Another Threading Question

According to that manual you must install the 86/91 gear with the 86 tooth gear on the outside in order to get a 1.5mm pitch. Can you explain why you have been unable to do that?
 
I can do that and have without success. It's possible it's operator error? I will give it another try. Thanks for the input and I'll report back.
 
If the machine will allow it, put the lathe in the gear of choice, engage the half nuts, put a dial indicator against the carriage and rotate the spindle by hand.
The distance moved in 1 revolution is the lead of the thread. Do this before turning any threads of course (-:

Some machines do not make this possible.
 
Note that you also must install the G gear so that it engages the 86-tooth gear. This means reversing it from the position shown in fig. 47.
 
I'm working my way through this. The 86/91 tooth gears can be reversed. I knew that but had not accepted them as part of the change gear equation. I roughed out another blank this afternoon and will have another go tomorrow. Worst case I'll take the blank to an experienced friend who offered his machine and expertisee while I sort it out.
 
Secure a Sharpie to your toolpost instead of a cutter. That way you can find out if you've got the gearing right without using up any material.
 
Steve, when cutting mertic threads on an imperial leadscrew lathe, you must leave the half nuts engaged, and reverse the lathe to return the carriage after each pass. Same thing if cutting imperial threads on a metric leadscrew lathe.
Don't give up. You'll get it. The gear train needs sorting out and the technique will come.
Do you have a metric screw pitch gage? It will help.
Lots of folks advise practicing cutting threads on scrap pvc pipe until you get the technique down. I did that myself. Coat the pvc with a colored sharpie to make the threads stand out.

Chuck
 
chucketn said:
Steve, when cutting mertic threads on an imperial leadscrew lathe, you must leave the half nuts engaged, and reverse the lathe to return the carriage after each pass. Same thing if cutting imperial threads on a metric leadscrew lathe.
Don't give up. You'll get it. The gear train needs sorting out and the technique will come.
Do you have a metric screw pitch gage? It will help.
Lots of folks advise practicing cutting threads on scrap pvc pipe until you get the technique down. I did that myself. Coat the pvc with a colored sharpie to make the threads stand out.

Chuck
Click to expand...
another great suggestion Chuck.
 
when you aren't sure what thread you are getting do this: set your lathe up as normal. dykem blue the part and take a .002" cut measure with a thread pitch gauge. this will tell you what thread you just cut. if its right then continue if its wrong reset your lathe reblue and take another skin cut this slight cut will not show up on you finished thread. and you wont need to remake the whole part. plus it might lead you to figuring out where you are making your error. bill
 
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