fixing the index screw for the Sherline Lathe threading attachment

[j ferguson]

I was not impressed by the little screw used to index the thread cutting drive gear to the spindle. There is a small hole in the spindle and you drive this small screw into it which then occupies a notch in the drive gear for the threading attachment. It is certainly simple and it does work, but there is a problem.

The end of the screw protrudes into the bore of the spindle enough to block the tube I'd hoped to cut. I have a Proxxon stone-burr which is long enough to reach the protrusion and grind it flush with the inside of the spindle. Doubtless I'd also grind a bit of the spindle itself out of basic clumsiness. Does anyone see anything wrong with this scheme?

It doesn't look like anything else among the hundreds of Sherline attachments depends on the quality of that end of the bore. Is that correct?

If you don't like this idea, what would you do? I'm not in Wisconsin, but I like the idea of a small Cheesehead screw for this job. a lot more than what Sherline provided. and inserted in a proper drilled and tapped hole.

 

[mikey]

Why not cut the screw shorter, then insert it?

 

[john.oliver35]

I think I tapped the little hole in the spindle to 4-40 and just screw in a pan head machine screw. The little sheet metal screw that came with the threading attachment interfered with the collet-closer drawbar.

 

[j ferguson]

Why not cut the screw shorter, then insert it?

Mikey, it's pretty small. Don't you have one of these things?

I like john oliver's idea, mostly because I feel I can deal with a 4-40 screw a lot easier than what looks like a hardened sheet-metal screw.

 

[mikey]

Yeah, I have one. I just shortened it and it doesn't interfere with the drawbar or anything that passes through the spindle. Go with what you think best and I'm sure it will be fine.

 

[kvt]

Installed it to make sure it fits, then pulled it out and ground the bottom of and then reinstalled and check to make sure I got enough off.
I did this a couple of time as I did not want to grind to much off.

 

[photopro]

I just used a Dremel tool to grind the excess length off the inside of the spindle while the screw was installed. No problem since. This is a necessary modification if you ever want to use the head on a vertical mill adapter. If you don't, you can't get the drawbar inside the spindle.

 

[j ferguson]

Hi Photopro, What you did is what I'm about to do. There is no doubt that this screw is probably the simplest way to solve the problem of indexing the dirve gear for the threading attachment, and it certainly works, but it makes my skin crawl. But then nothing I ever do is that simple.