Myford ML4 half nuts

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Myford ML4 half nuts

This topic has 9 replies, 4 voices, and was last updated 23 May 2020 at 07:15 by Andrew Byron.

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22 May 2020 at 12:10 #473880
Jon Cameron
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@joncameron26580
Hello guys,

While stripping down and replacing refurbishing my ML4 lathe, I have taken the apron off and removed the half nuts, When I removed them one of the screws that holds the half nut for engagement was bent, (this explains why they were getting difficult to engage and disengage). The bolts are fully threaded, and I will have to make some more when I get the lathe fully assembled before I can continue to use the lead screw for feed..

Should the portion that runs in the engagement lever not be a smooth turned piece to aid in its movement, instead of the threaded stud that it is now?

Also the ones that came out are mild steel, is it best to keep it mild steel. Is this a designed weak point to save further damage to other parts?

I find it interesting having designed weak points on my lathe such as the 3/32" pins that join the gears in compound, and also to the lead screw that breaks in the event of a crash, (or a dimwit that doesn't disengage the banjo before turning the handle on the end of the lead screw, Yes twice now!).

I would also appreciate anyone been able to comment on how to make a 6mm repair washer have a 1/4" hole, how would that be possible to set up?

Jon
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22 May 2020 at 12:10 #13904
Jon Cameron
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@joncameron26580
22 May 2020 at 12:42 #473887
Nick Clarke 3
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@nickclarke3
Any info on the use or final location of the washer?
22 May 2020 at 12:59 #473894
Brian Wood
Participant
@brianwood45127
Hello Jon,

As I remember them, the half nut studs were threaded at the point of attachment and left in plain shaft diameter to engage with the slots in the operating lever. On my Dad's old lathe, there was a screwdriver slot across the end of the stud to help screwing each into the half nuts. The studs were in nothing fancy, I imagine mild steel.

On your washer question.

May I suggest a short turned sacrificial stud that fits into the existing hole in the 6 mm washer, with a turned face at the rear to support the washer, Attach A to B with your favourite instant adhesive and when set open up the bore to 1/4 inch diameter

Kind regards Brian
22 May 2020 at 13:53 #473914
Jon Cameron
Participant
@joncameron26580
Posted by Nick Clarke 3 on 22/05/2020 12:42:34:

Any info on the use or final location of the washer?

Certainly.

On the back of the apron the pinion and shaft for the saddle traverse, run on the plain casting. There is a very small 1/4" washer (maybe 3/8" OD) that sits at the back of the gear. The teeth of the pinion are not fully contacting the rack, only around half of the toothed gear makes contact. The apron has a machined flat projection where the gear comes out at the rear of the apron, and I was thinking to "shim" the pinion out with the washer so that 3/4's of the gear tooth width, makes contact with the rack. I looked at the other option of actually packing the rack out but then this interferes with the saddle so is not an option.

This is just two of the issues that I was experiencing when using the lathe before it was stripped down, so I would like to try and get them sorted so I can move onto slightly easier ones to sort, which are basically just replacement washers, bolts, oil cups and so forth.

Jon
22 May 2020 at 13:58 #473918
Jon Cameron
Participant
@joncameron26580
Posted by Brian Wood on 22/05/2020 12:59:51:

Hello Jon,

As I remember them, the half nut studs were threaded at the point of attachment and left in plain shaft diameter to engage with the slots in the operating lever. On my Dad's old lathe, there was a screwdriver slot across the end of the stud to help screwing each into the half nuts. The studs were in nothing fancy, I imagine mild steel.

On your washer question.

May I suggest a short turned sacrificial stud that fits into the existing hole in the 6 mm washer, with a turned face at the rear to support the washer, Attach A to B with your favourite instant adhesive and when set open up the bore to 1/4 inch diameter

Kind regards Brian

Brian thank you, that is what I suspected it has obviously been repaired in the past.

On the washer would it not try to break free of its Loctite holding as soon as the spigot is removed, I know the pad to the rear would support it, but I feel it would possibly go flying to back and beyond once the hole is opened to 1/4" even with gentle boring. Worth a try I suppose, get it back together to make the parts then strip the apron to fit it.
22 May 2020 at 14:12 #473929
Brian Wood
Participant
@brianwood45127
Jon,

Make sure you allow a good cure time, these adhesives are stronger than you perhaps imagine.

Don't go hard at it though, you don't want it to heat up on machining, that will break the bond prematurely

Brian
22 May 2020 at 16:21 #473969
Jon Cameron
Participant
@joncameron26580
Brian thanks and noted, I still feel its a bit precarious, but i'll trust you. Having had an item of brass I was machine, twice jump out the chuck due to bad work holding, (gave up that night before serious injury) i'm dubious, but happy to prove myself wrong, it can only go to back and beyond.

Jon
22 May 2020 at 17:55 #473998
Brian Wood
Participant
@brianwood45127
Hello Jon,

Nice to be trusted, thank you. The most you are going to lose will only be an M 6 washer, as long as you have a proper grip on whatever the turning fixture is made from.

Not a lot to risk in my book!!

I would be interested to hear how it went

Regards Brian

Edited By Brian Wood on 22/05/2020 17:56:06
23 May 2020 at 07:15 #474119
Andrew Byron
Participant
@andrewbyron13518
Hi Jon,

I stripped down the apron on my ML4 and found a similar problem with these halfnut engagement studs, they're 3/16 bsf, i have some 3/16 BSF bolts that have the correct length of thread on them and are the same length as the original studs once you've cut the heads off them, i can stick a couple in the post to you if that would help.
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