How I Refurb Old 3-Jaw Chucks (17 pictures)

[benmychree]

The above post is not mine, somehow mine deleted and the above came in its place; my comments were essentially as by CA just above; I may try again later with more details.

 

[Kernbigo]

When grinding your jaws i always clamp in the direction of use, i have tried it with the ring and had less success. I use 3 square gage blocks set at the 120 deg angle that was reground in the article to lock the chuck for regrinding. I also have converted a standard 3 jaw into a ( buck chuck) by adding 3 flat ground set screws.

 

[benmychree]

What I have done to accomplish stressing the re grinding operation in the same direction is to drill holes in the face of the chuck jaws closest to the opening (can be done with a carbide drill) and inserting pins in the holes that project about 3/16 - 1/4"; I then chuck down on a ring of tube or pipe of a diameter that allows entry of the grinding wheel; this stresses the setup at the best point to remove the tendency to bell mouth and holds the jaws in the direction of chucking stresses. For chucks with two piece jaws, I insert short pieces of cut off Allen wrench into the inner set of bolts and use the same ring device, only sized larger.

 

[benmychree]

To further elaborate on the regrinding job, I have found that most internal grinding wheels that I have come across are too hard of a grade of abrasive, and they quickly glaze over and chatter badly. More or less by accident I found that a marked reduction in RPM makes the wheels act softer than their apparent hardness rating; I used a combination ID/OD tool post grinder that ran 3450 RPM, much less than the approx. 12,000 RPM rating of internal wheels around 1 1/2" diameter; when used with the extension spindle that screwed onto the tool post grinder shaft and used on chuck jaws, hardly any sparks resulted, but grinding was rapid; this was a defining moment! Look on the Dumore grinder speed chart and see what is recommended for your size wheel, try it, and if you experience dulling and chatter, try reducing the speed until the wheel settles down to work and grinds efficiently. Generally grinding wheels act harder with more speed and softer with less speed; when speeding up a wheel, of course the maximum RPM should not be exceeded unless the wheel is worn down in diameter; feet per minute surface speed defines the upper limit.

 

[Silverbullet]

To some degree when a chucks abused its almost not worth messing with. But if it's a quality chuck I sure would try . My old Logan's three jaw was messed up from years of use and I guess some abuse. I didn't go to the extent as you did but I stripped it cleaned it polished it up with emory cloth and yes I ground the jaws there were tapering from the back to front. I used a ring to old the jaws tight to grind them . I ground them till they all matched and then cut slots with a small cut off wheel. Spacing with a dial indicator. The outside jaws were fine so I didn't grind them. Lucky I have both sets.
If you have old chucks your gonna throw , throw them to me .

 

[mx5mke]

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