Tip: Source for Undersized Hinge Pins

[Ironflight]

There are times, when using hinge material as joints and fasteners (for things like cowlings) that it is convenient to use an undersized pin to make things mate up more easily. Van suggest this in several; places, such as for the firewall cowl hinges. I find that generally, if you do a really good job of lining things up during the build, cowl hinge pins can be a bit of a pain to remove and replace for a hundred hours or so when they are still wearing in. There are numerous ways to fix this, including grinding a point, or a flat ?bit? and point on the end and spinning them in with a drill motor. The good news is that they will almost always eventually get easier. We used hinge material for the side cowl fasteners on our RV-3 because I like the clean lines you get with the hidden hinge, and by putting the hinge pin in from a hatch in the back, they are completely invisible. Unfortunately, they are still nice and tight, and need to be spun in the last foot or so and this means spinning a drill motor perilously close to our new paint job.

So this thread isn't about debating all of the various ways you can rig hinges - it is just to point at a source for smaller hinge material, if you choose to go that route.

David Howe, an RV and Rocket builder from California, suggested a great source for marginally smaller pin stock ? good old McMaster-Carr. I thought I?d pass this on to other interested builders ? just go to www.mcmaster.com and search for Tool Steel Tight-Tolerance Rod. They sell it in 3? lengths in fractional sizes below the stock .090? that comes in the hinge as standard ? I got several lengths each of .088?, ,085?, and .081?. The .085? size fit really nice right now ? I expect that it will eventually loosen up a bit, and we?ll go to the .088?, and if that loosens up, we?ll be back to the nominal. It?s pretty cheap BTW ? less than $3 per length.

Paul

[rv9aviator]

Boy do I need that information. My pins are so tight I have to clamp vice grips
on the hinge pins 2 inches from the cowl and push them in 2 inches at a time. Thanks Paul!

[krwalsh]

While you're placing your order for the wire, you can also order the PTFE tubing to make the stainless/Teflon hinge pins:

5335K17 HI-Temp Chemical-Resistant PTFE Sleeving .066" ID

Don't forget to order smaller wire if you do this!

[ColoRv]

Reviving an old thread. I'm searching for these different size hinge pins and not finding them. A friend at the airport has several that he got from small parts inc but they appear to be out of business. Anyone have a source? Are to we supposed to use hardened stainless on the cowls?

[KRviator]

Originally Posted by ColoRv

Reviving an old thread. I'm searching for these different size hinge pins and not finding them. A friend at the airport has several that he got from small parts inc but they appear to be out of business. Anyone have a source? Are to we supposed to use hardened stainless on the cowls?

It's still listed in their catalog, to find it, do this:

Goto McMaster.com
In the search box, top left, lookup "Tool steel rod"
Narrow the search to "Rods"
Select "Multipurpose O1 tool steel"
Scroll down to "Tight tolerance rod, precision ground"

And there you are... You may need to create an account as it seemed a bit fickle when I went back a second time, asking me to log in or some such rot...

[ColoRv]

Thanks. Will give those a try, but the sizes are limited. Those I have from my friend are tighter in sizing. .087,.088, .089 etc. If anyone stumbles in here with a source for the tighter sizes, post it plz.

[HFS]

I just looked in McMaster's catalog and they still listed Drill Rod in the O-1 condition in AWG (American Wire Gauge) sizes - and more specifically for the size hinges we use most - .081, .085, .086, .088, .089 / .110, .111, .113, .115, .116. Those sizes should pretty much cover the need for the two hinge sizes Van's has used forever.

I have been using this product for "tight hinge syndrome" since 1989 and have had very good success with it - 2500 hr+ and counting.

The standard length from McMaster is 3' - but they are originally manufactured in 12' lengths and then cut for McMaster into more manageable sales lengths. If you need longer lengths - IO540's for example, McMaster will, on request have them cut to your specs. You may have to buy more than you wanted, but then you can become a local distributor!

YMMV
HFS

[bullojm1]

Instead of sourcing a thinner hinge pin, I enlarged the opening of the hinge eyelets slightly. I took a length of hinge pin and heated up the tip with a blow torch until it was glowing. I then used a hammer and flattened the tip. I then filed the end to a point. This increases the diameter of the pin at the tip. See below:



I chucked the modified pin into a drill and ran it at a low speed through my hinge eyelets that were binding. Slowly but surely, it opened up the hinge eyelets.

Another trick that really does make a difference is to lube up the hinge pins with BoeLube. I recently did some maintenance where I wiped down some hinge pins to remove oil. Upon reinstallation, I was having a heck of a time getting them to go in smoothly. After I added some BoeLube, they slid right on in. I was amazed at how much of a difference it made.

[Norman CYYJ]

What I have doing on the last few builds is to set the hinge pin in the holes even if I have to use a drill and maybe a hammer to tap them in. Making sure there is no resin in the eyes. Then I take a heat gun and get the cowling very hot along the hinge line then let it cool off to cold to the touch then repeat the process a few more times. This sets the cowling as though there were many hours of engine operation. On the last cool down the pins always slide in and out with just a push.

[hqcook]

Perfect. Ordered the 0.085s. Feels much better. Moving on!