should already be with the lathe, parked on top of the 56T gear at the QC gearbox. It's included with the lathe because you swap the 20T spur gear with the 40T when you want to cut 4-7 TPI threads (rare). If it's missing, it's easy enough to find because originally every lathe had one, usually unused.

    And yes, it is exciting to find a set since tools4cheap is gone and no one else has stepped up to the plate to import more sets. These transposing gears sets can get a little pricey now if you find one and I'm glad I bought mine when I did. That $200 doesn't seem so bad now. :)

    Just to reiterate, the set that I have is for my lathe, a 10K which for this is the same as a 9A. The Heavy 10 gears are different.
     
  7. wildo

    wildo Active Member Active Member

    Likes Received:
    345
    Trophy Points:
    63
    City:
    Indianapolis
    State:
    Indiana

    -Return to Top-

    Ah! So it is... I missed it on there. So sure enough- I have a complete set. Sweet! Thanks for the info on all this!
     
  8. Surprman

    Surprman United States Active User Active Member

    Likes Received:
    136
    Trophy Points:
    43
    City:
    Clifton Park
    State:
    New York

    -Return to Top-

    Sounds like you got the ideal gear set. For any others out there reading this- I built the gear/bushing described in this link:

    http://ixian.ca/gallery/metric/metric.htm

    It works great and was pretty easy to make. Probably all you need unless you are threading something really long.

    Rick
     
  9. Splat

    Splat Active User H-M Supporter-Premium

    Likes Received:
    114
    Trophy Points:
    63
    City:
    here and there...
    State:
    New Jersey

    -Return to Top-

    FWIW, I remember seeing a metric gear set on Ebay ....I think it was new and they wanted $300 IIRC. Jeff @ Tools4cheap's a good guy and you got a great deal. I'm saddened to have found out only a month or two ago that he's no longer in biz. I wish him the best..
     
  10. Sparky

    Sparky United States Swarf Registered Member

    Likes Received:
    0
    Trophy Points:
    1
    City:
    Madison
    State:
    Wisconsin

    -Return to Top-

    Hi,
    Recently I had need to cut metric threads on my SB 10K. I fabricated a 37/47 transpose gear. I then looked at published setting guides an learned that my 20T stud gear needed to be changed to 32T for a 1mm screw pitch. Unfortunately I do not have the 32T gear. Darnit. I also realized that there may still be a way to cut the 1mm thread. I wrote a spread sheet in OpenOffice which I have attached in MSExcel format, (I have not run this in Excel Yet). Using this tool I found a setting for use with my 20T stud gear. So beware that some of the public resources are not complete. If you use the Excel sheet attached please let me know if it is understandable, and useful or not. thx dan
    P.S. The formatting may not have transferred to the xls file from OpenOffice,....
     

    Attached Files:

  11. jocat54

    jocat54 Active User H-M Supporter-Premium

    Likes Received:
    218
    Trophy Points:
    43
    Location:
    Lindale, Texas
    City:
    Lindale
    State:
    Texas

    -Return to Top-

    I have a full set of shop made gears for metric threading on SB9A using the 37/47 transposing gear, they are made from aluminum but work well. I no longer have the SB9A, when I sold it the buyer was in a rush and I just plumb forgot about the gears and have no way of contacting him now.
    If anyone has any interest in them let me know.
     
    Last edited: May 4, 2017
  12. rmd5555

    rmd5555 United States Swarf Registered Member

    Likes Received:
    0
    Trophy Points:
    1
    City:
    Katy
    State:
    Texas

    -Return to Top-

    Are the gears still available?
     
  13. mark_f

    mark_f Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    2,121
    Trophy Points:
    113
    City:
    Mercer
    State:
    Pennsylvania

    -Return to Top-

    I don't believe this works on a QCGB lathe, but for the SB 9 "B" you can cut metric threads without buying expensive gears.
    Transposing gear is made from two existing change gears. A 44 tooth and a 56 tooth gear. I bought two spare gears off eBay so l dont have to take them apart.
    20170909_105608_HDR.jpg

    20170909_105603_HDR.jpg
    You can see the transposing gear made by bolting the two gears together. I have used this several times and it works great. There is a very small error but you would have to thread two or three feet of threads before the error would cause a problem. There is a chart on what gears to use for the various threads. All this is on the internet somewhere but I can't remember the site. It can be found by searching "cut metric threads on a SB 9 lathe".
     
    Ulma Doctor likes this.
  14. Ulma Doctor

    Ulma Doctor Infinitely Curious Active Member

    Likes Received:
    3,027
    Trophy Points:
    113
    Location:
    Ethereal Plane
    City:
    Tracy
    State:
    California

    -Return to Top-

    Great stuff Mark, thanks for posting! :)
     
  15. mark_f

    mark_f Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    2,121
    Trophy Points:
    113
    City:
    Mercer
    State:
    Pennsylvania

    -Return to Top-

    If anyone wants to make this gear, i will post the chart.
     
    Ulma Doctor likes this.
  16. jocat54

    jocat54 Active User H-M Supporter-Premium

    Likes Received:
    218
    Trophy Points:
    43
    Location:
    Lindale, Texas
    City:
    Lindale
    State:
    Texas

    -Return to Top-


    Yes, I still have them.
     
