Jacobs Ball Bearing Chuck Rebuild (14N) Done My Way

[darkzero]

I wasn't going to document this as I'm sure there are plenty of posts on how to do so on the net. But what the heck, here it is my way, more like a refurbish since my intent was not to replace anything. Plenty of pics so beware....

First off, I'm a keyless chuck guy, they're what I prefer to use on the lathe & the mill, but there are times where I would like to use a keyed chuck. Knowing that Jacobs is now owned by the Apex group & has moved manufacturing off shore I set out to find me a nice used USA made Jacobs Ball Bearing chuck (I hear people have complaints about the non-USA made ones). Well I ended up with 3 of them, all for a total of $125 acquired at different times. Finally got around to working on them.

The ones I have are the ones that say "Made In the USA, Hartford Conn.". Then there are the ones that just say "Jacobs USA" on them & the ones that list a SVC Kit P/N on them. As I understand it the ones listing a service kit # on them are the offshore ones & the replacement parts do not interchange with the older USA made ones. Perhaps the internals might look different but disassembly/assembly should be the similar I would think.


Here are my chucks. Worst looking one in the middle, best condition one on the right.






Started with the worst looking one which was also the most filthiest internally.



After cleaning.




Well it turns out this one had way too much run out after reassembling it. I visually tested each one & I could have sworn this one didn't have that much runout when I got it even though the jaws condition did not look that great. I even tried switching jaw hole positions with no improvements. Ok, this one is going off to the side, I ordered some new jaws for it.

This is the rebuild instructions from Jacobs. They say to extend the jaws half way then press off the sleeve by pressing directly on the jaws. Now I don't know if this caused any damage to the jaws on the first one but I'm not taking anymore chances on the next ones.

on the next one I pressed the sleeve off with the jaws retracted just under the nose face but not fully retracted/bottomed out & had no issues at all by pressing on the nose. Finished that one & it came out very nice!

Ok, enough jibber jabber, on to refurbishing the last one which was the best looking one. Here it is....


You don't need to remove the arbor but it makes it easier to work on. Since I was replacing the arbors that came on them anyway I took them off first. I have the Jacobs wedges which didn't work on any my chucks. All 3 of my chucks already had through holes from the factory unlike the newer ones. Torched them slightly, let some Kroil seep in, & used a punch from the front to pop off the arbors.


First I pressed off the sleeve. Again, not wanting to press directly on the jaws, this time I found a suitable spacer in the scrap bin.



Half way there.



Sleeve fully removed.



Be careful not to loose any ball bearings if you are reusing them. Here you can see the slot where they come out. This one barely had any grease if at all unlike the first 2. Almost looks like it only had oil.



There are 32 3/16" ball bearings. Once they are all removed the jaw scroll halves/race & lower bearing race can be removed.



Use your favorite purple or green cleaner to clean all the parts. In my case I'm not replacing anything, just removing & replacing the dried up grease.



I decided to give my chucks a polish to make them look purdy again.





Ready to be reassembled but before that I demagnetized all the parts. I don't actually set the parts on the demagnetizer as shown below then turn it on, you should wave the parts across it.



Jacobs says to use a high quality grease but they don't recommend what kind. I was just going to use Super Lube but well I have Gleitmo 805 which is what Bison recommends to use in their chucks. Expensive stuff so it's got to be "high quality" right? Just for consistency I put the jaws back in the same holes they were removed from.



EDIT: I made the mistake of lubing all the ball bearings with grease. Don't do that, still usable but they are stiff. Since then, I have taken them apart, cleaned all grease off the bearings, & just used oils on the balls. I only used grease on the scrolls.



Press the sleeve back on.





But don't press the sleeve on too far so you'll be able to press it back off later if you need to service it again. Leave a lip, that's how they come from the factory. I suppose if you did go too far it can still be pressed back off.



Here are the 2 completed ones. They're like brand new to me & will stay with me for a lifetime of use. Under .002" runout without replacing anything so I'm happy with that.




I'll update this thread when I get the new jaws & the results for the first chuck.

 

[darkzero]

Jacobs says to extend the jaws half way then press off the sleeve directly on the jaws. Now I don't know if this caused any damage to the jaws on the first one but I'm not taking anymore chances on the next ones.

