MadModder

The Shop => Tools => Topic started by: John Rudd on March 23, 2014, 01:03:18 PM

Title: Compound lead screw repair
Post by: John Rudd on March 23, 2014, 01:03:18 PM

 :worthless:

I recently acquired a second hand Chester 9x20 lathe....
Sadly the threaded bush for the lead screw in the compound slide is stripped....

Now it looks like this bush is a press fit? If it is how would I remove it as it's in a blind hole?

Drilling? Hum mm.... :dremel:  stud extractor?

Fortunately the repair could be easy as it has a std lh thread (6mm)


Anyone else had this?

Title: Re: Compound lead screw repair
Post by: Pete W. on March 23, 2014, 01:39:28 PM

Hi there, John,

One way could be to drill out the thread and ream the resulting hole to suit a length precision-ground steel rod (maybe silver steel would do at a pinch).  Then fill the cavity behind the bush with grease, offer up the said rod to the hole and 'it it with an 'ammer!  The hydraulic pressure should force out the bush.

I should add that I've never actually tried this method - I think it's mentioned in an old Percival Marshall booklet on 'Workshop Hints and Tips'.

Please do let us know if you try it and if it does work. 

Title: Re: Compound lead screw repair
Post by: awemawson on March 23, 2014, 01:50:24 PM

I second the 'pack it with grease' method. It works but don't wear a white shirt, it can get a bit messy as grease can fly everywhere.

Title: Re: Compound lead screw repair
Post by: Jonfb64 on March 23, 2014, 02:29:05 PM

What Pete said. This is the standard method for removing the pilot bearing that the input shaft on a car gear box fits into in the end of the crankshaft behind the clutch. Any close fitting bar should do the trick.

Title: Re: Compound lead screw repair
Post by: John Rudd on March 23, 2014, 02:52:26 PM

Thanks guys, yup I know the old grease trick.....from working on cars In my younger days :clap:

A further look at the casting reveals some threads, maybe it's screwed in?
I'll need to have a further look and try the easy outs... :dremel:

Title: Re: Compound lead screw repair
Post by: John Rudd on March 24, 2014, 06:28:43 PM

I removed it tonight....
There should be a toll pin that locates the nut but this was missing....
A small easy out inserted and turned to grip resulted in extracting it from the casting....
I just need to make new nut then good as new..... :)

Update,
New nut made and in situ, works like charm..... :)

Dunno why I was worried about getting it out in the first place.. :doh:  Although there is a roll pin adjacent to it to stop it rotating, and a screwed bush that stops it from coming out....( but that's missing too....!)
The rebuild continues....

Title: Re: Compound lead screw repair
Post by: Meldonmech on March 26, 2014, 02:32:53 PM

Hi John
                 
           Glad you have solved that one, it definitely renews your enthusiasm. Could have been nasty.

                                                               Well done   

                                                              Cheers David