How to clean up threads on prop flange bosses and prop bolts

szicree · #1 10-18-2008, 07:39 PM

Is it possible to run a tap/die over the prop bolts and bosses to simply clean them up. I've got a couple that thread in easily with my fingers and a couple that are a bit stiff. I'm told that AN threads are rolled and use a slightly different thread profile so I wanted to check with the experts. Anybody know?

Mel · #2 10-18-2008, 07:46 PM

Do not under any circumstances run a die onto prop bolt threads.
Yea, they are rolled threads. Do not cut them please.

terrykohler · #3 10-18-2008, 08:01 PM

I know of no studs or bolts used on the airframe or engine which do not have rolled threads. This is not the issue. Mel is absolutely correct. Even if you know specifically the PD, major and minor diameters of both the fastener and the die, the possibility of introducing any stress point in the fastener should not be risked. Buy new bolts.
Terry

Geico266 · #4 10-18-2008, 08:24 PM

You can certainly run a tap through the prop bosses to clean them up. You can't roll internal threads. They can only be cut with a tap. In theory I agree with the "buy new prop bolts" side, but for me, I would carefully run a thread file over the few threads that are causing the hang up, if the tap thing doesn't work. You should be able to see what threads are suspect and dress them up alittle by hand. Typically its the starting threads and they are sticking out 3-4 threads past the end of the boss anyway.

JMHO.

Ted RV8 · #5 10-18-2008, 09:18 PM

Sorry Larry,

You are wrong. There are specific taps for rolled threads and specific tap drill sizes for rolled thread taps. Rolled taps form the thread, they do not cut.

Ted

szicree · #6 10-18-2008, 09:32 PM

Well, I've just spent some time with a magnifying glass looking at my bolts and bosses, and it's definitely the bosses, really just one. So what is involved in changing these things out? I'm sure it can only be done with some ridiculously high priced tool made of unicorn hooves, right?

az_gila · #7 10-18-2008, 11:23 PM

Quote:

Originally Posted by szicree

Well, I've just spent some time with a magnifying glass looking at my bolts and bosses, and it's definitely the bosses, really just one. So what is involved in changing these things out? I'm sure it can only be done with some ridiculously high priced tool made of unicorn hooves, right?

....to do with a 6 inch C-clamp and some correct sized spacers. You don't need the high priced Lycoming tool (which is ST-115, if you must...

...)

They push out (and squeeze in) quite easily as long as you apply the force evenly and square to the prop flange.

Replacement ones (used = cheaper) can be obtained easily from your local engine overhaul shop. Every time they scrap a crankshaft, they end up with six used prop bushings....

I changed two on my Tiger (longer ones per a prop STC option) and was surprised how easy it was. My spacers were a stack of some sort of special thick Bonanza wheel washers. Bonanza parts are easy to find at our airpark....

The part numbers you need are detailed here...

http://www.lycoming.textron.com/supp...fs/SI1098G.pdf

If your existing part is oversize, it will have a "Pxx" number etched on the back of it. None of mine were.

Geico266 · #8 10-19-2008, 02:16 AM

Quote:

Originally Posted by Ted RV8

Sorry Larry,

You are wrong. There are specific taps for rolled threads and specific tap drill sizes for rolled thread taps. Rolled taps form the thread, they do not cut.

Ted

Well then, learn something new every day.

The sizes of the threads are still the same (IE; 1/2-13NC) and can be "cleaned up" by using a cutting tap to clean the threads out.

Mel · #9 10-19-2008, 07:16 AM

Quote:

Originally Posted by szicree

Well, I've just spent some time with a magnifying glass looking at my bolts and bosses, and it's definitely the bosses, really just one. So what is involved in changing these things out? I'm sure it can only be done with some ridiculously high priced tool made of unicorn hooves, right?

No problem. Just cut a piece of steel tubing that is slightly larger diameter than the boss. Put a large washer on both ends with a bolt running through. Nut on the other end. Tighten the bolt/nut so as to push the bushing out. Use the same method to insert the new bushing. This time the tubing will go on the forward side. Confused? 972-784-7544