Tailstock fittigs

[Spindle]

Hi Mark

The normal design of a Jacobs chuck is such that turning the sleeve anti clockwise, (when viewed from the nose), loosens the grip. Gripping the sleeve in a scroll chuck imparts the same force.

Edited to correct terminology

Regards Mick

 

[Mark Hancock]

Hi Mark

The normal design of a Jacobs chuck is such that turning the body anti clockwise, (when viewed from the nose), loosens the grip. Gripping the body in a scroll chuck imparts the same force.



Regards Mick

I see what you mean but doesn't happen because it's the body of the Jacobs that is held in the parallel jaws of the scroll chuck and so cannot move. I don't hold the Jacobs on it's morse taper.

 

[CHJ]

...because it's the body of the Jacobs that is held in the parallel jaws of the scroll chuck and so cannot move. ...

You are holding the actuating sleeve Mark, not the chuck body, any turning forces on the item held in the jaws can turn the body in a clockwise direction undoing the grip.

Grip the chuck actuating sleeve in your scroll chuck and turn the body of the Jacobs chuck in a clockwise direction (the direction of any drilling or turning forces) you will see what we are referring to, as the body of the chuck rotates in a clockwise direction the jaws will open.

 

[Jonzjob]

Am I the only one with a 3/4" Jacobs chuck that is screwed onto the 1MT? It just screws straight onto the headstock screw. So there is no problem and no danger in using the Jacobs chuck in the headstock at all.

If I am drilling anything on the lathe then I mount the Jacobs in the tail stock on its 1MT and spin it into the bit being drilled and for doing things with a hole right through them I drill first and then turn the object after that. That ensures that the hole is dead centre, it can't be owt else can it..

I use Carol drum sanders in my pillar drill too and on the very odd occasion the quill has come out. Tapped back in with my watchmakers 4lb hammer (hammer) (hammer) (hammer) it doesn't move again for ages (only kidding about the watchmakers hammer :mrgreen: )

I made myself a rig for sanding flat surfaces on the lathe and I turned a plate the same size as the normal sanding disks, 6" I think?. That just munts onto my Odonnel jawed K10 chuck. I turned 3 sizes on the back of the plate so that it doesn't matter which jaws I have in the chuck. Works fine and there is also a built in dust extract on the sanding bed too 8) 8)

 

[Mark Hancock]

Mark, assuming you are referring to a 'standard' keyed 'jacobs' style chuck, as you are gripping the actuating sleeve of the chuck, which is rotating towards you in an anti-clockwise direction in use.
Any turning loads applied to a drill etc. mounted in its jaws is trying to move the jaws and the body in a clockwise direction, which, if it happens will undo the chuck jaws.

I now see what you are saying Chas :roll:

But isn't this the way a Jacobs style chuck works on a hand drill as the rotation of the actuating sleeve of the chuck is the same in both situations and the load applied to say the drill bit is in the opposite direction?

 

[CHJ]

Yes the drill loads are the same but they are only transmitted into the chuck body which is held by the tanged taper, (to prevent galling of the taper if it should spin)
The actuating sleeve is just a passenger and of a relatively low mass in comparison with the tightening torque on the jaw scroll and does not have enough inertial energy on start up to slacken the scroll.

 

[Spindle]

Hi Mark

The torque is transmitted through the chuck body in normal operation, (not the sleeve as per your application), therefore there is no tendency to loosen the chuck.

Regards Mick

 

[Mark Hancock]

Chas & Mick

I obviously have to check this out in the workshop tomorrow. I use this method (Jacobs in scroll chuck) for many different applications. Maybe it's the way I tighten things :lol:

 

[CHJ]

As I said Mark, if your chuck has a relatively thin actuating sleeve you may well be distorting it enough to grip onto the chuck body, or you have never put enough turning load on whatever you have in the chuck jaws to counteract the torque load you applied with the key. The latter may well be the case if your tightening torque matches the power of Big Blue :lol:

Just so long as you are now aware of the risk, best option is to look for a chuck with a parallel shank.

 

[Robbo3]

I bought a 1/2" x 20 TPI male (1/2" UNF) adaptor from boffin53 on Ebay to suit a 3/4 x 16 TPI lathe. This allowed me to mount a 13mm keyless drill chuck on the headstock.

Since upgrading the lathe & wanting to utilise as many of my old lathe bits as possible, I now use an M33x3.5 to 3/4"x16 adaptor with the old adaptor & keyless chuck screwed on the end with no discernable run out.

I find it much easier to use two hands to clean up the bottom of turned pieces with a small sanding pad in a drill chuck mounted on the lathe, rather than one handed with a drill.

 

[chipmunk]

I hate to throw a spanner in the works here but most Jacobs chucks are held on an arbor with two tapers - one on each end.

So, a draw-bar through the headstock only really secures the Morse taper and not the Jacobs (JTX) or Metric (B16 usually) taper in the chuck body - There is still the possibility that the other taper will pop out which is much shorter unless, as others have suggested a screw mounting is used.

