G9729 Half Nuts

[jbolt]

Lets try a couple ideas.
I hope this helps in some insane way

On the carriage are you getting plenty of oil on the bed ways between the carriage and the bed? think of the oil as millions of tiny ball bearings, it will help the carriage slide without causing friction/drag that can effect carriage movement and the cut finish.

Now for the half nut.
That is what I needed to see. looking at the manual and the half nut and wear on it, it appears that the halfnut rest in a cradle and held in place with a pin and that assembly possibly threads on to the half nut lever shaft? if so you should be able to adjust the halfnut assembly closer to or away from the lead screw, does that make sense or am I out in left field? the halfnut thread wear appears to be primarily on the outside of the thread if so I am thing that the halfnut needs to be closer to the lead screw.

I was thinking the same thing. Looks like the half nut is not fully engaging the lead screw or the lead screw is deflecting some under load.

Also check the lead screw threads along the key-way cut for sharp edges and burrs.

 

[LX Kid]

I was thinking the same thing. Looks like the half nut is not fully engaging the lead screw or the lead screw is deflecting some under load.

Also check the lead screw threads along the key-way cut for sharp edges and burrs.

I also was concerned about these sharp edges of the key way. I had asked earlier about the possibility of rounding each and ever thread edge on both sides of the key way. What the heck does this key way do anyhow? I don't see any real function for it unless it is to collect chaff out of the threads.

 

[jbolt]

I also was concerned about these sharp edges of the key way. I had asked earlier about the possibility of rounding each and ever thread edge on both sides of the key way. What the heck does this key way do anyhow? I don't see any real function for it unless it is to collect chaff out of the threads.

It drives one of the bevel gears on the apron which gives you the cross slide power feed. I have the same setup on my Smithy Granite 1324 except it drives a a full gearbox in the apron that does the power feed for both X & Y(Z on lathe). The key-way slot allows the apron to move while driving the bevel gear.

A full featured lathe will have a feed screw and lead screw. The lead screw has no slot and is used only for threading. The feed screw is a smooth rod with the key-way slot that drives a bevel gear in the apron gearbox.

 

[LX Kid]

I also was concerned about these sharp edges of the key way. I had asked earlier about the possibility of rounding each and ever thread edge on both sides of the key way.

What about using a pencil die grinder, with a conical stone attached, to grind in between each two threads? Then just touch up the crest of the thread for any burrs.

I'm also thinking of pulling the gib out, for the way lock, and do some polishing with 600 grit paper to smooth out any possible high spots. I'll also round and polish the detent holes where the adjusting screws mate.

 

[LX Kid]

Things are getting better and better with all the help that is being offered here! Thanks!

I removed the carriage gib and polished it with 600 grit paper and used valve grinding compound to smooth the detent holes to fit the adjustment bolts I made. I made the bolts with a rounded end instead of the pointed set screws that came installed. I found I could now adjust the gib more accurately. I also lubed everything with motor oil and that really made a difference! Everything is operating much better and I'm now more optimistic about about my new machine. I also made a way scraper from a piece of acrylic material.

Before properly adjusting the gib I could not turn the hand crank, on the lead screw, to move carriage back towards the chuck. (Lead screw in "neutral" with half nut engaged.) Now that works so much better and I'm sure when my new half nut gets here it will even be better.

 

[jbolt]

What about using a pencil die grinder, with a conical stone attached, to grind in between each two threads? Then just touch up the crest of the thread for any burrs.

I'm also thinking of pulling the gib out, for the way lock, and do some polishing with 600 grit paper to smooth out any possible high spots. I'll also round and polish the detent holes where the adjusting screws mate.

I would just use a jewelers file to knock the edge off is there is one. It does not need much.

 

[jbolt]

Sounds like your getting there. One comment about motor oil. Most motor oils have detergents in them that are designed to suspend particles in the oil. Good for engines but not as good for machines that see more abrasive materials. Non-detergent motor oils are fine. True way oils are really unnecessary for the hobby size machines that don't have much mass. Generally use standard 30w machine oil on my Smithy. I do use way oil on my CNC mill which sees more severe duty.

 

[LX Kid]

Well it's been raining here all day so it was a good day to stay out in the shop. "What to do?" Sooo I took the whole carriage off, table, gear box and cleaned everything in solvent. Blew every nick and cranny with air, oiled and put everything back together. Did an inspection of the half nut and there is wear but not as bad as I had thought there would be. Now I'll have a spare when it get's here from Grizzly. This was the second time that I have tore everything down and was really surprised at how much casting sand, grit and grime was "still" in the parts.

 

[4GSR]

One thing not mention, when I get ready to do any threading, I squirt oil on the lead screw in the length I'm going to be using. Sure extends the life of the half nuts.

 

[LX Kid]

One thing not mention, when I get ready to do any threading, I squirt oil on the lead screw in the length I'm going to be using. Sure extends the life of the half nuts.

I'm pretty sure that my excessive half nut wear is going to be a thing of the past! Since I properly adjusted the gigs and using better oil, it has really been a much smoother operation. It's like the old saying goes, "Experience cost! How much you wanna pay!"