Locktite on rail button screws?

[Zman1961]

I use blue Loctite on machine screws and allow the buttons to rotate. And they do wear out, sometimes dramatically, so it is good to be able to replace them easily. I do not use any adhesive when I use machine screws going directly into wood or other solid backing material.

 

[jqavins]

Wouldn't machine screws placed directly into wood and without adhesive fall right out? That is exactly what wood screws are for, after all.

 

[Zman1961]

Wouldn't machine screws placed directly into wood and without adhesive fall right out? That is exactly what wood screws are for, after all.

Sorry, I meant wood screws directly into the wood, that's what I get for trying to type late at night, thanks for the catch.

 

[jahall4]

Yes, always, can't hurt because ideally the rail buttons are anchored through the airframe into a weld nut or similar via a countersink machine screw where Loctite Purple (or even Blue) would be appropriate to use. This obviously does not apply to guides anchored with wood or sheet metal screws.

Here are a couple of more involved examples of anchoring rail guides: https://tinyurl.com/334pkx7m

 

[Bill S]

What's up with the "missing" Facebook part of your post, jahall4?

 

[DAllen]

Rotating rail buttons is a mystery to me. I glue or otherwise secure all of my buttons so they don't rotate. Unless something really unusual happens with the flight I have never ever seen them get chewed up. My suspicion is that if buttons are getting chewed up the rails need to be cleaned.

 

[jqavins]

My suspicion is that if buttons are getting chewed up the rails need to be cleaned.

Or it's a bit chewed up itself and needs to be repaired or replaced. Or we're wrong, and just rubbing hard on a rail really does harm a button sometimes.

I'd leave mine to rotate anyway (and use a dry lubricant on the screw shoulder), if only to reduce friction during launch by just that tiny bit.

 

[rocketman328]

I wonder if every rocket inspector checks them for tightness?

Think that’s the fliers job!

 

[DaHabes]

I've never used Locktite on my rail button screws and never kept them loose enough to rotate. They won't rotate anyway; they are not that tight in the rail slot. I've never had them come loose, dozens of flights. Just tighten the screw down and fly.

P.S. If I ever need to do airframe repairs and repaint, I want to take the rail buttons off. Red thread locker is overkill. If you feel you need to use it, blue is sufficient.

Reading this thread further, and never having had a rail button need to be replaced, my conclusion is not all rail buttons are created equally. They all are (for the most part) black and it's not usually known what plastic is used. If your rail buttons are failing, switch vendors. I've used Apogees almost exclusively and have never relaced one.

The last batch I bought was from Rocketarium. The only reason I was confident in doing so is that Rocketarium explicitly noted they were made of Delrin. Delrin is as hard as rock. I'm also an astronomer and have had eyepieces in the past where the body is made out of Delrin. Delrin won't expand or shrink with the temperature, essential in an eyepiece that could be used in temps anywhere between zero- and 100-degrees F. It's a pretty much bullet proof component. Buy Delrin rail buttons and hand tighten them down, no spinning necessary. Blue Loctite if you insist. Never red; if you have to do repairs, you're screwed with red.

 

[berlinetta]

I tighten my rail buttons, no loctite or anything. They don't rotate, but they aren't so tight where I can't get them out if I need to replace them. I did, epoxy them to the rocket when I first started using rail buttons, but I no longer do that.

 

[jqavins]

I've used Apogees almost exclusively and have never relaced one.

The last batch I bought was from Rocketarium. The only reason I was confident in doing so is that Rocketarium explicitly noted they were made of Delrin.

Apogee's rail buttons are also Delrin. (Their website also explicitly says so.) Note that their rail button standoffs are nylon. The standoffs are not wear parts so it should be fine, but my inner overbuilder wants them to be something tougher, like Delrin or aluminum. Fortunately, aluminum standoffs are easy to find in hardware stores.

I've got some home made rail button kits that consist of two washers and a short bit of aluminum standoff. The project they were for ended up going a different direction, but I'll use them someday for something.

 

[Joekeyo]

Think that’s the fliers job!

Just checked mine. 2 were slightly loose. All are now nominal.

 

[Fireball]

I’m putting rail buttons on my mid pow WAC Corporal and I’m using wood screws into plywood centering rings. Can I use blue loctite with wood for a better hold on the screw and still allow the screw to be removed down the road?

 

[SolarYellow]

Wood screw into the edge of plywood doesn't seem like a totally awesome idea to me.

 

[g.pitts]

I’m putting rail buttons on my mid pow WAC Corporal and I’m using wood screws into plywood centering rings. Can I use blue loctite with wood for a better hold on the screw and still allow the screw to be removed down the road?

