The International Cessna^® 170 Association

Dear Fellow Members:

Does anyone know a source for the new prop bolts. I have C145-2 with the 8 bolt flange and a McCauley prop and my parts catalog says the part number is AN6H-45. The bolts are drilled in the head but not in the shank.

Aircraft Spruce has AN6H-45A, but their web site shows an AN6H-45A with both the head and shank drilled for $3.45 each and on the same page, they show a AN6H-45A with a picture of the head drilled only for $5.21 each. Can't figure out which is which as they have the same part number. Does anyone know what is going on?

Is there another source where ordering might be more clear?

Thanks,

Curt

CBogle wrote:Dear Fellow Members:

Does anyone know a source for the new prop bolts. I have C145-2 with the 8 bolt flange and a McCauley prop and my parts catalog says the part number is AN6H-45. The bolts are drilled in the head but not in the shank.

Aircraft Spruce has AN6H-45A, but their web site shows an AN6H-45A with both the head and shank drilled for $3.45 each and on the same page, they show a AN6H-45A with a picture of the head drilled only for $5.21 each. Can't figure out which is which as they have the same part number. Does anyone know what is going on?

Is there another source where ordering might be more clear?

Thanks,

Curt

I would go by the # not the picture. If you order an AN6H-45A thats is what you should get?

Tim:

I'll have to call Aircraft Spruce as they don't show a AN6H-45. They show two with an "A" suffix, but, one has the shank drilled, the other doesn't, and they are both the same part number on their web site.

Are prop bolts different from other bolts? In other words, will any AN6H-45 bolt that I find suffice, or, is there something special about prop bolts?

Thanks,

Curt

CBogle wrote:Tim:

I'll have to call Aircraft Spruce as they don't show a AN6H-45. They show two with an "A" suffix, but, one has the shank drilled, the other doesn't, and they are both the same part number on their web site.

Are prop bolts different from other bolts? In other words, will any AN6H-45 bolt that I find suffice, or, is there something special about prop bolts?

Thanks,

Curt

AN6H-45 is drilled head and drilled shank. AN6H-45A is drilled head and undrilled shank. The six is the diameter and the 45 is the length.

There use to be special prop bolts that had each flat on the head drilled from memory they where AN76 they are hard to find anymore. The spruce catalog should explain this. They are all the same strength.

Tim:

Thank you for the clarification. The old bolts that I just took out today only have one hole drilled in the head and I know that they are only about 10 years old, but, they have been on and off enough that I need to replace them.

The aircraft spruce web site also shows an AN6H-45 for $15.20 each. A very confusing web-site!

Thanks,

Curt

Call Spruce and quit guessing. Their parts person can go to the shelf and place their hands directly on the product and tell you what they've got.

Just a foot note:

I drove to Aircraft Spruce in Atlanta to get new prop bolts and fortunately, took one of my old bolts for comparison. Even though my 1948 Cessna Parts Catalog on page 96 calls for a AN6H-45, it turns out the the correct bolt is a AN6H-37A. The -45 bolt was too long. My plane has the original McCauley prop and the C145-2 flange hasn't chaned, so, I don't know if this is a mistake in the parts catalog, if bolt numbering has changed since 1948, or something else is going on.

Regards,

Curt

Hmmmm.
The B model calls for the same size bolt, a -45. the -37 would be an inch shorter as the - number is the length in 1/8" increments or 37/8".

And you are sure that your bolts are showing at least nearly through the back of the crank flange and the threads aren't bottoming out on the crank inserts when torqued.

Hmmmm.

Bruce:

I'm sure. When I thread the bolts though without the prop, the threads can go all the way through the nuts in the flange maybe about 1/8 inch. When the prop is installed, the threads still just come almost flush with the back of the nut, or, slightly stick out. Therefore, I'm sure that the end of the shaft of the bolts are not hitting the nut threads, and that the head of the bolt is torquing against the prop.

As best I could tell, the threads on the 45 bolt aren't much longer than the threads on the 37, but, yes, the 45 bolt is about an inch longer. Therefore, if I were to use the 45 bolt, it would run out of thread prior to the head pressing down against the prop. There is just no way the 45 bolt would work.

Curt

Do you guys know how to read those bolt sizes?

An AN bolt with a -45 length is four and five eighths inches long. (4 5/8")

An AN bolt with a -37 length is three and seven eighths long. (3 7/8")

They run up to seven eighths and then jump to the next ten.

For example the next size after a -37 is a -40 or four inches, the next after a -47 would be a -50 or five inches, etc.

A -37 is NOT 37 eighths! 37 eighths would be 4 5/8" which would be a
-45.

Maybe thats where the confusion comes between a -37 and a -45.

I found the same. The 45's were too long. Needed a washer or use original.

John

I just bought some from Genuine aircraft hardware, I walked into Spruce and was told that they don't carry those bolts and I was looking for the AN6-37 with a drilled head as that is what I removed from the airplane.http://www.gen-aircraft-hardware.com/

blueldr wrote:Do you guys know how to read those bolt sizes?

You are right BL. I did know this once but since I don't use it everyday I forgot. Then when I quickly looked it up on the web to refresh my memory either that bit of important detail wasn't there OR I missed it. Where is that plastic bolt gauge from Univair when you need the darn thing.

Now that I've been schooled in front of everyone I'll never forget. At least till the next time I want to measure a bolt.

If the proper propeller bolt size is a -37, my IPC is also wrong. It calls for a -45 too. The publication date of my IPC is 1956.

I have in mind there was a change in the AN bolt identification system many years ago. I seem to think that when I worked at Lockheed back before WWII, the bolt lengths were all in total eighths and did not use the ten-for-inches system. If that is truly the case, a current -37 would have been a -45.
Does anyone know if that is possible?

For a good many years after WWII, my time in aviation was spent flying and I was away from the nuts, bolts, and tools part of it. If they did have a change, I missed it. I do remember that when I got back into working with it, the ten-for -inches system seemed strange.

n3833v wrote:I found the same. The 45's were too long. Needed a washer or use original.

John

The IPC illustrates the use of a washer.

(It also indicates that -45 bolt is for use with a wood prop. Kinda makes one realize that some things are not cast in stone...eh?)