# Jacobs Drill Chuck Repair Info



## EmilioG

After trying to repair 4 Jacobs USA 14n drill chucks, I learned what to do and what not to do.
Here is my experience and some observations;

Jacobs drill chucks when purchased used are like the proverbial "Box of chocolates", you never know what
you will get until you disassemble them.  Jacobs had made some design changes along the way.
1. Do not rush this process. Quite a few things can and will go wrong.
2. Use a small arbor press to press on and off.  I made the mistake of going with this machinists' advice to
       to use a 20 t arbor press.  BIG mistake.
3. Although you can identify jaws/hole number placement, it's easier to keep track before removing each jaw.  Mark or photograph them to return them to their proper hole locations.

I ruined a decent 14n USA this way.  Pressing the sleeve back on.  The 20t press exerts way too much force and you can't feel if something is wrong.  The Jacobs body is just too soft, not hardened, which I don't understand why it wasn't part of the manufacturing process.  If the body/jaw holes are moved by "bending/warping" the metal in the slightest, say good bye to that chuck.  Hence, use small arbor press with proper metal rings to hold chuck for pressing on/off.

Keeping the sleeve/chuck body aligned is very important.  I've seen where machinists warm up the sleeve before pressing it back on.  One person suggests using a light bulb. No direct flame. 



DarkZeros' write up on this forum, lays out the best way to go about this process.   

Do not doing any grinding or metal removal unless there is high spot.  Use Bluing to find any
high spots in the chucks taper.

Cleaning:  DarkZero used Purple Power with good results.  Other cleaners of this type may dull or tarnish
the metal.  I would not soak the parts, spray and scrub with a brass brush.  Certain cleaners may have an adverse affect on the metal.  I'm not a metallurgist, but these are my observations.

I will add a part II to this with some photos.


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## EmilioG

The parts for these Jacobs chucks are matched, at least the jaws and half nuts. They seem to be machined at the same time for smooth action of the threads, so keep careful matched sets of jaws and half nuts together.  Before assembly, you can run the jaws against the half nut threads to check for any binding or chipped spots that can be stoned down carefully.

I would not go crazy with a Dremel or other super abrasive tool to clean up any burrs or high spots.  Work on small areas at one time and check.  Before pressing the sleeve back on, you can do a cursory check of things by putting the chuck together with the sleeve loose and spin it around.

AFA grease, I've tried Dow Cornings synthetic and ChuckEeez.  Both seem to work very well. ChuckEeez does not wash out easy, even with solvents.  Very tenacious.


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## EmilioG

While writing this, I was able to acquire a brand new Jacobs USA 14n!  It came with a real Jacobs 1/2" straight shank JT3 arbor, which I don't really need right now, but it's a real Jacobs.  This chuck still has original factory grease on it and it looks like it was only used one time.  Great score! $35.00

I was able to pop off the 1/2' arbor with a Starrett 1/8" pin punch through the chucks body taper hole with two easy whacks. No shoulder for the wedges.  It was pristine inside and the arbor looks as new as the chuck.

There seem to be quite a few real Jacobs super chucks around.  I even saw a brand new 14n in a box on Ebay sell for $180.00!  The chuck came with a Jacobs K3 chuck key, which appears brand new as well.
The person that sold me this new 14n didn't really know what they had.   Anyway, all good things to those who wait.   I'm glad I learned and made my mistakes with those old crummier chucks.  I will not mess this one up.

A lot has been written on this subject but I wanted to put in a few things. If I can save just one USA Jacobs from being destroyed, it will have been worth it.

Last, be sure when pressing the sleeve on and off, run the jaws half way up and press on the nose face and not the jaws themselves.  Having the right diameter steel and/or aluminum rings is a big plus.  See DarkZeros' write up.  He made his on a lathe to size.  Thanks Will.


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## 4GSR

The Molycoat grease as shown or Texaco with moly grease is what I use when I rebuild drill chucks.  A little dab here and there is all you need.  Anymore than that and you'll be wearing it when running at high speeds.


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## EmilioG

Here's a great old Jacobs chuck catalog
http://www.vintagemachinery.org/pubs/2864/4337.pdf


The good old days.


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## 4GSR

I don't consider that Jacobs chuck catalog old even though it is a 1974 vintage.  It's probably the last one showing all of the different items ever built by Jacobs. 
Lots of good old information though.


