Stuck Chuck

[Martin WParticipant @martinw]

Even if you get the adapter out its not worth the risk of using it again so just accept that it is scrap. If it were mine I would find someone with a suitably sized lathe and get them to bore the adapter out and then remove what remains. Should be able to bore close to the root diameter of the thread so there is minimum material remaining to get out.

No brute force or special tools required and much gentler on the chuck

Martin

PS If this has already been suggested then ignore this post

Edited By Martin W on 08/01/2020 10:59:06

[HopperParticipant @hopper]

It has a screwdriver slot for a reason.

You need the proper tool for the job: a simple impact screwdriver with wide, straight bit. The basic old type you rap with a hammer while twisting. Available on eBay for 15 quid. Search for Impact Driver Motorcycle.

Or take it to a local motorcycle shop and have them use theirs on it. Probably only cost you 30 quid there!

Impact driver will jar screws loose that you can never shift with a screwdriver and pliers etc. It;s the impact wot does it.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 08/01/2020 10:53:34:

[…]

However much force could be applied with the screwdriver shown in the pic on the first page, at least four times the torque would be applied using the full width of the slot with that same force! Simple physics.

With two spanners. One operating on each side would likely increase that torqe available at the scew slot by another factor of two.

.

…

(a) Really ?

(b) Contradicting your assertion on another recent thread

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 08/01/2020 12:52:49:

It has a screwdriver slot for a reason.

You need the proper tool for the job: a simple impact screwdriver with wide, straight bit. The basic old type you rap with a hammer while twisting. Available on eBay for 15 quid. Search for Impact Driver Motorcycle.

Or take it to a local motorcycle shop and have them use theirs on it. Probably only cost you 30 quid there!

Impact driver will jar screws loose that you can never shift with a screwdriver and pliers etc. It;s the impact wot does it.

.

With the greatest respect to your experience and expertise, Hopper … I must beg to differ

The screw [in its present setting] should be free-running in the chuck thread: it is therefore not 'over-tightened' but 'stuck' ; so I am not entirely convinced that impact [unless, perhaps, applied repeatedly] will have the desired effect.

MichaelG.

[Howard LewisParticipant @howardlewis46836]

A suddenly applied load will have twice the effect of a gradually applied one. (Draw the force vs time graph. A rectangle as opposed to a triangle )

Hence my suggestion of an air impact gun, applying multiple sudden loads, to hammer it loose!

Keep hammering, it will eventually slacken.

Removing the crank shaft dog bolt from a Rover/Honda engine, that had been tightened to 285 lb ft took time, even with a 3/4 drive gun, but it came loose in the end!

Howard

[old martParticipant @oldmart]

The good thing about the humble impact driver that you hit with a hammer is more than just the instant high torque, as you hit it the axial pressure is also instantly high, which stops the bit slipping out of engagement.

I would tend towards screwing the adaptor out in the opposite direction from the original assembly. That is clockwise viewing from the head with the screwdriver slot. There must have been a bit of swarf trapped as it was screwed together.

I would start by giving the 3/8" end a sharp rap with a copper hammer, and the slotted end likewise with a soft drift.

[Mike PooleParticipant @mikepoole82104]

A square drive screwdriver in a carpenter’s brace can shift a lot of tight screws. An impact driver seems a big expense for one job but it will be useful on other jobs sooner or later.

Mike

[Martin WParticipant @martinw]

If the adapter has become that difficult to remove and this is due to the threads galling or having jammed because of swarf/detritus etc. then using force to unscrew the adapter could leave both the chuck and the adapter with damaged threads.

It's your choice at the end of the day but I know how I would proceed and it would be with a minimum of force.

Hope you can free it up without damaging the chuck.

Martin

[HopperParticipant @hopper]

Posted by Michael Gilligan on 08/01/2020 14:00:39:

Posted by Hopper on 08/01/2020 12:52:49:

It has a screwdriver slot for a reason.

You need the proper tool for the job: a simple impact screwdriver with wide, straight bit. The basic old type you rap with a hammer while twisting. Available on eBay for 15 quid. Search for Impact Driver Motorcycle.

Or take it to a local motorcycle shop and have them use theirs on it. Probably only cost you 30 quid there!

Impact driver will jar screws loose that you can never shift with a screwdriver and pliers etc. It;s the impact wot does it.

.

With the greatest respect to your experience and expertise, Hopper … I must beg to differ

The screw [in its present setting] should be free-running in the chuck thread: it is therefore not 'over-tightened' but 'stuck' ; so I am not entirely convinced that impact [unless, perhaps, applied repeatedly] will have the desired effect.

MichaelG.

I am. That's what impact drivers are for: freeing stuck threaded fasteners. Works on screws ranging from 1/4" to 1" and more on 80 year old motorbikes that have sat out in the weather in some farmer's paddock half their life and on every other piece of machinery I've ever worked on. Well corroded threaded aluminium inspection plugs etc etc etc included. Yes you will often need to hammer on it multiple times.

For bigger stuff such as fork top nuts with say a 1-1/8" very fine thread, torqued to 140 foot pounds when it left the factory in 1975, I'll use a half-inch drive air impact gun hooked up to appropriate socket. Not much in the typical home workshop will stand up to that.

