# Opinions Wanted-headstock



## markba633csi (Jul 26, 2016)

Just bought a 618 headstock and I'm seeing quite a bit of taper/wear on the 1" x 10 spindle threads. Looks almost like it's been filed on or something. I'm measuring about 40 thou difference from the nose end diameter to the shoulder. Is this excessive? The thread depth at the nose looks to be less than 50%- not a lot of meat there. 
The bearings on this unit seem to have issues too, I can feel some notchyness there, so it's going to need a bearing change at the very least.  The gears all look good.  Is there a tutorial for replacing Timkens?
I'll post a couple pix later
Mark S.


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## schor (Jul 26, 2016)

I have a couple videos on my youtube that shows spindle removal on a th54. I would think the 618 is similar.


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## wa5cab (Jul 28, 2016)

Mark,

The Atlas Technical Bulletin on the 612/618 headstock is in DOWNLOADS.  It details how to disassemble and reassemble the headstock.  Read the DOWNLOADS use instructions in the Stickies before you look for it.  This will probably save you a bunch of time.

The original threads on the spindle should be straight and may be a few thou smaller than the unthreaded part near the flange (the two together are called the Register and are what centers the chuck, not the threads).  It does sound as though someone filed the threads down.  However, all else being equal, the taper alone won't really hurt anything.  The diameter of the register should be 1.0000/0.9995" if they didn't monkey with it, too.


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## markba633csi (Jul 28, 2016)

Hi Robert- I just got a substantial discount from the seller so I'm not out too much money.  But it will need another spindle I'm pretty sure.  Here's a picture of the threads: 
The bearings are a little tired but serviceable.  A good cleaning should help. 
	

		
			
		

		
	



Atlas parts seem to be more scarce than usual this year,  particularly for the 6" lathes. I hope this is just temporary. There's just nuthin' out there, and prices keep climbing.   MS


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## wa5cab (Jul 29, 2016)

OK.  That's what I thought you were describing.  It looks almost like tapered pipe threads.

I also have noticed a significant decrease in the number of hits some of my long-running (because so far they've only gotten false hits) eBay searches are getting compared to even 6 months ago.


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## Randall Marx (Jul 29, 2016)

Hi Mark
If I may, I would like to ask where you got that headstock. I'm still considering making the conversion on my MK2.
Thanks and have a great weekend!

Randall


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## markba633csi (Jul 29, 2016)

On Epay.  I missed some (I think) better ones last year.  This one was 100$ after the discount, but it is complete with tumblers. I'm planning on doing a MK2 conversion too.  It may take a while, too many projects going on. LOL


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## Randall Marx (Jul 29, 2016)

I know what you mean about "other projects" taking time. That's most of why I haven't done mine yet!


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## Randall Marx (Jul 29, 2016)

I figured that was what you bought the headstock for, as I remember having a conversation with you about doing that a while ago.


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## markba633csi (Jul 29, 2016)

Hey Randall-I think there's about 4 of us who wanted to do it, maybe I'll blaze the trail.  Not that I dislike my Mk2 headstocks all that much, I'm really just curious if it can be done, and how many parts need to change.  I also wanted to do an upgrade to one of my MK2 heads to improve the situation with the sliding coupler which is one of the real weak points of the design and could be improved.  But yeah, too many projects. Plus I just bought an arc welder I need to run an outlet for.


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## Kevin J (Aug 2, 2016)

Nice welder.  Is it 1930's era?


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## markba633csi (Aug 3, 2016)

Early fifties as near as I can tell.  The Smith welding equipment company in Minnesota made gas welding equipment, acetylene generator units,  and arc welders.  Also had a talent for art deco design apparently. 
Mark S.


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## LF_WS (Aug 3, 2016)

So you are planning to replace the square head on an MK2 with an older 618 head?  I'd be interested in hearing more about the reasons for doing so.

(Later edit - disregard above - found an earlier post where you detailed the reasons.)

(Love the arc welder!  Maybe one of R2D2's cousins, or something from a Buck Rogers set?)


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## markba633csi (Aug 4, 2016)

The MK2 isn't so bad really but I don't like how they did the sliding coupler.  The one little woodruff key has to carry all the force from the pulley to the spindle- they should have used 2x 180 degree keys or a spline design.  There's also noticeable deflection with heavy cuts especially with the ball bearing version.  
Mark S.


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## chips&more (Aug 4, 2016)

Just because the major diameter [of the 618 spindle nose threads mentioned in an earlier post] has a taper, does not mean the pitch diameter is tapered. Check it with thread wires or a pitch micrometer.


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## markba633csi (Aug 5, 2016)

You are correct, only the major diameter has been filed down.  Probably have little or no impact on usability.
MS


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