Thread: Repairing Jacobs No. 34 chuck.

Title should actually have a question mark, because I'm not sure it is worth repairing


Grabbed a chuck from the pile of stuff, put it in lathe tailstock, saw it pushing the drill way off centre. Threw it aside to look at later. Well, "later is now!"

1. Scraped many years of swarf out. Used a key to turn it all the way open and tried to turn it back down, but very hard going. Sprayed with a semi-penetrating kerosine-based oil and left for a few weeks.
2. Tried to turn in and out, but still stuck. Looked hard at it, trying to work out how to open it. Couldn't see any pin spanner holes et c.
3. Tried bashing front face on the floor to release more swarf. It did loosen a but of junk, but then I realised the rotating ring was moving down toward the front. Aha, that is how it opens!
4. Got it open, took out the loose bits, cleaned & degreased, then inspected.
5. Problem 1: A huge burr down one jaw's inside edge (the one just outside the ground radius that holds the drill shank). Filed that away – jaw is not as hard as I thought it would be.
6. Problem 2: Chuck is numbered, jaws not so much. I think jaw #3 was the burr'd one.
7. Problem 3: Try to re-assemble, but jaw #3 is very tight unless it is hanging out near the very closed position.
8. I try to file any burrs of the back edge, but there are none. Measure the jaw diameter, 11.98mm. Take a 12mm drill, use it to de-burr the chuck body. Jaw #3 still tight.
9. Turn on the lights, take a photo:

IMG_20200609_180233_692.jpgIMG_20200609_172016_669.jpg

• Looking closely at jaw #3, it has a different inside radius. Probably stolen from another chuck by previous owner.
• Putting a ruler beside the jaw, it is bent outwards by 0.8mm (using my dodgy "verniers and holding everything by hand in the air" measuring system).

So, there are a few options;

A) Purchase new jaws,
B) Press this jaw straight and either
B1) grind the others to match, or
B2) leave this a few teeth higher to match the others' clamped radius



or, I could just throw it away or leave for swaps with the next Jacobs I find?

Yeah just save
It for parts. New jaws will just be Chinese Jacobs parts and I'd doubt they fit any better.

Sent from my SM-G973F using Tapatalk

Hi Guys,

Jacobs chuck quality went to the dogs when they started production in China. In my opinion a UK made chuck is worth repairing and keeping. Otherwise I agree, just ditch it !

Hi All.
Nigelpearson, caskwarrior and BaronJ
Just saw your post about the Jacobs chuck No 34.
Was just wondering what you were intending to do with your Jacobs chuck.
I also got a No 34 Jacobs Chuck as a bundle purchase and was so stoked that it looked ok, but if you look at the picture below you'll see that mine has a MASSIVE crack from top to bottom on the sleeve. I didn't mind paying for NOS jaws but the cost of a new sleeve as well would put the repair over the top.
Don't want to sound pushy, but if you ever want to part with it hope you keep me in mind.
Thanks guys

1. Mr GS, I sent you a PM

2. It must be the week for broken chucks. Here is a Jacobs No.3 from the USA:
IMG_0729.jpg
with chowdered teeth on both the bottom of the jaws and the (half) nuts

t
Thx for the PM. Keep us in mind next time your cleaning out.
Im always interested in acquiring tools