jacobs chuck question

[Jenny Brandis]

I have a jacobs chuck and find it useful but very, very annoying the way it walks out of the MT#2 all the time

Any ideas?

[Tankstand]

Drive it in harder?

If it keeps happening after trying the above, I'd look at the taper and the hole (swallow) and look for any obvious shiny high spots. Then take to all surfaces with some 1200 wet and dry.

Hope this helps.

[Gil Jones]

Yup, it irks me too. Grind a flat on the back end of your #2MT, then drill and tap for a 1/4" bolt (what ever thread size you need). Then get two bolts; one the length to fit your headstock, and one to fit through your tailstock, to the threads you tapped in the MT. Put a washer on the bolt, and screw it into the MT you have inserted in the head or tailstock. Snug it down, and no more loose chucks. To remove the chuck, loosen the bolt a few turns, and tap it loose, and unscrew bolt.

[Skew ChiDAMN!!]

I rarely use a jacob's chuck in the headstock end of my lathe... it's usually in the tailstock with the workpiece in the chuck. For the odd times I do (the occasional lace bobbin) I always use the tailstock as well, so it's not a problem.

What are you doing that needs the jacob without tailstock support? :confused:

[Hickory]

Morris taper requires a perfect fit to stay put, surface contact is what holds it in place. It should be a PITA to get it from the hole except for a gentle tap from the rear. You may have a nick or dent in either the shaft or the hole. When you dent metal a equal amount of metal is raised surrounding the dent so surface contact fails.

Like was stated earlier, smoothe the surface wit super fine emory cloth or w/d paper. Dont neglect the drive head. the hole may be where the nick or dent is located. Maybe even rust. Is the shaft of the Chuck longer than the shaft of the Spur center? could be there is a buildup of Gunk past where the Spur seats and it is preventing a good seat. Could be you nicked the inside with your knockout bar.

After you checked the above and all is clear, set the chuck with a deadblow hammer or a lead head mallot.

[Gil Jones]

Skew, Sometimes I will mount my 1/2" Jacobs chuck (#2MT) in the headstock, and chuck up a sanding disk holder so I can sand the foot/pedestal bottoms while holding the piece with two hands. Also, I use the 1/2" Jacobs chuck (#2MT) to hold small metal parts and turn them. The draw bolt just eliminates the MT coming loose from chatter or any other reason.

[Jeff]

Is the jacobs coming off the MT, or is the MT coming out of the headstock or out of the tailstock? Details, we need details! If the jacobs is coming off the MT it may have funky threads on the back of the chuck. Perhaps some automotive thread locker would help this. If the MT is coming out of the headstock or tailstock, check the tailstock and headstock alignment. If they are off, this can cause the MT to walk out at either end. If the MT is fouled, as mentioned above, that could be the problem. On my machine the tailstock has to be run up about a quarter inch (6mm) before the MT will set up solidly. If you're using the MT/jacobs at the headstock and have a hollow drive then by all means use a through bolt as mentioned above. This will also work at the tailstock but shouldn't be necessary. I use my MT/Jacobs in the tailstock to turn up to a 200mm Forstner into end grain of various species of some tough wood, including oak. Also, there is a possibility that the problem is related to the bit(s) you're using. The bit may be encountering too much resistance and pulling the MT out of the tailstock if that is how you're using it. Is the bit good and sharp and straight? Are you allowing the shavings to get out of the hole? Does the MT spin around in the tailstock? The more info you can provide, the more likely your question can be accurtaely answered.

[Jeff]

Uh I think that should be accurately...

Also, uh, the obvious is sometimes the answer.....what direction are the threads on your Jacobs, and what direction does the lathe turn?

[Jenny Brandis]

The jacobs is coming out of the headstock, but Chris (DH) says it is because I am too gentle putting it in, I should be thumping it in hard rather than strongly placing it in (same as I do the point thingy).

The jacobs is smoothish, the MT seems ok too. I am using the jacobs to hold the turnings while I hollow out stuff eg: tiny pots.

I like the idea of the through bolt but am at a loss how to get the thread into the jacobs (does a drill bit do that???)

I do not use it in the tailstock as I dont (as yet) have another chuck to hold the headstock end.

[Gil Jones]

Jenny, if you have a #2 MT shaft attached to the back end of your Jacobs chuck, I am suggesting that you drill and tap (or have someone drill and tap) a hole in the back end of the #2 MT shaft to accept the bolt. If you take a correct length/size bolt, and the chuck/MT to a machine shop, they could do it easily.

[Ashore]

Jenny use white chalk to cover the motse taper push it in as you normally do then remove , where to comes in contact with the sleve the chalk will be rubbed off.
You should have 90% contact, what you may find is you have some bumps etc on the taper not allowing the full contact remove any high spots with a FINE FLAT file , taking care not to remove too much and using 300 or finer paper to smooth , chalk again and check again . Continue doing this until you get at least anything over 70% contact.

Rgds

[ribot]

Rather than cutting a thread in the back of the Jacobs chuck I welded a length of allthread to it and use a nut and wingnut to lock it in.

[Skew ChiDAMN!!]

I do not use it in the tailstock as I dont (as yet) have another chuck to hold the headstock end.

That makes sense. We do what we can with what we've got.


I like the idea of the through bolt but am at a loss how to get the thread into the jacobs (does a drill bit do that???)

You might try sanding the end of the morse taper with a bit of 80grit s/paper and then using 2-part epoxy (eg. araldite) to glue a threaded shaft to it. This would only be a temporary fix... overtightening the nut when mounting it on the lathe would break the glue joint, but it should last for a few turnings with a bit of care.

Until you can get something more permanent made up, anyway.

[Toasty]

Sometimes I will mount my 1/2" Jacobs chuck (#2MT) in the headstock, and chuck up a sanding disk holder so I can sand the foot/pedestal bottoms while holding the piece with two hands.
Dang, another excuse to spend more money. Thanks! ;)