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## mattthemuppet2

you can press them on and off using a hydraulic press, you just have to be very careful to press them straight, otherwise the inner bit can cock within the body and jam. Also, when putting them back together again, you can press the body on a fair way by holding the body in your hand and tapping the inner bit with a plastic dead blow hammer. That should get everything lined up well for the pressing.

I've done a bunch of Jacobs chucks and they're really not hard to work on. One thing that I've found though, is that if the chuck key holes are wallowed out, most likely the chuck is junk. If the chuck looks like ass but has perfect chuck holes, there's a good chance it'll work smooth and run true, however much rust and crud is on it. I've used purple power and a wire wheel to clean up mine, although I'd probably use electrolysis in the future.


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## EmilioG

mattthemuppet said:


> you can press them on and off using a hydraulic press, you just have to be very careful to press them straight, otherwise the inner bit can cock within the body and jam. Also, when putting them back together again, you can press the body on a fair way by holding the body in your hand and tapping the inner bit with a plastic dead blow hammer. That should get everything lined up well for the pressing.
> 
> I've done a bunch of Jacobs chucks and they're really not hard to work on. One thing that I've found though, is that if the chuck key holes are wallowed out, most likely the chuck is junk. If the chuck looks like ass but has perfect chuck holes, there's a good chance it'll work smooth and run true, however much rust and crud is on it. I've used purple power and a wire wheel to clean up mine, although I'd probably use electrolysis in the future.



You're right, but if I can do it with an arbor press, I would rather do it that way.  I was doing all of the pressing at work where I didn't have a lot
of support.  I had to rush through it.  I'll never do that again.Haste Haste makes waste.  
I;ve never had a chuck with a lot of rust and I don't know how electrolysis will affect the metal.  I would do a test first.  Having good metal rings for
pressing on and off is key.   Also, I like to use brass and aluminum to protect the chuck against wedges and other repair tools to avoid marring the soft
chuck parts.  Brass tube brushes work well for the jaw holes.
I know a lot has been written on this subject, but until DarkZeros' write up, there wasn't too much on doing it correctly or at least a different approach
that is sound with good photos.  More up to date.

Here is my theory on what may have gone wrong with one of the rebuilds;
If the jaws and half nuts are not matched, this will cause mis-alignment, throwing the
moving parts off center which will make pressing the sleeve back on to bind.
Looking at Jacobs Tech info, I'm wondering if pressing on the sleeve with the nose down may be better.

When pressing, especially back ON, if something doesn't feel right, STOP and remove the chuck and examine it.  If the pressing rings are smooth, round and
level, and have a bit of a counterbore to sit in, things should proceed well.  I like the tapping idea with a plastic dead-blow.
Yes, it becomes easier once you know what to do.  
Thanks.


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## mattthemuppet2

for sure, I just don't have an arbor press  I did use a bench vise for a small 3/8 cap chuck, but that didn't go so well for a 1/2 cap one! With my hydraulic press I use a couple of press plates with a hole that's about the size of the chuck outer body and an appropriately sized socket over the jaws. I agree 100% about the "if it's too hard, stop!" advice, that's how I screwed up one of my chucks and cracked the sleeve.

Electrolysis won't remove metal, so it won't make the accuracy any worse than it is with the rust. Both of the rusty chucks that I've refurbed came out within new runout specs, but it mostly seemed to be surface rust on the outside and crud inside so I've no idea how it would work with a more heavily rusted chuck.


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## EmilioG

I blew up a decent chuck once when I forgot to remove this small round neo magnet I had on it
to hold the chuck parts in place while transporting.  I put it in a hydraulic press to press the sleeve back on,
after working on it for hours cleaning it up. 

I knew something was wrong but kept pressing and
pressing, until BOOM...the chuck shattered into a dozen pieces plus ball bearings!  I was so lucky
that I didn't catch any of that shrapnel.  I will never forget that day.


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## 4GSR

One thing I do before pressing the sleeve on.  I rotate the nut enough to make sure the jaws move freely and align up to tell me that they are in the right sequence.  I usually take a sleeve bored out to the right ID slip over and take my dead blow hammer and give it a couple of small whacks to make sure it is aligned right.  Then drive the sleeve home.  It doesn't take much force to get the sleeve to go on.  Even on the 20N chuck!


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## EmilioG

Here's an interesting find I recently purchased.
A Jacobs USA No.3 HD plain bearing drill chuck.
It's very old but in remarkably great shape.  Even the key is new, vintage, before Jacobs started oxiding them.
	

