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  #21  
Old 07-13-2011, 07:09 AM
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Bullseye Bullseye is offline
 
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Quote:
Originally Posted by LifeofReiley View Post
I went to the chart and pulled the correct bit and then drill them all up to the correct size for the tap...
I didn't drill them up...

Would that have made the tap cut too much?

This morning at work, I grabbed a better quality tap (4 flutes) and threaded it in by hand. That tap was loose. I have a feeling my Harbor Freight tap was a little oversize.
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  #22  
Old 07-14-2011, 07:50 PM
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Bullseye Bullseye is offline
 
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I know this wasn't my thread, but I did learn a little last night:

After some thought (and a trip to work), some of the guys were convinced that 1) I didn?t ruin the part, especially since I had only tapped the 1″ shown on the plans (and the rings are like 1 1/2″ long), and 2) it must be the tap quality.

They lent me a really nice tap (as opposed to the $7.99 tap and die set from Harbor Freight.)

I screwed in the nice new tap, and once I got past the first inch, I immediately felt a difference. When I turned 1/2 turn in, the tap felt like it was cutting, instead of just pushing material out of the way. There was significant resistance at the end of the 1/2 turn. Once you start the 1/4 back out, there is some more resistance, then a ?release.? I could tell immediately that the release was the cutting of little chips from the material.

It was like I heard angels. This is what tapping is supposed to feel like.

(The old one was just steady increase in resistance in, then decreasing resistance out.)

Just one more reason why I should have bought the $80 tap and die set, instead of the $8 tap and die set.

Lesson learned.

From the following picture, you should be able to tell that the thread cutters on the left are nice and sharp, and the apex of each blade comes to a point. The one on the right is not sharp, and the apex is kind of rounded.

http://n999za.files.wordpress.com/20...-003-large.jpg

So now, I have about 1″ of slightly loose threads, and 1/2″ of perfect (remember the angels?) threads. I am okay with at least four threads perfectly engaged, and 16 threads mostly engaged. If my airplane blows away, you all get to say "I told you so."

Hope this additional information helps someone.
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  #23  
Old 07-15-2011, 12:02 PM
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Lemmingman Lemmingman is offline
 
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I can confirm this about the Harbor Freight tap/die kit. I was trying to make some threaded rod using the kit I got there and simply could not get it to work. It just wouldn't bite into the metal. It made a very nice single ring. I took the rod stock to a friends house and he made my threads in no time at all with his 15-year old craftsman kit.

Seems you get what you pay for in tap/die kits. Lesson learned for me, too.
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  #24  
Old 07-15-2011, 03:44 PM
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Flyfalcons Flyfalcons is offline
 
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Chinese threads are like that; we get odd threading when using Chinese hardware (nuts/bolts) in the RC world.
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  #25  
Old 07-15-2011, 10:27 PM
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Default Buy American Taps!

It's hard to make SAE threads on metric machines. They never convert over just right. Thats why China threads are just a tad off. Just find a local Ace hardware and get some Irwin Taps. I bought a Harbor Freight Tap set for some non airplane related stuff. What a waste of money. The tap handle was junk.
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  #26  
Old 07-16-2011, 08:20 AM
Lux Wrangler Lux Wrangler is offline
 
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Quote:
It's hard to make SAE threads on metric machines. They never convert over just right. Thats why China threads are just a tad off. - Wingtime -
Huh? I don't believe anyone is making SAE threads using "close" metric pitches. SAE taps made on metric machines can and should be exact.
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  #27  
Old 07-16-2011, 12:25 PM
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You'd think so but it doesn't happen.
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  #28  
Old 07-16-2011, 02:16 PM
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Default The problem with "cheap" taps is not thread pitch!

It's burrs! Look at the cutting threads on a cheap tap. You will likely see large burrs. These burrs cut the threads too deeply.
Taps are one of the many places you shouldn't cut corners on price. You get what you pay for.
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