South Bend 9 Compound Condition & "weld up" fixes?

[SLK001]

Would you prefer true "metal-to metal"?

I don't think that any of the plastics can take the load. If they "compress" during use (as in threading), then that will result in an oversized thread. Since the compression would be different for each loading, you might just end up chasing your tail trying to hit your mark.

Chalk me up for a "metal-to-metal" solution.

 

[martik777]

I recently made 2 crossfeed nuts for my 2 9A's, one from Al 6061 and one from black delrin. I already had the LH 7/16-10 acme tap so it was quite easy. Both work with close to zero backlash but I cannot account for durability in such a short timeframe, however, others have observed no major wear issues with Delrin.

 

[graham-xrf]

I recently made 2 crossfeed nuts for my 2 9A's, one from Al 6061 and one from black delrin. I already had the LH 7/16-10 acme tap so it was quite easy. Both work with close to zero backlash but I cannot account for durability in such a short timeframe, however, others have observed no major wear issues with Delrin.

OK - we know that various plastics can be tough and wear resistant, but how about your impressions of deflection and rigidity. I mean the kind of things @SLK001 was mentioning. Also, does the point at which "chatter screech" begins, get adversely affected.

If I were to set about making a replacement, I would be thinking single point threading, but I did notice a 10TPI ACME tap in HSS costs about £17.50 (that's about $24.32 bucks). It may be OK for aluminum, or brass, or Delrin nylon, but I thought it would be hard going for that size of thread in any kind of steel.

This is where we are allowed to suggest any and all sorts of Acme screw/nut combinations.

 

[SLK001]

If I were to set about making a replacement, I would be thinking single point threading, but I did notice a 10TPI ACME tap in HSS costs about £17.50 (that's about $24.32 bucks). It may be OK for aluminum, or brass, or Delrin nylon, but I thought it would be hard going for that size of thread in any kind of steel.

Remember the tap has to be a LH version. If you use bronze or steel, single point to ~85-90%, then finish with the tap.

 

[graham-xrf]

Remember the tap has to be a LH version. If you use bronze or steel, single point to ~85-90%, then finish with the tap.

Eh! ?? It's right in front of me and I am looking at it . See the pictures and the video in post #1. That is definitely a RH right-hand screw.

Which way things move depends on which of the slides has the screw, and which carries the nut.Turning clockwise on the compound pulls the nut pegged into the underside dovetail towards you, like any RH nut. Since it can't come towards you, the compound with the screw moves away from you.

The situation is reversed for the carriage cross slide. Here the screw is mounted into the lower slide, which is the "non-moving" one, and the nut is in the moving part. Turning it clockwise requires a LH thread, to have the slide with the nut, and hence the compound and tool above, to move away from you, towards the work.

[I must admit, I always have to look at these things twice, and if I have to turn on a bolt with a spanner, and it's driving towards me, I always get it wrong! ]

 

[SLK001]

Eh! ?? It's right in front of me and I am looking at it . See the pictures and the video in post #1. That is definitely a RH right-hand screw.

Oops, my bad... I just automatically thought "left handed" tap. You're correct - it is a righty!

 

[graham-xrf]

@SLK001 : Can one reasonably do this without using a tap at all?

I have the ACME gauge, and a tool that came with the lathe that looks like the right one that should be OK after a minute or two touch-up with a hone. Getting an ACME right, turning on the thread sides separately, with a flat bottom is not as straightforward the more usual 60° tool advancing square-on. Maybe I should just bite the bullet, and order in the tap. You can see why I was considering the metal-loaded mold short-cut

 

[martik777]

Here's one for $18.49 inc shipping: https://www.ebay.com/itm/New-1pc-AC...536389?hash=item4dbadd2305:g:9YcAAOSw9yZdDiPP

Definitely go with delrin and make a few. I would not be too confident using that import tap in steel or brass, maybe ok after a partial single point machining.

 

[graham-xrf]

Here's one for $18.49 inc shipping: https://www.ebay.com/itm/New-1pc-AC...536389?hash=item4dbadd2305:g:9YcAAOSw9yZdDiPP

Definitely go with delrin and make a few. I would not be too confident using that import tap in steel or brass, maybe ok after a partial single point machining.

Yes - hardly any backlash, and just change them if they get worn.
Would you anticipate any of the compression under load issues as described by @SLK001 in post #31?

I agree about the tap in metal. The advice is to get it 90% cut, and then finish with the tap.

 

[martik777]

Yes - hardly any backlash, and just change them if they get worn.
Would you anticipate any of the compression under load issues as described by @SLK001 in post #31?

I have not experienced any differences from the metal nut other than no backlash and I've made approx 30 parts with 5 tens tolerance since installing the delrin nut. I no longer use my compound for threading but feed with the crossfeed only. I would focus my attention on that before spending too much time on the compound.