By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale May 23

1947 M type myford, imperial or metric ?

I'm looking at buying some tools solely for lathe

All Topics | Latest Posts

Search for:  in Thread Title in  
Grant Allen 124/03/2019 14:54:28
48 forum posts
5 photos

Hello all, from memory can anyone tell me what type the nuts and bolts are and grub screws are they metric, imperial and the threads unc, unf, bsw?.


David George 124/03/2019 16:29:42
783 forum posts
282 photos

Hi Grant most screws and bolts are either BSW or BSF with a few BA screws.


Grant Allen 124/03/2019 16:36:28
48 forum posts
5 photos

Thank you David, I assume that spanners and Allen keys are imperial then. ?

SillyOldDuffer24/03/2019 16:46:13
4271 forum posts
880 photos

Perhaps an Imperial expert can help Grant navigate the mysteries of spanner sizings in the context of his M Type? I'm wondering about pre- and post-war Whitworth, BSW vs BSF, BA, UNC and Across Flats as it might affect buying for a 1947 lathe. Will a set of modern AF spanners fit, or is it a bit harder than that?


Grant Allen 124/03/2019 16:55:52
48 forum posts
5 photos

I have just remembered you can get whitworth spanners but what is the difference between imperial and whitworth, this has the potential of creating confusion

Clive Brown 124/03/2019 16:59:56
229 forum posts
6 photos

Whitworth/BSF hexagon sizesare denoted by the thread diameter. Their AF dimensions generally do not match the  hexagon AF sizes for either unified or metric fasteners, so using these will result in a poor fit.  The appropriate spanners really need to be obtained.

Many spanners have 2 marked sizes, BSF being 1 size larger. eg 5/16" BSF is the same hexagon as 1/4Whit.


Edited By Clive Brown 1 on 24/03/2019 17:40:16

SillyOldDuffer24/03/2019 17:36:10
4271 forum posts
880 photos

'Imperial' includes a number of different fastener systems one of which is Whitworth, and they've changed over time. In addition some members of the imperial family specify spanner size by the distance between the hexagon flats, others by the diameter of the threaded part of the bolt. This picture from Wikipedia's Whitworth entry shows an example of two spanners, both labelled 5/8":

Yes, it's confusing, especially when ordering spanners to fit. Spanners labelled 'AF' are easier because that's the actual distance between hexagon flats: if you measure 1/2" across a bolt head, then 1/2" AF will fit.

Repairing cars in the 1970s was a right nightmare. Almost every conceivable variation in use - old and new British, USA, Unified, BA and metric. Often mixed together on the same vehicle. I've even come across metric bolts with imperial heads. I never had the right spanner, and many the confusing conversation I've had trying to buy them. Back then most sellers delighted in humiliating buyers who didn't quite understand what they needed...


Nicholas Farr24/03/2019 18:35:04
1839 forum posts
914 photos

Hi, basically any spanner that is not metric is imperial. Metric spanners are measured across the flats, but are not normally denoted as AF. AF spanners are across the flats and are associated to UNF and UNC in most cases and will be an imperial measurement, the AF being the dimension of the hexagon head of the bolt, i.e. 5/8 AF as shown by the chrome one in SOD's photo above. Whitworth and BSF spanners are denoted by the bolt size, again in SOD's photo, the larger one is 5/8 Whit' or BSF, but before WW2 Whitworth spanners were one size larger than BSF. So, a 5/8 Whit' spanner would fit a 5/8 Whitworth bolt. During the war I believe, to save on metal, Whitworth bolt head sizes were reduced down to that of BSF sizes and thereafter a 9/16 Whit spanner will fit a 5/8 Whitworth bolt and BSF remained the same, i.e. a 5/8 BSF spanner will fit a 5/8 BSF bolt. BA spanners are the bolt size and although the bolts have imperial measurements, they are in essence, metric I believe.

Regards Nick.

Edited By Nicholas Farr on 24/03/2019 19:03:53

Grant Allen 124/03/2019 19:27:49
48 forum posts
5 photos

Found a chart on internet which I've screen shot but I'm unable to load it onto here?? So basically if I understand what has been said as long as I've an imperial set of spanners ultimately regardless of size it will fit a bolt or nut that is bsw,unc,unf.

Nicholas Farr24/03/2019 20:25:24
1839 forum posts
914 photos

Hi Grant, if you have a set of post WW2 Whitworth/BSF spanners, you will be able do undo/do up any Whitworth of BSF bolts and nuts. If you have any UNF of UNC bolts and nuts, you will need a set of AF spanners also, both of which are imperial. Very few metric spanners will fit any imperial bolts and nuts properly, but 7/16 AF and 11mm are a good match and so is 3/4 AF and 19mm.

Regards Nick.

Edited By Nicholas Farr on 24/03/2019 20:34:45

peak425/03/2019 02:27:45
739 forum posts
65 photos

Grant, broadly speaking BSW/BSF and UNC/UNF (AF) spanners, whilst both "Imperial" are not interchangeable.

BA are different again, and whilst sometimes thought of as "Imperial" since they are mainly not of obvious metric measurements, are actually a metric series starting with 0BA as 6mm x 1mm pitch;

N.B. metric spanners don't fit them correctly.

Half way down THIS PAGE is a table which gives the spanner sizes for most common threads.

Re. Allen screws; a set of "Imperial " keys will fit both BSW/BSF and UNC/UNF sockets.


Hopper25/03/2019 02:47:08
3595 forum posts
72 photos

For the M-type lathe you will need BS spanners, to fit the BSW and BSF nuts and bolts used.

It matters not if the spanners are pre or post-war. All that changed was the sizes marked on the spanners. Actual dimensions of the spanner jaws remained the same.

No metric. No AF. (unless of course a previous owner has fitted dodgy bolts etc.)

But regular AF allen keys will fit any grub screws etc that use allen heads.

And congrats on your new lathe. Quite a few M-type owners on here. The 1947 is a good model, V-belt pulleys and all.

Lots of good info available on the Yahoo Groups site for Drummondlathe group. Their FILES section has downloadable manuals, parts drawings and tips and mods etc.

Grant Allen 125/03/2019 03:56:07
48 forum posts
5 photos

That's brilliant Hoppper. I shall get myself a set of bs spanners. With regards to the Yahoo drummond site I even though I've joined I canr seem to select the file section??

Hopper25/03/2019 05:53:30
3595 forum posts
72 photos
Posted by Grant Allen 1 on 25/03/2019 03:56:07:

With regards to the Yahoo drummond site I even though I've joined I canr seem to select the file section??

Maybe be you have to make a post or two first? IDK. I just click on the folder that says "Files" at the top next to "Conversations" and "Photos" and it loads up. Takes a slight pause to load up.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
Eccentric July 5 2018
Eccentric Engineering
TRANSWAVE Converters
Allendale Electronics
Subscription Offer

Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest