Checking My Nuts

[EdK]

I'm still not sure how to deal with this yet. I think I'll try to make some 29 degree and 30 degree gauges out of sheet metal in an attempt to find out what type of thread these lead screws are. I'd much rather make new nuts to fit the existing lead screws if I can. I hate that my mill is going to be down and out for some time but I'm glad I decided to check the nuts prior to deploying the X power feed. Just rambling here.  

Ed

[f350ca]

Just throwing out ideas for you Ed. While your rambling anyway. This was the arrangement on the cross slide of my lathe. The one half of the nut is fixed, the other half rotates to take out the backlash. That part has two little spring loaded pins that alternately drop into the notches to hold the setting. A much more elegant way of tightening it up. The way yours was, pulls the nut out of alignment causing that vee shaped wear pattern. The Hardinge used a similar arrangement but I don't recall the particulars. Would be much easier to turn a round shaped nut to drop into this bracket, or if there's enough material bore out the existing bracket to take two nuts like this. Just rambling too.

[EdK]

I'm not visualizing how those spring loaded pins work. What's that gear for on the left side?

Ed

[dallen]

that gear looking part is the second half of the acme nut, the spring loaded pins fit into the notches to stop the nut from turning after being adjusted for end play

Greg has a thread of part of a thread on how he made when his lathe crashed.
DA

[f350ca]

Exactly as Allen said, thanks. You can see the holes where the pins go in the broken part. They could be off to the side if there's no room at the bottom.

[EdK]

OK, that's much clearer now and seems like a good design. Do the pins also hold the rotatable nut from coming out of the mount. I see the stationary nut is pinned in to keep it from rotating and coming out of the mount.

Ed

[f350ca]

The nut simply rotates in the bore, once the preload is set the pins stop it from turning and changing the preload. The shoulder on the nut holds it from moving in. The holes are spaced so that when one of the pins are engaged the other one is half a tooth out from engaging, giving you twice as many settings as there are cogs in the nut.

[EdK]

Greg,

A couple of more questions about your nuts.

Do the spring loaded pins have a shoulder on them that bears against the nut flange so they don't pop out when engaged in one of the cogs?
Are the two nut pieces about the same length or is one long and one short?

Thanks,
Ed

[f350ca]

Yes, the pins are necked down to about 1/8th to fit in the cogs, the main body of them was about 1/4 for scale. Didn't measure them but would say both halves of the nut were the same length (that would prevent one wearing faster than the other), the fixed one was a press fit then pinned with tapered pins to lock it in place.
Haven't got a picture of the fixed one, kept the adjuster out while I was turning the shaft, to test the fit.

[Sunset Machine]

(02-17-2015, 06:57 PM)EdK Wrote: I'm still not sure how to deal with this yet. I think I'll try to make some 29 degree and 30 degree gauges out of sheet metal in an attempt to find out what type of thread these lead screws are. I'd much rather make new nuts to fit the existing lead screws if I can. I hate that my mill is going to be down and out for some time but I'm glad I decided to check the nuts prior to deploying the X power feed. Just rambling here.  

Ed

Just a thought, but wouldn't a standard fishtail gauge tell a story? go/no-go?