Mirage_Man
Flashlight Enthusiast
Anyone know the correct number for the 38mm Aleph window? I found a post that said it's a #31 but that seems a little big to me.
Best flashlight O-ring material..and more.
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donn_
Flashaholic
I use a metric size, 36mm x 3mm, in Buna-N. McMaster-Carr item # is 9262K295.
Mirage_Man
Flashlight Enthusiast
Yeah, I saw that you did for Erin's 38mm head. I was just wanting to know what the spec'd one is for the original A3.
+1 Viton rings are also used in sprayers that contain solvents used for auto paints. VERY good chemical resistance. Ironically, hf sells a set of them item # 95450. I don't know about the quality from hf, I've just seen the assortment set in the store.
RocketTomato
Enlightened
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- Jul 20, 2008
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Viton is a great material but it can be a little expensive and the extra chemical resistance is not really necessary for flashlights.
EPDM is relatively cheap and holds up better to steam, ozone and sunlight then Buna-N (A.K.A. Nitrile)
Silicone is more expensive then both EPDM and Buna-N and has a very large useful temperature range (-80 to 400 F) but it abrades and tears easily so it is not recommended for dynamic seals, i.e. like on a piston light or a twisty.
Kalrez is even better then Viton but very expensive.
I have also compiled a large list of o-rings used in flashlights over here.
EPDM is relatively cheap and holds up better to steam, ozone and sunlight then Buna-N (A.K.A. Nitrile)
Silicone is more expensive then both EPDM and Buna-N and has a very large useful temperature range (-80 to 400 F) but it abrades and tears easily so it is not recommended for dynamic seals, i.e. like on a piston light or a twisty.
Kalrez is even better then Viton but very expensive.
I have also compiled a large list of o-rings used in flashlights over here.
wykeite
Newly Enlightened
Good job I read through the thread, it's more or less what I was going to say without mentioning any dimensions. The dimensions of the groove both radially and axially are critical if you wish to make an efficient seal. To get the correct size for an existing piece you can work back from the groove width and internal groove diameter. If you just want to stiffen a threaded part it's not near as critical. Not to mention backing rings
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RocketTomato
Enlightened
- Joined
- Jul 20, 2008
- Messages
- 475
Good job I read through the thread, it's more or less what I was going to say without mentioning any dimensions. The dimensions of the groove both radially and axially are critical if you wish to make an efficient seal. To get the correct size for an existing piece you can work back from the groove width and internal groove diameter. If you just want to stiffen a threaded part it's not near as critical. Not to mention backing rings
In my experience, I have found that a lot of o-ring grooves are not cut to spec on flashlights. But then again, as you said, it is not really a critical application.
I didn't know there were so many materials used in o-rings. I just got a few inexpensive cree LED's and the o-rings are about +/-1.mm thick. They all stretch about 50% of the original diameter. Some are red, some black. I checked out a couple links posted here and it's pretty confusing.
I thought I'd replace them with something a little better. I just looked at several sizes at FastTech and they're all silicone and most are 1.mm to 1.5mm thick which will work. I'm not sure how much silicone o-rings stretch. Should I just get them with the I.D. a couple mm smaller than the dia. of where they'll be going.
I'm not sure how well silicone handles heat. The one on the bezel is the only one that'll get warm and that shouldn't get too warm with my use. My biggest LED's are the XML T-6 with 3100mah to 3400mah Panasonic ncr18650b li-ions.
I did find this chart that gives me a better idea of what to expect from a t-6. I've read enough to know not to pay much attention to the lumens that are posted with Lights from China web sites. XML T-6 LED's are said to have anywhere from 500lm to 2000lm. I don't want the heat from a 2000lm, I'm satisfied with 600 to 800lm and longer battery life.
So much for posting the LED chart from my pictures folder, you have to enter a URL...I'm not that computer savy.
Thanks for any info.
David
I thought I'd replace them with something a little better. I just looked at several sizes at FastTech and they're all silicone and most are 1.mm to 1.5mm thick which will work. I'm not sure how much silicone o-rings stretch. Should I just get them with the I.D. a couple mm smaller than the dia. of where they'll be going.
I'm not sure how well silicone handles heat. The one on the bezel is the only one that'll get warm and that shouldn't get too warm with my use. My biggest LED's are the XML T-6 with 3100mah to 3400mah Panasonic ncr18650b li-ions.
