Jacob’s Chuck Rebuild

This topic has 10 replies, 6 voices, and was last updated 13 May 2026 at 10:26 by Andrew Tinsley.

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12 May 2026 at 07:42 #847945
Alan Charleston
Participant
@alancharleston78882
Hi,

Came across this on YouTube. Shows how to pull a Jacob’s chuck apart.

Regards,

Alan C.
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12 May 2026 at 09:48 #847962
Andrew Tinsley
Participant
@andrewtinsley63637
I did this on a couple of Jacobs chucks, I was fortunate to find the appropriate Jacobs repair kits. The procedure is laid out in T D Walshaw’s (Tubal Cain) book on twist drills in the Model Engineering series.

BEWARE! I followed the description to the letter. When the chucks were reassembled, I found they would not tighten!! Careful examination showed that the outer (scalloped )sleeves had split form top to bottom! I had taken great care in the pressing operations, making up any required tooling. So NOT a bodged job!

I had to make two oversized sleeves, which I pressed over the split sleeves and all was well. They have given excellent service ever since. Am I the only one to have had this problem on not one but two chucks?

Andrew.
12 May 2026 at 10:29 #847966
Martin of Wick
Participant
@martinofwick
Definitely not the only one!

Happened to me, fortunately I had a new spare ring (no idea now whether it came with the rebuild kit or whether it was acquired elsewhere). Pretty annoying but not a total disaster at that time.

‘Spose there could have been previous damage or embrittlement due to old age (thereby ducking personal responsibility!). It was taking quite a few pumps on the press and released with a hell of a bang!

If doing it again, I would would warm the chuck up first (gas mark 1!).
12 May 2026 at 14:44 #847986
Dave Halford
Participant
@davehalford22513
There is an official Jacobs document that says the same – it didn’t work on my Jacobs chuck :O(
12 May 2026 at 18:13 #848011
mark costello 1
Participant
@markcostello1
I have had one or two chucks that the ring was broken when I took it apart. It looked like it had vertical grooves that functioned as controlled breaking points. Put back together and works correctly since then.
12 May 2026 at 18:24 #848013
Clive Brown 1
Participant
@clivebrown1
The ring is broken to enable assembly. If you buy a Jacobs repair kit, the ring in the box comes already broken.
12 May 2026 at 18:29 #848014
Andrew Tinsley
Participant
@andrewtinsley63637
That is interesting, Tubal Cain makes no mention of the sleeve being split. Quite how the chuck can close tightly with a split ring, I really don’t know. My two chucks would not grip at all!

Are there two types of chuck, one with a split ring and one without. That seems to be a likely explanation.

Andrew.
12 May 2026 at 18:54 #848017
Clive Brown 1
Participant
@clivebrown1
Is there there some confusion in this discussion between the ring that closes the jaws and the outer sleeve in which the ring is a tight fit?
12 May 2026 at 19:32 #848024
Andrew Tinsley
Participant
@andrewtinsley63637
As far as I am concerned the sleeve is the outer of the chuck. All of my Jacobs chucks have vertical grooves around this sleeve, most chucks have these grooves coloured black. This outer sleeve has the teeth cut in its base for the chuck key to engage.

It is these outer sleeves which have split vertically on disassembly.

Andrew.
12 May 2026 at 20:43 #848030
Clive Brown 1
Participant
@clivebrown1
Something seems badly wrong there. Splitting of the outer sleeve will effectively scrap the chuck if not reinforced. The ring, or “threaded nut” as Jacobs call it, seems to be a modest interference fit into the outer sleeve on the several chucks that I’ve dismantled over the years.It’s important that the jaws are reassembled in the correct order.

Note that the repair pack describes the threaded nut as broken in halves.
13 May 2026 at 10:26 #848054
Andrew Tinsley
Participant
@andrewtinsley63637
You are quite correct Clive, if the outer sleeve has split (as happened with my two), the chuck is effectively scrap, Unless a larger diameter sleeve is made to fit over the split outer one. This is what I did to retrieve my two chucks from the scrap bin. It has proved quite an effective repair and I am still using them!

Andrew.
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