Jacobs chuck body bore finish?

[Rata222]

Does anyone know what the finish of the bores should look like in a Jacobs chuck body ?
I acquired a Jacobs 6A chuck and decided to disassemble, clean and lube – since it had a gritty feel when turning. This was the first time I had disassembled a drill chuck. I noticed that the bores in the chuck body, where the jaws slide into, had pronounced annular lines as though they were just drilled and not reamed. One of them had a pretty rough finish with a few very heavy score marks going around the bore. (Sorry I did not take any pictures of this chuck). The hardened jaws on the other hand looked ground with no wear marks. They fit tightly in the bores. I did not know if these lines are from, use, misuse or acceptable factory finish.
Also, the ends of the nut, where it was split in half were rough as if they broke the nut in half, instead of cutting. Perhaps small metal shards are what caused the gritty feel or the marks in the bore. But I cannot imagine them scoring around the bores instead of linearly.
The rest of the chuck looks to be in good shape, not abused or worn. The flats on the jaws were even the entire length. Currently the chuck arbor does not fit any of my machines to test accuracy

 

[benmychree]

The finish on the ends of the scroll ring are normal, they have always split the ring by scoring and breaking it. It would not work properly if it was somehow "cut", because it would be out of round when pressed into the sleeve. I'd have to think that the holes for the jaws would have to be reamed to fit the jaws snugly, as they do --- if nothing else, the annular scores will hold lubricant!

 

[ddickey]

I'll be taking my No.36 apart tonight. I will look closely.
I threw my junk 18N in the garbage and the trash went out today or I could've checked that also.
I don't remember them being scored up though.

 

[ddickey]

The bore where the jaws run or the jaw guide in the body are nice and smooth on mine. The guide or bore under the sleeve below the split nut is not as smooth. I wouldn't call it rough though and nothing is scored.

 

[Rata222]

An old "machine builder" friend of mine happened to call me tonight and I questioned him about the marks or scoring in the holes. He said that he has serviced about six Jacobs chucks over the years and had seen the same scenario - where the finish on a few of the holes was poor but the fit was tight. He felt it was just poor machine finish. All the chucks were the plain model - not the more expensive bearing models.

ddickey glad to hear yours look smooth. So I still wonder what is normal. I cant visualize how grit could cause circular scoring in these holes - but surely open to that possibility.

Thank you all for the replies. I appreciate any input by others that have serviced their chucks.
Thanks. Jim

 

[Nogoingback]

I've overhauled a couple of Jacobs spindle chucks and in both cases installed rebuild kits while I was at it. The kits consist of a new split
nut and replacement jaws. Both of mine were a rough in the bores though I don't remember annular lines in them. My impression
was that swarf made its way in there over time and caused wear and scratches. There were also burrs around the edges of the bores.
In both cases I had difficulty installing new jaws into the bores: some would fit well and some would bind. De-burring was the solution.
I doubt that many people clean and lubricate their chucks very often, if ever, so it doesn't surprise me that they get pretty rough.

You might already know this, but there is a specific order for jaw installation.

 

[Rata222]

Nogoingback
Since originally posting this, I have cleaned and lubed all my chucks (6). Three had rough annular lines - looked like drill marks, two were smoother and one very smooth. None seemed wore. The smooth bore chuck had one spot where it did not want to turn freely. After cleaning and deburring it turned nicely.
Thank you for passing on your experience.
I am thinking the specs on the bore are just not very stringent or different for the different models.

Jim