I did find this chart that gives me a better idea of what to expect from a t-6. I've read enough to know not to pay much attention to the lumens that are posted with Lights from China web sites. XML T-6 LED's are said to have anywhere from 500lm to 2000lm. I don't want the heat from a 2000lm, I'm satisfied with 600 to 800lm and longer battery life.
So much for posting the LED chart from my pictures folder, you have to enter a URL...I'm not that computer savy.
Thanks for any info.
David
I learned long ago when I got into r/c cars, planes with plastic/nylon parts/gearboxes with bearings that silicone doesn't attack plastic so I planned to use silicone shock oil or better, silicone differential grease on the tail cap and bezel threads.
On my focusing lights, the head slides forward and back and they slide better when you turn the head as you push or pull it back but this tends to unscrew the head from the body on a couple of them. I thought about using a little thread lock on these threads.
On my focusing lights, the head slides forward and back and they slide better when you turn the head as you push or pull it back but this tends to unscrew the head from the body on a couple of them. I thought about using a little thread lock on these threads.
After a lot of reading it's said not to use silicone oil on silicone o-rings. I saw several threads here on CPF and it's confirmed though said that it may not be that important for this application, it's more important where o-rings are used under pressure as in hydraulics...
I was considering the use of diff grease I have for r/c car diffs but it's too thick. I have silicone shock oil for r/c shocks. It comes in different weights (thickness), I have 20wt, 30, 35 to 50wt and I'll use the latter until I replace my o-rings.
I can use my silicone oil but will need to go back and check some links to find a source for Buna-N (nitrile) o-rings which are safe with silicone.
If I get silicone o-rings, the best lube I've found for them on CPF is Nygel 760G. $20.00 for a 57g tube at batteryjunction.
"It's a silica thickened, medium viscosity, synthetic hydrocarbon grease used to lubricate and protect electrical contacts. A dab on the threads & o-rings of your flashlight will protect it from the elements and water." Good stuff but a little expensive.
I was considering the use of diff grease I have for r/c car diffs but it's too thick. I have silicone shock oil for r/c shocks. It comes in different weights (thickness), I have 20wt, 30, 35 to 50wt and I'll use the latter until I replace my o-rings.
I can use my silicone oil but will need to go back and check some links to find a source for Buna-N (nitrile) o-rings which are safe with silicone.
If I get silicone o-rings, the best lube I've found for them on CPF is Nygel 760G. $20.00 for a 57g tube at batteryjunction.
"It's a silica thickened, medium viscosity, synthetic hydrocarbon grease used to lubricate and protect electrical contacts. A dab on the threads & o-rings of your flashlight will protect it from the elements and water." Good stuff but a little expensive.
I'm thinking about getting Buna/Nitrile o-ring at smallparts.com. How much does a Duro 70 stretch? I just need them to stretch down over the threads into the groove below the threads on the bezel and tail cap.
To go in a 16mm dia. groove they have a 15mm(ID) x 1mm, for a 23mm they have a 22mm x 1mm. Is going 1mm smaller going to be tight enough or should I get them with a 2 or 3mm smaller ID?
The o-rings that came on them are like rubber bands, the o-ring that's in the 31mm groove on the bezel has an ID of 17mm.
savumaki
Enlightened
I worked for Parker at one time and I would say Viton covers all the bases.
Buna (nitrile) or Viton are great options as the resist everything, wear slowly, and are cheap. EPDM breaks down and gets gummy with some lubricants, so I don't like it. Silicone can't be used with silicone, and it's more expensive. Fluourosilicone are cool and blue but only good for decoration; they are very expensive and they are pretty soft. PTFE are hard and cannot be stretched. Those are some of the ones I have experimented with. I'd just go with Viton and be done with it.
Thanks for all the info, I found metric Viton V75's at the o-ring store. 1mm x up to 25mm ID. I need a few 31mm which they have in 1.5mm and the 1.5's are about 1/2 the price of the 1mm so I'll try them. It may be a little snug but it's on the bezel so it won't be getting screwed on/off all the time like the tail cap.
After researching some terms in the post by underwatermike, he mentions the "max interference fit is .28" which is 7.112mm. If that's the maximum you want to "stretch" them, I'll get them 2mm smaller than needed. That should give me a snug fit without excess stress on the o-ring.
After researching some terms in the post by underwatermike, he mentions the "max interference fit is .28" which is 7.112mm. If that's the maximum you want to "stretch" them, I'll get them 2mm smaller than needed. That should give me a snug fit without excess stress on the o-ring.
precisionworks
Flashaholic
FWIW here's an unscientific test of Buna-N O-rings ...
