Breaking gears in a Myford ML7

[drnewcombParticipant @drnewcomb]

Has anyone ever broken a gear (Bull, back, etc.) on a Myford ML7 while removing a chuck? I had a discussion with my mentor about my concerns over using the back gear to lock the spindle to remove the chuck. He replied that it would take so much torque to break a tooth that he wouldn’t worry about it. I just don’t want to be that guy who finds out. I’ve asked someone to 3D print a bull-gear lock for me, so I won’t have to. Thanks!

[alecsParticipant @alecs]

My ML7 came with a couple of teeth missing from the back gear thanks to previous owner using it to remove chucks. And I have seen other instances over the years. It very definitely can and does happen. The back gears are cast iron so those small gear teeth are more brittle than on steel gears. They don’t bend or deform like steel, they just crack right off. You are right to get a locking block made up. Use it religiously.

 

[noel shelleyParticipant @noelshelley55608]

As Alecs has said it will and does happen, so DO NOT lock gears to undo the chuck.  Noel.

[Robert Atkinson 2Participant @robertatkinson2]

As said, they will break. The plastic gear locks work because they are more compliant than the cast iron gear and spread the load over many teeth.

Robert.

[drnewcomb]

On 6 June 2026 at 12:24 drnewcomb Said:

Has anyone ever broken a gear (Bull, back, etc.) on a Myford ML7 while removing a chuck? I had a discussion with my mentor about my concerns over using the back gear to lock the spindle to remove the chuck. He replied that it would take so much torque to break a tooth that he wouldn’t worry about it.

That’s a yes and no. If it was new and you were using the flat of your hand and not a hammer the bull won’t break. But consider an ML7 has had multiple owners by now and someone else may have swung the hammer already and that crack is just waiting to propagate.

 

[Andrew TinsleyParticipant @andrewtinsley63637]

Robert is correct! I trialled a free printed plastic gear lock, which a forum member provide a couple of years ago. They work well and don’t break the bull wheel teeth for the reasons Robert gave.

I have threaded the chuck on the mandrel nose by half a turn and then turned on the lathe at maximum speed! This really jams the chuck on very tightly. The plastic gear lock undid it with no problems.

Andrew.

[Andrew Tinsley]

On Andrew Tinsley Said:

…………………..

I have threaded the chuck on the mandrel nose by half a turn and then turned on the lathe at maximum speed! This really jams the chuck on very tightly. ………………………..

Andrew.

Why on Earth did you do that?

The S7 instructions given for freeing a tight chuck was to put a block of wood between a jaw and the lathe bed to stop the chuck rotating. Then, in back gear, try to rotate everything backwards by hand using the belt between the spindle and clutch shaft. This worked for me a couple of times.

Hammers and lathes DO NOT mix.

JA

[bernard towersParticipant @bernardtowers37738]

My S7 has a stop pin for just that job

[JA]

On JA Said:

On Andrew Tinsley Said:

…………………..

I have threaded the chuck on the mandrel nose by half a turn and then turned on the lathe at maximum speed! This really jams the chuck on very tightly. ………………………..

Andrew.

Why on Earth did you do that?

The S7 instructions given for freeing a tight chuck was to put a block of wood between a jaw and the lathe bed to stop the chuck rotating. Then, in back gear, try to rotate everything backwards by hand using the belt between the spindle and clutch shaft. This worked for me a couple of times.

Hammers and lathes DO NOT mix.

JA

Probably because a jammed chuck is, generally, so rare that folk don’t read the instructions.

Always assuming they actually have the instructions.

Given the high frustration index when a chuck does jam its the tendency to do teh quick, dirty and obvious with stuff immediately to hand is understandable.

Clive

[Clive Foster]

On Clive Foster Said

Probably because a jammed chuck is, generally, so rare that folk don’t read the instructions.

Always assuming they actually have the instructions.

Given the high frustration index when a chuck does jam its the tendency to do teh quick, dirty and obvious with stuff immediately to hand is understandable.

Clive

Page three of “Myford 7 Lathe Notes on Operation Installation and Maintenance also Pictorial Parts List” booklet says “DO NOT OPERATE THE LATHE UNTIL …….. The instructions have been carefully read, and the controls and adjustments are understood”. At least the Myford instructions are easy to understand compared with those for my camera.

If anything goes awry, push the big red button, turn off at the mains, shut down the workshop, fix yourself a coffee, better still a stiff drink, sit down in your comfortable chair and have a long think. Then start taking action or seek advice.

JA

[bernard towers]

On bernard towers Said:

My S7 has a stop pin for just that job

Hmmm – I used the stop pin on my S7 to attempt to remove the stuck 9 inch faceplate that I had used to shape a large piece of 4 mm MS plate that had involved intermittent cutting on the OD.

I engaged the lock pin, fitted two clamps to the faceplate 180 degs apart near the OD, and heaved on a soft pine 2×4 engaging with the clamps.

Then I felt something give way, the brass/bronze gear/bush that is pressed into the ID of the CI cone pulley had turned in the pulley, the press fit is  the only thing that is holding it.

The condition of the brass gear teeth wasn’t good, caused by the previous meshing of the back gear assembly being too slack.

I bought in a new-old-stock pulley/gear from a company in the Netherlands.

Before fitting it all up, I drilled and tapped 3 equispaced M8 tapped holes down through the bottom of one of the pulley grooves through into the part of the gear which serves as the bush which the pulley/gear runs free on the spindle when in back gear, then turned the lock points off the ends of three long M8 socket grub screws and loctited them in to lock the bush/gear to the pulley ( I have another lathe an old ML7)

Now, before fitting a chuck or faceplate to the headstock spindle, I brush a little NeverSeez onto the spindle thread and location diameter and face.

[alecsParticipant @alecs]

I drilled and tapped a 5/16″ hole in the side of my ML7 bull gear and screwed in a silver steel pin, with a bit of Loctite for luck. Then made a C spanner that fits around the spindle. The pin engages with a hole drilled in the C spanner and the spanner handle rests on the headstock casting.  Ive an idea the design was in MEW. And that disassembly of the spindle was required to drill the hole.

And as Howard found, Never Seez is essential on the spindle nose.

[Author]

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