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  1. #1
    Join Date
    Sep 2020
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    Australia
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    Default Cutting imperial threads on a metric Sheraton Defiance

    Can anyone please provide some guidance on cutting imperial threads on a metric Sheraton Defiance?
    The end of the lathe has a chart showing the gears that need to be changed as well as the position of the lever on the head and the position of the lever on the box. Setting this up is straightforward but there is no mention of what setting to put the feed/pitch selector in on the front of the machine. Above the pitch selector there is a nameplate that gives the metric pitch but no mention of what to use for imperial.
    Today I needed to cut a 12TPI thread so I followed the setup but then had to find the correct pitch on the front selector by trial and error. It turned out to be the middle one, but its unclear if this varies for different imperial threads or if its always the middle one. I can't understand why there is no mention of this anywhere on the machine. Can someone please provide some guidance?
    I've attached some pictures for reference. I'm aware when cutting the threads the half nut will need to stay engaged and the spindle reversed for each cut.
    Attached Images Attached Images

  2. #2
    Join Date
    Aug 2010
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    Toorloo Arm, VIC
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    Default

    When you say feed/pitch selector, are you referring to the seven position lever?

    I would assume that given there are seven columns in the table, it's a direct correlation, but if you had to put the lever in the middle position (position 4) to get 12tpi, something is wrong. The table has 12 TPI in the fifth column, so the lever should have been in slot 5, one to the right of the middle.

    Same slot should also give you 6 TPI, if you change the other lever from C to B. And if you then set that lever to A, and move the seven position lever to position seven on the far right, you should get 4 TPI.

    All the blanks are positions that don't give useful TPI counts, probably result in things like 9.5472817 TPI.

  3. #3
    Join Date
    Aug 2019
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    Revesby - Sydney Australia
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    Default

    Some large lathes had a lever to select Metric vs Imperial,
    but your lathe has a metric leadscrew, so Imperial TPI is a compromise.

    You (or a previous owner?) has had to remove some gears,
    and swap them around, to get any Imperial pitches.



    1) Your lathe is meant to be a copy of a late Leblond Regal:
    (see Sheraton Lathe - South Bend Copy & Conquest page2.html )

    e.g. from the LeBlond "Regal" manual:

    https://ia601004.us.archive.org/34/i...the%201951.pdf


    QUICK CHANGE GEAR BOX
    The mechanism within the quick change gear box transmits motion from the main spindle in the headstock to the feed rod and leadscrew. The feed gears may be shifted while the machine is in motion. By use of the quick change levers, any thread or feed on the feed plate may be quickly obtained. Metric translating gears as well as special gears for odd threads may be obtained.

    p7



    METRIC AND ODD THREADS
    Metric threads can be cut through the quick change gear box by the addition of compound gears between the drive gear on the head and the gear on the feed box.

    p49




    2) I think the LeBlonds were all Imperial,
    so their gear/pitch selector had 8x3 positions:
    http://www.lathes.co.uk/regal/img47.jpg
    instead of the 7x3 that your Metric one has.

    With Coarse & Fine, that should be the 48 positions they talk about here:

    On the 13" and 15" lathes the eight feed changes ob- tained through the tumbler gear and quick change gear are multiplied three times by means of the three posi- tions of the lower lever (see 7, figures 3-4), which oper- ates a sliding gear and gives different gear ratios to the feed shaft. In the feed train two ratios are obtained by compounding feed gears in the head. They are con- trolled by the small handle near the center of the head (refer to 5, figure 3). The 13"-15" Regals provide 48 changes of feeds and threads. The 17"-19" Regals offer 56 feed and thread changes; the 21"-24", 63 changes.

    p10




    3) Your third photo lists the gears that have been inserted; 32, 120, 127, 60.

    If you are keen, you could make a chart, the same size as the one in your first photo,
    that covers the gearbox selection chart with the top 7x3 boxes from your third photo.
    Nigel, from a cave FULL of unfinished projects and lost tools.

  4. #4
    Join Date
    Aug 2012
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    Greenmount, W.A.
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    70
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    274

    Default

    The "English Index Plate" is really an overlay (a replacement really) for the Metric Plate fitted on the front of the lathe - to be used when you want to cut English threads. Essentially you are replacing the Metric Plate with the "English" one - for English theads - and from the plate determine the lever positions to be used.

    12TPI appears on the fifth lever position from the left - where 12TPI appears on the "English Index Plate."
    Apart from the gear selection - which it would appear you understand, the other lever settings are - as per the "English Index Plate" are "COARSE" and "C."

    There are ways of opening the half nuts to return the carriage to the beginning of the cut, but unless you are in production it is not worth the effort to manufacture the equipment required to do this.

  5. #5
    Join Date
    Sep 2020
    Location
    Australia
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    7

    Default

    Thanks everyone for the replies. I've realised I made an error when I changed over the compound gear to the 120/127 gear and I put it on backwards. My bad. Hence the feed rates didn't match up but I obtained the correct feed rate by selecting the next higher feed gear. I see it makes sense now looking at the table.
    BTW, my lathe is nothing like the Lebond Regal. Its much more modern that that one and I'm yet to find a manual that is similar.

  6. #6
    Join Date
    Aug 2019
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    Revesby - Sydney Australia
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    Default

    Quote Originally Posted by Straydog01 View Post
    BTW, my lathe is nothing like the Lebond Regal. Its much more modern that that one and I'm yet to find a manual that is similar.

    1) It looks like this manual is close:

    https://triplesmanuals.com/Sheraton-...det-Challenger

    but might not cover metric versions?


    2) I think Lathes.co.uk is saying the internals and dimensions are the same as a Regal. All the castings, and some of the operating levers, are modernised. Of course, they could be mistaken.

    They do sell a manual that they claim covers it: https://store.lathes.co.uk/print/ms527a
    but I would ask for a few sample pages, or a money back guarantee, before paying anything



    3) http://maxonmachinery.com.au/wp-cont...ance-Lathe.pdf
    Nigel, from a cave FULL of unfinished projects and lost tools.

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