Adjusting A Taper Bore

Very nice, you must be proud of that. Might we see your pin wrench too?
 
I must admit that I am but Ha Ha, the pin wrench is just a length of 8mm stainless
 
When I made my chuck, I ground the taper ( using a Dremel mounted in the tool post). I also made sure the register in the back was a good fit to the spindle register. The nut was a $4 nut from China ( but a very pretty one... don't know the accuracy). I did all the machining and grinding while installed on the spindle. I WIPE THE INSIDE OF THE CHUCK AND WIPE THE COLLET AND THE NUT BEFORE USING. I tested several collets and get between .0002 and .0008 runout. These are Chinese collets advertised at .0006 tolerance , so I can't expect anything better. I believe grinding the finish in the taper helps because the finish machining is too rough even if it feels great to the touch. The slightest piece of trash and the tinyest will throw everything off a LOT.

Edit: if you don't have the means to grind the taper, a light polish with some 400 grit paper while spinning may help as it will reduce the machine marks a little and improve any high spots. But just a light polish to not alter the angle.
 
Hi Mark, I found out the hard way a tiny bit of trash throws it out. When I first tried it I thought it was clean but it showed almost 0.01
' run out, I was flabergasted, all that care and that much run out, when I removed the collet I found a very thin speck of swarf stuck to it.
Good idea on the polishing.
I saw somewhere on the web someone who added 4 screws to make a sort of set true version, it may be worth an experiment as it wont destroy anything.
I will also test the position of the collet in the chuck to see if the run out moves with it.
 
savarin said:
Hi Mark, I found out the hard way a tiny bit of trash throws it out. When I first tried it I thought it was clean but it showed almost 0.01
' run out, I was flabergasted, all that care and that much run out, when I removed the collet I found a very thin speck of swarf stuck to it.
Good idea on the polishing.
I saw somewhere on the web someone who added 4 screws to make a sort of set true version, it may be worth an experiment as it wont destroy anything.
I will also test the position of the collet in the chuck to see if the run out moves with it.
Click to expand...
You have to make sure that the nut and the taper are very clean as well as the collet. This is all very important to keep the runout down. Even a little tiny bit of dirt in the collet or the nut where the collar seats will throw it off.

It sounds as though your machining was done very well. It is now just a matter of polishing and cleanliness to get rid of the run out.
 
<irony> Thanks pal, another project to do. A pencil grinder in the tool post. </irony>:laughing:
 
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