I'm just suggesting the hammer blow type here because of cost. And if that and/or a propane torch won't shift it, you might as well machine the thing out and buy a new one. Or maybe try filing two flats on the protruding threaded bit and turn it with a wide-jawed shifting spanner.

Edited By Hopper on 09/01/2020 12:40:42

Edited By Hopper on 09/01/2020 12:42:25

[Michael GilliganParticipant @michaelgilligan61133]

Fine, Hopper … I will keep out of the discussion, and await Steve’s failure analysis.

MichaelG.

Edited By Michael Gilligan on 09/01/2020 14:10:55

[Steve CrowParticipant @stevecrow46066]

I've managed to remove the adaptor.

I used a split nut held in a large vice (at work) and a bar held in the jaws. It was very stiff for the first turn and after that ran free.

There appears to be no damage to the adaptor, I've tried it in my 3-jaw and rotary table and it screws in by hand.

It looked like there was a small amount of damage to the thread in the chuck about 3/4 of the way in but it was hardly visible. I'd ordered a 3/4 ANF tap which arrived today which I ran through the threads and now that is fine.

So, a happy ending with everything left servicable. I'm going to clean up and deepen the slot in the adaptor next.

I'm so glad I didn't do anything destructive and tried a gentle approach.

A big thanks for all the suggestions. I didn't expect this thread to run to 3 pages!

Steve

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve Crow on 09/01/2020 17:40:51:

I've managed to remove the adaptor.

I used a split nut held in a large vice (at work) and a bar held in the jaws. It was very stiff for the first turn and after that ran free.

There appears to be no damage to the adaptor, I've tried it in my 3-jaw and rotary table and it screws in by hand.

It looked like there was a small amount of damage to the thread in the chuck about 3/4 of the way in but it was hardly visible. I'd ordered a 3/4 ANF tap which arrived today which I ran through the threads and now that is fine.

So, a happy ending with everything left servicable. I'm going to clean up and deepen the slot in the adaptor next.

I'm so glad I didn't do anything destructive and tried a gentle approach.

[…]

.

Great news, Steve

MichaelG.

[Nick WheelerParticipant @nickwheeler]

Is it just me that prefers gentle use of a thread file for cleaning up potentially damaged threads? They're also good for scraping Loctite out of threads. Although they're not cheap, it only takes one job to pay for one – a mangled air fitting on a Yak that would have taken hours of dismantling to replace in my case.

[JasonBModerator @jasonb]

I've never got a thread restoring file to work well on a female thread

[Ian PParticipant @ianp]

I'm glad that Steve has solved his stuck adapter problem but there are two points I am not clear on.

What metal Is this 3 jaw chuck made from? I have a sneaking feeling its not the usual steel or cast iron.

Also I have not come across ANC threads, is that the same as UNC?

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

For your first clarification, try Sherline’s website [*]

For your second … This is a good summary, I think

**LINK**

https://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

.

MichaelG.
.

[*] From the link that I posted on page_1 …

Chuck Body Material	12L14 Steel
Chuck Jaws Material	12L14 Case Hardened Steel

Edited By Michael Gilligan on 10/01/2020 11:34:57

[HopperParticipant @hopper]

12L14, that's leaded steel so unlikely to be the culprit as far as seizing goes, being "self-lubricated". But it is not as strong as normal mild steel so may be more prone to damage. It is used for its ease of machining, not its superior strength, hardness or durability.

Could be the thread on the adaptor had a bit of a burr on it or even a bit of swarf.

[old martParticipant @oldmart]

Time to buy a metal bottle brush to clean the chuck threads before mounting, and having your own airline is useful if used carefully.

[Steve CrowParticipant @stevecrow46066]

Posted by old mart on 10/01/2020 14:06:18:

Time to buy a metal bottle brush to clean the chuck threads before mounting, and having your own airline is useful if used carefully.

I would love to have my own airline. I wouldn't buy any of those 737 MAX though…

Seriously, I have put an old toothbrush in the box with my chucks to remind me to clean them everytime they are used.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 10/01/2020 13:00:29:

12L14, that's leaded steel […]

.

That had me a little worried, in relation to the ‘case hardening’ of the jaws …

But happily, I found this: **LINK**

http://www.interlloy.com.au/our-products/bright-steels/12l14-bright-mild-steel/

MichaelG.

[Howard LewisParticipant @howardlewis46836]

ANC = American National Coarse.

Effectively superceded by UNC = Unified National Coarse. Same 60 degree thread angle, and pitch.

American practice is to quote the t p i so 5/16 – 18 UNC

The smaller threads are quoted in a similar way, 4-40 UNC etc, although 10-32 is UNF while 10-24 is a non preferred UNC.

Well worthwhile to buy a set of Zeus charts for details of most of the threads that you nare likely to meet, plus some other useful data, and mathematical tables.

Howard.

[Neil WyattModerator @neilwyatt]

Posted by Nicholas Wheeler 1 on 10/01/2020 11:07:29:

Is it just me that prefers gentle use of a thread file for cleaning up potentially damaged threads? They're also good for scraping Loctite out of threads. Although they're not cheap, it only takes one job to pay for one – a mangled air fitting on a Yak that would have taken hours of dismantling to replace in my case.

For metric threads a saw sharpening file works and is cheap.

[Author]

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