Sieg SC2/SC3 what involute cutter for gears?

[addertooth]

I want to replace my tumbler gears with metal ones. I bought the "metal gear set" for my Sieg SC2 (family) lathe, but it did not include the tumbler gears.
I am an experienced with lathes, so I am not concerned about needing a "weak plastic gear" in the gear train for "protection".

What cutters are used to make these gears (14.5/20) degree? What "M" size are they? Etc..

Could anyone provide a link to the proper sized cutters? I could do some measurements and probably guess them, but I am certain
that someone out there has already cut gears for these very common 7 X 10/12/14/16 lathes.

 

[Ulma Doctor]

The mini lathe will have metric 1.0 modulus gearing

 

[addertooth]

Is this also true of the lathes which do both metric and standard, and require a 21 tooth change gear to do metric?

 

[Ulma Doctor]

there are many different gear combinations to get metric threads.
on larger lathes they use 100/127 transposing gear


these may be useful:
http://conradhoffman.com/metricthre...text=The purpose of metric transposing,have%2

and

Change Gears for Threading

This calculator determines the correct change gears for any thread pitch. Works for all mini lathes and HiTorque Bench Lathes.

littlemachineshop.com

 

[hman]

Thanks! That Conrad Hoffman article is a real gem ... packed with good information!

Just for completeness, here's a table of possible transposing gear ratios I've gathered from several sources:

I hadn't thought if it previously, but Conrad Hoffman makes a good point about gear sizes. If (as he says) 80/63 is nearly as impractical as 100/127, then 91/86 would even more impractical. I can only speculate that gear sizes like 91, 86, 80 and 63 gain practicality because the tooth counts are NOT prime numbers.

 

[addertooth]

More to the point. are they 14.5 degree or 20 degree teeth?

 

[Downunder Bob]

My lathe came equipped with 120/127 gears I fail to see what is impractical, they are the smallest gears that will give the perfect pitch for metric threads, all others are only approximations.
.

 

[Ulma Doctor]

More to the point. are they 14.5 degree or 20 degree teeth?

they use both 14.5 and 20° pressure angles in modulus 1.0 gearing
generally speaking the smaller the gear, the larger the pressure angle

if you are to examine your gearing already present, you'll see that if the teeth are like triangles, you'll most likely have 20° PA gearing
if the teeth are more parallel, you may have 14.5° pressure angle gearing

 

[addertooth]

Ulma Doctor, I will take a peek at some of my spare change gears.

 

[Jim F]

Here is a calculator that I use.

Ride The Gear Train free software by Evan Lewis