Thread: 4 jaw dismantle

Are the press in retainers for the jaw-screws, supposed to be so tight that they won't knock out with a hammer and drift?

Not normally.

Agree, they should be right, but a good whack should have them moving.

Ok I'll make up a tool that will contact both sides at once and try again.

Hi Phil,

Originally Posted by ptrott

Ok I'll make up a tool that will contact both sides at once and try again.

I just use a pin punch to tap them out, they are normally quite tight, so make sure that they are aligned properly when you put them back in.

Originally Posted by BaronJ

Hi Phil,
I just use a pin punch to tap them out, they are normally quite tight, so make sure that they are aligned properly when you put them back in.

I have given up John. I made a tool up to contact both sides, and it bent after hitting it several times. I ground the end of a pin punch so that it would sit flat on the top of the retainers, but the punch eventually burred, and there was slight damage to the retainer, so I gave it a miss as I don't want to bugger them up. They are either a very tight press fit, or they are glued in.

Hi Phil,

Bashing the fork is a waste of time, all you will do is damage them ! You need a solid pin punch that fits the bottom of the curve, then you need to support the chuck body on something solid like an anvil. If you think that the pegs might have been glued or bonded a bit of heat on the chuck body around the pin will help. I've never had any that didn't come out without a bit of persuasion, they are a tight fit.

Cleaning them before you put them back and clean the hole in case there has been any swarf trapped. A wipe with a greasy cloth helps.

Good luck.

Originally Posted by BaronJ

Hi Phil,

Bashing the fork is a waste of time, all you will do is damage them ! You need a solid pin punch that fits the bottom of the curve, then you need to support the chuck body on something solid like an anvil. If you think that the pegs might have been glued or bonded a bit of heat on the chuck body around the pin will help. I've never had any that didn't come out without a bit of persuasion, they are a tight fit.

Cleaning them before you put them back and clean the hole in case there has been any swarf trapped. A wipe with a greasy cloth helps.
Good luck.

Agreed, bashing the forks is a waste of time as there is only about 2mm of the edge of each fork available to wallop can be seen here:

Jaw drive retainer 2.jpg

Inserting the pin punch with an angle ground on the end at about 15 degrees gives more contact area, but they still will not budge.
Jaw drive retainer 1 .jpg

Using a tool that sits on the edge of the forks, and applying pressure with a press results in a bent tool after a lot of pressure, which also doesn't budge them.
Jaw drive retainer 3.jpg


Your statement, "you need a solid pin punch that fits the bottom of the curve"
has me bamboozled as there are no curves that I can see, and the only area I can see to access is the ends of the forks, which doesn't work.

Hi Phil, Thanks for the pictures.

There was a hole through the middle of the screws on the one I took the forks out of, and the tines of the fork barely reached half way across the screw. Obviously no hole in yours to get a pin punch through. Based on what you have said and done they should have come out. I agree there is very little room to get at them.

Just a thought, are the pins staked in and could the fork have been bent when the jaws were tightened.

I still think impact is the key, with some applied heat. Another possible way would be to drill and thread a hole in the back and pull them out with a screw.

Sorry I'm out of thoughts, someone put the buggers in so they must come out !

EDIT: I've just been looking at the pictures again, those forks look to be very wide and from the marks made by your tool quite soft. May be you need a much wider tool to apply force over a wider area.

Is the chuck very old? ( just curious ).
Have you removed any backing plate?
Have you checked to see if there may be anything retaining them from the rear?
Can you recall the load / tonnage you tried with the press?

The retainers are not staked in.
No hole through the screws.
Forks are not bent.
Chuck is near new, never been tightened hard.
No idea of the pressure applied by the press, but a fair resistance on the handle for a couple of pumps before the tool bent. (10T press)
A wider tool might be possible, but it would be a job to machine one up. It would have to be made to slide in the way the jaws do from the outside edge of the chuck.
Drilling & tapping the buggers might be the go John.

This is the exact same chuck, rear view: Doesn't appear to be anything holding them other than a tight fit.


Chuck rear view .jpg

Phil,
If the attached picture is correct, then there appears to be a central portion to the larger insert / retainer, is it possible this is screwed in, would be unusual, but suppose anything goes. If so I would drill 2 small holes in the outer section and use a pin spanner to see if they turn, or put some heat onto it, as others have said maybe loctited in, cheap and quick. Alan






Chuck rear view .jpg

I just had a look at my 4 jaw off my AL335 after seeing the photo you posted. On 3 of the 4 pins, the rear of the chuck shows a very clear depression in the cast body next to the pins, where they've been peened with something fairly large. The 4th one is hard to tell, but I think it's been done as well, just more centred over the pin. Looks like probably the flat face of a ball peen hammer was used by the shape of it. It's going to take some force to move it, a press will be a better bet. Why do you want to take them out though?

I see what you are saying, but mine are not the same (see picture)

Attachment 388090


I have another problem now. I decided to do what John suggested, tap and use a bolt to remove but it turned to poop.
I have tapped hundreds of holes over the decades, but never come across anything like this.
When I tried to tap these holes, (M8) drilled to 17/64", the starting tap was jamming up and having great difficulty, but I managed to get the 4 done.
When I tried to follow up with the intermediate tap, things got ugly, and I destroyed two good quality tap handles, one P&N and one British Eclipse.
I increased the holes to 7mm, well over sized for M8, and still the tap was jamming up.
It feels like the metal is super "sticky", or what you might expect if the hole was tapered and full of setting epoxy. No amount of cutting oil made any difference at all, and i ended up retrieving the tap with a shifting spanner!!
These are near new P&N taps. When they lock up, there is a distinct loud "CLICK" just as it locks, and again each time I managed to get a fraction of movement reversing them out. There are NO chips in the holes, and all the holes behave the same way. It is like some kind of steel that I have never encountered before

Tapping hndles destroyed.jpg

Attachment 388089
Attachment 388089Attachment 388089

Attachment 388089

FWIW.
In the last 12 months I have had 2 CROWN 4 jaw Chucks to revamp.
One came apart quite easily. Just a light tap with a punch at the side of the screw got the plugs moving. Was able to clean out the crud and reassemble. Aligning the plugs was just do-able.
With the next chuck I went through all the anguish you have experienced. I made a tool from mild steel and it collapsed under the pressure. In the end I gave up, and partly the reason was that I thought I might have trouble realigning the plugs. I sloshed cleaner through the screws as best as I could.
Hope this helps.