		
			
		

		
	













It's unusual to find United States of America instead of just
USA. also there are numbers for the jaw holes instead of Roman numerals.  It is very well made.
Possibly in the earlier days.  I have a Jacobs No.3 but not as in good shape so I bought an NOS rebuild kit for it.
You can see the old jaws and nut halves, they were badly worn.  One of the two is a little beat up but the internals and sleeve are excellent.
This time I took great care in pressing off the sleeves, using a 17/64" drill bit to bring the jaws to half capacity. The chucks are 0-17/32" Cap.

We have a nice 3 ton arbor press where I work so I was able to do it without any problems.  Now I just have to finish degreasing and lubricating.


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## randyc

18N's are some great chucks !  I have an old one that has seen lots of use but still worked well.  This is somewhat off-topic but may be of interest:

About a year ago, I scored three Albrecht chucks from craigs list and I already had two so the Jacobs became superfluous to the 1/2 inch chuck collection.  I made a live tailstock chuck from it, shown below.

Unhappily, the lathe it was intended for has a small MT-2 tailstock taper so there wasn't much material to work with when making an MT-2 shank with bearings.  I ended up using a three inch long oilite sleeve bearing plus a 1/2 inch hardened ball for thrust.  (Live chucks experience little, if any thrust, so nothing more sophisticated is required.)

These types of tailstock chucks are rarely used but when they are needed, they are usually REALLY needed, LOL .  A typical example would be taking a clean-up cut on worn commutators for a motor or generator armature.  Many of these have hardened shafts and no center drill


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## EmilioG

Do all lathes require a Morse taper or can straight shanks be used?  What about R8 collets?  
I understand that all lathes are different and use different size tooling.  Where can I find more information
on lathe tooling?  Thanks.  I would like to buy a Hardinge HLVH lathe in the next few years. If I find the
"right" one in good shape that doesn't need a lot of restoration.   I plan on spending my retirement years
in a home hobby shop tool room.


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## randyc

EmilioG said:


> Do all lathes require a Morse taper or can straight shanks be used?  What about R8 collets?
> I understand that all lathes are different and use different size tooling.  Where can I find more information
> on lathe tooling?  Thanks.  I would like to buy a Hardinge HLVH lathe in the next few years. If I find the
> "right" one in good shape that doesn't need a lot of restoration.   I plan on spending my retirement years
> in a home hobby shop tool room.



HLVH ?  Wow, I wish that I had one !

To the best of my knowledge, U.S. made engine lathes universally use Morse taper tailstocks.  U.S. made turret lathes use 5/8 straight shank tool holders.  I've never heard of any kind of lathe that uses R-8 collets.

Not sure where you'd find the kind of information on lathe tooling that you need but I think I'd start at "lathes.co", a British site that is probably the most comprehensive machine tool site in the world !


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## EmilioG

Nice MT2.  Why the bearings ?
Also, Lathes.co no longer exists Btw.


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## randyc

EmilioG said:


> Nice MT2.  Why the bearings ?
> Also, Lathes.co no longer exists Btw.



Hi Emilio,

Bearings are required for a "live" tailstock chuck so that it is free to rotate.  The chuck is not used to hold tooling, like drills or reamers.  It serves the same purpose as a tailstock center or a steady rest.

The workpiece is held in the headstock at one end and the tailstock is located at the end of the work.  The live chuck is tightened over the end of the work and rotates along with it.  The work is therefore supported at both ends, reducing flex just as a center or steady rest would.

I should have explained all of this in my first post, sorry -

Tony's site:  http://www.lathes.co.uk/


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## darkzero

randyc said:


> 18N's are some great chucks !
> 
> These types of tailstock chucks are rarely used but when they are needed, they are usually REALLY needed, LOL . A typical example would be taking a clean-up cut on worn commutators for a motor or generator armature. Many of these have hardened shafts and no center drill



I scored a nice used 18N a few months ago. I haven't got around to reconditioning as I have a 5/8" keyless Bison chuck that I use on the lathe & a 1/2" keyless Glacern chuck I use on the mill. But I do have 3 very nice 14Ns that I reconditioned for use on both the lathe & mill (R8, MT3, & straight shank).

That live drill chuck is pretty cool. A while back I needed to work on something that needed tailstock support but with no center drill. I had a couple of micro chucks laying around so I got a live center for one of them. Haven't used it a second time but at least it's there if I ever need it.


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## EmilioG

Nice.  I can't wait to get started on my own lathe.  I'm moving to LA so I will wait
to make any major purchases.  Lot's of folks really like Glacern tooling.  Must look into it. Thanks


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## randyc

darkzero said:


> ....A while back I needed to work on something that needed tailstock support but with no center drill. I had a couple of micro chucks laying around so I got a live center for one of them. Haven't used it a second time but at least it's there if I ever need it.



Your usual flawless workmanship - why would anyone expect less ?


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## EmilioG

CadillacSTS  was kind enough to make some aluminum tubes for me to press on/off my Jacobs drill chucks.
The photo shows my collection of various tubes in aluminum, steel and brass with some delrin rings that sit on the
nose face to protect it.  All non marring.  Thank you Cadillac STS.  The guys at work provided some of the other rings and tubes.


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## Cadillac STS

I'm glad they worked out.  Looks like you will be set up for whatever comes your way.


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## EmilioG

One thing I forgot to mention. When you have your drill chucks pressed off, you will notice on the bodies
jaw hole ends that the metal is thin and flaky.  There is no way around this when making the chuck holes
because of the angle and thickness.  Do not be tempted to "fix" this by filing or Dremel.  The metal is very thin
here and not hardened.  You can cause the jaw holes to deform.


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## EmilioG

4gsr said:


> The Molycoat grease as shown or Texaco with moly grease is what I use when I rebuild drill chucks.  A little dab here and there is all you need.  Anymore than that and you'll be wearing it when running at high speeds.


The DC MolyKote grease is a little "stiff" for drill chucks.  I only use ChuckEezz now. ChuckEez is very tenacious and doesn't wash out easily, even with grease
cutters and solvents.  I only used oil on the balls, no grease.


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## EmilioG

Here are the dimensions for all Jacobs wedges:
#1 Wedge:   ID  0.442"         Thk.  0.163

#2 Wedge    ID 0.585"          Thk.   0.167

#6 Wedge    ID 0.720           thk.    0.162

#3 Wedge    ID 0.850           thk.    0.170   (jt3)

There are no wedge sets for JT6 and JT33 tapers.
These dimensions are not available anywhere on the internet.


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## EmilioG

One other bit of information that I'd like to share for those planning on removing their arbors by using a pin punch to knock them out.
It would be a good idea to protect the chuck inner body where the jaws ride or any metal around any drill chuck when knocking out an arbor with a pin punch. 

Try a piece of brass tube cut to size and place it in the chuck, then put your pin punch in to protect the chuck body or jaws.

I would also protect the nose of the chuck with some round brass, aluminum etc.. in case you miss with the hammer and dent the nose of the chuck or other part (if it's an Albrecht i.e.).

I've seen a lot of Jacobs chucks with dents and dings and always wondered, and now it seems that it may have a mis-strike with a hammer.


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## 4GSR

On all of my 14N or larger chucks, I drill a 33/64 hole through the web to the arbor.  Once in a while, I'll drill into the arbor a bit to relieve some of the radial stress that is holding the arbor to the chuck.  Do this only if the arbor is junk.  Next, I take a piece of 1018 CRS bar or equivalent, not a pin punch, about 6" long, drop int the hole. IF the jaws are movable, bring the jaws in and snug by hand against the the CRS drift.  Support firmly, hit with a 2 lb engineers hammer.  If the first strike doesn't drop the arbor, strike again. After the second or third strike it doesn't come loose, cut off arbor on back side in the saw.  Put up in the lathe and drill and bore out whats left.  Don't do what I did, bored out too big and took out the taper!   I have an older 20N chuck that is threaded internally with a 1"-14 thread for extraction of the arbor.


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## EmilioG

33/64" hole, that is quite large. I only went 2.5mm and just past the web to the arbors center hole. I didn't touch the 1/2" JT3 stub arbor at all! I wanted to save it because I've never seen a hardened 1/2" JT3 stub arbor.  It is in perfect shape but no shoulder for wedges. I used a Starrett 1/8" pin punch. Came right out. 3 wacks.


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## 4GSR

EmilioG said:


> ...snip.... I used a Starrett 1/8" pin punch. Came right out. 3 wacks.



You were lucky.  Several of the one's I have, I would have wadded up a 1/8 punch using it to punch out the arbor. Glad it worked out for you!


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