what o ring size do i need?

Hi.

My new aluminum flashlight takes 3xC cells, the included Duracell alkaline battery`s fit fine and work without a problem, but i have some 5000mah nimh battery`s i would like to use, my problem is the the nimh battery`s must be fractionally longer than the alkaline ones and this is causing the switched end cap not to work when screwed all the way down the light stays on all the time unless i unscrew the end cap a bit, then i can go though the 3 settings of high/low and flashing.

So i thought a thicker o ring should increase the space slightly enough for switch to work.

The en-cap o ring diameter needed according to my vernier is 25mm x 2mm , but should i use 23mm or 24mm for a tighter fit that will not move, the thickness is 2mm but i dont think i can reduce.

I have tried an couple of online calculators but i cannot make head or tails of them.

Anyway i know nothing, ask your question, see photo in link below.

http://imgur.com/a/x3KJP

Thanks

John.

Thats a hard one. I would envision you may have to test a few sizes. I am guessing the smaller ones would be what you want to try. If it is too loose, you know it will roll up into the threads and cause a mess. It seems every time I measure for O rings things never work out right. Also the material can have a difference. Some will stretch thinner than others it seems.

I bought an 225 piece diy kit for £3.99 delivered it has 5x 20x2mm and 5x 22x2mm amongst the multitude of others sizes.

It was going to cost me £2.15 for 10x 22x2mm so i opted for the big kit, they are most likely lower quality but once fitted you only open the flashlight to charge the battery`s and if i keep them well lubed hopefully they will last a while.

John.

Yup, you basically did what I did. I got the kits too.
First I bought some cheap Nitrile ones from China. They would dry out in less than 8 months! Total junk. I ended up finding some silicone ones locally. They hold up much better. I want some of those Aircraft ones (blue and orange??). Maybe someone can give us a link to a quality kit?

My flashlight, I bought 2, they both have the same problem, they came with 3x Duracell C which fit and work fine if a bit loose, I just measured with the battery inside and the end-cap off using an vernier, there is 10mm between the bottom of the battery`s and the end of the flashlight, with the 5000mah nimh C cells fitted there is only 8mm, can 2mm make this much difference?



Thanks

John.

TinderBox (UK) said:

I bought an 225 piece diy kit for £3.99 delivered it has 5x 20x2mm and 5x 22x2mm amongst the multitude of others sizes.

It was going to cost me £2.15 for 10x 22x2mm so i opted for the big kit, they are most likely lower quality but once fitted you only open the flashlight to charge the battery`s and if i keep them well lubed hopefully they will last a while.

John.

Click to expand...

Here in the States a place called Harbor Frieght has kits like that.

One is for plumbing sized stuff.
The other is for automobile sized stuff.

I use 'em for various seals on my old jalopy and so far they've kept oil inside the motor about a year now...

Str8stroke said:

Yup, you basically did what I did. I got the kits too.
First I bought some cheap Nitrile ones from China. They would dry out in less than 8 months! Total junk. I ended up finding some silicone ones locally. They hold up much better. I want some of those Aircraft ones (blue and orange??). Maybe someone can give us a link to a quality kit?

Click to expand...

Ask and ye shall seek, seek and ye shall find. http://ph.parker.com/us/17563/en/o-ring-kits-ord

The problem with purchasing a kit, is that you have gland diameter, o-ring ID and OD, then o-ring profile, and finally material type.

Parker makes more O-rings than anyone else in the world. They don't typically make a multitude of colors as their production runs may be 100k of one diameter/material before switching to the next diameter.

OBTW, the Harbor Freight O-rings are all Chinese made.

"OBTW, the Harbor Freight O-rings are all Chinese made."
Yup! Thats one of the kits I got. Totally worthless. Unless you only need it to last a few months.
Thanks for the Parker tip. Going check them out now.