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Metric threads on an ML7

this is NOT a screwcutting question....

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David T21/08/2018 15:53:08
74 forum posts
14 photos

Good afternoon All,

As mentioned in the thread title, this is NOT a question about screwcutting. I wonder how many people will miss that?

I'm not expecting a definitive answer from this thread, more just sharing my confuddlement. My Myford ML7 dates from around 1951. I have no reason to believe that my lathe is a "Frankenlathe"* assembled from donor parts. Recently I found that the mounting screw for the thread dial indicator is tapped M6, but I didn't think much about it at the time. Then last night I found that the mounting screw for the travelling steady is also M6, rather than the 1/4 BSF or BSW that I was expecting.

What is the reason for metric threads on a 1950s lathe? I appreciate that a damaged thread may be drilled out and re-tapped, but M6 is smaller than the 1/4" it should be. Can anyone offer an explanation?

Thanks!

* or more faithfully to Shelley's novel, Frankenstein's lathe

Robert Dodds21/08/2018 16:20:41
268 forum posts
36 photos

David,
You are probably looking at 0 BA 6x1mm. Same pitch and dia as M6 but thread form slightly different, but for many applications you could mix and match without problem.

Bob D

chris stephens21/08/2018 16:23:43
1045 forum posts
1 photos

Cannot give complete answer, but could they be 0BA rather than M6 both being 6x1mm?

edit, not very quick on the keyboard today, or, great minds think alike, your choice.

Edited By chris stephens on 21/08/2018 16:26:12

DMB21/08/2018 16:37:07
992 forum posts

I think it likely that Myfords favoured BA rather than Metric. I believe the threads for the leadscrew bearing brackets are 2BA, e.g. Probably as far back as 1950s, very unlikely to have any metric threads on a Myford.

John Haine21/08/2018 16:54:18
3017 forum posts
160 photos

On my S7 the bolts holding on the LS bearing brackets are I think 4 BA. There's a row of holes on the back of the bed to attach accessories which I was surprised to find were M6 - now I realise they must be 0 BA.

Roderick Jenkins21/08/2018 17:11:19
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1855 forum posts
471 photos
Posted by John Haine on 21/08/2018 16:54:18:

On my S7 the bolts holding on the LS bearing brackets are I think 4 BA. There's a row of holes on the back of the bed to attach accessories which I was surprised to find were M6 - now I realise they must be 0 BA.

Myford generally favoured 1/4" BSF rather than 0BA but that may depend on the age of the machine.

Cheers

Rod

Mike Poole21/08/2018 17:45:09
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2545 forum posts
60 photos

Myford certainly do slip in the odd metric fastener on some of the later machines. I was convinced the holes on the bed rear mounting pad would be 1/4 BSF and put the difficulty starting a screw in the hole to paint and crud, I ran a BSF tap in and took out a bit more than crud, now they are all BSF as having one odd one would be a nuisance. I am surprised that they used metric on a machine of that vintage but on the Super 7 they used 8mm cap screws to bolt the headstock to the bed and the cross slide locking screws are 5mm. the gib adjusters are 2BA just to keep you on your toes.

Mike

Richard S221/08/2018 18:30:35
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177 forum posts
109 photos

Have only BSF on mine (48-49 K5711) on the areas mentioned, with the exception of the machined face on the rear for Taper Turning Attachment which are 0BA

Michael Gilligan21/08/2018 20:13:48
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15484 forum posts
668 photos

Preferred practice throughout British industry was to use BA threads for diameters less than 1/4"

... This is not a Myford conceit.

The 'unusual' ones were those that continued to use small BSW or BSF threads after BA was introduced.

MichaelG.

Bill Pudney22/08/2018 06:38:30
442 forum posts
16 photos

I felt the Earth move out of it's orbit.............we're headed for the Sun..................

cheers

Bill

Hopper22/08/2018 07:04:40
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4414 forum posts
94 photos

Is it at all possible that the lathe you have is a Myford copy/clone made in Taiwan or the Continent? There were a few of them apparently. Does yours have a Myford serial number on the bed shear? Bit of a long shot but you never know with used machinery of unknown provenance.

Michael Gilligan22/08/2018 08:32:02
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15484 forum posts
668 photos
Posted by Bill Pudney on 22/08/2018 06:38:30:

I felt the Earth move out of it's orbit.............

.

... or perhaps you just nodded-off, Bill

MichaelG.

David T22/08/2018 15:56:21
74 forum posts
14 photos

Posted by Hopper on 22/08/2018 07:04:40:

Is it at all possible that the lathe you have is a Myford copy/clone made in Taiwan or the Continent? There were a few of them apparently. Does yours have a Myford serial number on the bed shear? Bit of a long shot but you never know with used machinery of unknown provenance.

The bed definitely has a Myford number on it; it dates the lathe to 1950-1951 (without looking it up, I forget exactly). Metric threads aside, I have no reason to believe that the carriage came from a later machine. All the gib screws are definitely 2BAs rather than the later M5s.

I guess the holes must have been 0BA then. Unfortunately I don't have anything 0BA with which to check the fit of the threads with.

David T22/08/2018 15:57:08
74 forum posts
14 photos
Posted by Bill Pudney on 22/08/2018 06:38:30:

I felt the Earth move out of it's orbit.............we're headed for the Sun..................

cheers

Bill

????

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