Clausing 8520 mill refresh

[GerryinBelleRiver]

I purchased this mill in the summer of 2019 after looking for one for close to 2 years. Although it was cosmetically challenged it was a fairly tight machine and came with a load of tooling.

As I needed to complete a number of machine restorations I put it into immediate service with the intent on tackling a total refresh; clean , paint, shine at a later date.

While the time has come and I spent the morning doing a complete tear down. Ended up with quite the pile of parts. This may take a while.

I did discover enough wear on the lead screw for the y axis to justify replacing it and the bronze nut. It currently has about 12 thou of backlash. If I can not find new ones I may have to make them which might be difficult without the use of a mill. Worst case I will put it back together, make what I need and replace the parts. Will make some accurate drawing of original parts just in case.

Also noted some small gouges on one of the ways but I don't think they will really effect the accuracy of the mill. While I am at it I will probably put a DRO on the mill.

Anyway, trying not to turn a simple refresh into a full fledged restoration. Wish me luck.

 

[JReimer]

That is an awesome project. I am currently doing a refresh on a lathe I picked up and likewise trying to not let it 'scope creep' into a full fledged restoration. That is the size mill I have been looking for and wish you the best of luck. will look forward to seeing the progress and final result

 

[Susquatch]

I purchased this mill in the summer of 2019 after looking for one for close to 2 years. Although it was cosmetically challenged it was a fairly tight machine and came with a load of tooling.View attachment 21513

As I needed to complete a number of machine restorations I put it into immediate service with the intent on tackling a total refresh; clean , paint, shine at a later date.

While the time has come and I spent the morning doing a complete tear down. Ended up with quite the pile of parts. This may take a while. View attachment 21512View attachment 21514

I did discover enough wear on the lead screw for the y axis to justify replacing it and the bronze nut. It currently has about 12 thou of backlash. If I can not find new ones I may have to make them which might be difficult without the use of a mill. Worst case I will put it back together, make what I need and replace the parts. Will make some accurate drawing of original parts just in case.

Also noted some small gouges on one of the ways but I don't think they will really effect the accuracy of the mill. While I am at it I will probably put a DRO on the mill.

Anyway, trying not to turn a simple refresh into a full fledged restoration. Wish me luck.

Hey Gerry, if you run into trouble, give me a shout. I'd trust you using my machines in a heart beat - or do it for you. Gotta beat temporary rebuilds all week long!

That said, I've seen quite a variety of parts like that on line. I bet you can find what you need.

Having seen your machine first hand, it's a very worthy project. She is a beauty!

 

[Susquatch]

I did discover enough wear on the lead screw for the y axis to justify replacing it and the bronze nut. It currently has about 12 thou of backlash.

I confess that I am surprised that you think 12 thou is enough to justify a replacement. From what other forum members have told me, that is quite acceptable.

What is the backlash at the two ends? Can a better split nut get rid of the biggest chunk?

 

[GerryinBelleRiver]

The majority of the wear on the lead screw is in the middle 4 inches of the screw, hardly any at the ends. A new nut would certainly help.

 

[GerryinBelleRiver]

Had the time to clean up the y axis lead screw and nut today. Close inspection shows thread wear in the middle 3 inches of the screw, although not as bad as I first thought.

The real problem wear is in the nut where the threads are worn to a point.

What puzzles me is what looks like a weird diameter of .693 on the screw. When I look at the location for the screw there is plenty of room for a .750 diameter screw.


Thinking I will investigate getting a length of 3/4" -10 tpi left hand acme rod and and a chunk of broken to make a new nut. Could always get a LH 3/4-10 tap for that. Anyone here have dealings with McMaster Carr?

Any other suggestions?

 

[Susquatch]

Something I have wondered about. For a worn leade screw like yours with all the wear in the middle, does it make any sense to cut the screw to even out the wear and then make a new nut with a profile to match the revised screw and/or modify the nut to fit the new profile a bit better?

