Trim Adjustment Screw - B12-406

[anotherstevest]

Greetings All,

It's time for me to replace the trim adjustment lead-screw in my elevator trim tab mechanism. If anyone one has one or knows of anyone in business that still sells them (long shot) please get in touch with me. I'm assuming I'll do a drawing (I have access to one I can borrow to make measurements) and have one machined. If anyone already has a drawing please get in touch with me. If I end up having to make a drawing, I'll be sure to post it here so others can use it as well.

I'm sure others have already done drawings... It would be great to start with what's already been done so please speak up if you have one.

Thanks,

Steve Stearns
BC12D N43732
Boulder CO

[Hank Jarrett]

Re: Trim Adjustment Screw - B12-406

I talked to a machine shop locally that said they could make them, BUT they need the specifications for the thread profile. The threads in the male and female parts are NOT normal threads!! They are free running and they would have to make a cutter to make them. Not a big deal, but you can't reproduce the profile from a worn out part.
I have talked to several people lately about making new threaded screw parts. We need to get together and pool our resources.

Hank

[Robert Lees]

Re: Trim Adjustment Screw - B12-406

Hello Steve, and welcome to the Forum!

I made a couple of batches a few years ago. (Well I had them made). No cutters were made; they were done on a lathe.

http://vb.taylorcraft.org/showthread.php?6138-Elevator-trim-screw-making-new

Cost for a new batch would be a lot more than the £170 back then. It's not worth making less than 5. I might get the cost down a bit for 10.

Rob

[Hank Jarrett]

Re: Trim Adjustment Screw - B12-406

I think the male part was pretty easy to make on a lathe, it was the female threaded part that looked a bit harder to make.

Hank

[Robert Lees]

Re: Trim Adjustment Screw - B12-406

Indeed. Hence the (then) cost.

[anotherstevest]

Re: Trim Adjustment Screw - B12-406

I'm happy to be part of a group to have them made if such a group can be brought together within a month or so and the costs are reasonable. I think the vast majority of the wear will only be on the male-threaded part as I'm sure the brass will wear much faster than the steel so that's the only part I'm planning on making. And, as was just said, this is the less tricky part to make. Fortunately, I do have a not-worn-out part I can borrow to determine the measurements if I can't find prints (still hoping someone will either send me a print or, better, post one for all on the forum). And also, fortunately for me, I have machinist friends so doing one just for me is not unreasonable either.

Rob, I'm assuming that since it wasn't worth doing less than 5 the last time you had them made that they were being made by CNC since, otherwise, I don't see much setup related cost. In other words, for manual machining with this part there shouldn't be much, if any, of a low volume penalty. If you did have them done by CNC, it's possible the programs still exist and the costs for additional parts might still be reasonable. How come you decided to have both the brass and steel parts made and not just the brass one?

Steve Stearns
BC12D N43732
Boulder CO

[Guest]

Re: Trim Adjustment Screw - B12-406

Greetings All,

It's time for me to replace the trim adjustment lead-screw in my elevator trim tab mechanism. If anyone one has one or knows of anyone in business that still sells them (long shot) please get in touch with me. I'm assuming I'll do a drawing (I have access to one I can borrow to make measurements) and have one machined. If anyone already has a drawing please get in touch with me. If I end up having to make a drawing, I'll be sure to post it here so others can use it as well.

I'm sure others have already done drawings... It would be great to start with what's already been done so please speak up if you have one.

Thanks,

Steve Stearns
BC12D N43732
Boulder CO

I suspect that purchasing a used elevator may be an attractive alternative to making the trim actuator.

Dave

[anotherstevest]

Re: Trim Adjustment Screw - B12-406

I hadn't even thought of purchasing a used elevator but <sigh> I would hate to take a whole elevator out of circulation just to pull out one part... Not sure I could bring myself to do it...

Steve Stearns
BC12D N43732
Boulder CO

[Guest]

Re: Trim Adjustment Screw - B12-406

I was thinking of just replacing your elevator.

However when you figure out what the cost of making the parts is you may change your mind.

Another thought is to buy a busted up elevator. I did that and got it cheap just to get at the trim parts.

Dave

[astjp2]

Re: Trim Adjustment Screw - B12-406

if I ever get my lathe up and running, I could build them pretty easy. They are a fairly simple part. I would like to convert to ACME threads for my own airplane, they are stronger and hold better than a standard pitched NF thread. Tim

[Hank Jarrett]

Re: Trim Adjustment Screw - B12-406

I finally pulled an elevator out of the pile with a complete trim system and the threads don't look like NF or ACME. We REALLY need to get the drawing specified thread call out.

Hank

[astjp2]

Re: Trim Adjustment Screw - B12-406

diameter x pitch + machinist handbook will have your answer.

[Hank Jarrett]

Re: Trim Adjustment Screw - B12-406

The thread profile is the problem.

Hank

[astjp2]

Re: Trim Adjustment Screw - B12-406

That is why they make a cutter grinder

[Hank Jarrett]

Re: Trim Adjustment Screw - B12-406

Understand, but the machinist needs to know how to profile the grinder and a used thread may be worn and not give the right profile.

Hank