I have a 1/4 inch tap for putting some threads in a hardwood block. The block is about an inch in depth. The threads are deep and well cut into the last half of the block but are pretty light (i.e...they don't hold very well) in the first half of the block. I used the drill bit that came with the tap set and rotated the tap clcokwise like I was turning a screw. Did I do this right and is there anyway to deepen the threads in the first half of the block? I hardened the threads with CA so it's pretty tight with the wingbolt in but I'd feel a whole lot better if the threads were cut deeply the whole way through. First time using a tap so please enlighten me!

Thanks,

Mike

I wouldn't bother with trying to tap a wingbolt holddown. Even if you soak it with CA, the threads will eventually smooth over from use. Save yourself some headaches and just put blind nuts into hold down blocks now. Much easier and those threads won't strip! Buy some nylon bolts that will fit whatever blind nut you want and you're off!

Tapping into a hardwood block is standard procedure with me. Should be no problem running the tap in and out several times to loosen the threads. Wing bolts have 1/4-20 threads. Your tap should be the same. I you got a 1/4 - 28 tap then you have the wrong tap.

After re-reading your comments it sounds like when you drilled the block prior to tapping, you let the drill wobble in the hole making it to large. This will result in shallow threads. If you have about 1/2 of the block with full depth threads and the nylon bolt penetrates the block, you should have plenty of hold down strength. 1/4" bolts in the wing are over kill any way. A 10-32 nylon bolt is sufficient. Typically you will find that in a crash the 1/4" bolt will not fail as it's supposed to do. The blocks will tear out of the fuselage.

The quality of the wood you are trying to tap makes a big difference. If it is to soft, it won't work. Do drill the hole with the proper drill first. Now, put some thin CA into the hole and give it time to set up well before tapping it. After tapping it, put thin CA in the tapped hole and let it set up then retap again. This will result in pretty well defined threads that last. When running the tap in the first time, back it out every 3/4 turn or so to clear any chips or debris that will foul up the threads.

From your description, it sounds like you will be ok as long as your bolts are long enough thread all the way through the blocks. If you are still concerned, you can drill out the blocks to say, 3/8" and glue in some 3/8" hardwood dowels, then redrill and tap new bolt holes.

Scott

Shoot! You are telling me I have been doing it wrong for almost 30 years on everything from small models to 14 foot wing giant scale! Man, glad you told me. Sorry for the sarcasm. Drilling wing bolts is not that hard and I have never had one "smooth over" as you call it.

Mike, take the advice given by others. If you think you need to do them over, take and drill the hole out, epoxy in a dowel and re-drill it. If you have to, use smaller drills to get the starter hole, and make sure you are using a numbered bit as your final. Not a 1/4 inch bit. Then when you tap it, make sure you are going straight and don't wabble the tap. Use thin CA on the threads and then run the tap through them again after the ca is dry. You will be fine. Make sure the bolt holds well by pulling on it.

Hey, take a valium or something there FLYBOY. I never said using blind nuts was the ONLY way to do it or that he was "doing it wrong" in any way. I just said that I use blind nuts routinely INSTEAD of trying to bother with tapping a block and then soaking it with CA. Perhaps you should get out more and not get so worked up about a radio controlled airplane.

Rick, if you reread your post, you should be able to find the issue. You basically implied that tapping the wing hold down blocks is going to lead to failure due to smoothed over threads. Flyboy was probably not the only one to take issue, but perhaps just one of the few to comment. I learned this method at least 25 years ago, I've used a tap to make threads in many hold down blocks and I too have never encountered the smoothing over that you imply will happen.

In fact, in thinking through tapping the blocks versus over boring and using blind nuts, I think drilling and tapping is far superior. The reason I feel this way is since the threads in the tapped block are much closer to the wing, there's significantly less bolt between the head and start of the threads. Since nylon is known to stretch, it seems this would be a good thing. The taping method also eliminates any possible play that the over-sized hole needed for blind nuts would allow. I have used blind nuts for a few wing hold downs, but when I do so I use a metal bolt instead of nylon.

Hey Mike, sounds like we have another controversy bruin here on RCU. The amount of good thread you need is dependent on the size/weight of your plane. I use ¼ in of ¼-20 threads in hardwood (maple/oak) per 10# of model. Also You want to make sure that the screw comes through the block enough to grab on to, in the case you should ever break off the head of a screw.

Lastly, I screw my wing bolts into the anchors for storage. In the tapped wood I can turn them in two or three times and their good to go, But if I do that with blind nuts the nut usually falls out of the anchor from the weight of, and side loading caused by the screw. So I end up threading the screw all the way in for storage to keep positive pressure on the blind nut.

Good luck

Joe

I did re-read my post and there is NOTHING in it that says that tapping a block is a BAD WAY TO DO IT! If you read the first line, I believe it says "I wouldn't bother..." emphasis on the word "I". That doesn't mean that someone else can't do it any other way. In fact, I could care less how anyone else sets up their planes. And I have had problems with tapping hardwood blocks after a while. It seems logical that the wood will eventually soften with use and repeated threadings. My point in replying to his thread was that he already seemed to be dissatisfied with the threads he got with tapping. It seems a whole lot easier to just drill out the block for a blind nut rather than epoxy in a dowel, fill it, sand it flush, then re-tap it and possibly get the same results. I get enough of the people who think their way is the only way to do it and reply to other ideas with that kind of sarcasm at the flying field...I really don't want to deal with it on an internet board too.

