G9729 Half Nuts

Taps run about $200-$350 for an Acme thread. I'm still haven't learned to thread yet and it's my understanding that it can be made by single point cutting. It still has the same question to be answered, "why is it failing and what will make it reliable?" And I know that I'll be asked how deep cuts am I making? Just light cuts, little by little!
 
If its brass it will wear , period . Once you find out the pitch look for a cheap tap . I have some and will let you use it . Single point cutting is chasing btw , so that is true .
 
C932 Bronze is better suited for this. I've seen them made from Delrin, 6061 and cast iron.
 
You can single point the half nut, and it looks like you can make the nut full round and cut it in half for two usable pieces. You can also grind the tool yourself. It still looks to me like there is drag in your carriage somewhere. Are you sure you release both the carriage locks when you thread or feed? Is the lathe reasonably clean, no grit hanging around back there by the half nuts?
 
Bob Korves said:
You can single point the half nut, and it looks like you can make the nut full round and cut it in half for two usable pieces. You can also grind the tool yourself. It still looks to me like there is drag in your carriage somewhere. Are you sure you release both the carriage locks when you thread or feed? Is the lathe reasonably clean, no grit hanging around back there by the half nuts?
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There are two locks on the cross feed table and one lock on the ways gib. The two locks on the cross feed don't effect the half nut "unless" using it under power feed, which I don't really use. The ways lock is not interfering and is loose. I do clean and lube my lead screw often.
 
mmcmdl said:
If its brass it will wear , period . Once you find out the pitch look for a cheap tap . I have some and will let you use it . Single point cutting is chasing btw , so that is true .
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That would be great if you have a .780" x 6TPI x 29 deg Acme tap. I do have some round delrin that I could try it out with. If that works out for me I could also buy some bronze round stock.
 
I looked at the operation manual online. Are you using the half nuts for feeding when you are turning metal to size? The feed lever is for that, and the half nuts are only for threading or other precision feeding. Normally it takes a LOT of threading to wear out the half nuts. Use the feed lever for feeding, and the half nuts for threading. Also, and it is usually not even possible to do, but make real sure that the feed lever and the half nuts are not engaged at the same time. The manual did not seem to address that.
 
Good point Bob . That would be a pretty high feed rate thus wearing them out .
 
Bob Korves said:
I looked at the operation manual online. Are you using the half nuts for feeding when you are turning metal to size? The feed lever is for that, and the half nuts are only for threading or other precision feeding. Normally it takes a LOT of threading to wear out the half nuts. Use the feed lever for feeding, and the half nuts for threading. Also, and it is usually not even possible to do, but make real sure that the feed lever and the half nuts are not engaged at the same time. The manual did not seem to address that.
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I think Bob is correct about the wear. I have a Clausing 5418 that started its life in a high school shop in 1963 (my dad was the shop teacher and bought the lathe from Atlas/Clausing). It had a lot of use in the shop for around 10 years, then not so much. The half-nuts are cast iron and look like new.

Either Grizzly has a really bad design, bad half-nut material choice or you have something causing your carriage to drag putting a real load on the half nuts. I can freely push my lathe carriages back/forth the length of the bed with no drag. If yours is moving really hard maybe your carriage gibs (manual page from my Grizzle G0709 is below) need adjusting. Good luck!

Bruce


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One way is to use epoxy filler (bronze type) to may one I have never did others have
It looks like Grizzly is using cheep brass for the nut.
They not hard to make I like bronze pins for large truck transmission

Dave
 
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