Rockwell 11x36 Lathe and metric threading

Does anybody know if it is possible to get a set of tumbler gears (or
any other approach) for a Rockwell 11x36 Lathe to let you cut metric
threads? I remember reading a mention about it somewhere, but cannot
remember where or find it again.
Thanks,
Bob
Reply to
MetalHead
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=============================== To get true metric you will need a 127 tooth gear somewhere in the gear train. In many cases you can get very close [better than the lead screw can cut] by using a geat set that approximates 1.27:1. [several possible ratios]
Problem with cutting metric threads with an inch lead screw [or inch threads with a metric leadscrew] is that you cannot disengage the halfnut or you will loose lead/registration. You will have to stop the lathe, back the tool out, and reverse the motor to move the tool back for another cut. If at all possible, it is better to use a tap/die, possibly in a holder in the tailstock.
An old-fashioned accessory that is almost a necessity for doing this is a spindle hand crank. Threading is entirely manual, no power applied. see
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you do this I suggest removing the spindle drive belt as the crank will do major damage to anyone in the way if the motor is turned on while it is attached.
Uncle George
Reply to
F. George McDuffee
=============== Follow-up to my own post:
Some of the possible gear combinations for approximating the ideal 127:100 gear set [1.27:1] are: 85/67[1.2687], 66/52[1.2692], 70/55[1.2727], 71/56 [1.2679], 75/59 [1.2712] 80/63 [1.2698], 85/67 [1.2687], 94/74 [1.2703] There are many others. A lot will depend on what gears you have, what gears you can get, and how much space is available in the lathe.
For home shop use, plastic [nylon/delrin/minlon] gears should be adequate. You should be able to get the #teeth and required pressure angle as a stock item [do a google search]. You may have to carefully enlarge or bush the bores and/or file a keyway. If you bond the gears together [epoxy? Dowel pins?] you can most likely skip the keyway. If you are lucky, Emco will have a brass bushing with the right id/od and possibly the right length. If not, time to machine one.
Let us know how this turns out as metric threads are becoming more common.
Uncle George
Reply to
F. George McDuffee
On this lathe, it's very difficult to remove the drive belt, but it has neutral.
Pete Keillor
Reply to
Pete Keillor
Either 100/127 or 60/127 or 50/127 ... whatever your lathe calls for.
For lathes which call for 100 or 50, 37/47 will approximate all conventional and model maker's metric pitches to 0.020% error (for all).
For lathes which call for 60, 60/53 will approximate most conventional and some model maker's metric pitches to 0.016% error, and most model maker's and some conventional metric pitches to 0.046% or better error. The "better" can be achieved by a combination of not using any transposer at all, and by using additional stud gears.
One problem is ...
1) coarse pitches are based on 0.25mm increments (0.25, 0.5, 0.75 ... mm), whereas
2) fine pitches are based on 0.05mm increments (0.25, 0.30, 0.35, ... mm)
... so an approximation which is good for 0.25mm increments is not necessarily good for 0.05mm increments.
An approximate transposer which is intended for 0.25mm increments also happens to deliver the same low error on 0.25mm and 0.5mm, but not on any of the others below 1.0mm.
Regardless of which transposer you employ, you are likely to require up to eight stud gears in addition to the transposer.
Reply to
Peter Haas
Thanks for the replies everybody! Bob
Reply to
MetalHead
Rockwell sold a metric tansposing gear set, with seperate models for their 10", 11" and 14" lathes. The 11" lathe was P/N 25-630 - you might lucky and find one on Ebay. Good luck, though. I've been watching for a similar kit for my Clausing 5900-series lathe and the last two brought over $700 each and you will probably see similar prices for a Rockwell kit.
Mike
Reply to
Mike Henry
Good grief! I'd put a LOT of thought into making some before I'd pay that kind of money.
Pete Keillor
Reply to
Pete Keillor

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