Working on my South Bend 9C

[Golem Pens]

I see. I thought you single pointed them.

I think at least one of the members there has a surface grinder and could get rid of the shoulders on both sides. Then you can use the normal start side to cut the thread and then flip the die to cut a complete thread right to the shoulder.

Alternatively cut the thread relief afterward. It is kind of contrary to the purpose but it would improve the cap fit and nobody would ever know.

I'm hoping to graduate to single point in time, but that'll be a while.

I did cut the relief after the threads actually. I usually chamfer the mating surface a bit as well. Will grab a photo showing the assembly pieces later.

Grinding down the die is an excellent idea!

 

[140mower]

I'm hoping to graduate to single point in time, but that'll be a while.

I suggest sooner rather than later. The reason I say that is there seems to be a shroud of black magic that only gets stronger with time which is a shame because single pointing threads really defines the "screw cutting engine lathe" . It's much easier than you might think, I mean, I can do it and am a lifter of heavy things....... 🙄 😛

 

[Golem Pens]

I suggest sooner rather than later. The reason I say that is there seems to be a shroud of black magic that only gets stronger with time which is a shame because single pointing threads really defines the "screw cutting engine lathe" . It's much easier than you might think, I mean, I can do it and am a lifter of heavy things....... 🙄 😛

My main hesitation is that the threads I currently work with are "complicated" (metric and multi start). But doesn't mean I shouldn't learn the basics!

 

[Chicken lights]

I suggest sooner rather than later. The reason I say that is there seems to be a shroud of black magic that only gets stronger with time which is a shame because single pointing threads really defines the "screw cutting engine lathe" . It's much easier than you might think, I mean, I can do it and am a lifter of heavy things....... 🙄 😛

While this wouldn't matter on this piece- dies can wander on longer stock, whereas if you hold the loose end in a rest, single pointing threads will be more uniform. I'm sure you knew that just throwing it out there 🙄

 

[Golem Pens]

That is a fully functional brass section, all shaping done on the SB. Tomorrow we take the whole thing to the wood lathe for sanding and polishing.

 

[BaronJ]

Hi Michael,

You can use a lathe handle to turn the chuck whilst threading. I occasionally use my lathe handle for threading fine 40+ tpi threads. Also useful for internal threading, particularly when you cannot see inside the bore.



This is my lathe handle made using an old washing machine plastic pulley. I put a handle on the rim to give me better control, but you do have to be careful not to start the spindle whilst its in place.



This is a picture of the end of the shaft that secures the handle in the spindle bore. It is a simple expanding collet, expanded by a tapered wedge pulled by a screw. The nut seen on the winding wheel is used to nip the expanding collet into the spindle bore.

 

[Golem Pens]

Clever addition!

 

[Susquatch]

Clever addition!

I made one too. I used it at first and then discovered that I get much better control just using a chuck key without the T. The backside crank got converted into a different tool.





You can easily turn the chuck with your face buried right up close and personal to the threading process. You can't easily do that with a backside crank.

 

[Golem Pens]

The brass section turned out well for a first try. Needed a slightly different taper but it's fine for a prototype. Cap and body externals also came out nice. Kicking myself for deciding not to do the full internal sand and polish, not sure why I thought it wouldn't need it!

 

[Golem Pens]

Ran into some noticeable concentricity issues on a part today, and if I'm checking things right, I'm looking at about 10 thou in spindle runout (going off of my collet chuck and a 3-jaw chuck with a basic indicator - I don't have a 4-jaw chuck or a dial test indicator). That's not ideal. I believe I have a replacement spindle, but not sure what else I should be checking or changing first...

 

[DavidR8]

There's a test you do that involves putting a bar inside the spindle and measuring how much it moves.
I can't find the link at the moment but I will look for it

 

[Golem Pens]

There's a test you do that involves putting a bar inside the spindle and measuring how much it moves.
I can't find the link at the moment but I will look for it

I've seen that, for checking play/headstock clamps. Recommended to run that with a DTI - maybe I can approximate with a regular dial indicator?

 

[DavidR8]

I've seen that, for checking play/headstock clamps. Recommended to run that with a DTI - maybe I can approximate with a regular dial indicator?

You likely need the resolution of a tenths indicator to see the movement. Let dig around in my tickle trunk

 

[Golem Pens]

At that resolution, I suspect the indicated play would only represent a small part of the exhibited runout though. I'm sure it's compounded from several sources...

 

[Golem Pens]

Well, my cheap dial indicator is pointing to about 6 thou of spindle play, so that's not nothing and probably somewhere to start.

 

[DavidR8]

Well, my cheap dial indicator is pointing to about 6 thou of spindle play, so that's not nothing and probably somewhere to start.

What is the spec supposed to be?

 

[Golem Pens]

What is the spec supposed to be?

1-2 thou

 

[Model Citizen]

Golem, buy a MT3 ER32 collet chuck & some 3/8-16 all thread & make a draw bar for it.
Both parts’ll be fairly cheap and i think it’ll be pretty close.
Thats assuming your MT3 taper in your spindle is true.

 

[Golem Pens]

Golem, buy a MT3 ER32 collet chuck & some 3/8-16 all thread & make a draw bar for it.
Both parts’ll be fairly cheap and i think it’ll be pretty close.
Thats assuming your MT3 taper in your spindle is true.

If my collet chuck was the issue, sure. And it may be part of it, but I think I've got a bigger spindle/headstock problem and I'm not sure how that would help there?

I also suspect the spindle has actually been modified, it does not look like an MT3 internal.

 

[DavidR8]

If my collet chuck was the issue, sure. And it may be part of it, but I think I've got a bigger spindle/headstock problem and I'm not sure how that would help there?

I also suspect the spindle has actually been modified, it does not look like an MT3 internal.

South Bend lathes don't want MT tapers if I recall correctly