How do I tap an engine mounting hole on nylon engine mount? I do not have access to a tapper. I also do not know anyone that has a tapper. Thanks.

Well, if you are committed to the hobby you should get set up with a tapper. It is just another expense, I know!

I use 6/32 for most of my 40-90 sized planes. Cost for the tap should run about $5 +/-??. A reversing electric drill is a big help but not totally essential over a straight drill. You will need to drill a simple pilot hole first with a smaller sized bit.

You don't have to tap them, although I do and I think most do, too.

Just through-drill for the size of your bolt and secure with a flat washer, lock washer and a nut or a flat washer and nylon lock-nut. If you use the lock washer and nut you might want to use a little loc-tite on the threads.

The through-bolt method will last longer than the plane.

Good luck!

As someone else said, if you plan to stay in the hobby you need to get one. I bought a set of em at Orchard Supply Hardware. Pretty sure it cost less than $20 and has a set of 5 or 6 drill and tap pairs along with a T handle chuck for the taps. I drill and tap ALL my nylon mounts leaving the last bit un tapped. I have yet to have a socket head screw loosen.
I do add a nylon insert nut on the end JUST in case.

snyperx:

You can also drill the mount slightly undersize for the screw, then cut some slots in the end of a screw and drive it through; that will cut the threads for you.

The proper way, as has been pointed out, is to buy a tap and tap handle, or a complete tap and die set.

Bill.

PS: You could also visit the shop where you get your car services, someone there should have the set. wr.

www.microfasteners.com sells taps and dies, and if I recall, they are like 3 bucks a piece. Just buy the ones ya need for now. I found them looking for nylon bolts (which they sell in bulk cheap)

A sheet metal screw in a nylon mount works great also. I've been doing it for about 10 years now. It aint coming out either!

I know that I will get flak from this..................

But I go and buy the aluminum pre tapped motor mounts.
OS sells very nice ones and Saito has nice ones also.
Yes they are pricey but I feel that the aluminum also helps dissipate the heat also. I have tried to use a drill press and I just cant do it as well as the aluminum.
Thats how I do it!

av8r4aa:

No reason to shoot you down for that. If that's what you want to use, then do it.

Unless a metal mount comes with the plane I prefer the FRP mountings, they do give a little bit of isolation and vibration damping.

Bill.

Thanks for all the responses. I ended buying a 4-40 tap, T-handle and #43 drill bit.

T-handle= $3.99
4-40 Tap=$1.99
#43 Drill Bits= $2.4

Mounted the motor and marked the holes. Drilled the holes using the #43 bits. Then tapped the hole. Left a few mm of untapped nylon so the bolts hold good. Seemed to work ok.

Another related pointer: If you make a mistake doing a tap job, or if the tapped threads strip out, you can "start" over by filling the hole with a mixture of epoxy and microballoons, let it dry for a day or two and then retap. The mixture should be just thin enough to still flow slowly. I have done this a few times, even in wing bolt holes! As always flow some thin CA into the redone threads and let dry.

Save your money. Drill the holes slightly undersized and just scew the the screws in. Believe me, them nylon mounts act like nylon lock-nuts. I have done this a few times and even pulled the motor out and replaced it several times without any problems.

From this thread I get the impression that mounting and unmounting the engine repeatedly is a bad thing...

I built a PT40 from great planes from a Kit. Duing the build process I mounted an OS46LA engine on the nylon engine mounts. To complete the build, I must have installed, and then uninstalled the engine at least 10 times. Each time removing the 4 engine mount "machine screws" that tap themselves into pre-drilled holes.

Should I be concerned that the engine could work itself loose?

I do check things likle that every couple of times I go to the field, but I have not noticed any problems with the engine mount (although I did find that the rear cover of the crank case had come loose at one point (made the mounting frame of the remote needle rattle around).

Thanks for any input in advance.

gus

Gus:

I've done the multiple mount/remove myself and never had a problem.

Bill.