Hercus 260 Apron Problem

[mixotricha]

Hullo everyone. This is my first post. I am currently restoring a Hercus 260 lathe. I've had to replace the half nut engagement handle as it was broken. I pulled the unit down. Reassembled it. Confident I put parts back together the right way and setup the clutch correctly. However I notice the cam and the plunger pin tend to jam up. The Idler gear shift lever will go in to the middle position and the pin will go in to the detent in the cam and lock up. I pulled it all down again till I was just left with the cam and the pin and it is not clear to me if this is working as it should. If I wiggle the cam a little from side to side the pin pushes out and slides over. Now many years ago when I did my apprenticeship with one of these lathes I do not recall ever having to struggle with the idler gear shift lever or to wiggle it to get it to shift at all. I definitely don't recall the shift lever locking up. I wondered if the detent in the cam was worn but on checking it more closely it looks to be a nice sharp cutout. Could the plunger be worn? It is hardened steel(?) and I would expect the cam to wear long before it does. Does anybody have any suggestions as to what else might be wrong with this mechanism and causing it to lock up? I see replacement cams are available but the hardened pin seems harder to find.

[pete]

Not to dissuade you from posting here, but Hercus would be much more common in Australia. Afaik they were an improved version of a South Bend and by all accounts even better. Boxford in the UK was as well, but I've no idea how well the parts arrangement follow the original SB or even the Boxford lathes. A hardened replacement pin should be easy enough since that's what pin gauges are and should be fairly cheap for one of the correct size. Then you'd need to set up some kind of rudimentary grinding set up to form that pin end if it's as simple as it looks. If it were me I'd try here for much more accurate Hercus information. https://metalworkforums.com/f189 If I recall correctly you do have to join to see most of the pictures and certainly to post any questions. But for sure someone there could provide some answers or what might need replacing/adjusting to get it to work as it should.

[whateg0]

How well does the pin fit the hole? It looks like it is at an angle in the picture. Any wear in the home could allow it to bind up.

[mixotricha]

It is I think very similar to a South Bend 9a. Some parts may even interchange. The hole the plunger slides in is actually on an angle. I will go and ask over at the forum recommended. Thanks.

[armscor 1]

Fiora machinery in Perth is a Hercus dealer, they might be able to help, I bought a tailstock quill for a model 9A some 30 years ago.

[Harold_V]

I'd suggest you follow up on what whateg0 said. The amount of extension for the pin makes it pretty easy to bind if there's any significant wear. The pin should be a snug slip fit in order for that to not happen. It should also have some lubrication. Don't try to move it dry.

If you find that the pin fit is not acceptable, you might enjoy success replacing it with a drill blank piece. You may have to open the hole to the next larger size to make it round and straight again. Drill blanks are hardened and precision ground to specific sizes and would serve exceedingly well for that purpose. They can't be machined (typically as hard as 62Rc), but they can be ground quite easily. To shape the end of the pin, it can be inserted in a drill motor and run against a belt sander. With a little care you can create a very nice end with the proper angle.

I'd also suggest you pay attention to the area where the pin makes contact with the cam. There should be no irregularities in the surface of either the pin or the cam. Both surfaces should be quite smooth. The pin should not have a sharp point, but a nice radius that would encourage movement.

H

[armscor 1]

I think we lost him, her.