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kcleere
07-10-2009, 05:18 PM
I have a Jacobs 3B chuck with 45/68-16 THD thread mount and has the same stamped on it.

t's a 5/8" capacity chuck.

Jacobs only lists a 3B as having 5/8-16 thead mount.

What the heck do I have here? I can't find any reference to an arbor I can use or what this chuck was for.

I called Jacobs but both tech guys are out untl Monday.

Any words of wisdom?

TGTool
07-10-2009, 06:17 PM
I have a Jacobs 3B chuck with 45/68-16 THD thread mount and has the same stamped on it.

t's a 5/8" capacity chuck.

Jacobs only lists a 3B as having 5/8-16 thead mount.

What the heck do I have here? I can't find any reference to an arbor I can use or what this chuck was for.

I called Jacobs but both tech guys are out untl Monday.

Any words of wisdom?

I've got at least a word of curiosity. How! How did you determine that you had a 45/68-16 thread? Are you saying it has "45/68" stamped on the chuck body?

kcleere
07-10-2009, 06:35 PM
I've got at least a word of curiosity. How! How did you determine that you had a 45/68-16 thread? Are you saying it has "45/68" stamped on the chuck body?

Yes as stated in my opening line.....

doctor demo
07-10-2009, 07:26 PM
Can You verify that it is 16 tpi?
Can You measure the bore with a inside caliper or hole guage etc. ?
I was going to ask if You were just yanking our chains, but I am curious as to what You have.

Steve

kcleere
07-10-2009, 08:23 PM
LOL...nah...not jerking chains. I went ahead and took a pic. The pic makes it look like 45/84 but that 8 is really a 6 and when I measure the bore I get the 45/64th. As far as the threads go yes I can poke a thread gauge down there lather tonight and check it but I have no reason to think oherwise due to the markings on the chuck. It's a nice smooth chuck that does not look used at all but considering the thread size I think we know why.

http://img.photobucket.com/albums/v359/kenwc/102_1415.jpg

CCWKen
07-10-2009, 08:24 PM
It should be 45/64 not 45/68. It is a Jacobs option on some of the 3B & 3xB series chucks. So what's the problem?

CCWKen
07-10-2009, 08:26 PM
That's a 45/64-16. Someone stamped over the 6.

kcleere
07-10-2009, 08:43 PM
It should be 45/64 not 45/68. It is a Jacobs option on some of the 3B & 3xB series chucks. So what's the problem?

Problem is I'd like to use it eiher with an MT2 or 1/2" straight shank and I can't find any arbors to fit much less any reference to that thread size.

And yea fatfingered the 68 in the original.

Carld
07-10-2009, 08:53 PM
45/64" is 1/64" over 11/16" and IF the bore measures 45/64, as you say it does, which is .703 then you may have a 3/4"-16 thread. That's because the 3/4"-16 thread uses an 11/16" drill to thread the hole.

Have you tried a 3/4"-16 bolt in the hole?

kcleere
07-10-2009, 09:04 PM
45/64" is 1/64" over 11/16" and IF the bore measures 45/64, as you say it does, which is .703 then you may have a 3/4"-16 thread. That's because the 3/4"-16 thread uses an 11/16" drill to thread the hole.

Have you tried a 3/4"-16 bolt in the hole?

You could be right...and that's worth a try.
Thanks

KiddZimaHater
07-10-2009, 09:04 PM
Problem is I'd like to use it eiher with an MT2 or 1/2" straight shank
Why can't you make a special 45/64-16 threaded straight shank on your lathe?
Problem solved.

Alguy
07-10-2009, 10:08 PM
It is easy to make a shaft to put it on, 1/2 or any size. The thread fit should not be snug The most important thing is to have it fit against a shoulder, then it will be true. I recomend you single point the threads and cut the shoulder it rests against.

J. R. Williams
07-10-2009, 10:28 PM
I expect the chuck was made for an OEM product by Jacobs.

JRW

DR
07-11-2009, 12:21 AM
It could well have been made for a special machine. As in, "You need a new chuck? Sure, we have the specials and they list for a thousand bucks".

I recently bought some tooling with a 5/8-23 thread on the shank. I called the manufacturer to verify what I was seeing, they grudgingly admitted it was so they would be the only source for replacement parts. Unless you have a CNC lathe, that is....


A simple solution here is to get a blank #2 or #3 Morse arbor and thread it accordingly.

CCWKen
07-11-2009, 01:05 AM
The 3B only comes in 5/8-16 and 45/64-16--No 3/4-16. You can get a 36B in 3/4-16. These chucks are still sold. The 3B, 45/64-16 is about $200 new.

My next question is: Why did you buy it? :rolleyes:

As DR says, just cut a MT-to-JT arbor down and thread it. What size is your Morse Taper? The JT side will probably need to be a 4JT. I've only seen this size with an MT3 shank though. If you need MT2, you may have to make your own.

kcleere
07-11-2009, 09:55 AM
Problem solved. A member on another forum I'm on needs this oddball for an old motiser he has plus he has a new "normal" Jacobs 3B for swap so that works out for us both.

As far as why I bough it....ok I'll say it...I wasn't paying attention to he "tiny" print in the Ebay posting....just the low prce....:p

Thanks for all the replies...

JMS6449
07-11-2009, 10:07 AM
It would be nice if people read the previous posts. The poster stated that the 45/64 looks like 45/84 in the picture. Why does everyone have to be such a smart ass, or try to prove the other guy wrong.

Paul Alciatore
07-11-2009, 10:11 AM
Four words: chuck it, bore it, thread it.

I have several Jacobs chucks with threads Jacobs never made. Like M12-1. I simply cut them myself to fit. There is pleanty meat there for rethreading.