Delicate Machine Adjustment Question

[Bent Ramrod]

I bought (used) a Jacobs 6A Chuck, 33 Taper, 0-1/2” capacity that appears to be in great shape. But it has a straight arbor on it, which I want to replace with a Morse #2 taper arbor so I can use it in a lathe tailstock.

I opened the jaws all the way, put a steel drift over the center of the inner arbor end, and tapped, then banged on the drift with a hammer. The chuck was over an opening sufficient to let the arbor drop out, but it wouldn’t budge.

I mounted the chuck in my little 2-ton hydraulic press and pressed on the arbor end till I couldn’t push the lever any more. The arbor held fast.

I put some oil around both ends of the arbor where it goes into the chuck, and am awaiting whatever lubricating or penetrating process that might happen.

Am I going about this removal right? I haven’t seen any pictures of the chuck that would lead me to believe the arbor is threaded in or anything. I don’t see a screw head, like the chuck in my electric drill has. Should I just get a bigger hammer and hit it harder? The chuck has been well-cared-for, I don’t want to wreck it.

TIA for any advice.

[Handloader109]

Kroll if you can get it will work better than anything.

Sent from my SM-S908U using Tapatalk

[M-Tecs]

That chuck uses a self-locking Jacobs taper. I have removed a bunch but I have always used wedges that were designed/made for that application. With the straight arbor wedges will not work alone. Since you are replacing the straight shank clamping the arbor in a vise and wedges should work. Since its a self-locking taper penetrating oil will do nothing. When you install the new taper make sure it's 100% oil free.

On the 1/2" chucks I don't remember what size or even if there is a knock-out hole in the chuck. A visual here on a larger chuck

https://www.youtube.com/watch?v=Rcr0_JDJI0M

How to use/make the wedges https://www.instructables.com/Wedges-for-Drill-Chuck-Removal/

Amazon sells them. https://www.amazon.com/s?k=Jacobs+Wedge+Set&crid=3L7LASQTLGA60&sprefix=jacobs+wedge+set%2Caps%2C106&ref=nb_sb_noss_1

[M-Tecs]

At 9:11 it does show a thru-hole. It is smaller than the end of the arbor. All my chucks are Jacob N14's or Albrecht keyless chucks. The N14's don't appear to have a thru-hole but my Japan 33N has full access to the arbor from the front of the chuck. Shock is your friend in this case. Make sure the base of the chuck is on something very solid when you try to drive it out.


https://www.youtube.com/watch?v=hTmbZXiLca4

one more option. https://www.homemadetools.net/forum/broken-jacobs-jt2-taper-favourite-drill-chuck-79725

[Nobade]

I'm with M-Tecs on this one. I always did them against the mill vise, so that I got as little bounce as possible and used a big heavy hammer. Everything has to be really solid for it to work.

[jdsingleshot]

I have come across Jacobs chucks that didn't have a knockout hole. I just drilled a 1/2" hole from the inside. Then using a punch nearly as big as the hole, it was easy to knock the arbor out. (The part that gets drilled is not hardened and drills nicely.)

[M-Tecs]

For the people that have never seen self-locking tapers used for this type of applicant they tend have a hard time believing friction is the only thing holding the arbor to the chuck.

Bent Ramrod. When you the arbors replaced let us know what worked for you.

[Bent Ramrod]

Will do, M-Tecs. And thanks to all for the advice.

I have a big vise to clamp the arbor in, but I’ll have to see about making or getting a wedge.

Nothing like decades of friction when you’re trying to get something apart. Screw threads the same way. You don’t even need rust or fossilized lubricant, just close contact, tightness and time.

[HWooldridge]

It is not impossible that it’s threaded - just like older lathe chucks and spindles. I once owned a 1943 Sheldon lathe that started life on a Navy tender. The tailstock for the Jacobs chuck and the headstock were both threaded, even though the machine came standard with reverse. I could do some operations in reverse but nothing strenuous.

[M-Tecs]

It is not threaded. Per the OP it's a Jacobs 6A Chuck, 33 Taper, 0-1/2”. The 6A is the model number. The 33 taper is the taper going into the drill chuck.

http://www.jacobschuck.com/uploads/ueditor/file/20200604/1591238129286207.pdf

Currently it has a straight shank arbor, and the OP wants a #2 morse taper like this https://www.mcmaster.com/2811A31/

[Green Frog]

Reading with interest. Coincidentally I have an 11” Sheldon made lathe with a #2 Morse taper in the tail stock and a #4 MT in the headstock. A machine class project I did once upon a time was making a #4 male MT to #2 MT adaptor so I could put Jacobs chucks and other such tools into the headstock to do milling and other similar functions using tooling I had. I also purchased a little Atlas bench top horizontal mill that takes tooling with… #2 MT! Are you beginning to detect a pattern here? ;)
Froggie
PS There is an aftermarket vertical head available for use with the Atlas. It comes in several variants, but one is… #2 MT. If I ever get off my lazy adze and get serious in the machine shop, that will be an early addition.

[Gtek]

What about placing outside on something black (truck bed liner) about ten in the morning and go get and try about five.

[country gent]

you need a straight push to remove the arbor, when the wedges are set together thats what you get. I always removed them in the arbor press. Another would be to seat and use a bench vise to provide the force, but that will tale 3 hands

[Cap'n Morgan]

A little heat, quickly applied and in the right place, can sometimes works wonders.

[ulav8r]

My post last night is not here now. If you have wedges, drive them in tight. if it doesn't pop off right away tehn tap the side of the nose of the chuck on one side, then the other. Often the vibration from the side taps will loosen the chuck quicker than trying to drive the wedges in further.