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

David

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?

Dave

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

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

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

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.

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.