As a fan of Axminster chucks I favour a Morse Taper carrier for holding my drill chucks rather than gripping them in the chuck. I have a standard one for my C-jaws and a modified one with dovetail to fit my 50mm O'Donnell jaws. I could use a draw-bar on my chuck but don't.

I personally think that if the user is aware of the dangers i.e. that the taper(s) may pop out it is perfectly possible to counteract the effect by either being ready to hold it in while the lathe is switched off (!), position the tailstock to prevent the tapers popping out or to position the edge of the toolrest in such a way as to prevent the chuck body moving too far off either taper.

HTH
Jon

 

[CHJ]

The main saving grace if the chuck taper should let go is that the chuck will only stop or have to move a short distance before it drops onto the lathe bed. (Not as likely a scenario as a dusty or abused Morse taper socket letting go)

When a Morse taper lets go the attendant wobble developing as the taper moves out driven by the extra centrifugal force of the chuck can be quite alarming.

Must admit using a 'Jacobs' style chuck in a headstock is something I personal don't ever do as I have a 100mm scroll chuck that will grip down to 6mm for sanding pads if needed.

 

[chipmunk]

The main saving grace if the chuck taper should let go is that the chuck will only stop or have to move a short distance before it drops onto the lathe bed. (Not as likely a scenario as a dusty or abused Morse taper socket letting go).

I agree Chas, the chucks are usually so jammed on that getting them off the other taper is usually the main problem if you ever want to. But I had a B16 taper chuck on my cheap drill press that was always dropping off until I replaced it - there is so much cheap tat around these days.

Must admit using a 'Jacobs' style chuck in a headstock is something I personal don't ever do as I have a 100mm scroll chuck that will grip down to 6mm for sanding pads if needed.

Yes, it's often worth using engineering jaws in the scroll chuck for this type of thing or perhaps best of all a collet chuck like the Junior chuck. If it's good enough for milling machines, it ought to be good enough for wood lathes :wink:

Jon

 

[woodndrum]

Wow, interesting points raised by a misunderstanding. When I mentioned fitting a Jacobs chuck in the headstock, that is what I meant. The Jacobs chuck on, in my case a MT2 into the headstock spindle. Had I thought of something being mounted and held in a scroll chuck That is the wording I would choosen.
I would have thought that the seasoned turners here would have credited me with some intelligence NOT to recommend trying to grip a taper fitting in a parallel jaw. (To the MOD's Sorry I started this. Keith)

 

[Spindle]

Hi Keith

It was another member that stated he mounted a taper in a scroll chuck - have a re-read - threads have a tendency to wander somewhat

Regards Mick

 

[chipmunk]

- threads have a tendency to wander somewhat

...never a truer word :wink: :wink:

 

[winemaker]

Just to add to the debate
https://www.facebook.com/photo.php?fbid ... =1&theater :?: :?:

 

[Mark Hancock]

...because it's the body of the Jacobs that is held in the parallel jaws of the scroll chuck and so cannot move. ...

You are holding the actuating sleeve Mark, not the chuck body, any turning forces on the item held in the jaws can turn the body in a clockwise direction undoing the grip.

Grip the chuck actuating sleeve in your scroll chuck and turn the body of the Jacobs chuck in a clockwise direction (the direction of any drilling or turning forces) you will see what we are referring to, as the body of the chuck rotates in a clockwise direction the jaws will open.

Chas

I checked this out to day in the workshop and found whatever I did I couldn't get the Jacobs chuck jaws to loosen their grip. But if I tried on the body (where the chuck key goes) the jaws do loosen. :?:

 

[Spindle]

Hi Mark

That is what I was referring to, when you bore into the work the drill encounters resistance which tries to stop it turning - this resistance, (reaction), is transmitted to the chuck body, the sleeve is still being driven by the lathe which will tend to loosen the jaws.

You can simulate this by holding the chuck body still whilst rotating the lathe, (by hand), in it's normal direction of rotation - the jaws will open. Was this what you observed?

Regards Mick

 

[Robbo3]

Wow, interesting points raised by a misunderstanding. When I mentioned fitting a Jacobs chuck in the headstock, that is what I meant. The Jacobs chuck on, in my case a MT2 into the headstock spindle. Had I thought of something being mounted and held in a scroll chuck That is the wording I would choosen.
I would have thought that the seasoned turners here would have credited me with some intelligence NOT to recommend trying to grip a taper fitting in a parallel jaw. (To the MOD's Sorry I started this. Keith)

Keith, it's all about passing on the knowledge that we have acquired, especially to those that are learning.

Sometimes I am surprised that something that I think is common knowledge, isn't, & conversely, when I read something by someone who has overcome a problem that I have perhaps not solved, or solved differently, I get that 'doh' moment when it crosses my mind that I should have thought of that particular solution.