I agree with @SolarYellow on putting a wood screw into the side / edge of plywood. But as I understood it, Loctite is really intended for metals. BUT... I found this article that suggests it may work in wood, although it seemed to be somewhat conflicting in a couple of sections. If it were me, and I really wanted to go this route, I'd probably clean the screws with isopropyl alcohol or acetone and use epoxy instead of a red or blue Loctite product.

YMMV...

 

[SolarYellow]

Loctite is basically a specialized CA, as I understand it. No reason it shouldn't work OK in wood as long as the screw is metal. Loctite for some reason wants active metallic ions available to promote its cure. It is less effective on stainless for that reason. It's generally lame on plastic-only joints, and can also chemically attack and make brittle just about any thermoplastic.

 

[jqavins]

Loctite is basically a specialized CA, as I understand it... Loctite for some reason wants active metallic ions available to promote its cure.

CA needs hydroxide ions to kick. If Loctite blue or red threadlocker needs metal, that means it's not CA (probably). Its ingredients, according to the SDS, are:

Chemical ingredients	CAS-No.	Proportion
Polyethylene glycol 200 dimethacrylate	25852-47-5	50-< 80 %
Propane-1,2-diol	57-55-6	< 10 %
α, α-dimethylbenzyl hydroperoxide	80-15-9	1-< 3 %
1,4-Naphthalenedione	130-15-4	< 1 %
non hazardous ingredients ~		20- < 70

So there is an acrylate, but I don't see any cyano- anything or any nitrogen at all, if I'm reading all that stuff rfght.

The threadlockers are the brand's flagship products, but they do sell many others, including some CA adhesives.

 

[Fireball]

Wood screw into the edge of plywood doesn't seem like a totally awesome idea to me.

Just to be clear...3 stacked centering rings epoxyed together...plenty strong enough. Im going to do alittle test on theblue loctite and see if it holds up

 

[jqavins]

My concern is that the plywood may delaminate and thus fail to hold the screw, Loctite or no. You could drill a rail button size hole into the CR and it would still be plenty strong, that's the the problem.

 

[SolarYellow]

CA needs hydroxide ions to kick. If Loctite blue or red threadlocker needs metal, that means it's not CA (probably). Its ingredients, according to the SDS, are:

Chemical ingredients	CAS-No.	Proportion
Polyethylene glycol 200 dimethacrylate	25852-47-5	50-< 80 %
Propane-1,2-diol	57-55-6	< 10 %
α, α-dimethylbenzyl hydroperoxide	80-15-9	1-< 3 %
1,4-Naphthalenedione	130-15-4	< 1 %
non hazardous ingredients ~		20- < 70

So there is an acrylate, but I don't see any cyano- anything or any nitrogen at all, if I'm reading all that stuff rfght.

The threadlockers are the brand's flagship products, but they do sell many others, including some CA adhesives.

I didn't go very far in chem. I was just remembering the ideas communicated by a Loctite regional sales rep who was an SME about the products on a motorcycle forum several years ago.

Re: the plywood edges, I would probably do a couple test pieces. One, whatever is being planned with a wood screw. For another, I'd drill a hole, harden the wood grain with CA, tap it for machine screw threads, do the hardening again and chase it. Another, the same but with epoxy. Maybe a few of each concept. Then break stuff and see what you like best.

 

[jqavins]

Another reasonable test would be to drill a hole to take a pin of some sort, a rod with a head and no thread at all. Like a rivet (not a pop rivet.) Then just glue it into the hole with epoxy.

 

[Tractionengines]

Guides rather than buttons... no need for locktight. There's no torque on the screws.
Here is what I use. Direct from 80/20; then modified. (# 6797 for 1010 rail, and # 6897 for 1515 rail) Low cost raw part. Takes me 10 minutes with hacksaw, sander, and drill press to finish into 1 screw or 2 screw versions. Made from UHMW-PE (plastic, very similar to Teflon, with an even LOWER sliding friction). So VERY smooth sliding in the rail, even if a little dirty. (No chance of damage to rails, like Aluminum guides.)
Only issue is you can NOT bond to the UHMW-PE. (Glue or Epoxy) SO SCREWS ARE REQUIRED. I drill out the pilot hole and then countersink for 8-32 flat-head screw.

You'll NEVER wear these out. [Well, never say never, but I have used these on machines that run 24/7 for years.]

 

[kjhambrick]

Guides rather than buttons... no need for locktight. There's no torque on the screws.
Here is what I use. Direct from 80/20; then modified. (# 6797 for 1010 rail, and # 6897 for 1515 rail) Low cost raw part. Takes me 10 minutes with hacksaw, sander, and drill press to finish into 1 screw or 2 screw versions. Made from UHMW-PE (plastic, very similar to Teflon, with an even LOWER sliding friction). So VERY smooth sliding in the rail, even if a little dirty. (No chance of damage to rails, like Aluminum guides.)
Only issue is you can NOT bond to the UHMW-PE. (Glue or Epoxy) SO SCREWS ARE REQUIRED. I drill out the pilot hole and then countersink for 8-32 flat-head screw.