Anyone know why Jacobs says to extend the jaws half way & press on the jaws? I can't understand why. Well the jaws don't seemed to be hardened, maybe just a little bit but I was still able to take a file to them. Knowing what it looks like on the inside I see no reason why you can just press directly on the nose as I did on the second.

I'm not sure if pressing directly on the jaws damaged mine, I wouldn't think it would but I don't remember that first chuck having such excessive runout to begin with.



To add (unrelated), although all 3 of my chucks state Hartford on them, the lower body on one of them is still slightly different. Doesn't matter but just wanted to add this in this thread.

 

[darkzero]

Got my replacement jaws (NOS). Installed them along with the new half nuts. Made a big difference. Not as great as the other two that I didn't replace anything but good enough as this third one is a secondary for the mill (1/2" straight arbor).

 

[Holescreek]

I used to rebuild them once a year while I was running a horizontal boring mill in the 80's~90's. Pretty sure I still have the tools in the bottom of my roll around. I don't remember there being any special tricks at all.

 

[davidh]

Reserved

consider where the "press forces" are going when you push down onthe jaws. thru the threaded half parts that the outer sleeve is actually press fit on. if you press on the nose of the tool, the forces are in a different place related to the threaded half parts. . . trying to pull the innards from the sleeve instead of pushing them out. or do i need more coffee ? ? ?

 

[4GSR]

On certain sizes of Jacobs chucks, if you retract the jaws all the way, you will damage the tail end of the chuck jaw. I know this for a fact, I've damaged the jaws on a chuck because I retracted the jaws all the way.

I've run into the same problem as you have rebuilding some 16N chucks. The only thing I can come up with is that some Gorilla before me tighten the crap out of the chuck many times in the past and warped the holes the jaws run in. I've always had to go in with files and carefully file out the high spots until the jaws will go in without jamming up.

 

[110octane]

On certain sizes of Jacobs chucks, if you retract the jaws all the way, you will damage the tail end of the chuck jaw. I know this for a fact, I've damaged the jaws on a chuck because I retracted the jaws all the way.

I've run into the same problem as you have rebuilding some 16N chucks. The only thing I can come up with is that some Gorilla before me tighten the crap out of the chuck many times in the past and warped the holes the jaws run in. I've always had to go in with files and carefully file out the high spots until the jaws will go in without jamming up.

Your experience parallels mine. I have had problems with both 11N and 14N runout problems even though things seemed to be in order. I think a lot of the runout was caused by the previous owner (a municipal maintenance dept.) allowing the jacobs taper to turn on the arbor. I know of no other way to correct this short of regrinding the taper in the chuck. I heard years ago of machinists truing up the chucks on the arbor, etc. and then using a small tool post grinder to even up the jaws. This reduces the minimum capacity the chuck will grip, but certainly puts things in order radially.

Thanks, Geoff

 

[EmilioG]

Great write up, thanks.
Where do I get replacement jaws for my Jacobs 16n Super Chuck BB? How much?

What did you use as a cleaning solvent and how did you polish the metal?
Btw, I don't think all of the USA made 16n Jacobs chucks have Hartford, Conn. stamped on them.
I'll fact check this more.

 

[110octane]

Great write up, thanks.
Where do I get replacement jaws for my Jacobs 16n Super Chuck BB? How much?
Btw, I don't think all of the USA made 16n Jacobs chucks have Hartford, Conn. stamped on them.
I'll fact check this more.

MSC used to have them (ENCO discontinued them a couple of years ago) but the price has increased geometrically. I obtained mine on ebay and I had to be patient to get the price at around $25. The designation for the repair kits has changed in the last few years, something about the part designation on the chuck - later manufactured chucks must have some internal differences from the older production items. You can determine this by reading the "fine print" in the catalog description or by visiting the Jacobs Chuck website.

I have a strong suspicion that Jacobs is now manufacturing all chucks overseas (China?). I'm sure that the Hartford plant has been closed for a long time with manufacturing transferred to North Carolina (?). I have had some good results with Rohm chucks. I also have a big ball bearing chuck made in China (Double Duck!) that is very nice and accurate. The problem with that is the one made the next day might wander all over the shop.

Thanks, Geoff

 

[zmotorsports]

Nice job on the documentation, as usual, Will.

Thanks.