Is it bad practice to lock my Myford lathe using the slow speed lever

[David KParticipant @davidk77137]

When I remove a chuck or tighten a collet on my Myford Super 7 I lock the spindle by engaging the back gear , effectively engaging two gears to lock the spindle. I realise there is a locking pin at the back of the spindle but its just easier the way I do it.

Is this bad practice or is it normal for other Myford users.

[David KParticipant @davidk77137]

[Robert ButlerParticipant @robertbutler92161]

Yes – broken gear teeth can be the unfortunate result

Robert Butler

[old martParticipant @oldmart]

If you do that, never clout the chuck key with a mallet to unscrew it. It shock loads the gears and can split the ends of the screws on four jaw chucks. Use a strap wrench and gently increase the torque. If the spindle can be locked properly, then get in the habit of using it correctly. Tightening a collet should not require as much effort as unscrewing the chuck.

[Jon LawesParticipant @jonlawes51698]

I do it myself, with care. Luckily my chucks are never that tight. If I got to the stage where I was hitting things with mallets I might change my mind, or hide my mallet.

[not done it yetParticipant @notdoneityet]

I must admit to doing that, but I am very careful. Only a thump with the palm of my hand – not a hammer or mallet – seen too many broken back-gear teeth to risk breaking mine! The gears should be strong enough to absorb full motor torque, but not an impulse force.

If the chuck is tighter, then a protective board over the ways and either a spanner on a chuck jaw, or a large hex key in the jaws, and a sharp clout with whatever it needs (with the lathe in slowest normal range speed). The inertia of the belt drive is always enough to loosen the chuck.

Some kind-hearted soul drilled a hole trhough the back end of the spindle to use a bar at that end (after using a pipe wrench on the spindle – grrrr!). Unfortunately, while a good idea, it is now usually sealed up with insulation tape to prevent any swarf falling close, or on, the gear train. A previous owner was thoughtful, but not thoughtful enough!

[SillyOldDufferModerator @sillyoldduffer]

Broken gears are a rather common fault on second-hand Myford lathes. Almost always caused by chaps ignoring the instructions whilst trying to shift a stuck chuck. Don't do it!

The other too common mistake seems to be injecting grease rather than oil into the nipples. Grease blocks oil-ways and running dry soon damages the bearing surfaces.

Dave

[BazParticipant @baz89810]

I always use the proper spindle lock to remove chucks and keep a length of 1/2 inch square brass handy which goes between the chuck jaws, I thump that instead of hitting chuck key.

[David George 1Participant @davidgeorge1]

The back plates on my chuck have a keyway for a C spanner and I only have to give a sharp blow with the palm of my hand to unscrew the chuck. You dont have to lock the spindle just inertia is enough and if it dosnt unscrew after a heavy job i jusg use a small size A copper mallet.

David

[John HaineParticipant @johnhaine32865]

My Super 7 has a sliding pin at the LH end of the headstock that engages a hole in the pulley to lock the spindle – I'm not sure if that's only on the later big bore version.

[BazParticipant @baz89810]

John, the sliding pin at LH end of headstock is standard on normal size super 7 and ML7R machines.

[speelwerkParticipant @speelwerk]

It is the wrong way of doing it but in 40+ years the backgear on the lathe I have is still fine with no damaged to the teeth. Several small taps is better than one big blow with a hammer. Niko.

Edited By speelwerk on 24/06/2019 10:28:48

[Chris BradburyParticipant @chrisbradbury76252]

I read somewhere to put a paper washer between the Mandel and the chuck this seems to work as I have not had a problem removing any chucks. I do use back gear (lazy) and just the palm of my hand

[brickyParticipant @bricky]

I always use the locking pin and use a rubber strap wrench to undo my chucks.what can also happen if useing the gears as a lock is the bull the small gear comeing unstuck from the pulley.

Frank

[RobinParticipant @robin]

On my ML10 I flip the belt cover back, grab the drive belt and squeeze it in the middle whilst lambasting the chuck key with a rubber mallet. I then look at the hand that held the belt and wish I had put on a rubber glove. If the chuck resists I lock the shaft with the back gear. I know I shouldn't but it is so convenient and expeditious.

[John HaineParticipant @johnhaine32865]

Posted by Baz on 24/06/2019 10:14:04:

John, the sliding pin at LH end of headstock is standard on normal size super 7 and ML7R machines.

Well then, that's the answer, use the proper spindle lock!

