Is there a brand that is preferred?  The last several times I have purchased from the LHS it seems there are always several in the package that have threads that are messed up causing the bolt to cross thread.

Thanks,

James

I like McMaster-Carr for most of my hardware needs.

If you're using blind nuts for engine mounting, I suggest that you throw away the blind nuts and simply tap machine screw threads into the maple mounts.  Use a tap drill size that gives you 100% thread depth rather than the usual tap drill for metal which gives somewhat less.  The engine is held very rigidly, with 1/2" or so of thread engagement they never work loose and you'll never have a blind nut come loose on the back side of a motor mount where it's almost impossible to correct.

I never heard of anyone using that method.  I have never done it that way.  Maybe it has worked for you but I am staying with blind nuts.  I would be concerned about oil soaking into the wood and eventually softening it.  I have never had a blind nut come loose or strip out.  I epoxy them in.  I also coat the inside of the hole in the maple mount with epoxy to guard against oil soaking the wood.

Dubro blind nuts are plated brass?  The wheel collars are made that way but magnets stick to the Dubro blind nuts I have.

At times I have had to run a tap through blind nuts, no matter what brand, to clean up the threads.  I do not see that as a big issue.

I get mine from RTL Fasteners.   Another alternative is to use aluminum plates on the other side of the engine mounts that are drilled and tapped.

4-40 blind nuts are a frequent failure point.  I believe that this is very much related to the comparatively small circle of the prongs in relation to the bolt.

Both 3 mm and 6-32's have bigger "prong circles" and thus a better chance of holding.

Always confirm that the blind nuts are clean before burying them.
When doing the final assembly, leave a greased bolt in the blind nut.
One more point.  If the bolt is going in hard, don't force it.  Heat up a bolt and oil it, then ease it into the blind nut. 

I gave up long ago with commercial blind nuts, much happier with home made dural ones. Thread o.d + 1/16" is enough as outside diameter. And lenght same as thickness of engine bearer, so they touch the engine mounting pads.
I knurl them, allready wet of epoxy, by rolling between 2 flat files and press in holes that are pre-impregnated with epoxy. Then curing in oven, at 70..80C.
Maybe an overkill but much less work than when you have to fix one that's gotten loose and oily

I wouldn't trust threads in wood in engine mounting, but in secondary places like tank mount and lead-out guide they're more than strong enough if done well.
Normally I just wax the screw and force it into a slightly small hole (something like 2,7..2,8 mm hole for M3 bolt, or 2,6..2,7mm for 4-40 bolt) impregnated with epoxy.

By the way, those square machined Du-Bro blind nuts WERE plated brass at some point. That's when I stopped using them.


L

Of course not, but I get (sick) pleasure from things well made.
L

I cannot ever recall an engine flying off into space because of a blind nut failure.  Has anybody ever had that happen?  I sometimes think we have a tendency to over engineer things. 

Mike

They usually fail the other way, start spinning and you can't get the screw tight or out.
So now you have to cut into the model to get at them.

Pat MacKenzie