How to determine the proper shaft packing diameter

[Maine Sail]

This question gets asked a LOT here and I finally decided to post a very simple "how to" for determining the proper packing size for your boat.#1 Measure the ID of thread to thread of the stuffing nut with a set of calipers.The nut on my old box measured 1.38 inches and I know my shaft is 1". #2 Simply subtract the shaft diameter of 1" from the nuts ID of 1.38" as in:1.38" - 1" = .38" inches#3 Now divide this number (.38) by two as in : .38 divided by 2 = .19 inches.3/16 of an inch, in decimals, is .1875" or about as close to .19 as you're going to get!! So I know my packing is 3/16 not 1/4 because that would be .25"Simple huh...

 

[Don S/V ILLusion]

good suggestion

for those of us mere mortals who don't own a caliper but have a tape measure, simply measure the circumference (inside) the nut and that of the shaft if you don't already know it and convert these measurements to their respective diameters. Almost as precise if you measure carefully.

 

[Stu Jackson]

And even easier with a tape measure

is to measure the distance between the shaft and the gland and not have to divide by two. MS's and Don's descriptions work well if the material is disconnected. When it's still in the boat, just measure the clearance between the shaft and the nut.

 

[Don S/V ILLusion]

Stu

Even better - sometimes a straight line from A to B is the shortest route ;D

 

[Bill Roosa]

Ahhhhh why not measure the old one?

Seems I've been doing it the hard way. I just pulled out one of the old ones and went to WM to match it up. Then I laid the old one down and used it as a guide to cut the new one to length.Course I then wrote both numbers in the maintenance logbook so I can skip that step next time. course the next time I'll just use the rest of the packing I didn't us the first time.Guess I'm just dumb.

 

[Don S/V ILLusion]

measuring the old "stuff"

BillEvery time I've repacked, I never seem to get the old stuff out intact such that I could measure it. Maybe it's technique - I use a dental pick as the corkscrew tool sold for this purpose isn't small enough to fit.

 

[Fred Ficarra7897]

Have you guy's priced those calipers?

They're practically free. I bought one last year on Amazon.com for $13.00 along with a set of conventional outside mics. Using the 'standards' that came with the mics on the calipers, the reading is always perfect. How do they do that? Calipers aren't suppose to be accurate to .000 but they are. OK, I confess. I let my son use them at his house (200 miles away) and missed them. I bought a new, even nicer set last week. Spent $20. And these even came with instructions!

 

[Ross]

Just get some proper measuring tools. Measure the

inside circumference of a nut with a tape measure? You must be kidding.

 

[Don S/V ILLusion]

who;s kidding?

engineers don't kid...

 

[Maine Sail]

yeah...

Quote:"inside circumference of a nut with a tape measure? You must be kidding."Yeah I got a kick out of that one too.. #1 Measuring the old packing is not an accurate way to determine the size as it's compressed and distorted. I've measured 1/4" that measured out at 3/16".. I've know many folks who have installed the wrong pacing by doing this.#2 Good luck measuring the ID of that nut on the shaft with a tape measure!#3 Measuring the distance between the shaft and nut would be fine if you know it was EXACTLY centered on the shaft something it usually will not be once backed off the shaft log. A couple of tenths one way or antoher is the difference between 3/16 and 1/4 inch and that is not always visible to the naked eye when working in a bilge.#4 Calipers are CHEAP! That is a nice set of stainless ones and I think I paid less than a quart of Cetol for them.. If you own a boat a decent set of calipers should be a tool you own..The reason I posted this is because a guy over on SailNet just installed the wrong size and he's wondering what the mass of melted black goo is that has built up like a volcano so that it's now actually a mini mountain touching the stuffing nut..!!Just trying to help...

 

[Seattle Scott]

Stu, what is that picture thing

under your Kazoo? And that yellow tube thing is a total mystery!

 

[Bill Roosa]

Technique is everything

yea Don, I put myself through college being an auto mechanic so I got a lot of experience getting to things in tight places. I use a paperclip bent into an L shape at the very end. The tip is used to find the end of the packing then it is just a matter of getting behind the end and snaking it out.For the record I believe you will find that the weave on 1/4" and 3/8" packing is different and you clearly do not want a new packing that is smaller than the old one so if your old packing is exactly 1/4" you should buy the next larger size. But I do things the hard way.

 

[Ross]

If you can't gain access to the nut for measuring then you

can take the root diameter of the threads on the stuffing box, it will be the same.

 

[Stu Jackson]

Scott, the critical feature is the coffe mug

It says "Nagivator" and I keep drinking more and more until I figure out where I could possibly be, or not.

 

[Calif. Ted]

After seeing the picture of Stu's bucket in

the other thread about antifreeze I'm not surprised to see him using a golf scoreing pencil to navigate and resist buying a fancy pair of $20 calipers intead of a tape. He's got what looks like a metal bucket that's been coated with tar for waterproofing.I say we get him a NEW plastic bucket in thanks for all his help.