Fork drain screws ( 1965 B40F)

[Phil C]

I meant to say "I thought",  not "no thought". Big fingers, small phone.

[Phil C]

I should perhaps just clarify that although, at the time, I was a bit annoyed about Draganfly wanting me to return the items before refunding me, I did try not to show it. I didn't have a go at him or anything like that. He was just doing as his boss had advised him. And, as I say, on reflection I guess maybe it's fair enough. Just seemed they were such small items, one of which by then was damaged, that the trouble and cost of returning them would be silly. And they were semingly the wrong item, ie too short. I'm not sure he was convinced they were wrong. Phil

[Mike40M]

Is it really 2BA? Checked the spare parts manual for the -67 B40 Mk1. It states the screw #41-5141 is a "SCREW, MACHINE BSC, steel, cadmium plated, 3/16 in. x 11/32 in." It should have 32 tpi.
Though the -65 B40 parts manual  has part number 01-02-1309. No mention of dimensions.
2BA and 3/16BSC are quite close in dimensions. o.d 4.7 to 4.762 mm. thread 31.36 vs. 32 tpi or in metric 0.81 vs 0.79mm.
Of course BSA could have changed dimensions, but for what reason?

[Phil C]

Very interesting, Mike. Thanks very much. Having read this I've had another look at the screws, old and new, armed with my 0-1mic, my tpi gauge, and my 6" rule. As best I can tell (whilst cursing the fact that my eyes water more and more as I get older), the 32tpi gauge fits the old screws better than the new ones. And the length of the old ones does actually look more like 11/32 than 5/16 as I previously thought. The dia of the old ones is about 0.183" towards the shoulder and about 0.177" towards the end. They are loose in the hole when screwing in, very loose to begin with. The dia of the undamaged new one is about 0.187" towards the shoulder and about 0.182" towards the end. I believe 2BA should be 0.185". Presumably 3/16 BSC should be about 0.187". So considering all that,  I guess you could be right; maybe they should be BSC. But then Bess seemed pretty confident they should be 2BA. I've attached a photo showing the old and new. You can see the damage on the new one I screwed in. All very interesting. And frustrating. And a bit concerning, worrying I might have damaged the female thread by screwing in one of the new ones. I wonder if BSC screws are very available - I'll have a look online. Might be worth trying them as well as the BA to see which is the better fit.   Phil

[Bess]

Hi,
    Here is the part drawing from the member area showing part number for your year, if you google the part number the dimensions come up as a 2BA.

https://www.bsaownersclub.co.uk/members_area/parts_page.php

Best wishes...

[Phil C]

Been looking online. 3/16 BSC screws are a bit like hens' teeth.

[Phil C]

I think the old screws, rightly or wrongly, are 3/16 X 32 BSC. But I can't find any. Phil

[chaz]

Phil
when you compare your sizes, 32tpi =0.031" pitch, 0.7mm =0.027" 2BA = 31.4tpi , 5mm threads are normally topped so 4.8 or 4.9mm diameter.
5/16" =0.312" or approx 7.928mm, thread angles are 60 degrees so all points to metric 5mm supplied , its the easiest option to supply nowadays.

[Phil C]

Just to let you know what I did in the end. The 2BA x 5/16 cheesehead screws arrived promptly from BA Bolts and I have fitted them. Very slightly stiff, but only  very slightly. They are mild steel and don't appear to have any kind of plating on them, so I just gave the heads a smear of grease. Put the oil in (10w30) and all okay. Thanks again.  Phil
PS after what seemed like six months of constant rain until spring came along, this sunshine is very nice, isn't it?

[Phil C]

But actually I think I'll replace them next time I change the oil with some plated or stainless ones, which I see are available online.  Phil

[Blackthou]

Don't worry Phil, being in contact with oil they shouldn't rest, well not internally.