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

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David Kenyon 223/06/2019 21:45:06
193 forum posts
144 photos

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.

Robert Butler23/06/2019 21:47:25
76 forum posts
1 photos

Yes - broken gear teeth can be the unfortunate result

Robert Butler

old mart23/06/2019 22:17:37
310 forum posts
26 photos

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 Lawes23/06/2019 22:50:10
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313 forum posts

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 yet24/06/2019 09:08:23
3140 forum posts
11 photos

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!

SillyOldDuffer24/06/2019 09:09:40
4519 forum posts
970 photos

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

Baz24/06/2019 09:35:46
224 forum posts

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 124/06/2019 09:41:50
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839 forum posts
292 photos

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.

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David

John Haine24/06/2019 09:59:16
2573 forum posts
133 photos

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.

Baz24/06/2019 10:14:04
224 forum posts

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

speelwerk24/06/2019 10:27:23
323 forum posts
1 photos

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 Bradbury24/06/2019 11:06:19
16 forum posts

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

bricky24/06/2019 12:04:45
373 forum posts
47 photos

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

Robin24/06/2019 12:19:10
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312 forum posts

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 Haine24/06/2019 12:19:53
2573 forum posts
133 photos
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 Lewis24/06/2019 13:04:39
2138 forum posts
2 photos

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 Kenyon 224/06/2019 16:46:44
193 forum posts
144 photos

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 Wyatt24/06/2019 17:04:01
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Moderator
16246 forum posts
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74 articles

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!24/06/2019 18:04:49
492 forum posts
41 photos

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 Bennett25/06/2019 12:03:59
292 forum posts
11 photos

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.

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