ML4 headstock bore

[Andrew TinsleyParticipant @andrewtinsley63637]

I wish to fit a chuck backstop to this machine. The mandrel bore is 5/8″, However where the mandrel bore changes to the MT2 taper, there is a slight decrease in diameter, enough to prevent my 5/8″ o/d tube from entering the MT2 taper.

I assume (perhaps incorrectly) that the mandrel is hardened, so this may make the removal of the small restriction difficult. I am reluctant to dismantle the headstock to better get at the restriction, however the thought of using a 5/8″ drill in a battery drill, makes my hair stand on end!!

To the best of my measuring technique, the short restriction is about 13 thou under 5/8″ Maybe a 5/8″ hand reamer would cope? I could of course turn down the 5/8″ tube, but I would rather get rid of the root cause of the problem.

Andrew.

 

 

 

 

 

 

 

[Michael GilliganParticipant @michaelgilligan61133]

This may be a daft question, Andrew, but …

Why not drill from the tailstock ?

MichaelG.

[Clive Brown 1Participant @clivebrown1]

I’d be surprised if the ML4 mandrel is too hard to drill. My first lathe was a Grayson, fairly similar to the ML4. It got the treatment with a 5/8″ drill held in the tailstock.

[GeorgineerParticipant @georgineer]

According to lathes.co.uk, the spindle of the ML4 was bored through 19/32″ (which is about 31 thou smaller than 5/8″), so if yours is indeed bored 5/8″ my guess is that it was drilled from the outboard end and the drill stopped just short of the Morse taper.

I would be very surprised if the spindle is hardened.

George

[Georgineer]

On Georgineer Said:

According to lathes.co.uk, the spindle of the ML4 was bored through 19/32″ (which is about 31 thou smaller than 5/8″), so if yours is indeed bored 5/8″ my guess is that it was drilled from the outboard end and the drill stopped just short of the Morse taper.

…

George

I love this forum!  Forced back into bed by belly ache shortly after reading Andrew’s question, I pondered on my sickbed what on earth Myford could have been thinking to leave a step inside the spindle.  Andrew describes a severe quality fail!  Then I come back to find George’s guess, which I like:  needing a bit more room, a previous owner drilled the spindle out to 5/8″ and botched it.

If drilled out from the back as George suggests, it’s unlikely the 5/8″ section is straight or round.   How about boring the spindle to remove the step and correct 5/8″, assuming it needs TLC?  Make a long boring bar, that just fits through the existing hole, take the chuck off to get closer, and bore from the cross-slide.   I expect the bar will chatter, but no need to remove much metal.

Dave

 

[Clive Brown 1Participant @clivebrown1]

The “step” arises from the fact that the small end of the 2MT spec. is 19/32″; ie just under 5/8″. I found that being able to pass 5/8″ bar was a considerable improvement in the utility of my old Grayson, hence the mod. The original dimension effectively limited the mandrel to passing only 1/2″ bar. Removal of this tiny amount of metal has no effect on the accuracy of the MT nor its driving ability.

[David George 1Participant @davidgeorge1]

I recently made a new spindle for my lathe and the mose taper was finished in situ to make sure no run out. It was a No2 mose taper and i just user a 10mm boring bar with no problems. Put a pice of bar in the chuck and bore it to size and set dial to zero with corect bore size. remove chuck and bore spindle bore to zero setting. the spindle is made from a tough steel not hardered to much.

David

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello,

I have sent two replies to this topic and neither has appeared so third time lucky!

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

Clive has it in one, so I will try Michael G’s obvious (to all but me!) suggestion of drilling from the tailstock. The lathe in question is an ML10 NOT an ML4. Previous posts tried to make this point, but they appear to have disappeared !

Thanks everyone,

Andrew.

[Michael GilliganParticipant @michaelgilligan61133]

Perhaps worth noting this, Andrew … copied from the current Myford web-site:

The first ML10 lathe left the production line on the 14th of October, 1968, and featured a hardened steel spindle which ran directly in the cast iron bore of the split headstock bearing.

 

MichaelG.

[Clive Brown 1]

On Clive Brown 1 Said:

The “step” arises from the fact that the small end of the 2MT spec. is 19/32″; ie just under 5/8″. I found that being able to pass 5/8″ bar was a considerable improvement in the utility of my old Grayson, hence the mod. The original dimension effectively limited the mandrel to passing only 1/2″ bar. Removal of this tiny amount of metal has no effect on the accuracy of the MT nor its driving ability.

Makes sense to me.  Very educational this forum!

Ta,

Dave

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