 

[GerryinBelleRiver]

Took me a couple of minutes but I get what you are saying. That would be an option.

 

[Susquatch]

As a bonus, cutting the thread a bit like that could be "mostly" done on the lathe axis. I'm not sure you would even need a steady to do that. But I'd prolly use one anyway.....

But most likely, it would have to be cut a bit both ways (push & pull).

But if you can get a new screw to fit, that's the easiest.

 

[GerryinBelleRiver]

Managed to find the technical drawings from Atlas for the bronze nut. Turns out it is for a 11/16 -10 lead screw. Could not find threaded rod that size but I can find 3/4-10 and I do have the room for a bigger size. Given I really can't single point left hand threads on my lathe that has a thread mount chuck buying threaded rod and reworking it is my best option

Now I need to find a 3/4 -10 lh acme nut I can rework to fit. If all else fails I could silver solder a bronze sleeve in the original nut and tap it the correct size or just get a slug of bronze and make a new one.

In the meanwhile I am continuing with the cleaning and prep for painting

 

[Susquatch]

Could not find threaded rod that size but I can find 3/4-10 and I do have the room for a bigger size. Given I really can't single point left hand threads on my lathe that has a thread mount chuck buying threaded rod and reworking it is my best option

Now I need to find a 3/4 -10 lh acme nut I can rework to fit. If all else fails I could silver solder a bronze sleeve in the original nut and tap it the correct size or just get a slug of bronze and make a new one.

Or bring your bar 45 minutes East and use my lathe. I'd be happy to host you and feed you too. Just gotta put up with a messy shop.

 

[Susquatch]

Could not find threaded rod that size but I can find 3/4-10 and I do have the room for a bigger size.

I think this is what I will end up doing to repair my mill/drill too I just can't see myself conning some poor guy on Kijiji who wouldn't notice the 11 pitch thread that's in there now, and a proper lead screw will cost more than the mill/drill is worth.

 

[RobinHood]

Given I really can't single point left hand threads on my lathe that has a thread mount chuck

Why?

Run the lathe forward and reverse the lead screw and thread from the HS end towards the TS. I should make perfect LH threads for you.

As as general note:

Any time the lead screw and the spindle turn in the same direction ==> RH threads
Any time the lead screw and the spindle turn in opposite direction to each other ==> LH threads

It does not matter if the spindle is running FWD or REV; it only matters which direction the lead screw is turning wrt the spindle if you get RH or LH threads.

 

[GerryinBelleRiver]

Or bring your bar 45 minutes East and use my lathe. I'd be happy to host you and feed you too. Just gotta put up with a messy shop.

Thanks for the generous offer but I have a friend with a well equipped shop only 3 minutes away.

 

[trlvn]

11/16 -10 lead screw. Could not find threaded rod that size

Did you try here?

Threadall Manufacturing - Home Page

My Store

www.threadall.com

They're located in Cambridge, ON so it is at least within the province.

Craig

 

[Rauce]

I bought precision acme threaded rod from McMaster-Carr when I replaced the worn lead screws on my excello. The price was very reasonable for the lead screw stock but the bronze nuts were a bit pricy. They will only ship to a business though, when I order I get it sent to my work.

 

[Susquatch]

I bought precision acme threaded rod from McMaster-Carr when I replaced the worn lead screws on my excello. The price was very reasonable for the lead screw stock but the bronze nuts were a bit pricy. They will only ship to a business though, when I order I get it sent to my work.

Or start a business (on paper).

 

[Rauce]

Or start a business (on paper).

I think they go as far as saying no residential addresses either… never looked that hard into it though since I’ve always been able to just get stuff sent to work.

 

[Susquatch]

I think they go as far as saying no residential addresses either… never looked that hard into it though since I’ve always been able to just get stuff sent to work.

They might say that, but how the heck would they know the difference?

 

[GerryinBelleRiver]

Ya, I have been down that road with McMaster Carr