Trying to find primary and timing stainless screw set for N15CS, replacing chewed-up cheeseheads

Don't know who provides sets, but timing cover are 1/4 - 20 (BSW) X 1" and primary cover screws are 1/4 - 26 (CEI) X 1". 1/4-20 BSW are 55 degree threads while 1/4 - 20 UNC are 60 degree. Some people use UNC screws in the BSW threaded holes, but the mismatch angle will be weaker.

Timing cover screws are the same thread form for Atlas, N15/G15, early Commando and P11. '71-up Commando are UNC. N15/G15 and P11 primary cover screws are the same thread form.

I buy the stainless screws by the bag from the UK and cheesehead or allen head are usually available.
 
Ron L said:
Don't know who provides sets, but timing cover are 1/4 - 20 (BSW) X 1" and primary cover screws are 1/4 - 26 (CEI) X 1". 1/4-20 BSW are 55 degree threads while 1/4 - 20 UNC are 60 degree. Some people use UNC screws in the BSW threaded holes, but the mismatch angle will be weaker.

Timing cover screws are the same thread form for Atlas, N15/G15, early Commando and P11. '71-up Commando are UNC. N15/G15 and P11 primary cover screws are the same thread form.

I buy the stainless screws by the bag from the UK and cheesehead or allen head are usually available.
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Thanks Ron,

I'd like to find a set ideally, but that's good info. I believe that mine are original but will do a thread check as I don't like to have the wrong ones in there.

Thread creep (haha) - do you 'seal' them in any way at the head? I have good luck with Hondabond 4 or an equivalent type of sealant. I think some models used a crush washer.

~Tom
 
Www,britishfasteners.com

They have timing cover screws in sets.

My Atlas originally had aluminum washers under the heads. I never found a part number for these, or a source for a direct replacement. Www.aircraftspruce.com has 1/4" flat aluminum washers that I turned down to 0.400" and work fine.

Best to use an anti seize compound when putting a stainless bolt or screw into an aluminum body.

Slick
 
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mdt-son said:

Use of a washer for load spreading is pointless in these applications due to the low load and the sparse cutout. A washer may serve a purpose if coated by PTFE or similar, thus reducing the risk of galvanic corrosion. A dab of epoxy under the screw head may serve the same purpose.

- Knut
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Agree! I placed washers under to heads to prevent Galvanic corrosion.

Slick
 
texasSlick said:
I placed washers under to heads to prevent Galvanic corrosion.
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Pure aluminium washers will not prevent galvanic corrosion. Besides, covers are also made of aluminium, so what's the point? If allowed to eat away, galvanic corrosion will cover large chunks of the base metal.
For washers to be effective, you need to coat them, thus eliminating the electrochemical potential differences. Same goes for the shank and threaded portion of the screw.

- Knut
 
gpzkat said:
Thanks Ron,

I'd like to find a set ideally, but that's good info. I believe that mine are original but will do a thread check as I don't like to have the wrong ones in there.

Thread creep (haha) - do you 'seal' them in any way at the head? I have good luck with Hondabond 4 or an equivalent type of sealant. I think some models used a crush washer.

~Tom
Click to expand...
Atlas, N15/G15, P11 and (I believe) early Commando, used 1/4" fiber gaskets under the head of the timing cover screws. Andover supplies a set of (zinc plated) timing cover screws with the gaskets. Personally, I don't use them as they were not used on Commando with no issues. I have never had an issue without them.
 
Here's some zinc plated ones - may be better than stainless.

Classic Fasteners

Supplier of nuts, bolts, screws. Specialising in obsolete threads types, automotive and stainless fasteners.
www.classicfasteners.com.au www.classicfasteners.com.au
Cheers
 
robs ss said:
Here's some zinc plated ones - may be better than stainless.

Classic Fasteners

Supplier of nuts, bolts, screws. Specialising in obsolete threads types, automotive and stainless fasteners.
www.classicfasteners.com.au www.classicfasteners.com.au
Cheers
Click to expand...

Thanks, thinking it over, I can buy a few rather than a whole set and try for zinc, as some of mine are not maimed.
 
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