Changing gears for 1 1/4 TPI and using QC gearbox

[Dave Paine]

I do not know what the original poster needed, but I have needed to single point external and internal 1 1/4in x 8 tpi threads to make items for my wood lathe. It seems this thread is common for many wood lathes. Another common size is 1in x 8 tpi.

 

[Bob Korves]

I do not know what the original poster needed, but I have needed to single point external and internal 1 1/4in x 8 tpi threads to make items for my wood lathe. It seems this thread is common for many wood lathes. Another common size is 1in x 8 tpi.

The OP is trying to cut 1 1/4 TPI, not 1 1/4" diameter, per his post. A VERY coarse thread.

 

[benmychree]

I do not know what the original poster needed, but I have needed to single point external and internal 1 1/4in x 8 tpi threads to make items for my wood lathe. It seems this thread is common for many wood lathes. Another common size is 1in x 8 tpi.

You misunderstood what was proposed, the proposition was to cut a 1-1/4 threads per inch LEAD, not 8 threads on a 1-1/4 inch diameter part as you suggest.
This sort of thing is possible, but highly questionable on such a lightly built machine with pot metal gearing (and other parts) I have done such jobs, but mine is a 19" swing lathe with iron and steel change gears and no pot metal.

 

[kd4gij]

The OP is talking about winding coils not gutting threads. To wind 1 1/4 turns per inch you set the lathe to thread pitch to match and wind the wire around a non conductive cylinder such as wood or plastic.

 

[benmychree]

The OP is talking about winding coils not gutting threads. To wind 1 1/4 turns per inch you set the lathe to thread pitch to match and wind the wire around a non conductive cylinder such as wood or plastic.

I stand corrected, he is talking about a LEAD of 3/4" (pitch between threads), but the issues with strain on the machine still exist.

 

[kd4gij]

He is winding wire not cutting threads. The tension on the wire is the only strain witch isn't much.

 

[benmychree]

The strain is not on the rotation, it is on the vastly speeded up gear train that drives the lead screw.

 

[Bob Korves]

He is winding wire not cutting threads. The tension on the wire is the only strain witch isn't much.

It is also trying to move the at rest carriage assembly, all in one big bump. Inertia at rest must be overcome. Can lead to a failure in the drive train.

 

[wa5cab]

The Atlas gears and some other parts are NOT made of pot metal. They are made of Zamak V which is a well known Zinc alloy. Pot metal may contain Zinc but also typically contains a significant percentage of lead, contamination with which being thought to be one of the causes of Zinc Pest in Zamak. Repeating the pot metal statement when aimed at a specific badge is considered deliberate badge bashing, and therefore an attempt to insult any member who owns the badge, neither of which are tolerated on this site, let alone this particular Forum.

 

[wa5cab]

Gearhead (if you are still around), I believe that I have identified the Version of the MOLO that you are using as V8, because it appears to be the only one where the chart for cutting odd threads with a lathe equipped with a QCGB appears on page 133. The A,B,C,D positions are in the case of A and B, somewhat arbitrary and once you have determined that one of the two 64T gears needs to be mounted in the top longest slot, you just need to mesh it with the 20T gear after you have meshed the other 64T gear with the gear in the gearbox (using a strip of typing paper to set the gear clearance). After both nuts are tightened, raise the quadrant (AKA Banjo and Change Gear Bracket) with the strip of typing paper between the left 64T and the 32T half of the 32T/16T compound gear and tighten the clamp. Then remove the paper.

Put the lathe into back gear and position the belts for 28 RPM. With no left or right load/resistance applied to the carriage (which there won't be), the force needed to move the carriage will be approximately the same as it would be with the GB set to 15 TPI, the lathe in back gear, and the spindle RPM set to 345. Carriage speed would be approximately the same.

Note that if you were actually cutting a thread, the situation would be a little different after the first several passes because the coarser thread is deeper.