13" Single Tumbler Metric Thread Kit

[joeuser01]

This should clear up any errors I made above. At some point I will convert this to a fancy new PDF that folks can print out. If I find time I'd like to convert my lathe to metric. I'd just need to build a custom yoke & spindles, then 3d print some gears.. seems far from impossible.

 

[joeuser01]

Side note I read in another forum that running a 17t stud gear with a few other change gears will let a single tumbler QCGB/6TPI English lathe "closely approximate" several common metric threads..

For posterity, quoting here from: "https://www.practicalmachinist.com/forum/threads/want-to-cut-metric-threads-on-sb-13.264872/"
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For your single tumbler 13, the real trick is to use a 17 tooth stud gear instead of 18. That makes your 6 tpi screw act like a 6.353 tpi screw, which happens to be 3.999 mm per turn. That will let you cut 11 common metric pitches with less than 0.05% error (1 part per 2000). A smattering of other pitches can be made with a few other gears, with slightly worse error. All of these are more than good enough for making fasteners and the like. A couple pitches cannot be made by this method and are left blank. Long story short you can do pretty well if you can get 17, 23, 25 and 35 tooth gears. The usual warning about leaving the half-nuts engaged applies with all of these, BTW.

MMpt Gear Gearbox Error%
6.5 23 5 0.14
6 17 4 0.05
5.5 35 9 0.22
5 23 6.5 0.14
4.5 35 11 0.22
4 17 6 0.05
3.5
3 17 8 0.05
2.5 23 13 0.14
2 17 12 0.05
1.75
1.5 17 16 0.05
1.25 23 26 0.14
1 17 24 0.05
0.9 23 36 0.17
0.9 25 44 0.22
0.75 17 32 0.05
0.6 17 40 0.05
0.5 17 48 0.05
0.45 23 72 0.17
0.4 25 88 0.22
0.35
0.3 17 80 0.05
0.25 17 96 0.05

hope this helps.

allan
Last edited: Apr 30, 2013
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Enjoy!