spanners and nuts

I need to replace the topside lock nuts on my lathe (1956 made in Yorkshire). The spanner that fits them is 13/16. Can anyone direct me to a table that will tell me what size nuts to buy ?.

allowing for a bit of slack then either 7/16" Whit or 3/8" BSF have a 0.82" AF against your 13/16" (0.813) spanner so just need to check the OD of the thread.

Just put "nut AF sizes" into your search engine

Edited By JasonB on 27/06/2015 07:31:56

Cap'n,

1956, Yorkshire : The threads will almost certainly be either BSW or BSF

Spanner sizes are the same for each, except that newer BSW nuts are one size smaller than the original ones [and are the same across-flats as the BSF].

Whitworth spanner sizes are not, however, in the normal "AF" series ... so you might want to double-check the fit.

MichaelG.

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P.S. ... You might find this previous thread of some interest.

Edited By Michael Gilligan on 27/06/2015 07:39:04

Hi Capnahab, spanners don't normally fit exactly snug on the size nut they are made for and there is always some amount of slack. The slackness varies from one manufacturer to another and ring spanners very often have a little tad more than open ended ones. A 13/16" AF spanner should fit a 9/16" unified (UNF & UNC) nut/bolt, however it will fit a 1/2" BSW or BSF nut/bolt. On an old spanner, you may well see the spanner marked as 7/16" BSW/1/2"BSF as shown in the photo below.

In this photo is a 1/2" whit bolt with a clearance for a 0.2mm feeler gauge, but in the next photo is the same nut in a 13/16" AF spanner but it will only accommodate a 0.05mm feeler gauge.

So if you can only get a similar feeler gauge or smaller or none at all in with you 13/16" AF spanner, then your nuts are most likely 1/2" BSW or BSF, you will need to find out the diameter of the bolt and the TPI.

It is also possible that your nuts are old enough to be from before Whitworth nuts/bolts were reduced down to the same size as BSF in which case they could be 7/16"BSW.

Regards Nick.

Edited By Nicholas Farr on 27/06/2015 21:00:36

I thought the reduction is size was a wartime economy, so 1956 should be post that

Hi Duncan, yes 1956 was past the time of reduction, but they did seem to linger in stores stocks for quite some time. In a previous employment the stores still had a verity of the old ones as late as the 1980's.

Regards Nick.

Are you making the entire top slide from scratch? If you have a screw this nut is going onto why don't you measure it and if BSW or BSF see if you can get nuts at all before you worry what size spanner fits.

Hi Bazyle, you can get BSW & BSF at most industrial suppliers that sell nuts and bolts and failing them they are available at **LINK** although they are zinc plated. Just scroll down to Nuts and then choose Hex Full >

Regards Nick.

Thanks , I am renovating this DSG lathe. I cannot get the nuts out (which are rounded) without disassembling the topside (- my next problem) , Any tips welcome. I have been avoiding tackling the brass/bronze nuts holding the topside screw captive as there is so little room to get a spanner at them. Its the reassembly I am fearful of. I do need to do it tho because there is 58 years worth of castor oil crud in there which is now staining everything and making the topside very stiff to use.

> 58 years worth of castor oil crud

I bet it has the consistency of tar by now - but smells nice

Neil

Capn'

When you can't get a purchase on something threaded that is tight, one technique is to use a centre punch.

First pick a point as close to the outside edge as possible. On these nuts use one of the hex corners. Then tap the punch in a couple of times to get a bite. Now, in the direction of unscrewing, use the punch to drive it around.

Pick your angle to keep it digging in but also to push sideways. As it unscrews follow it round with the punch. You can take a fresh bite if necessary.

Given the circumstances of the clamp nuts I'm pretty sure it will work.

Interesting to see the details of a big top end lathe. For the rounded nut laboriously file new flats each side using old credit card to protect the cast iron.

Thanks for the link Nick, yes I do realise that imperial kit is available but look at the price, and those guys don't list BSW. Intersting in that yesterday I was derusting some some 1/4 BSF bolts thinking it was hadly worth the bother but I see they are 86p each and the nylocks 46p. So Ican see why you don't want to buy both BSF and BSW selection to cover both angles. You could check another similar bolt that you can extract to see if they considered it acceptable to tap cast iron with a fine thread.

Bazyle, thank you. I think if DSG wanted to put a fine thread on their metal , developed in house , they can do anything they want. Reminds me of the time Beavis and Butthead , famously disrespectful of anyone and anything said that Lemmy could do anything he wants. The video has been removed but this is just as good. If Lemmy had a lathe it would be a DSG, possibly a Holbrook.

ps don't think its fine from what I can see of the bolt.

Edited By capnahab on 28/06/2015 17:06:58

Edited By capnahab on 28/06/2015 17:19:41

.

Quite so ... and here's another thought: I have not had the pleasure of inspecting a DSG lathe, but it looks to me like those nuts must be on Tee-Bolts working in a circular track [square section or dovetailed].

From what I can see in your picture, my guess is that they are 3/8" BSF. or maybe 'later-version' 3/8" BSW ... , either of which should be reasonably easy to find.

If all else fails, you could probably drill into a face of the nut, and then split it with a sharp Cold-Chisel ... should unscrew very easily then.

MichaelG.

I have resorted to taking the topside off. Much old castor oil everywhere, - before and after. At least I can see the thread and have liberated the nuts.

this website thinks any image that is taller than wide must be the wrong way round and rotates it. Neil - any chance of getting some decent software ?. The pics below are rotated.

ps , when I was at school anyone who put those round marks near the bottom crosslide allen screw would have been for it...

Not much wrong with the software this end

Edited By JasonB on 28/06/2015 20:29:33

Good work, Capn'

So ... are they 3/8" BSF, or what ?

MichaelG.

Capn' - this usually means you are viewing the images with viewer or website that keeps orientation data in a separate file so you see the image rotated, but the image isn't really changed.

Neil

OK guys they are 1/2 inch , 12 tpi, so BSW. Have to get all the staining crud out and top half of the topslide off without disturbing the relieving mechanism.

Regarding image rotation , if it's my software in the viewer why is my post rotated and Jason's the right way up in the same window ?.