How do I get at the Mark V headstock lock?

bobroosth · Post by **bobroosth** » Tue May 10, 2011 7:35 pm

Vintage 1982 Mark V. The carriage lock on the headstock no longer turns very far either direction, hence does not lock. I have the end cap off the headstock but cannot see how to remove the lock without disconnecting the motor belt.

The belts I see do not appear particularly worn, nor do I see much rust.

Are there any good photos showing how to proceed?

damagi · Post by **damagi** » Tue May 10, 2011 7:51 pm

bobroosth wrote:Vintage 1982 Mark V. The carriage lock on the headstock no longer turns very far either direction, hence does not lock. I have the end cap off the headstock but cannot see how to remove the lock without disconnecting the motor belt.

The belts I see do not appear particularly worn, nor do I see much rust.

Are there any good photos showing how to proceed?

The headstock locks are on a long screw with opposing threads. you will need to turn it until the locks disengage, as well as past the point where they are seated...at that point the assembly can be removed.

bobroosth · Post by **bobroosth** » Tue May 10, 2011 8:02 pm

Do you mean that with the headstock off the tubes, the assembly will eventually come out the holes on either side of the headstock? Just keep turning in the unlock direction (ccw)?

Does you spare part collection include the parts I might need? You are a lot closer to LA than the factory store.

JPG · Post by **JPG** » Tue May 10, 2011 8:55 pm

If only it were that easy!!!

Since the lock does not secure the headstock, the headstock must be slid off the way tubes so you can remove the motor/motor pan to get access to the threaded rod. That involves getting the speed control set to 'fast'(if it is runnable, turn it on and set that before removing - otherwise manually rotate the shafts while setting the speed control to fast).

The belt cover must come off. the motor pan(with motor) must be removed( belt slipped off motor pulley and wires removed from power switch).

Now you have access to the wedges and threaded rod and should be able to determine which wedge is 'jamming' on the threaded rod. Removal of the threaded rod and wedges also requires driving the tension pin from the wing nut that rotates the threaded shaft and unscrewing it off that end of the threaded rod.

Judicious turning of the individual wedges may allow you to free them. Worst case is you strip the threads on the wedges and will have to replace them. The threaded shaft may get damaged(threads), but usually it is the softer wedges that strip out.

"""Reassembly""" is the reverse of disassembly!:rolleyes:

Ya get 'stuck', we be here!!!!

bobroosth · Post by **bobroosth** » Tue May 10, 2011 9:33 pm

Just got my hands out of the headstock. I can get to the wedges without dropping the motor, a job I really do not want to do. The wedge closest to the wing nut is stuck. The other moves freely.

I take it they are supposed to move in opposite directions. Is that correct?

When putting the headstock back on the rails, is the normal procedure to spread the wedges wide, put the headstock as far on as possible, then turn the wing nut until the wedges allow further motion onto the rails? Or set them far to the inside so the headstock will slide on all the way?

JPG · Post by **JPG** » Tue May 10, 2011 10:46 pm

bobroosth wrote:Just got my hands out of the headstock. I can get to the wedges without dropping the motor, a job I really do not want to do. The wedge closest to the wing nut is stuck. The other moves freely.

I take it they are supposed to move in opposite directions. Is that correct?

When putting the headstock back on the rails, is the normal procedure to spread the wedges wide, put the headstock as far on as possible, then turn the wing nut until the wedges allow further motion onto the rails? Or set them far to the inside so the headstock will slide on all the way?

That is correct. The wedge closest to the wing nut is left a hand thread.

To put the headstock back on the way tubes, the wedges need to be out as far as they will go(the raised collar pressing against the headstock casting) AND aligned so the wedges will clear the tubes. A paper towel core in each tube bore will help keep the wedges aligned. When fully expanded, the wing nut should also just clear the outer surface of the headstock and the wedge. The wedges should be nearly the same distance from the center non-threaded portion of the threaded rod.

More than likely, the left handed wedge has stripped slightly and debris is causing it to jam. Gentle turning back and forth MAY help relieve it!

Move the rear(right handed thread) all the way into the center of the rod so that you can concentrate on moving the jammed wedge and rod without the rear wedge interfering.

damagi · Post by **damagi** » Tue May 10, 2011 11:35 pm

bobroosth wrote:Do you mean that with the headstock off the tubes, the assembly will eventually come out the holes on either side of the headstock? Just keep turning in the unlock direction (ccw)?

Does you spare part collection include the parts I might need? You are a lot closer to LA than the factory store.

check your PM.

yes - with the headstock off the tubes. there are the two locking pieces on the screw part. if you twist each of them far enough towards the center then you can pull the bar out (assuming you have the handle taken off by punching out the roll pin)

JPG · Post by **JPG** » Tue May 10, 2011 11:57 pm

damagi wrote:check your PM.

yes - with the headstock off the tubes. there are the two locking pieces on the screw part. if you twist each of them far enough towards the center then you can pull the bar out (assuming you have the handle taken off by punching out the roll pin)

Only his rear wedge will travel to the center end of the threads. However that should allow pulling the wing nut end into the headstock so as to remove it. It is a whole lot easier to 'unjam' if out on the bench.

wannabewoodworker · Post by **wannabewoodworker** » Wed May 11, 2011 7:06 am

JPG40504 wrote:Only his rear wedge will travel to the center end of the threads. However that should allow pulling the wing nut end into the headstock so as to remove it. It is a whole lot easier to 'unjam' if out on the bench.

I agree that if you remove the motor/pan and get the headstock on the bench you will have a much easier time of fixing this. If it is stripped then just cut it off and get a new lock assembly. I happen to have a spare lock assembly from the headstock I damaged when rebuilding my 83' Mark V. But before you cut it off try to get it out the normal way. I agree with JPG that you should be able to get the left side moving with a little patience and determination. I find it a little hard to believe that someone totally buggered it up to the point you would have to cut it. But who knows some of these have really been handled by gorillas over the years.

dusty · Post by **dusty** » Wed May 11, 2011 7:35 am

wannabewoodworker wrote:I agree that if you remove the motor/pan and get the headstock on the bench you will have a much easier time of fixing this. If it is stripped then just cut it off and get a new lock assembly. I happen to have a spare lock assembly from the headstock I damaged when rebuilding my 83' Mark V. But before you cut it off try to get it out the normal way. I agree with JPG that you should be able to get the left side moving with a little patience and determination. I find it a little hard to believe that someone totally buggered it up to the point you would have to cut it. But who knows some of these have really been handled by gorillas over the years.

I would have agreed until I almost did just that. However, I had been cutting aluminum and apparently trapped some of the cuttings in the threads of the lock mechanism.