Making conical holes for tapered pins in titanium rods

[Carlos Trigo]

Hello everyone

You may remember that, after getting advice from some of you, I decided to use tapered pins (instead of AN bolts) on the tailwheel gear leg (and probably in the main gear legs as well).

Making the initial cylindrical holes (3/16” and 1/4”) was not easy, but I managed, using new drill bits, some Boelube oil, and a lot of patience...

But now that I’m using the B&S reamers to get the holes conical for the tapered pins, I’m having a hard time.
I know that it is because of the hardness of the titanium spring rod, so I need advice from those of you with a machinist soul and/or experience to teach me the best technique.

Some questions:
- what kind of drill should I use?
(In some holes, I cannot use a drill press)

- at what speed (rpm) should the drill be used?

- should I make the hole in dry, or should I use drilling oil?

- how about heating of the reamer? Should I stop when it is too hot?

All reaming technique tips are welcome

Thanks
Carlos

[sonex892.]

Hi Carlos

I believe using taper pins in this application is great idea. I used a taper pin in my Sonerai tailwheel spring which did stop all the play, but that spring wasn't titanium. I'd be too scared of destroying my reamer and or titanium rod to attempt this myself.

If I was brave enough I would probably, use drill bits, to incrementally updrill in a few small steps to get near the target cone or taper before using the reamer.

"This old Tony" video has a bit of titanium machining where he explains some of the complications when working with titanium.
https://youtu.be/kMcTFslVTgA

Some questions:
- what kind of drill should I use?
(In some holes, I cannot use a drill press)

- at what speed (rpm) should the drill be used?

- should I make the hole in dry, or should I use drilling oil?

- how about heating of the reamer? Should I stop when it is too hot?

All reaming technique tips are welcome

Thanks
Carlos

I used an 18v cordless drill for all the holes purely because it had lower RPMs than my drill press, also used cobalt drill bits. From memory the pilot holes were more difficult to drill than the 1/4". Probably due my slow as possible being too fast and not being able to dissipate the heat in the blind hole.

Once underway the RPMs should be as slow as possible whilst pushing as hard as possible.

I would use cutting fluid.

DO NOT get it too hot it will destroy your tools.

Good luck
Sonex 892

[racaldwell]

Hi Carlos,

I reamed the tailwheel spring both ends for a taper pin before the assembly was bolted into the fuselage. That way I could do it in the drill press. I went slow with lots of cutting oil. I could get lots of pressure with a drill press but I can't remember how much leverage I actually applied. It cut pretty fast. I had to be careful not to overdo it.

I have not tackled the main gear because of the difficulty of doing that with a handheld drill. I'm sure I would need to get a new reamer if or when I tackle that one. The tailspring did leave it a little toasty. So for now the mains will have bolts in them.

Good luck.

Rick Caldwell
Xenos 0057

[Carlos Trigo]

Thank you for answers, despite being only 2 ...

I did manage to make the first one, in the upper end of the tailwheel, with a handheld drill, some cutting oil and (most important) lots of patience ...
I did a bit every day, during 4 of 5 days.

Next will be the 2 holes in the bottom end of the tailwheel spring.
By the way, Rick, you wrote

Hi Carlos,

I reamed the tailwheel spring both ends for a taper pin before the assembly was bolted into the fuselage. That way I could do it in the drill press.

.... snip ....

Good luck.

Rick Caldwell
Xenos 0057

When you did the 2 holes in the bottom end, after having done the upper one, how did you guarantee the perpendicularity between them?

Thanks
Carlos

[racaldwell]

Hi Carlos,

I didn't. I have one vertical pin on each end. I do not think two pins are necessary. Bolts, yes, but taper pins, no. I had one vertical pin on my One Design tailwheel attachment and once or twice over eight years I had to tighten it up. It had a 36 kg load static on the tailwheel and touched down at 80 kts indicated with a powerful elevator putting a lot of down force on it during roll out. I am sure that is much more load than a Xenos will ever see.

Rick Caldwell
Xenos 0057