# Repairing and Fitting a Jacob's Collet Chuck



## Alexander McGilton (Dec 2, 2018)

Here is a short yet involved project that was near completed over Friday evening and Saturday, I got a discounted Jacob's collet chuck off of ebay missing the snap ring but otherwise in good condition. It came with a threaded spindle nose that I then convert to D1-4. 






First step was to cut off the excess of the chuck adapter then bore the taper to fit the d1-4 spindle. I initially bored it or a measurement with my calipers then left the final fitting to be done on the surface grinder. The trial and error process was much more forgiving when I need not have a chuck in place on the lathe. One could otherwise fly cut on the mill if a surface grind was not available.     




Once the tapper fit, I moved to the milling machine where I centered both the rotary table then the chuck adapter on top. 


The dimensions to the d1-4 are readily available online, and others have published instructions on how to make a backplate. 




Here is the new snap ring, had to fille the inside to make it fit on more easily.





Final step before assembly was to take a skim cut off of the back plate for concentricity.


After assembly I found less then .0005" of TIR to the inner taper, however in the collet with a ground rod I have noticed am error of 8 to 10 thou over the length of the bar. Far from acceptable. The problem is that Im using the wrong set of collets, these are intended to be used with the Jacob's  50 series collect chuck. They fit the tapper just fine but the cap doesn't fit to this particular chuck.  I got this set from a garage sail and had high hopes, now it turns out that I will need to make a swap on Ebay.


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## benmychree (Dec 2, 2018)

The collets are not interchangeable between the different types of collet master; you need to get the proper collet set for the master that you have.


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## middle.road (Dec 2, 2018)

*DROOL* 
Nice job. and D1-4 too! I'd enjoy one of those on the 14".
Did not know that the collets had to match, so that is something to keep in mind.


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## benmychree (Dec 2, 2018)

The original snap ring for that collet master is made in two interlocking pieces for ease of assembly.


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## Alexander McGilton (Dec 2, 2018)

The single piece snap ring is a lot easier to make and functions just as well


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## benmychree (Dec 2, 2018)

Alexander McGilton said:


> The single piece snap ring is a lot easier to make and functions just as well


True, but very likely, one would be available from Jacobs as a spare part.


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## Shootymacshootface (Dec 2, 2018)

I have one of these chucks on my Clausing. You are going to love the accuracy and the convenience of that chuck.


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