You'll NEVER wear these out. [Well, never say never, but I have used these on machines that run 24/7 for years.]

Very nice, @Tractionengines

Do you try to shape the underside of the pads to conform to the outer radius of your Air Frame ?

-- kjh

 

[DAllen]

Guides rather than buttons...

Those look nice but that's a tight fit. How do you deal with the inevitable crud that builds up on the inside of the rails? Seems like something that tight would bind up after a while.

 

[Tractionengines]

Do you try to shape the underside of the pads to conform to the outer radius of your Air Frame ?

-- kjh

Nope. Material is too hard to shape with that level of precision. On small diameter tubes either:
1) Add a little epoxy under it. (Not to bond it, but as gap filler. As noted it won't stick at all to the UHMW-PE, but it will support it.)
OR
2) Add a wood standoff/shim between the body tube and the guides. The wood is easy to shape to the tube. Wrap some sandpaper around the tube, and a few swipes of the wood, done.
OR
3) Be lazy, and don't worry about it. If the screw anchor is solid, it won't matter.

 

[Tractionengines]

Those look nice but that's a tight fit. How do you deal with the inevitable crud that builds up on the inside of the rails? Seems like something that tight would bind up after a while.

So far it has not been an issue. There is a little space around the profile. The main thing is the coefficient of friction is SO LOW with this stuff, it slides across even rough areas with no wear.

I DO take a rag, or paper towel, with me to the pads, to wipe the T-slot. Usually not needed. I just feel for resistance as I slid it on. If any give it a quick wipe. THIS IS GOOD PRATICE TO GET INTO REGARDLESS OF ANY FORM OF RAIL, ROD, GUIDE, BUTTON, or LUG.

 

[anbhtblr]

Very nice, @Tractionengines

Do you try to shape the underside of the pads to conform to the outer radius of your Air Frame ?

-- kjh

Guides rather than buttons... no need for locktight. There's no torque on the screws.
Here is what I use. Direct from 80/20; then modified. (# 6797 for 1010 rail, and # 6897 for 1515 rail) Low cost raw part. Takes me 10 minutes with hacksaw, sander, and drill press to finish into 1 screw or 2 screw versions. Made from UHMW-PE (plastic, very similar to Teflon, with an even LOWER sliding friction). So VERY smooth sliding in the rail, even if a little dirty. (No chance of damage to rails, like Aluminum guides.)
Only issue is you can NOT bond to the UHMW-PE. (Glue or Epoxy) SO SCREWS ARE REQUIRED. I drill out the pilot hole and then countersink for 8-32 flat-head screw.

You'll NEVER wear these out. [Well, never say never, but I have used these on machines that run 24/7 for years.]

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Found these at 80/20, but the shipping was more than the parts. Also found the 10 series parts on Amazon, so that solve the access/shipping problem. I was unable to find the same for 15 series at Amazon. Do you have any other sources with reasonable shipping?

 

[Tractionengines]

I order thru work ... so I don't shop around for them.

Taking a quick look. It seems like $ 5.00 shipping from Zoro. Must order 2min.

• Zoro #: G0811373
• Mfr #: 6897

https://www.zoro.com/8020-top-mount-pad-15-s-6897/i/G0811373/

 

[cerving]

If I'm using nuts inside the tube, no glue necessary... just back out the screw a tiny bit after tightening so the button rotates. In FG, sometimes I just drill a hole for the screw and epoxy it into the tube, and don't worry about the rotation... knowing that the Nylon ones are going to have to be replaced after 5 or so flights anyway. The epoxy will "break" free with a bit of torque, making them easy to replace.

 

[SolarYellow]

I order thru work ... so I don't shop around for them.

Taking a quick look. It seems like $ 5.00 shipping from Zoro. Must order 2min.

• Zoro #: G0811373
• Mfr #: 6897

https://www.zoro.com/8020-top-mount-pad-15-s-6897/i/G0811373/

Zoro is also the best place to get Krylon Acryli-Quik. Load up your cart with whatever you want, then wait. In a few days, they'll send you a coupon code for 20% off pretty much everything they have. $50 order total (that includes shipping and tax) gets you free shipping.

Top Mount Pad 10 S​

• Zoro #: G0810980
• Mfr #: 6797

https://www.zoro.com/8020-top-mount-pad-10-s-6797/i/G0810980/