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Myford taper turning attachment

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Andy Freeman 128/01/2017 18:29:46
50 forum posts
33 photos

Hi , Could anyone tell me what the tapped hole size is on the Myford Super 7 for the taper turning attachment? I'm planning to fit a linear scale to it.


Robbo28/01/2017 19:16:49
1504 forum posts
142 photos


On my old Mk 1 S7 they are 1/4" BSF. They may have changed to Metric (much) later, which would probably be M6?

NJH28/01/2017 19:26:04
2314 forum posts
139 photos

A very good question Andy !

I have a taper turning attachment fitted to my S7. My Wife gave me a DRO system for Christmas which, like yours, needs a scale fitted. I have been not been in the workshop much for the last 18months (following "close encounters" with the NHS) but as soon as it gets a bit warmer I will be back at it. My current project is the Trapezium Connecting Rod Engine which has tapered connecting rods and I want to press the taper turning attachment into use for this before removing the attachment and fitting the scale. I recall that the holes in the bed are 1/4" - but I'm not sure if these are BSW or BSF. I seem to remember that I struggled to get the bolts in and ended up running a tap through.

So I suppose my answer is "about 1/4 inch" - not much use to you I guess! (- sorry)



Quite right M6 it is !! - I see that I have bought a set of M6 taps and have some M6 screws - why else would I have a couple of M6 screws in my drawer.  I plead advancing years and onset of stupidity! ( but it is about 1/4 in !) 

PS Use socket headed cap screws to fit - much easier with an Allen key. Do gat some help though it is a heavy and awkward beast. 


Edited By NJH on 28/01/2017 19:36:51

Mike Poole28/01/2017 19:57:39
3306 forum posts
73 photos

Mine were M6 until I ran a 1/4BSF tap through, I couldn't get a 1/4BSF bolt to start and my first thought was to clean out the crud with a tap, it took a bit more than crud out and the penny dropped that it was M6 but was now BSF, I pressed on and did them all as having one odd one would be a bit of a nuisance. M6 would probably be more convenient as M6 is a bit more common than BSF these days, still the deed is done.


Lambton29/01/2017 10:07:50
694 forum posts
2 photos

A word of caution when fitting the taper turning attachment.

An M6 screw or bolt will easily fit into a ¼” BSF tapped hole but will be rather slack an only has a few % engagement. I have just checked this out trying various ¼” BSF nuts on some M6 fastenings.

Enthusiastic tightening will risk stripped threads in the lathe bed.

1/4” BSF thread is 0.25” x 26 tpi with a 55° thread angle whereas M6 is 0.236” x 25mm pitch with 60° thread angle.

Nottingham Myford only used metric fasteners where they had to after small head-size BSF fasteners became obsolete and so similar sized metric fasteners had to be used instead. This change commenced with ML7 serial number K125240 and Super 7 number SK124461. The only fasteners affected appear to be headstock securing bolts threaded M8 x 1.25 and gear box and apron M6 x1.0. (As detailed in Ian Bradley’s book Myford Series 7 Manual).

I very much doubt if Nottingham Myford changed from BSF to metric just for the sake of it.

Roderick Jenkins29/01/2017 10:35:50
2176 forum posts
608 photos

Definitely 1/4" BSF on my 1972 (102520) S7.


Edited By Roderick Jenkins on 29/01/2017 10:36:29

Michael Gilligan29/01/2017 10:51:43
20096 forum posts
1042 photos

Isn't it strange ?

Those of us familiar with Imperial fasteners would expect to make an 'engineering' choice between [say] 0BA, 1/4", 5/16" ... Yet the preferred Metric series jumps from 6mm to 8mm.

Goldilocks must be crying in her porridge ... 1/4" is, so often, "Just Right".



P.S. ... Yes, I know M7 exists, but it's not preferred.

Robbo29/01/2017 12:11:42
1504 forum posts
142 photos

I expected it to be Whitworth form as it is tapped into cast iron. But definitely 1/4" BSF, a good tight fit.

Jeff Chilver30/01/2017 00:11:04
25 forum posts
19 photos

My super7 (1995) has 1/4 B.S.F threads for the taper turning attachment .A useful tip is to fit a stud in the centre hole and use a nut and washer , this makes life a lot easier if you can't get behind your lathe . 3 studs may be better still but I usually manage with just the centre one

Andy Freeman 130/01/2017 20:33:38
50 forum posts
33 photos

Thanks all for your replies. 1/4 BSF it is and new screws bought today.

Only problem is , I've lost (put down somewhere) the keys to my garage so can't get my imperial taps. The lathe lives at my Dads house so I end up with tools about 5 miles apart!

Imagine a workshop 5 miles long and you'll get the picturesmiley

Brian Abbott14/12/2018 15:49:12
491 forum posts
93 photos

Hello all.

Would some kind person be able to post the basic dimensions of the gip strip, have misplaced mine.

Thanks in advance.

Swarf, Mostly!14/12/2018 16:34:37
646 forum posts
70 photos

Posted by Michael Gilligan on 29/01/2017 10:51:43:


Goldilocks must be crying in her porridge ... 1/4" is, so often, "Just Right".



P.S. ... Yes, I know M7 exists, but it's not preferred.

An off-topic comment!!

I once had a Citroen GS Club Estate on which many, many, fasteners were M7. I guess when you're buying as many fasteners as Citroen do/did, the quantity discount exceeds the non-standard premium. Apart from which, their use keeps most owners as captive customers!

Best regards,

Swarf, Mostly!

Alan Johnson 714/12/2018 19:34:07
115 forum posts
16 photos

M7 is preferred (second series). In some parts of the world very common! The Citroen 2CV has many - I know as I had to buy taps and dies. Probably fell from use during rationalisation! Can we blame the Government for this?

DMB14/12/2018 20:42:58
1300 forum posts
1 photos

My "Supersonic" dates from around 1971 and takes BSF bolts in the gearbox mounting ( but I don't have or want one) and in the headstock side of the carriage, intended for mounting the travelling steady, as well as the threaded hole behind the Mandel nose. The latter for a lever operated collet system, I believe.

Robbo15/12/2018 23:16:44
1504 forum posts
142 photos
Posted by Brian Abbott on 14/12/2018 15:49:12:

Hello all.

Would some kind person be able to post the basic dimensions of the gip strip, have misplaced mine.

Thanks in advance.


Robbo himself is still incapacitated, but I asked him and he says the gib strip on the taper turning att. is the normal Myford 3/8" gib strip (with one bevelled edge) and you are best to get hold of an old ML7 topslide gib strip and shorten it to size. You will also need to drill new dimples for the adjusting screws.

Mrs Robbo

Brian Abbott16/12/2018 22:01:06
491 forum posts
93 photos

Thank you Mr & Mrs Robbo for the information,

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