Prop/Coupling bolts...

[H3LlIoN]

Who's got the specs on the bolts? Can't find the originals, looking to replace. Graded bolts okay to use? Thanks,

- JM

[hanleyclifford]

3/8" - 24 (NF) x 1 1/4" long should do it.

[ndutton]

Well done Hanley. There are few people who know how to properly name a machine screw these days. It's such a rarity that those who do stand out from the crowd.

[H3LlIoN]

Excellent, thank you!

[sastanley]

H3 - I used stainless in mine...not sure exactly what the materials are (i.e. different metals down there and all) - I did notice a small bit of corrosion around the coupler from the stainless seizing wire when I disassembled mine, so there was some reaction going on there.

[ILikeRust]

I bought Grade 8 bolts from Lowe's for mine.

[H3LlIoN]

I bought Grade 8 bolts.

That's the plan.

[67c&ccorv]

Well done Hanley. There are few people who know how to properly name a machine screw these days. It's such a rarity that those who do stand out from the crowd.

3/8" - 24 (UNF) x 1 1/4" long should do it.


There, fixed it for ya...:p

[ndutton]

Not to pick nits but UNF and 24 tpi for a 3/8" machine screw are redundant. We never used the terms coarse or fine to describe thread pitch.

[H3LlIoN]

You guys wanna translate all that for the laymen?

[ndutton]

The reference 67 made was for fine threads or coarse threads. UNF = Unified National Fine [thread], UNC = Unified National Coarse.

I'm sure there are several websites that describe it better but here's a remedial version:
The machine screw (commonly and inaccurately referred to as 'bolt') Hanley mentioned was 3/8"-24 x 1 1/4" HHMS.

3/8" = diameter of the machine screw or the hole it fits in.

-24 = the number of threads per inch (tpi, also known as thread pitch), fine threads in this case. Coarse threads for a 3/8" machine screw would be 16 tpi. Different diameter machine screws have their own common threads. 1/4- 20 is the coarse thread for 1/4" machine screws, 1/4 - 28 is fine thread.

x 1 1/4" = the length of the machine screw from the gripping part of the head to the threaded end.

HHMS = Hex Head Machine Screw.

There's a wide variety of head shapes:
Flat head = FH
Oval head = OH
Pan head = PH
Round head = RH
and so on ad infinitum.

A recent project on my boat had me replacing the lower chainplate bolts. I picked up 3/8-16 x 1 3/4" RHMS in 18-8 SS (18-8 is the common alloy of stainless fasteners, SS = stainless steel). That designation told the supplier exactly what I needed in size, thread pitch, length, head style and material.

A note on grading, steel machine screws can be had in a variety of strengths. This next statement may be inaccurate but as I remember, grade 3 is your garden variety common steel, grade 8 is serious strength. On the heads of graded hex head machine screws there are raised lines, the number and position of which identify its grade.

How'd we do?

[H3LlIoN]

The reference 67 made was for fine threads or coarse threads. UNF = Unified National Fine [thread], UNC = Unified National Coarse.

I'm sure there are several websites that describe it better but here's a remedial version:
The machine screw (commonly and inaccurately referred to as 'bolt') Hanley mentioned was 3/8"-24 x 1 1/4" HHMS.

3/8" = diameter of the machine screw or the hole it fits in.

-24 = the number of threads per inch (tpi, also known as thread pitch), fine threads in this case. Coarse threads for a 3/8" machine screw would be 16 tpi. Different diameter machine screws have their own common threads. 1/4- 20 is the coarse thread for 1/4" machine screws, 1/4 - 28 is fine thread.

x 1 1/4" = the length of the machine screw from the gripping part of the head to the threaded end.

HHMS = Hex Head Machine Screw.

There's a wide variety of head shapes:
Flat head = FH
Oval head = OH
Pan head = PH
Round head = RH
and so on ad infinitum.

A recent project on my boat had me replacing the lower chainplate bolts. I picked up 3/8-16 x 1 3/4" RHMS in 18-8 SS (18-8 is the common alloy of stainless fasteners, SS = stainless steel). That designation told the supplier exactly what I needed in size, thread pitch, length, head style and material.

A note on grading, steel machine screws can be had in a variety of strengths. This next statement may be inaccurate but as I remember, grade 3 is your garden variety common steel, grade 8 is serious strength. On the heads of graded hex head machine screws there are raised lines, the number and position of which identify its grade.

How'd we do?

So those are the bolts I need? :D



Just kidding...excellent translation. You're right about the graded lines, also the colors too....5's are blue, 8's are gold. I don't know about 3's....Any time I've ever needed a graded "machine screw," I was always told to get 5 or 8.

[67c&ccorv]

So those are the bolts I need? :D



Just kidding...excellent translation. You're right about the graded lines, also the colors too....5's are blue, 8's are gold. I don't know about 3's....Any time I've ever needed a graded "machine screw," I was always told to get 5 or 8.

Colour is nothing more than an indication of what what finish the manufacturer used on the bolts - gold would most likely be zinc plated - blue is probably an anodized finish of some sort - it's not a guide to the type or strength of the bolt or nut.

Just saying!

:)

[ILikeRust]

More than you ever would want to know about bolt/screw grading... (http://www.americanfastener.com/technical/grade_markings_steel.asp)

But for purposes of this discussion -

This is the head of a Grade 5 bolt:

http://www.americanfastener.com/images/techspec/n23a.gif

This is a Grade 8:

http://www.americanfastener.com/images/techspec/n23e.gif

I have found both at Lowe's - and both were a gold-ish color. But as has been said above, I've also seen Grade 8 bolts that are just a plain steel color.