# Threads inta threads outa



## kopcicle (Dec 23, 2020)

This will be a bit painful without access to my home server as I'm traveling. I'll attempt this anyway. 


So this begins with a '70's vintage Honda Engineering Ltd. GVS-27A, Valve seat grinding set.
What this amounts to is a geared down air grinder (1,100 rpm) with a 6mm (.2362") down the center for a pilot that is inserted into a valve guide. 

Simple enough? In a word, no. 

You see the "nose" of the tool (not shown in the above pic) is M10 x 1.0mm. 
grinding stones with a M10 x 1.0mm center have not been made for nearly 25 years. 
Finding original pilots for the set is a futile pursuit at best. 

Enter  Woodward Equipment Customer Service . As I can't post links you'll have to trust your google foo. 

After a series of patient and informative phone calls it was first determined that M10 x 1.0mm was not going to happen. Next there was an extensive selection of Black & Decker stones with a 9/16 x 16 TPI center. 

So what's the issue? 


I doubt the MKII Atlas needs any introduction here. This is where it begins. The hole was drilled and tapped because I didn't have the gears to do the M10 x 1.0. Note to self, next time use a fresh, high quality tap. For the uninitiated, tapping brass can be a chore. 
Cutting off a M10 x 1.0 bolt for a mandrel was no difficulty but centering it on a 3 jaw chuck was a study in patience and a few leaves of Zig Zag rolling papers. After all this threading 9/16" - 16 tpi was a cinch.


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## kopcicle (Dec 23, 2020)

The whole of holding zero taper across more than 6" at .236" was an exercise in chasing taper with decreasing dimension by nudging tailstock location and paying close attention to cutting tool height and geometry. 
Finally being able to take a predictable .002" finish cut was the reward. 
I could not have done any of this without Swift Tool, Kent Washington ,for the tooling  , mymachineshop,net for the metal gibs* , and the patience of several Atlas Clausing employees. 

*Just a note on plastic gibs. What were they thinking? The metal gibs were a total, complete, unprintable, pain in the ...
The removal of the cross and compound lead screws and the application of several decreasing grits of lapping compound plus many (many) hours of hand lapping the new gibs in was something , fortunately, I'll not have to repeat on this lathe. (okay , yeah take a breath here)
It's worth every hour of sweat you put into it. I'd gladly do it again for the result. Just not any time soon. 
 Even the Phase II piston post (this smaller one is no longer made by them) is at times not rigid enough for precision turning and I have to resort to one time setups on the lantern post. 
Possibly an OXA clone or a custom tool holder is in order. I wouldn't say that the headstock bearing replacement was easy but it was straight forward. Getting the tailstock sorted was a bit of the tail wagging the dog so to speak but we are now on acceptable terms. Plastic gibs, what were they thinking? 

~kop


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## Nutfarmer (Dec 23, 2020)

The same thought that went into the zinc alloy they used. Price point. The machines do have there place. Think of how many who couldn't afford a Hardinge still have a lathe to turn parts on. It is amazing the quality of work that has been accomplished on these machines. Many  of the members here run them. The plastic gibs seen to be one of the first up grades made.


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