Centec Mk3 vertical head

[Julian PalmerParticipant @julianpalmer95876]

Whilst fitting DRO scales I undid the stud to attach a fixing plate. On tightening it started to spin freely. It will push into the head but won't come out. Can any one help with what it does please …

Hmm, struggling a bit to get a photo to show using the image button (first post on here), but here's the URL …

http://www.palmergroup.co.uk/Centec mystery stud.jpg

Really appreciate any help with the function of this mystery stud and indeed the dismantling sequance of the head to correct the problem.

[Julian PalmerParticipant @julianpalmer95876]

[Keith Rogers 2Participant @keithrogers2]

The stud locates in a groove in the quill to stop it turning. You could cut a shallow slot in the end of the stud for a screwdriver and tighten the nut, it would save you dismantling the head. If I recall correctly there's nothing inside to hold to stop the stud from turning anyway.

Keith

[Julian PalmerParticipant @julianpalmer95876]

Thanks Keith, I'll give that a try, but I've remove it a couple of times previously and it didn't come loose.

Also, I have a grub screw on the left-hand side of the head which appears to do the same thing (revised the photo and circled it in yellow) … http://www.palmergroup.co.uk/Centec mystery stud.jpg When the quill is extended a slot for the grub screw is visible.

[Julian PalmerParticipant @julianpalmer95876]

Ah, ha … managed to put the photo in and album to make it visible in the thread … how do you insert photos from elsewhere on the web, the "insert" button didn't seem to work.

[Keith Rogers 2Participant @keithrogers2]

Sorry Julian I may have mislead you, now you point out the other grub screw. It's many years since I owned my Centec perhaps memory's failed. My suggestion for tightening the top one still stands tho'.

Keith.

Edited By Keith Rogers 2 on 08/09/2017 12:08:45

[duncan webster 1Participant @duncanwebster1]

The one circed in yellow engages with the slot in the quill, at least it does on mine. I've always wondered what the one circled in red does, and have avoided doing anything with it as a consequence

[Julian PalmerParticipant @julianpalmer95876]

Keith, no problem … I'm glad I'm not the only one that's bewildered by this little critter.

I initially thought it may be the pivot for the swivel, but then came to my senses as the quill's in the way.

I have vague recollections of reading some years ago that the castellated nut at the top of the quill was left-hand thread … can anyone confirm this?

[Julian PalmerParticipant @julianpalmer95876]

Ok, answering my own question here, but in the hope it may help others with the same machine, here's what I found …

 

Yes, the castellated nut at the top of the quill is a left-hand thread. Given that I didn't have a mill to make a suitable spanner this is what I quickly cobbled up from a piece of 2" angle …

 

 

Pretty rough I know but with the help of a large shifter it did the job well.

 

Having got that off I removed the three cap screws holding the top bearing flange to the casting and immediately realised that I didn't need to remove the castellated nut.

 

Doh! The whole top bearing assembly comes out complete with castellated nut and bevel drive gear just by removing the cap screws …

 

 

 

This gives access to the inner end of the mystery stud. It's an upper stop for the quill. If the quill rose any further it would hit the bevel gear on the horizontal drive shaft opposite …

 

 

 

 

Apologies for the blurred photo. I was standing on a bucket on a box and couldn't see the viewfinder, but it gives a vague idea of the arrangement.

 

As I hope can be seen from the photos, the stud terminates in a flange and pin. The pin acts as the stop. There appears to be no mechanism to stop the stud turning, strange given that mine was fitted with a dome nut. Keith, I will indeed employ your suggestion of the screw driver slot and use a standard nut (although bringing the quill hard up against the stop seems to have a similar effect). There's no chance of the stud falling into the head as it hits the vertical quill drive so, provided you don't run the machine with the nut removed and stud pushed in, you can't loose it or do any damage.

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