Shaft packing

I ended up using the same shim that was previously there. It was the only way to get the shaft placed in the log in the best location. I temporarily installed the coupling about 3/4" onto the shaft, placed some wood shims in the log to hold the shaft in place, and did the initial engine alignment. I then bedded the strut in 4200 using the coupling as the forward locator. Tomorrow I'll add the safety collar, gland and nut, install the coupling, and then fine tune the alignment by moving the engine.

I'll also need to install the cutlass bearings as all of the alignment was done using 1/8" drill bits at both ends of the strut. The drill bits fit perfectly between the shaft and the strut and eliminated any movement during the alignment process.

I guess I'll find out tomorrow if my theory proves correct. At least I used 4200 instead of 5200, so I can take it a part if needed.

It's interference fit. I just tapped it on until it was snug.

TRBenj wrote: Being able to start it 3/4" without any heat seems a bit excessive... I'd check with the experts to make sure your interference fit isn't mucked up.

I agree that's you shouldn't be able to get the coupling on by tapping no matter how far it goes on.

Don,
How was the coupling removed and did you get some decent measurements of the shaft and the coupling bore? With only 3/4" on the shaft and what sounds to be a poor fit, there's a good chance the coupling face is not true to the shaft.

I've never seen a good fit that loose. Even a known fretted fit (junk) was hard to fit together after the fact. No heat? Ha! Better measure the shaft, it might be undersized.

Spacing between log and gland isn't critical. They don't usually touch but probably no harm in getting them pretty close.

Ok. I'm at the lake and didn't bring my calipers, but drove to the parts store and borrowed a set of dial calipers. The shaft is .001 undersized, consistantly across the mating surface. The Coupling is 1" exact again consistant across both ends of the opening.

I'm going to take it. The "machinist" who fit it has a lot of experience with inboards from our size up to "ship" size. He knew what I had when I brought it in, and I trust his work.

What I wrote earlier is that the coupler appears to be un disturbed from the factory at 1" exactly. The shaft is .001 undersized. Given that I'm .001 away from the recommended clearance, I'm going to try it and check it later when I get home.

My earlier statement that I had the coupler tested on the shaft by 3/4" is BS. It was 1/4-3/8" at best. I guess I didn't get a good look at it when I was lining up the shaft. My apologies.

I tried twice to install it, and didn't succeed either time. 1st time the coupler was 400•, and wouldn't slide on all the way. 2nd try I got it to 500• and it slid on about 1-1/4" like butter, but then stopped. After further inspection, I think the keyway wasnt clear, and the key was getting in the way. I'll try again tomorrow now that the key fits properly.

There's not a lot of room to work, what with the log and the safety collar, trying to get everything lined up, and not having much time to work. Once the heat is transferred to the shaft, the coupler stops moving, and then it's time to start over. I can't imagine what .005 of interference is like to deal with.

From Buck-Algonquin, the manufacturer of the coupler.

      Please see the attached drawing for our 50MC004 couplings. In regards to fit of our couplings, on the most technical level, the correct term is a Locational Transition fit. The terminology we use is a “light press” fit. An interference fit is not ideal for this application. For proper installation, our couplers should be fit and faced to the propeller shaft. The fit & face process involves either machining the shaft to match the coupling bore or honing the coupling bore to match the prop shaft. Regardless of what method is used, the maximum difference in tolerance is .002, since this is also the amount of acceptable runout on the coupling face and pilot. Our couplers are bored +0.001” – 0.000” as per SAE specification J756. Propeller shafting is typically machined with a tolerance of +0.002” -0.001”. When properly matched, the bore of the coupling should be the same as the shaft diameter. Please let me know if you need further assistance.

Propeller shafting is typically machined with a tolerance of +0.002” -0.001”.

I'm glad I trust him too.

I can see where some of this confusion has stemmed from my reading things wrong. Like misreading .005 for .0005.   Being 1 thousand off when the difference is between 0- .005 is not a big deal. Being 1 thousand off when the difference is between 0-.0005 is a big deal. Except when it's within the tolerances given by the manufacturer, as noted above. I wouldn't be surprised if he had to resurface the face of the shaft to .001 under to get a good mating surface for the coupler. I also led the conversation awry when I first said that the coupler went on 3/4".

What I don't appreciate is the continual bashing of the person and shop I chose to do the work, who I trust. Continually saying things that aren't beneficial to the conversation. Pete's continual reference to "Im sure glad you trust him" and                     "machinist", and "he should check his manual, if he has one, and something else about not knowing ANSI standards.

I appreciate the help of people here who make positive suggestions even if they are counter productive to the work I'm doing. I am new to this particular work, but I'm not stupid.

AlfaDon wrote: Propeller shafting is typically machined with a tolerance of +0.002” -0.001”. Being 1 thousand off when the difference is between 0- .005 is not a big deal. Being 1 thousand off when the difference is between 0-.0005 is a big deal. Except when it's within the tolerances given by the manufacturer, as noted above.

Don,
You are misreading. Please note the above is the shaft diameter tolerance and not the fit. You are confusing the two. As buck mentioned, and you quoted, the coupling is bored to match the shaft.

AlfaDon wrote: From Buck-Algonquin, the manufacturer of the coupler. When properly matched, the bore of the coupling should be the same as the shaft diameter. .

[/QUOTE]

SNobsessed wrote: I wonder if the coupler could be pull tested after it is installed.    Perhaps using the spacer/ long bolts & monitoring torque.   Might take some math to figure out the minimum torque acceptable. Give it a shot Pete!

Chris,
All the testing has already been done and published. If the tolerances are followed the interference fit will be a good one. It's the reason I referenced the Machinist Handbook.

Again from the manufacturers literature.

Our couplers are bored +0.001” – 0.000” as per SAE specification J756. Propeller shafting is typically machined with a tolerance of +0.002” -0.001”.

SAE J756
"6.5.5.1 Transmission Coupling End - The coupling end of the propeller shaft and/or the coupling shall be sized to a diameter that permits a maximum clearance of .001 in. (.025 mm). See Table IV and SAE Standard J756, Marine Propeller Shaft Couplings, Tables 4 and 5."