Dismantling the Pratt Burnerd Myford 3 jaw chuck

[duncan webster 1Participant @duncanwebster1]

I meant rotating at speed under power

[Clive FosterParticipant @clivefoster55965]

Faced with a similar issue many years ago I simply said “stuffitt” and put three tapped holes in the rear part to pull the back off.

Easy enough to measure the depth of the back part and set up so I didn’t drill too deep.

Obviously the main body ended up with three shallow conical holes to accommodate the tip of the drill but, pragmatically speaking, this would clearly make no difference to the performance of the chuck when it was rebuilt.

Clive

[Paul LousickParticipant @paullousick59116]

Youtube video dismantling Pratt chuck

https://youtu.be/HqKaJfYX4eE

 

[Charles LamontParticipant @charleslamont71117]

One reason he might have had trouble with that chuck in the video is stuffing the thing with grease. A little light oil only, so as not to end up with grinding paste.

[bernard towersParticipant @bernardtowers37738]

Obviously another you tube video by a P**t

[David George 1Participant @davidgeorge1]

When striping a chuck PLEASE mark the parts with a small dot in the back plate and the body to make sure that they are in the same place and not rotated to a diferant place radialy which may cause misalignment. PLEASE DONT USE A HAMMER,Or help release parts or screw drivers. A hide mallet and pieces of plastic or wood are the most you should use to lever unless you have some dificulties which may need levering and only use aluminium. The faces of all the parts should be checked for flatness and damage by rubbing over with a small flat India stone which will show bumps etc. Clean well and use a slidway oil on the gear and the three drive gears and alight oil on all the other parts as you assemble.Gently with only a hide mallet and correct tools. If you cannot release the back plate I screw a spare nose which I have for mounting a chuck on to the tailstock and tap out with a piece of wood or a piece of wood or plastic which will not go through the thread and tap out from front.

David

[David George 1]

On David George 1 Said. If you cannot release the back plate I screw a spare nose which I have for mounting a chuck on to the tailstock and tap out with a piece of wood or a piece of wood or plastic which will not go through the thread and tap out from front.

David

If it’s a screwed body chuck, and it looks like one, that won’t work

[Michael GilliganParticipant @michaelgilligan61133]

My Recipe for overcoming such problems:

• Patient Perseverance
• A substantial ‘dead blow hammer’ with Nylon faces
• PlusGas ‘Formula A’

With the screws removed !

Hold the chuck in your hand, and apply radial hammer-blows until a tiny gap opens on the joint-line.

Apply PlusGas in small quantity, allowing it to creep in by capillary action.

Repeat as necessary

MichaelG.

[iconParticipant @icon]

I had previously tried tapping around the joint with a nylon and hide hammer, but the lack of any feature for the hammer to get purchase on thwarted my attempts.

I’m happy to report that propping the slightly extended jaws on 3 blocks of wood and tapping on 3 long screws threaded into the fixing screw holes had it apart very easily.

[Author]

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