Lockhead back caliper thread ?

[The yaki]

What is the size and thread pitch of the hex blanking screw on the blind side piston ? I have unc, unf, and cycle bolts of the correct diameter but all wrong. Did they use a Whitworth or metric ?? Its not in parts diagrams! Thanks again, Roy.

 

[L.A.B.]

What is the size and thread pitch of the hex blanking screw on the blind side piston ?

There wasn't one as standard which is why there's isn't one on the parts diagram so the thread could be anything.

 

[The yaki]

There wasn't one as standard which is why there's isn't one on the parts diagram so the thread could be anything.

Could I therefore drill and tap it to suit myself ( and alloy) to screw in a bolt to remove a very stiff piston ?

 

[L.A.B.]

Could I therefore drill and tap it to suit myself ( and alloy) to screw in a bolt to remove a very stiff piston ?

Yes, I suppose so but can't you measure the existing thread diameter and tpi/pitch (possibly metric).
The hexagon size might also give you an idea if it's metric or not.

 

[2WheelsUp]

I believe I saw one or two rebuilt ones for sale either here or on eBay that looked great. Might be better than trying to salvage one that has a hole in it.

 

[The yaki]

Yes, I suppose so but can't you measure the existing thread diameter and tpi/pitch (possibly metric).
The hexagon size might also give you an idea if it's metric or not.

I have a multi thread file somewhere. Will check it. Thanks again, Roy. P.s I do remember that the 4 screws that hold the switch assembly to the master cylinder are metric ! These little things are just sent to test !!

 

[cliffa]

I believe I saw one or two rebuilt ones for sale either here or on eBay that looked great. Might be better than trying to salvage one that has a hole in it.

Yes, I have a couple of fully refurbished calipers for sale here.

Still available, 2 x Norton Lockheed calipers, fully reconditioned.

For Sale. Two completely refurbished Lockheed Norton brake calipers Stripped and meticulously cleaned, including the machined grooves for the seals, and all the fluid passageways. Fitted: New stainless pistons. New stainless end cap. New genuine...

www.accessnorton.com

Personally I wouldn’t use a caliper that has had the back drilled.

 

[The yaki]

Yes, I have a couple of fully refurbished calipers for sale here.

Still available, 2 x Norton Lockheed calipers, fully reconditioned.

For Sale. Two completely refurbished Lockheed Norton brake calipers Stripped and meticulously cleaned, including the machined grooves for the seals, and all the fluid passageways. Fitted: New stainless pistons. New stainless end cap. New genuine...

www.accessnorton.com

Personally I wouldn’t use a caliper that has had the back drilled.

Why would it be any less safe than the original hole when done properly ? I may not need to do this but cannot see the danger. It can't be because of the diameter. The blanking plate on the outboard side is a bit larger ? Am I missing something? Roy. Ps I have all the parts from RGM shown. I'll soldier on meantime without drilling yet. Thanks, Roy.

 

[cliffa]

Why would it be any less safe than the original hole when done properly ? I may not need to do this but cannot see the danger. It can't be because of the diameter. The blanking plate on the outboard side is a bit larger ? Am I missing something? Roy. Ps I have all the parts from RGM shown. I'll soldier on meantime without drilling yet. Thanks, Roy.

Hi Roy, if I understand you correctly there is a bolt or screw in the caliper body behind the inner piston?

If that is the case, it is not original.

 

[jan nelder]

the last standard caliper I overhauled: after removing the outer piston, the inner one had a raised threaded hole facing me, which made it very easy to remove! Is this what the Op means??

 

[B+Bogus]

I have a multi thread file somewhere. Will check it. Thanks again, Roy. P.s I do remember that the 4 screws that hold the switch assembly to the master cylinder are metric ! These little things are just sent to test !!

I've never had a Mk3, so can't be sure, but M5 screws are a close-enough match for 2BA.
I've repaired Concentric carb bodies with M5 Timeserts in the past with good results

 

[baz]

Exactly what thread/hole are we talking about here?
I'm assuming a hole drilled and tapped to knock out a seized piston?

 

[kommando]

To release a stuck back caliper piston I have used an oil gun with cloth to provide a seal and forced oil into the chamber whilst all the other holes were blocked. The piston slowly starts to move before popping out and releasing the oil. You can use air but the piston will be propelled out with some speed so using oil or grease is far safer.

 

[The yaki]

Exactly what thread/hole are we talking about here?
I'm assuming a hole drilled and tapped to knock out a seized piston?

There is an allen key bolt in the back centre of the blind side . A simple blanking screw? A 2in bolt tightened through it would ease the piston out? Even a little at a time with release oil. 11thread sizes it isn't!!! Roy.

 

[cliffa]

There is an allen key bolt in the back centre of the blind side . A simple blanking screw? A 2in bolt tightened through it would ease the piston out? Even a little at a time with release oil. 11thread sizes it isn't!!! Roy.

Have a look at this thread….

Caliper inner piston removal - simple method

A friend of mine asked me to remove the inner piston from his standard Norton Lockheed caliper. (He had already removed the cap and outer piston and dumped them) My normal practice is to heat the caliper up until it's really hot then holding it with a suede glove smack it down onto a piece of...

www.accessnorton.com

Basically I placed a number of 1/4” sockets into the rear piston (caliper held in a vice) but left enough room to get a 1/2” drive extension bar tightly in the middle of them. Then attach a ratchet handle and turn. The sockets will act like a sprag clutch and grab the piston. Keep turning while pulling upwards, and the piston will be out in seconds.

 

[The yaki]

Will give it a go. Similar principle as a stud extractor, in a way. Thanks, Roy.