Vertical Stabilizer Forward Spar

Jarrett · #1 05-13-2020, 06:18 PM

Just started working on my 14A empennage and I seem to of already made a mistake... I was match drilling the reinforcement plate to the forward spar and I got to the hole that was supposed to be match drilled to 1/4 inch. Through my reading I've read that for bigger holes it is best to use a unibit to avoid the metal catching and hole distortion. I ended up going too far resulting in the reinforcement plate being chamfered, and the hole on the spar being distorted. Starting to question my choice on using the unibit... Is there anyway to fix/adapt or should I order new parts?

Photos:
https://photos.app.goo.gl/GXVsUT1sHk1Wo5qb9
https://photos.app.goo.gl/qjZohtb7v9Mdw6iw6

Thanks
Jarrett

Allan Stern · #2 05-13-2020, 06:41 PM

If a 1/4 plate nut is attached on the otherside of that hole so a heim joint is screwed throuh it it should't be a problem. If you wanted to clean it up a bit you could use unibit to go one size larger. Call support at van's and double check.

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PaulvS · #3 05-13-2020, 06:43 PM

A normal good quality jobber drill bit should be fine for a 1/4 inch hole like that. Not sure if you are using a drill press? (recommend)
Unibits are not without their risks as it is easy to accidentally go oversize to the next step up especially in thicker material.
As for the hole in the pictures, I'm not familiar with the -14 but assume the hole is for a nut plate and if so I think it should be OK once deburred. If you want to clean up the hole itself then I suggest careful use of a 1/4 inch chainsaw file, you only want the hole smooth and not bigger.

Jarrett · #4 05-13-2020, 07:21 PM

Thanks for the help guys. I have a drill press and when I was drilling this hole I was not using it. Pretty sure once I went through the material it jump through and I drilled too far... I will definetly be using the drill press next time! I'll give a call to tech support tomorrow and see if I can go slightly bigger or I can touch up the hole. First time posting here so thanks for the support, really appreciated!

Jarrett

Jake14 · #5 05-13-2020, 08:34 PM

that looks like the mounting hole for the vert stab to the fuselage (see p 11-8 fig 1) and the bolt through that hole is held on with a castle nut to allow for movement between the spar and fuselage (the faying surfaces are lubed per step 1 on 11-8). It probably should be a snug fit, but see what Vans recommends.

Jetmart · #6 05-14-2020, 03:51 AM

When using a unibit I always put a piece of green masking tape around the entire bit on the top of the diameter I am drilling to. It is a great visual to know when to stop drilling.

JHartline · #7 05-14-2020, 06:11 AM

Might be able to just upsize it to an AN-5 and AN310-5. Calling Vans will answer that. As others have said, use unibits with care...they can cause things just like this very easily. I mark the next step with a Sharpie all the way around and drill (with a drill press) to the line.

Jarrett · #8 05-14-2020, 07:15 PM

Thanks for the tips, I will definitely be marking the steps on my unibit. Just got off the phone with Van's and they said the best thing to do would be to reorder the reinforcement plate as it's a very cheap part and the size needs to be 1/4 inch. Thanks!

JDA_BTR · #9 05-14-2020, 09:43 PM

I found that my drill press was too fast the first few times I used a Unibit. When I slowed it down <300 RPM the hole quality was excellent and I didn't end up running into the next step ever.

For 1/4" it is worth the investment to get a reamer from ACS or Cleaveland. Drill a hole slightly smaller than 1/4 the regular way, then let the reamer make a perfect hole. Has been very handy for me; I use #40 and #30 reamers all the time in finish drilling as they leave a lot less burr.

eliasj7 · #10 05-14-2020, 11:53 PM

Quote:

Originally Posted by JDA_BTR

I found that my drill press was too fast the first few times I used a Unibit. When I slowed it down <300 RPM the hole quality was excellent and I didn't end up running into the next step ever.

For 1/4" it is worth the investment to get a reamer from ACS or Cleaveland. Drill a hole slightly smaller than 1/4 the regular way, then let the reamer make a perfect hole. Has been very handy for me; I use #40 and #30 reamers all the time in finish drilling as they leave a lot less burr.

I purchased reamers also. Fair priced at Aircraft Tool Supply.