- Joined
- Feb 2, 2006
- Messages
- 1,151
12.42mm ID for A2's tailcap o-ring? Too small. When I re-spec an o-ring size I always measure the o-ring groove diameter for reference, then go for and ID slightly smaller, such that there's less stretching but still yields good fitment without going too loose. (Elsewhere outside the uS only the ID size is used, but not the OD)Thank you. I found a helpful o-ring size chart which also has metric equivalents here.
I found out that the original A2/L1 tailcap O-Ring should be #14 1/2" ID x 5/8 OD (here is a picture of the original surefire part size with 014 size). In metric it's 12.42mm x 1.78mm. This is a bit smaller than your specs, but I think the SF also smaller and you have to stretch them to fit. I will order both sizes and I will check which fits better.
I haven't found the head o-ring spec, but the size should be either #17 or #18 - which is either 17.17mm or 18.77mm ID.
I found a shop here that also has O-rings in the US sizes.
SF O-rings are Buta-N SH70 which I think is the same as standard NBR 70 O-rings in EU.
My local dealer also offers o-rings in various standards (ie. US and metric size specs). NBR does ring a bell (I probably have purchased that brand a lost). Sometimes the rubber material is a bit different in hardness so that's another factor to consider.
Once you've determined the specs of the o-rings you want, commit to that size and stick to that for a long time -- unless you come across a similar part which has the o-ring specs amended.
Also don't be afraid of getting something a bit off. It's a trial-and-error thing and oftentimes you'll need to acquire different o-ring sizes (eg. one size up and/or down) for reference purposes.