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Myford ML7 - Size of Mandrel Through Drilling?

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Swarf, Mostly!10/05/2019 11:17:47
505 forum posts
41 photos

Hi there,all,

I've recently had a gentle disagreement with someone about the diameter of the through drilling in the mandrel of the Myford ML7 lathe (i.e. the back end). Well, not so much about the diameter as about it's consistency, lathe to lathe. This dimension is of interest in connection with mandrel handles or depth stops and, more loosely, with draw-bars or bumper bars.

The published specification for the ML7 states that the through drilling is 19/32". (The same figure is given for the Super Seven. ) Please note, I'm not 'talking' here about 'big bore' or similar machines.

Please may I use this thread to take a 'straw poll' from ML7 owning members, requesting them to post the size of the through drilling of their ML7 mandrel, together with their machine serial number?

Thanks and best regards,

Swarf, Mostly!

Lambton10/05/2019 11:39:36
692 forum posts
2 photos


I have a standard bore Super 7. I have never actually measure the bore as I already know the answer - Not big enough!


Grindstone Cowboy10/05/2019 11:47:11
167 forum posts
3 photos

0.595" on serial number K14593, which is pretty close to 19/32" (well, by my standards anyway )

I'll be able to measure another a bit later.


Grindstone Cowboy10/05/2019 14:55:17
167 forum posts
3 photos

0.590" on serial number K24217. This one was probably measured more accurately than the first as access was easier.


Brian Wood10/05/2019 17:22:18
2058 forum posts
37 photos

0,630 inches (16 mm) on serial number KR 151488. Mine is the ML7R which has the S7 headstock and spindle


Edited By Brian Wood on 10/05/2019 17:23:27

Richard S210/05/2019 17:52:01
172 forum posts
102 photos

19/32" on my ML7 ......K5711.

Michael Gilligan10/05/2019 19:27:29
14592 forum posts
634 photos

It's difficult for me to access the machine at the moment, so I used items from the socket-set as convenient plug gauges ... and made an interesting discovery: The bore is not parallel.

Diameter 0.624" enters the bore at the tail, but only by about 1/2"

Diameter 0.619" goes much further, but will not enter at the nose.

Diameter 0.579" passes comfortably through.

Sorry, I didn't have anything exactly 19/32" [0.59375"] diameter to hand.

ML7R Ser. No. KR136508


Michael Gilligan11/05/2019 13:05:11
14592 forum posts
634 photos

< bump > ... surely there must be more users around dont know

mgnbuk11/05/2019 13:11:43
547 forum posts
23 photos

0.630" from a quick digital caliper measurement on my mid-60s Super 7 (can't easily get to see the serial number).

Nigel B

Brian Wood11/05/2019 13:32:15
2058 forum posts
37 photos


How can you miss it Nigel? It's on the front shear vertical face, right beside the gap and in the easiest position imaginable.


mgnbuk11/05/2019 15:11:51
547 forum posts
23 photos

How can you miss it Nigel? It's on the front shear vertical face

Not on mine, Brian.

Its at the back of the rear shear at the tailstock end of the bed and my lathe is close to a wall, so I can't get my head in the space far enough away to be able to focus on it (one of the "pleasures" of getting old ! ) . However, use of the camera in my phone has allowed me to see the number remotely , which is SK78311.

Nigel B

AJW11/05/2019 16:02:28
277 forum posts
117 photos

I've got 0.594 on a ML7 s/n K16170 and seems pretty parallel.



Edited By AJW on 11/05/2019 16:03:14

Brian Wood11/05/2019 18:33:07
2058 forum posts
37 photos


My apologies Nigel; mine is clearly a much younger model. Sorry to doubt you, especially as you found an ingenious solution to read it.



Mike Poole09/08/2019 23:34:23
2255 forum posts
52 photos

I have never measured mine fnarr fnarr but whatever the size if my work will go through then happy days and if it won’t the out comes the steady.


John Olsen11/08/2019 04:35:25
998 forum posts
86 photos
1 articles

Mine, of about 1953 vintage, measures at .590 inch. That's using a digital caliper, maybe + or _ a thou or so on that. It is of course too small, but anything will always end up too small because the jobs expand to exceed the capacity of the lathe.


Don Cox12/08/2019 14:25:08
44 forum posts

I have an ML 7 of (I think) 1949 vintage, no. K3475, it has a through bore of 0.58" although I reckon there may be some bits of swarf jammed in there which might have reduced it a bit.

I also have an S7 mk2 of (also, I think) 1963 vintage, no. SK62224 which has a through bore of 0.63"


ega12/08/2019 16:20:57
1379 forum posts
113 photos

My 1964(?) S7 SK 66266 will just pass 0.620" from the tail for most of its length.

This is the major diameter of my J A Radford stop bar. His was 0.621" and was "perfectly free in the mandrel except for the end nearest the chuck which was reduced to 0.580" ".

Edited By ega on 12/08/2019 16:23:08

Malc12/08/2019 17:45:35
63 forum posts
5 photos

Mine is 0.625”, serial No. K 76235.

Kenneth Deighton12/08/2019 19:56:55
64 forum posts

I think that the main question is how do you increase the bore ?


Mike Poole12/08/2019 21:32:03
2255 forum posts
52 photos

The 2 morse taper in the nose of the spindle would be compromised if the spindle is bored larger and there is not too much meat on the other end. The bore increase would be small which is probably why Myford did a major redesign when they made the big bore version.


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