Talk about needing medication, you really need to re-evaluate and chill. LOL

A few hours on the web showed that nylon comes in several "flavors", with differing mechanical properties, but using the best info I could find, for this thread I ran some strength numbers for nylon bolts:

each 1/4 -20 nylon bolt will fail under 156 lb in tension and 272 lb in shear

each #10 nylon screw is good for 48 lb in tension, 86 lb in shear...

To get a feel for the loads involved, in a drastically simplified crash analysis, if a 10 lb airplane impacts terra firma at 20 g's, it will develop 200 lb of force. If you have four wing bolts, ideally each bolt will see 50 lb in some combination of tension and shear... looks like the 1/4 inch bolt isn't gonna budge, but will likely transmit the load to the glue joint, which will likely fail (especially if CA was used since it is more brittle than epoxy) Using #10 screws might allow them to deform/fail without pulling the mounting blocks off...

This analysis is oversimplified, but shows me that the 1/4 inch bolt is probably overkill for wing attaching, but they are easier to handle than #10 screws, and are readily available.... Also, some factor of safety for normal operations has to be considered, which makes me uncomfortable with the strength of #10 screws in airplanes over 5-6 lb.

Maybe #12 nylon screws are the best comprimise? #12 nylon screw is good for 115 lb in tension, 200 lb in shear.... Hmm...

Anyone have thoughts or experience using #12 nylon wing bolts??

FYI, have been interested in using nylon bolts for engine mounting for the same reason we use them for wings - if the engine can part company from the airframe in a crash, might it suffer less damage than being firmly mounted when the model is nose planted???

Cheers!

Jim

Fight.....fight.....fight!!![sm=punching.gif][sm=punching.gif]

I just love dealing with people that have so much tact.

Hmmm, how can that be taken. I think many would take is as someone saying, "if you put threads in a wing bolt block, they will smooth over and cause your wing to come off"

I also clearly stated that I was being sarcastic about doing it wrong. Who is the one who needs a chill pill? Yea, we all know.

Okay, just for the fun of it. How about using a threaded insert? They work pretty well also.

Have used those when I screwed up a hole. They worked pretty well acutally. You can get them at Ace hardware or just about any hardware store.

Yeah, the threaded inserts work great...obviously though a blind nut wouldn't work though....uhh...right.

Never said blind nuts wouldn't work. Just the way you said it, it sounded like that was the only way you would suggest doing it. Came across a little strong. Don't worry about it. Wasn't a personal attack, just wanted him to know there are many ways. Lets move on eh.

Agreed. Sorry if my statement made it sound like tapping was a wrong way to do it. Not at all! I know lots of folks who tap their blocks and have great results. I just was offering another alternative since I personally have had some problems with tapped blocks wearing over time and cross threading the bolts, etc. Moving on...

As mentioned before, threaded inserts might be the way to go if the wooden threads are messed up. Great Planes make some - [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXK034&P=7]heres an example[/link] - or you can probably find them at a hardware store.

A blind nut should work too...

A threaded insert would work. Blind nuts would work. Dowel in the hole and redrilling and retapping would work (my personal preference). One day, I saw a guy use a bungie cord to put his wing on because he forgot to bring his wing bolts to the field! As they say, there is more than one way to skin a cat.

Scott

Scott, you better be careful talking about skinin cats! Look at all the trouble that liken fur got that Agulara babe in. With all the short fuses here, well, that’s, like liven on the edge.

LOL

Joe

Yea, those are the threaded inserts from great planes. You can get them at most hardware stores for about half that price or less though. The ones I use are hex driven instead of slotted, but it wouldn't matter much. The only thing you want to watch with metal inserts or blind nuts is if the screw is sloppy at all in the thread, it will back out. Same goes for wood blocks. Check them after every flight the first few times and down the road if you feel them getting loose as you put the wing on and take it off. You don't want the screws to get sloppy in there. The vibration will eat the threads off the bolts and they will pull out.

I prefer the the drill and tap method myself. Never had a failure. I did find something neat at ACE hardware I wanted to share with you guys. It is a blind nut without the spurs. It has a flat flange with holes drilled around the edge for small screws. A 1/4 scale arf I bought already had the holes drilled. They were to big to thread. Since the canopy was still off these were easy to attach and have worked great.


David

I tried the thread inserts once in maple blocks and maybe i did,nt use them right but they split the maple block. good thing i had the piece of maple epoxied solidly in the plane. many hours later i got the block out and cleaned up enough to put a new block in. i think it was the second post was right on the drill bit probably wobbled but figure a blind nut quarter inch has approx. 3/8" of threads so if you have at least that amount of good thread you should be in good shape. buy the way if you are running a 1/4 nylon bolt there is no way you will ever strip out a piece of maple that is one tough wood. used to use them as motor mounts back in the olden days.