1977 M20J Spinner Bolts & "Fiber" Washers

[katzhome]

Hi All,

After my flight last weekend to Tracy for fuel, I found a missing spinner bolt and washer while putting the plane away.

The plane is due for an oil change anyway, so I'm going to have the shop replace the bolt.  I did inspect the hole and the nutplate is still there and the threads look clean.
My prop is a McCauley.  Looking at the M20J IPC (see below),

The missing fastener is item 10.

Item 10 is an MS51958-62 Phillips, Pan Head (I have found this one at Aircraft Spruce), and the washer is identified as 6515 (Washer, Fiber) or 3129 (Washer, Fiber (ALT)).

 

None of my spinner bolts look to have fiber washers underneath them, they all look to be a clear nylon.

Does anyone have the commercial part numbers for either the fiber or nylon washers that I can source for my shop?  So far my mooneyspace searches are turning up spinner replacement, motor mount replacement, and bulkhead failure threads.

 

Thanks for any info folks have!

Regards,

R.Katz

N43CA

[katzhome]

These appear to be the right size, but not sure if there are others folks have used:

 

https://www.aircraftspruce.com/catalog/pnpages/04-00218.php

[MikeOH]

Probably of no relevance as I have a Hartzell, but this is the FIBER washer I use:

 

[47U]

2 hours ago, katzhome said:

I found a missing spinner bolt and washer

Forgive this unasked for advice… ask the mechanic to check the free-running torque on the nutplate.  With a new screw, it may be ok.  Or, maybe all the screws should be replaced.  You certainly don’t want to over torque spinner screws, but they shouldn’t be falling out in flight, either.

[katzhome]

11 minutes ago, 47U said:

Forgive this unasked for advice… ask the mechanic to check the free-running torque on the nutplate.  With a new screw, it may be ok.  Or, maybe all the screws should be replaced.  You certainly don’t want to over torque spinner screws, but they shouldn’t be falling out in flight, either.

Yes, I was planning to ask for that, to make sure we don't have an issue with the nutplate or that the screw has binding issues.  I'm buying a pack of 25 for the screws and washers, so I would have the ability to swap out the entire set if needed.

 

Regards,

R.Katz

N43CA

[A64Pilot]

The self locking comes from the nut plate, not the screw. Forgive me, but self locking is a little overrated if you will, for instance most of our engines are put together without self locking fasteners for instance. Proper torque and not self locking is what as an example holds the wheels on our cars. 

My bet is someone just missed tightening that screw on installation, but if for some reason I were concerned about the nut plates having lost their self locking, which does happen from use, I’d put a drop of blue Loctite on the screws instead of replacing all the nut plates, because I’m lazy.

I think our aircraft predate Loctite or we would see it required on some locations. Just my opinion.

Edited September 9, 2024 by A64Pilot

[RoundTwo]

I assume most shops will use standard nylon washers due to cost. If over-torqued, they will “squish” out from under the screw head which will be visually apparent. Spruce sells fiber washers that are much more expensive, but they are more durable and are pretty much a one time purchase. 

[A64Pilot]

On Hartzell spinner screws I think they are “special” if memory serves take a look at one, the screw threads stop about 1/8” of an inch before the bottom of the screw’s head.

Regular screws the threads go all of the way to the screw head.

I think the Hartzell spinner screws are structural screws and not regular screws.

This is from memory and may be wrong, and I don’t know if McCauley screws are different than just regular panel screws or not.