Drilling Elevator Horns, Protecting Center Bearing

StuBob · #1 03-08-2016, 02:59 PM

The RV8 plans say to fabricate a bushing of 1/4" O.D., 3/32" I.D. to stick through the VA-146 center bearing on the horizontal stabilizer to protect it during drilling of the elevator horns. Use any old metal, they say.

OK, but I can't find any 1/4" O.D. tubing of any material that isn't already larger than 3/23" on the inside. If it were too small, I could drill it out. But the I.D.'s are too large already.

One option is a centering punch, available from Amazon. But that looks like multiple opportunities for error in such a fine-tolerance part.

So what about this bushing? What did you do?

Thanks in advance.

Larkrv10 · #2 03-08-2016, 03:10 PM

Stuart, I machined a bushing on my metal lathe, drilled it out and then finished the inside hole with a reamer. Know anyone with a lathe?
Rick
#40956
Southampton, Ont

StuBob · #3 03-08-2016, 03:18 PM

No one close enough to be helpful, I don't think. Making phone calls, though....

wirejock · #4 03-08-2016, 04:01 PM

Quote:

Originally Posted by StuBob

No one close enough to be helpful, I don't think. Making phone calls, though....

Call McMaster
They have bushings all sizes. I used the 1/4-3/32" bushing for mine.
Another approach is a stack of brass tubing. Buy three or four from small to 1/4" OD.
The small one takes a #41 bit. Cut sections short enough for the drill bit and stack them inside each other.
That's how I match drill big holes.

cajunwings · #5 03-08-2016, 06:12 PM

I bought a 30 piece set of Transfer Punches to have the right sized one for this job. It worked well, fit in the bearing snugly and made a nice little punch mark in exact center of the bolt hole. I keep finding other places where they come in handy and the price was not excessive.

Don Broussard

RV 9 Rebuild in Progress.

az_gila · #6 03-08-2016, 07:30 PM

Does it really have to have a 3/32 ID?

Use 1/4 tubing with a 0.032 or so wall and pick the correct number drill for a smooth fit.

Don't use the drill to make the hole, just give the trigger a short squeeze to make a nicely centered "dimple" in the horn.

Then complete the hole and ream to size on the workbench.

StuBob · #7 03-09-2016, 10:54 AM

Gil, I like that idea a lot. Same idea as a transfer punch.

Thanks.

JonJay · #8 03-09-2016, 11:04 AM

Split points, which is what most builder use, can wander in a punched or partially drilled hole. Ask me how I know.
Also, you want to insure the hole is aligned with the bushing/bearing longitudinally. Probably not critical for the relatively thin elevator horn, but good practice, especially for thicker parts.
I would follow Vans instructions but as Gil noted, you don't need the pilot hole to be exactly what is called out.
I use my lathes more for making drill guides than I do for most anything else.

BSwayze · #9 03-09-2016, 02:38 PM

I did what Larry suggested... get a bushing from McMaster-Carr and you're good to go. I visited an RV-8 project under construction last weekend, and his not-so-exact drilling on the elevator horns resulted in his elevators not being perfectly aligned with each other. He's not happy at all, but what can he do now? I'd take the time to get the right tool for the job.

I'd offer to send my bushing to you, but I did this a number of years ago and I don't know what happened to it. I'll bet if you post a WTB ad, you'll find any number of builders who have one to offer to you.

edit: I should add a note here. The bushing I bought from McMaster-Carr was exactly 250-thousandths in diameter, or 1/4". It wouldn't fit inside the bearing, even though my 1/4" AN bolts fit just fine. I don't have a lathe, so I ended up chucking it in my drill press, and used some emery paper to hone it down a bit at a time until it just fit snugly in the bearing. Just something to keep in mind.

az_gila · #10 03-09-2016, 02:42 PM

Quote:

Originally Posted by BSwayze

I did what Larry suggested... get a bushing from McMaster-Carr and you're good to go. I visited an RV-8 project under construction last weekend, and his not-so-exact drilling on the elevator horns resulted in his elevators not being perfectly aligned with each other. He's not happy at all, but what can he do now? I'd take the time to get the right tool for the job.

I'd offer to send my bushing to you, but I did this a number of years ago and I don't know what happened to it. I'll bet if you post a WTB ad, you'll find any number of builders who have one to offer to you.

Probably more important than the bushing/sleeve used is holding everything tight in the correct location when performing this task.