Hardened screw holes
 

To harden the threads in hardwood servo mounting blocks or wing mounting blocks, drill the screw hole, install the screw or tap the hole, remove the screw and put a drop or two of thin ca in the hole and you now have a hardened thread. In the case of wing mounting blocks, you may need to re-tap the threads after you ca the threads.

Tom

RE: Hardened screw holes
 

One small caveat........When you clean up the threads, always use the tap, not a nylon bolt. Sometimes that thin CA doesn't all 'fire' and you'll have a permanently installed nylon bolt. Don't ask how I know this.

RE: Hardened screw holes
 

Tis true, tis true. In fact even though I mentioned in my post about re tapping the hole, I should have also mentioned that you should spray a little kicker in the hole or even a tap can seize up if the ca has not all gone off.

Tom

RE: Hardened screw holes
 

Good tip!

I mentioned what you said in the article on my site about how to mount a wing. You really do need to wait for the CA to totally set up even if using a tap. I've had wood chips glued in my tap thread before and picking it out isn't any fun. I just let it set up over night and work on something else. Then I re-tap the threads.

Good tip!

RE: Hardened screw holes
 

For wing bolts, I perfer a brass insert w/ the proper thread glued into the wood.
Haven't had much luck w/ CA hardened threads...

Just my .02 worths...

Allen

RE: Hardened screw holes
 

I have a different way of doing Servo blocks.
I drill a hole to fit the yellow nyrod and then insert
the yellow nyrod in the hole. Then CA the yellow nyrod
in place and you have a screw holder that will hold.
Works for me.


HLC

RE: Hardened screw holes
 

CafeenMan
Had small experience with the tap...decided picking it out was too time consuming..dropped tap in acetone 20 mins. later it was clean. relubed it and will wait longer next time.

RE: Hardened screw holes
 

After adding some thin CA I like (after 5-10 min) to spray in some 'Kicker' and WAIT for another 5 minutes before 're-tapping'. I think when you squeeze the wood with either the tap or the bolt, some of the uncured CA is squeezed out of the wood and now you get to re-drill, re-tap and #^@$%%^*$%( one more time :)

Jerry

RE: Hardened screw holes
 

I find where it is necessary to harden the screw hole I use "All Threads" These are plastic pieces specifically sized to take all sizes of small screws. All you do is drill a hole, insert the All Thread and thin CA it in place. The screw goes into the plastic hole and requires torque to screw in and remove. Great for cowl screws.....they won't vibrate out. All Threads are available from Great Planes in sizes #2 to #10. More optins in size than using a piece of yellow Ni Rod. Best i have found so far

RE: Hardened screw holes
 

I have to admit, I prefer using blind nuts and #8 button head stainless hex screws with a wide flat washer. They are small, strong, and have a rounded head so they don't have such a protruding look to them. For really large planes, #10 screws. Besides the shiny stainless looks nicer.:D

Patriot

RE: Hardened screw holes
 

I use those plastic dry-wall anchors. Buy a box of assorted sizes - drill a hole - pound in the correct size, secure with thin CA, then screw away. These hold tight - won't vibrate loose, and are relatively cheap.

RE: Hardened screw holes
 

For what purpose? There's no way I'm trusting a wing to these things.

RE: Hardened screw holes
 

I don't want to sound insulting but can't help it here. :D I have to agree with cafeen-man. It may work, but for how long? I would rather use some old baling twine and bubble gum if that's the case. :D Sorry, but I had to say it.

Patriot

RE: Hardened screw holes
 

Staying with the original subject.... The CA works well as a thread hardener on hardwood and balsa too. I've been doing that since my first plane. Another use for CA in wood, is around the hinge points and control horn mounting area. I have never screwed a control horn onto a control surface since I've been in this hobby. I think it looks tacky and adds to the drag. Instead, I carve a indent into the control surface a bit deeper than the thickness of the base of the horn, cut a cover plate from 1/64 aircraft ply and CA it all together. I then take thin CA and "harden" the balsa for about 1/4" all around the horn. I have never had a failure, even after a crash the control horns were still intact. I'd post a pic but I'm not at home.

RE: Hardened screw holes
 

Jim - Seriously - what do you use the dry-wall anchors for?

RE: Hardened screw holes
 

Skeletor, no screw at all? You are flirting with disaster if that is the case.

RE: Hardened screw holes
 

Flyboy - He buries it. Sounds secure to me. It's covered in wood. Sounds cool actually.

RE: Hardened screw holes
 

I can see using thin Ca to harden balsa and perhaps soft (pine, etc.) wood or ply thd's but why is it necessary in hardwood.? Used hardwood for years and never had a problem with the thd's pulling out? Usually, if you tighten nylon bolts down too much, the nylon breaks but the hardwood thd's, never! Another approach is to glue a steel "T" nut on the backside of the hole like you may do for motor mount bolts in a ply firewall and leave the hole smooth in the wing mounting block, then the nylon bolt engages the steel "T" nut th'd. only. Have used steel 1/4-20 "T" nuts and smaller th'd. sizes for years in ply blocks for wing mounts, motor mounts, cowls and landing gear blocks with great success!

Overkill can sometimes cause important airframe parts to break as a result of a crash and not easily replaced parts like mounting blocks, etc. A further thought is maybe your th'd taps are dull which cause poor quality thd's to be cut in hardwood blocks?? Just thoughts from an old frustrated machinist and engineer.:D:D:D:D

RE: Hardened screw holes
 

flicka - I put CA in hardwood to oil-proof the threads more than anything else. I agree with you about hardwood. It's strong enough to hold a thread without help, but oil seems to be able to creep everywhere - under landing gear, into holes, etc.

RE: Hardened screw holes
 

cafeenman is right. i once say a little p-51 kit that really tore up the sky. Then, one day tore off the wing while doing and outside turn. :(
Crash investigation showed the bolt holes in the hardwood mount were stripped out cuz just a wheee bit of nitro got in there one way or another, and over time, oops.[:@]

Patriot

RE: Hardened screw holes
 

Skeletor. That sounds like a superb and clean looking way of mounting control horns. Would you be so kind as to post a photo essay on the subject?

Brad

RE: Hardened screw holes
 

Well the way I did it was to first make the holes the way I wanted them. Then put some thin CA in it to harden it up. Give it about an hour, then use a tap are clean the threads from any expanding CA effects. Worked for me.

RE: Hardened screw holes
 

Ca in hardwood th'ds for oil proofing is a good thought but something I have never done: maybe because my models don't last that long to be a problem?:D:D:D

RE: Hardened screw holes
 

Ouch

RE: Hardened screw holes
 

LOL... I know just what you mean. If only my flying skills were at the same level as my building skills. I would have a serious storage problem. Last year I crashed my Raptor, I crashed Gonzo 3 times and it's a simple 3-channel airplane. All crashes were due to trying to find out how close I could get to the ground in a spin and then pull out. OK, avoidable, but still...

what else.... Stuck My Stick 30 into the ground on a touch and go - rolled it too much and the turf caught a wing tip causing it to cartwheel 75 yards across the field. One broken turbulator spar, two dented wing tips and a totalled fuselage. If you look at this plane on the site, you'll see two different fins. Those are actually two completely different fuselages.

Oh yeah.... I lost Great Gonzo in the statosphere. Had her so high that all I could see was a little dot - no color, no shape. Took my eyes off her and haven't seen her since. I think she's still up there somewhere.

So, I started out last year with 5 planes and am down to 2 - one of which is retired.

An exerpt from the inlays article on my web site that goes along with your comment which I can certainly related to: