Threaded reamers and wing splice plates

[ChiefPilot]

As I'm at the point where I need to install the splice plates for the last time, I discovered that I have no way of reaming the bottom holes - the reamer and drill motor just don't fit. My tech counselor suggested a threaded reamer on an angle drill, and while I've found some I haven't found any undersize threaded reamers.

I have the avery 0.249 and 0.374 undersize reamers, but can only find 0.250 and 0.375 threaded reamers. Does the extra 0.001 make a difference in these holes, especially considering that it's a hand tool and not a mill or lathe?

 

[BrownTool]

Threaded Reamers @ Brown Tool

Brad,

Threaded reamers are used extensively in the aircraft manufacturing and repair world and we have a fairly comprehensive selection in our catalog which are in stock and ready to ship.

For an undersize 1/4" (.250), we have a .247 Threaded Reamer here:
http://www.browntool.com/Default.aspx?tabid=255&CategoryID=153&List=1&Level=a&ProductID=1053

And for an undersize 3/8" (.375), we have a .372 Threaded Reamer here:
http://www.browntool.com/Default.aspx?tabid=255&CategoryID=153&List=1&Level=a&ProductID=1070

If you want to see the complete selection of 52 different Threaded Reamers, you can see them here:
http://www.browntool.com/Default.aspx?tabid=255&List=1&CategoryID=153&Level=a

Our Threaded Reamers are "piloted" with a smaller diameter which allows you to drill a smaller pilot hole in your work and step your hole up to its final size with the reamer in one clean step.

In all we stock 52 different sizes of threaded reamers for all sorts of aircraft fastener applications. Our factory will also manufacture custom sizes for applications not covered by our standard in stock sizes.

Hope this helps.

Michael Brown
Brown Aviation Tool Supply Co.
www.browntool.com

 

[C-GRVT]

are you sure you want to ream?

I recall that Van's said that the holes and spar bolts were designed for zero clearance - I don't think that they recommend reaming these holes in the 6 spar or plates. What about freezing the bolts to ease the fit?
I would confirm with Van's before reaming any spar holes. If you do check with them, let us know what the answer is.
Bill Brooks
Ottawa, Canada
RV-6A finishing kit

 

[Rick6a]

As I'm at the point where I need to install the splice plates for the last time......

....What about freezing the bolts to ease the fit?
I would confirm with Van's before reaming any spar holes....Bill Brooks

Those are close tolerance holes and the tighter the fit the better. Question: Did you prime the steel splice plates? They should be primed and primer thickness alone can prevent insertion of the close tolerance bolts. Consider using solvent and a wire brush to clean the holes out. Bill's advice is quite sound. Those critical holes are already full size. It is best to contact Van's before you go to reaming anything and do keep the close tolerance bolts in the freezer right up until the moment of insertion.

 

[ChiefPilot]

Thanks for the replies!

Actually, the spars and splice plates came primed from Van's, and there indeed is primer through-and-through as near as I can tell. I read somewhere about wrapping a piece of cloth soaked in MEK around a wooden dowl chucked in an electric drill for removing primer inside holes; I'll give that a go and see how that works. On freezing the bolts; I have a line on some free dry ice to pack the bolts in (every little bit helps) and will definately give that a go.

On an only-semi-related topic, Rockwell did something similar on the B-1 bomber. The pin about which the wings swing forward and back was soaked in liquid nitrogen before being inserted. They were probably smart enough to not get primer in the hole first though.

 

[ChiefPilot]

As a follow up...

I got all the bolts in this weekend....wow, what an effort. I was able to get all of the primer out of the holes in the splice plates fairly easily; once the primer was out, an AN6 bolt mic'ed to 0.373 fit easily through the hole although the close tolerance bolts were a bit tight but doable (I didn't force them for fear of removing the plating).

The wing spars were another matter entirely. The mandrel-and-cloth-with-MEK did nothing; the mandrel-and-emery-paper remove some paint but a normal hardware store bolt mic'ed to 0.368 wouldn't even start to go in several of the holes. In the other holes, I got a drift pin made from a 0.371 AN6 bolt stuck to the point where I wasn't sure I'd be able to get it out again (but did after about an hour's worth of effort). None of the holes would accept my 0.371 drift pin much less the 0.373 AN6 bolt, and all had the primer removed.

After talked with my tech counselor last week about this issue, reviewing the RV list archives extensively and finding a number of folks who had to ream their spar in place, I got out the .374 reamer and carefully reamed the holes appropriately using a drill guide and a low profile cordless drill.

All came out well; even after reaming, the NAS close tolerence bolts needed to be tapped in (which is how it should be, from what I read). Not sure how much freezing them helped; when I mic'ed them, they were halfway between 0.374 and 0.375. Perhaps my plane will fall out of the sky because of this, perhaps not. In any event, I'm moving on.

 

[apkp777]

I don't think you want to "ream" the holes. Van's says to lube the bolts with LPS 3 or "motor oil". You also, may try a to use a "bullet" ( a bolt with the head cut off and rounded to avoid scarring the hole.)

 

[ChiefPilot]

I don't think you want to "ream" the holes. Van's says to lube the bolts with LPS 3 or "motor oil". You also, may try a to use a "bullet" ( a bolt with the head cut off and rounded to avoid scarring the hole.)

I had tried the lube & drift pins - my micrometer showed my pin to be 0.371 and that wouldn't go in the wing spar (but fit the splice plates quite easily) (and trying to tap it in got it stuck to the point it took almost an hour to get out - argh).

After looking at it, I couldn't think of any reasons to not ream the holes undersize to .374 as called out in the plans. The holes were smaller than that; my suspicion is that the factory (at least for my spars) didn't ream to final size per plans, or perhaps did so with a well-worn reamer. Either way, there was too much material left in the hole to tap anything in.

 

[apkp777]

Certainly possible the holes weren't reamed to final size at the factory. I would call Van's on this one. See what they say. I know that similar bolts on Boeing aircraft are EXTREMELY difficult to insert and to remove. In fact, I have had to drill through the center of similar bolt to relieve internal pressure just to be able to barely knock it out with a 6x rivet gun (jack hammer). You might store the bolts in your freezer overnight and see if they'll shrink a little. Probably won't, but maybe a few thousandths. The problem with reaming is the hole may "work" over time and become loose. On the other hand, it would probably take for ever for that to happen. I'd probably ream, but only after a consultation call to Van's. In the end, your wings WON'T fall off no matter what you do, unless of course you skip the bolt installation all together.

 

[GAHco]

What about this possibility.

Maybe you mis matched the splice plate placement, they all have to be in the right place and facing the right direction.

They are marked for identification with center punch marks and the instructions tell you the orientation. The are ALMOST able to fit if you have them mixed up.

 

[ChiefPilot]

Maybe you mis matched the splice plate placement, they all have to be in the right place and facing the right direction.

They are marked for identification with center punch marks and the instructions tell you the orientation. The are ALMOST able to fit if you have them mixed up.

Double checked that - outside of the aircraft they fit together perfectly. The hangup is the holes in the wing spar itself; the bolts would not fit there and those holes appeared to be undersized. The aft splice plates aligned perfectly with the F-604 bulkhead as well, so it's just the spars themselves which were the problem.