[Howard LewisParticipant @howardlewis46836]

On my current lathe, (not a Myford, but belt driven ) I have drilled a radial hole in the backplate of each of the chucks, and made a lever with a silver steel pin in the end. With the belt tight (to maximise the inertia of the drive train by the addition of the motor through the belt reduction ), a smart blow on the end of the lever, with a copper/hide mallet does the trick.

I have had to make new gears for a chap who did use the backgear to lock the spindle. Then he took the advice!

Howard

[David KParticipant @davidk77137]

Seems I might have to change my ways then , I will try and get in the habit of using

the locking pin.

Drilling a hole in the back plate to aid unscrewing sounds like a good idea, thanks.

[Neil WyattModerator @neilwyatt]

As you can see, plenty of people get away with it.

The number of reports of broken backgear teeth I've seen over the years suggests that plenty of people don't.

Neil

[Swarf, Mostly!Participant @swarfmostly]

Next time I need to remove my ML7 mandrel from the head-stock (e.g. to fit new vee belt ), I intend to drill a ¼" hole through the bull wheel diametrically opposite the lock to the pulley gear. The plan is then to make a sort of spanner with a transverse dowel (to fit in that hole) and a handle suitably shaped to lock over the edge of the head-stock casting.

I don't think such a hole is going to cause significant out-of-balance problems.

To complement that, I'll use a bit of hex bar gripped in the chuck and a suitable spanner.

The slight problem with this project is that it has been on my to-do list almost as long as the project to make a mandrel handle!

Best regards,

Swarf, Mostly!

[Nigel BennettParticipant @nigelbennett69913]

On my S7 I have marked one of the two possible engagements of the little flick lever which gives the solid drive rather than back gear, so I always ensure it is only engaged in this one position. Hence when the spindle lock is engaged, my headstock spindle is always in a certain orientation. Having engaged the spindle lock, and properly fitted a chuck, I have then drilled a little dimple in each and every headstock spindle-mounted chuck such that the dimple points upwards. These dimples are painted black. Hence I can easily spin the chuck to rotate the headstock spindle more or less the correct orientation to engage the spindle lock.

Having engaged the spindle lock, each chuck was unscrewed very carefully until it just disengaged with the thread. Another dimple was drilled in each chuck at the vertical position at the point of disengagement and the dimple filled with red paint. Hence I know when the chuck is about to unscrew – or it has one more full turn to make – so I can take hold of it before it unexpectedly releases and smashes down on to the lathe bed. Also I can orient the chuck correctly to start it on the spindle threads (with the spindle lock engaged) so that again, it engages immediately and doesn't fall off when I release my grip on it.

I did the same thing with my ML7 years ago but I dimpled the spindle so I could orientate that correctly for chuck-changing as above.

I did this because I did something similar with M42 screw-mount lenses many years ago when I dropped a 400mm lens on to some concrete due to it not being in the correct orientation to start engaging the threads.

The spindle lock is provided for a purpose – use it and don't end up with a dentally-challenged lathe and a stupid expression on your face.

[Robert ButlerParticipant @robertbutler92161]

I use a piece of large AF hex formed to resemble a large allen key which I grip tightly in the chuck a tap with a hide mallet frees it off nicely. A piece of flat secured (bolted) to a face plate achieve the same end without engaging the back gear.

Robert Butler

 

Edited By Robert Butler on 25/06/2019 13:50:29

[Gordon AParticipant @gordona]

The advice from an original Myford manual is as follows:

"When removing a chuck (or faceplate), do not 'yank' the chuck off with the headstock locked with the back-gear,, but set the headstock for normal back-gear drive, and after placing a piece of hardwood on the lathe bed, pull the spindle round by means of the belt so that one jaw of the chuck or slot in the faceplate strikes the wood sharply. The most obstinate chuck is released in this way, and a great deal of the load is taken from the back-gear teeth".

Myford ML7 Notes on Operation, Installation and Maintenance (No 720G , M. 3M /11/64)

A method I do not recommend is that if you have a 3 phase inverter drive that is to set a short braking time and run a 9" faceplate (anything else heavy for that matter). The spindle stops very quickly but the faceplate doesn't which necessitates some nifty footwork!! Needless to say the inverter is now set to coast to a stop. Minor damage and no injury but lesson learnt.

[BWParticipant @bw]

See the "Sparey Spanner" discussed in this thread by ega.

Bill

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