  17. wileyone123

    wileyone123 United States Iron Registered Member

    Likes Received:
    2
    Trophy Points:
    3
    City:
    Burt
    State:
    Michigan

    -Return to Top-

    I wouldnt mind seeing the chart....thank U
     
  18. mark_f

    mark_f Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    2,121
    Trophy Points:
    113
    City:
    Mercer
    State:
    Pennsylvania

    -Return to Top-

    Here are the files for metric threading on a South Bend 9 "B" or "C" lathe.
     

    Attached Files:

    brino likes this.
  19. wileyone123

    wileyone123 United States Iron Registered Member

    Likes Received:
    2
    Trophy Points:
    3
    City:
    Burt
    State:
    Michigan

    -Return to Top-

    Much appreciated!

    Thank U :)
     
  20. terrywerm

    terrywerm New Member Liaison Staff Member H-M Supporter-Premium

    Likes Received:
    794
    Trophy Points:
    113
    Location:
    Neither here nor there
    City:
    Jordan
    State:
    Minnesota

    -Return to Top-

    Thanks Mark! I assume that the SB 9 B&C lathes use a lead screw with 8 TPI? If that is correct, your instructions would also work on a Logan 200 and a few other machines.
     
    mark_f likes this.
  21. wileyone123

    wileyone123 United States Iron Registered Member

    Likes Received:
    2
    Trophy Points:
    3
    City:
    Burt
    State:
    Michigan

    -Return to Top-

    Just wondering, other than using the most Helpful chart U provided, is there a Formula/equation to figure out Metric thread pitches turned with an 8TPI leadscrew?

    Obviously, there are few common Stud and Screw gears to use....but the Compound gear ratios are confusing me....specially when the Transposing gears come into play.
    In addition to that, others have posted % of error (in Thousands/ft) with the Transposing gear sets.....im wondering how to figure that?
    So far im aware of 4 different Metric gear sets.....100/127 (being perfect), and others with marginal error....but how much error?
    Those other Marginal gear sets: 63/80, 37/47, and 44/56.

    Any help with calculating formulas would be appreciated
     
  22. Asm109

    Asm109 United States Iron Registered Member

    Likes Received:
    7
    Trophy Points:
    3
    City:
    Poway
    State:
    California

    -Return to Top-

    Perfect ratio is 1.27:1 Take the other ratios and divide to get decimals 47/37= 1.27027027...
    Error = 1.270707/1.27*100= 100.0213%
     
    mark_f likes this.
  23. mark_f

    mark_f Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    2,121
    Trophy Points:
    113
    City:
    Mercer
    State:
    Pennsylvania

    -Return to Top-

    Yes, there are formulas to figure this stuff .... But ...... They hurt my brain and besides, even though there is a slight error, you will be hard pressed to measure it. You would have to thread about 3 feet before the error was noticable. THAT'S CLOSE ENOUGH for anything I do. Also, it can be done buy picking up the gears for around $10 on eBay instead of hundreds of dollars. But if you want to figure it out, it is just a matter of dividing the number of teeth on one gear into the number of teeth on the other gear to get the ratio and do this with all gears in the train to get the total ratio and then divide using the lead screw pitch to get the thread pitch ....... My brain already hurts. I would only calculate if I was making a special proprietary thread ..... Which I will never do ..... I think.
     
  24. mark_f

    mark_f Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    2,121
    Trophy Points:
    113
    City:
    Mercer
    State:
    Pennsylvania

    -Return to Top-

    You are correct.
     
  25. wileyone123

    wileyone123 United States Iron Registered Member

    Likes Received:
    2
    Trophy Points:
    3
    City:
    Burt
    State:
    Michigan

    -Return to Top-

    That said, .0213% error equates to What exactly in Thousands/Foot?

    I have no plans on threading extensive lengths either....but just wanted to see in perspective just how much difference(.0000/ft) there was between the different transposing gear sets.

    Reason being for the Equation/formula question and how to figure it out, is that i also have a 10" Rockwell that doesnt have the Impossible to fine Metric
    25-875 kit....nor can i find ANYone with specifics/pics of it.
    Its metric gears are change gears are totally different from most.
    I was contemplating fabrication of a banjo/quadrant to allow metric threading....while not having the typical Change gears of a SB, Logan etc...
     
    mark_f likes this.
  26. mark_f

    mark_f Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    2,121
    Trophy Points:
    113
    City:
    Mercer
    State:
    Pennsylvania

    -Return to Top-

    The transposing gears I am speaking of here are only for change gear lathes. You can make or get a set for QCGB lathes but they use other gears in conjunction with the QCGB to get the metric threads. There is a lot of calculations for this. For example, the SB lathe with a QCGB uses the 127/100 combo but comes with several other gears that must be used by following a chart supplied for the gears required and the settings on the QCGB to cut the desired thread.
     
  27. wileyone123

    wileyone123 United States Iron Registered Member

    Likes Received:
    2
    Trophy Points:
    3
    City:
    Burt
    State:
    Michigan

    -Return to Top-

    Thought id help others out by posting my latest find for Metric threading on a Logan 10" (and 11"?).

    Found a guy on Ebay that was willing to work with me and make up, via 3D printing, some Transposing gears(37/47t) for my Wards/Logan 10".

    He has other gears to accommodate the gearset as well: 20T - 32T - 40T - 80T - 100T (for metric threading)

    Gear Face Width = .4375" (7/16")
    Keyed center bore = .625" (5/8)
    Teeth are 16DP

    I suppose U can search on Ebay for them or contact Dennis at FDMprints@Gmail.com

    Other items he offers: gearsets for Southbend, threading dials; misc gears and a lathe bed clamp/indicator.
     
    bac1972 likes this.

Share This Page