I machined the Ti-6-4 shifter peg (below) for my H-D Road King. The Ti cylinder is grooved & Buna-N O-rings were installed as shown:
After less than 12 hours of outdoor exposure there was visible cracking on all O-rings. Then they started to break. Removed the remaining ones & installed silicone (red) O-rings. Can't detect any deterioration after 24 hours use & cost wasn't much more than Buna-N.
FWIW #2 ... I believe that McGizmo installs silicone O-rings on all his titanium lights. I use either Krytex PTFE grease or NyoGel 760G (which contains silicone). No O-ring issues on any McG lights & some are over 8 years old, still using the original O-ring.
FWIW #3 ... Jason (DarkSucks) includes silicone O-rings with his more expensive lights.
All of which leads me to conclude that maybe they're OK :nana:
I machined the Ti-6-4 shifter peg (below) for my H-D Road King. The Ti cylinder is grooved & Buna-N O-rings were installed as shown:
After less than 12 hours of outdoor exposure there was visible cracking on all O-rings. Then they started to break. Removed the remaining ones & installed silicone (red) O-rings. Can't detect any deterioration after 24 hours use & cost wasn't much more than Buna-N.
FWIW #2 ... I believe that McGizmo installs silicone O-rings on all his titanium lights. I use either Krytex PTFE grease or NyoGel 760G (which contains silicone). No O-ring issues on any McG lights & some are over 8 years old, still using the original O-ring.
FWIW #3 ... Jason (DarkSucks) includes silicone O-rings with his more expensive lights.
All of which leads me to conclude that maybe they're OK :nana:
Barry,
McG's old lights like the PDs used the red silicone rings, but he has been using EPDM on the newer models for years. Popular lubricants like Nyogel eat the EPDM. Grrrrr.
Jason uses nitrile rings on the Ready Mades and uses the blue fluorosilicone rings on the more expensive models. Not silicone.
Also, your peg experiment has me curious. I have a bunch of buna-n rings I purchased for my McGs - I will put some outside to cook. My supposition is that those were either overstretched or already dry rotted or you had some nasties on your boots from the shop that killed them. A half day in the sun should not destroy o-rings of any flavor as far as I can tell.
McG's old lights like the PDs used the red silicone rings, but he has been using EPDM on the newer models for years. Popular lubricants like Nyogel eat the EPDM. Grrrrr.
Jason uses nitrile rings on the Ready Mades and uses the blue fluorosilicone rings on the more expensive models. Not silicone.
Also, your peg experiment has me curious. I have a bunch of buna-n rings I purchased for my McGs - I will put some outside to cook. My supposition is that those were either overstretched or already dry rotted or you had some nasties on your boots from the shop that killed them. A half day in the sun should not destroy o-rings of any flavor as far as I can tell.
Yoda4561
Flashlight Enthusiast
Anything petroleum based will eat EPDM quickly( most "synthetic oils" are still petroleum based as far as EPDM is concerned). On the upside not much is as weather or solvent resistant (acetone/MEK) as EPDM. Silicone and krytox work best for EPDM as lubricants. I'm not sure about how EPDM reacts to extended exposure to skin oils though. There's a reason they make O-rings in so many different kinds of polymers, every one of them has an application they work best in. For a dive light or car painter EPDM will work great due to the water/hot solvent resistance, for a mechanic's light Buna/viton would be best since they work fine around most petroleum products like motor oils and parts washers.
precisionworks
Flashaholic
That shows how long it's been since I've purchased a McG. I wasn't aware ...
The O-ring size is -210 (3/4" ID x 1" OD x 1/8" wide). The peg groove diameter is .800" & generally a 5% stretch is acceptable. These are stretched 6.6% so that might be one factor.
Brand new in sealed package.
I never wear work shoes on the bike. And the shifter pegs are contacted only when shifting, a small percentage of total time on a highway ride.
Not sure why but the red ones still look like new & they are sprayed with silicone each time the bike is cleaned.
NoNotAgain
Flashlight Enthusiast
Buna-N is **** poor in regards to UV light resistance.
http://www.marcorubber.com/material_chart.htm
Viton is a trade name for a Fluorocarbon type rubber product. It possesses excellent resistance to hydrocarbons (fuel system parts) and UV light.
The materail with the best chemical properties typically doesn't win out in a down select. It's the product with the lowest overall cost verses physical properties that takes home the cake.
If you want an all purpose lubricant that can be used on all types of o-rings, try Boe-Lube. Works well for drilling, milling, turning and brass case resizing. Oh, and non-toxic.
