Thread: ARM Rebuild Questions

> - Colour numbers for Hercus green? (will probably get it mixed at bunnings in enamel)

for my 260ARM (made 1988) I found Killrust in wilderness green (a colorbond tone) a very good match. I bought it from Bunnings, they have it as rattle can and as tin for brushing. Unfortunately it is only a single pack epoxy paint. It does take an ETERNITY to dry. Several days just to get dry to touch. But to really harden it takes more than half a year. After that it becomes a tough and oil resistent paint though. If your lathe is much older than mine, then "wilderness green" may not fit. Hercus used a different tone in the early days, but I have no idea which year they actually changed.


> - The leadscrew thread has developed the usual burrs where the key runs. I was going to use a scotchbrite disc to de-burr the threads at the point where they intersect the keyway, any other suggestions or comments?

Completely new to me. I have not read here or on the Southbend lathe forum about burrs in the leadscrew slot. I know this is a major problem on chinese made lathes using a slotted leadscrew, but there the burrs are made at the factory when cutting the slot. If not carefully deburred by the owner before even tunrning on the lathe, the half nuts are eaten away in just a few minutes of using. But on a well made lathe like a Hercus or Sothbend etc never heard of anything like burrs in the leadscrew slot. Maybe one of the senior experts on this forum can talk from their experience. Maybe you want to check condition of the key inside the worm, and generally the condition of the apron innards.


> - The halfnuts have been well key and truly chewed out by the above burrs. My normal repair method is to bore the centre out of a machinetool nut, insert the thread coated with silicon spray and then pour in molten hard white metal. I'm not sure about using this on a thread with a key though, other suggestions or comments?

You can buy new halfnuts at a very reasonable price. I have heard of a method similar to the one you describe using "Moglice" (a metal reinforced 2 component epoxy casting resin used for machine bedway repairs etc, unfortunately not cheap). For a larger lathe where no spare parts are anymore available maybe worth a try. But if new parts can be as easily bought as in this case.... but in any case you must first solve your leadscrew slot burr problem, or risk your nice new half nuts be chewed away in a few minutes. Chris

Originally Posted by cba_melbourne

... Killrust ... It does take an ETERNITY to dry.

If you have suitable breathing gear, I have found that you can add a 2 pac hardener to Killrust and it will dry very quickly and gives a very durable, glossy finish.

Originally Posted by rickw72

....pour in molten hard white metal. I'm not sure about using this on a thread with a key though, other suggestions or comments?

Rick, how about a tight fitting, short length of key, out of soft material, brass maybe, and grinding or filing the thread into the key so you have a complete threaded portion of your leadscrew for as long as your nut is going to be. Pour your nut, and then remove the dummy key from the leadscrew.

Cheers Phil

Thanks for the comments and feedback!

The burs on the leadscrew were a little surprising, but I think it can happen if the leadscrew is mainly used for surfacing. I don't imagine them having done much threading on it.

With the white metal poured into the nut, I was not so much worried about managing to cast it, but more about the keyway gap helping to chew out the nut. In the end I decided to buy some nuts from Mal.

BTW white metal casting is an excellent method, but it tends to work best on bigger machines where the nut is larger and the amount of cast metal will be bigger.