Crossfeed screw castle nut/cotter pin

[DaveKamp]

Hi All!

So over the years, I've had slop accumulate in my 10EE's crossfeed. Having many other things more pressing, I just worked through it by accomodating the slack in my operation, but the slop seems to have started increasing at times, and I'm getting rather bad at accomodating the math, so i decided to do some investigating.

I started by checking for a difference between extremes and center wear. What I found, is that the slop was essentially unchanged regardless of position, which suggests that the leadscrew wear and the crossfeed nut is probably fine... so I dug in deeper, and found that the crossfed leadscrew end-bearing is where the slop is.

After lots of messing around, I finally got to the culprit... the nut on the back end of the leadscrew was a fair amount short of seated, and the screw was just sliding in and out.

Initially, it looked like there was no thrust bearing on that nut side, but I cleaned it all out good, and found the thrust bearings to all be extant and in good shape, just not snugged by that nut.

I see in Cal's photo, that his screw has a hole through, for passing a cotter pin against the castellations, so that nut won't unthread:



My leadscrew has no such hole, and as a result, no cotter, and as a result, the castellations do absolutely nothing, and I can easily back that nut off with my fingers. I double-checked closely in case that I was just not seeing it... but there simply ain't a hole in my leadscrew. I'm slightly perplexed as to how that would be, but in the end, it really doesn't matter... I just need'ta solve this and move forward.

So my plan is to clean the goo out'a mine, apply some clean machine oil, reassemble this thing, and make provision to secure that nut.

I haven't sized it, but I'm thinkin' it might be a common fine thread size, mebbie I'd put a thin nut on first, then lock the castellated against it, or drill the leadscrew for a cotter pin. I'd prefer NOT to drill it, but if running in a second (thin) jamb nut is unwise for some reason, I'll forego it and take a drill to this leadscrew.

Any suggestions, comments, or sage advise from experience here would be appreciated.

 

[Milland]

McMaster has quite a range of locking nuts, including nylon prevailing torque types, which is likely fine in this application. No need to drill holes or compromise on castle tine location.

Or, just a regular and jam nut, and don't use the castle nut. I'd want to square the end of the nut to the thread pitch in any case to maximize performance of the thrust bearings, which means cutting stub thread in your lathe for initial truing first.

[That does make things a little trickier if using a nylock nut...]

 

[Mr_CNC_guy]

Castellated nuts with cotter pins or jam nuts are hard to get exactly right when trying
to set the preload on bearings. You just can't get them exactly where you want
them. Lock nuts are much better in this application.

One thing that I have done in the past it to make a castillated nut into a lock nut.
I do this by slightly bending each castilation slightly inward. I screw the nut onto the
end of a bolt and clamp the bolt in a vice. Then I tap on each castilation using a punch.
Just the right ammount of tapping will make the nut grip the bolt securly. This
saves having to chase down the correct lock nut.

 

[DaveKamp]

Thanks for the input, Guys!

yeah, I really did NOT want to drill it, for exactly the reasons you both noted, and I was considering the other options.

I THINK this might be a 3/8-24 thread... I'm gonna hunt for a nut that'd match it, if so, I think I'll set it up as a lock-nut, and either snug up the castllations, or use a little bit of silicone gasket goo to assure that it won't loosen itself unintentionally.

I'd make a new set of nuts, but my lathe is down... :-D

 

[TBJK]

Shouldn’t be too hard to find a lock nut. Worst case, IIRC, Chevy 350 motor rocker arm nuts are 3/8-24 lock nuts. They are fully metal too.

 

[Cal Haines]

McMaster-Carr has all sorts of options in 3/8-24 lock nuts: link

If it is 3/8-24, I have a box of 3/8-24 hex jam nuts; they're like regular nuts, but thinner (0.215"). I can send you a few. I bought them to replace the compound clamp nuts on my round-dial (a box of 100 was the minimum).

Cal

 

[DaveKamp]

Shouldn’t be too hard to find a lock nut. Worst case, IIRC, Chevy 350 motor rocker arm nuts are 3/8-24 lock nuts. They are fully metal too.

Hee hee... I actually had one off a 250 Chev inline six that I used... ;-)