Looking for another mystery tool!

[preserved_killick]

I'm still working on getting my prop shaft fixed to the coupling, and need to drill an 8mm hole through a 7/8 inch diameter bronze shaft.

See:


Once free from the coupling, the shaft is free to move, and with me lying over the engine, head upside down this looks like it could be tough. I plan on bracing the shaft against the downward pressure of a drill so I don't torque the stuffing box & stern tube.

What I was thinking would help, is a tool I remember seeing that was just for drilling a hole in a cylinder. It was a clamp type thing that had a tube for a drill bit. It held the bit in center and perpendicular to the cylinder. Now, I can't remember where I've seen this or what it would be called. Google searches for "drilling holes in cylinder" doesn't help.

Anyone know what I'm talking about??

[Figment]

Why on earth do they want you to cross-drill the shaft? What's wrong with setscrews?

[catamount]

Something like this, maybe?

http://www.aircraftspruce.com/catalog/t ... llrite.php
Drill Rite Precision Drill Guide


But will it fit into that tight spot where your shaft is?

edit: looking at your diagram again, it almost looks like Vetus intends that you use the coupler itself as the drill guide for that pin!

[Oscar]

Why on earth do they want you to cross-drill the shaft? What's wrong with setscrews?

That's what the picture appears to suggest....although I agree with the premise of the question.

[preserved_killick]

I actually have a set screw in the coupling. Where you can see a hole in the coupling diagram, I have that and it is threaded with an allen head set screw inside. However, there's no corresponding hole in the shaft for the screw to sit in. The shaft has a long key slot that's a little mangled.

I did get the spanner wrench (see my other post) and tightened up the outer collar as best I could up to a point, but couldn't find a way to lock down the transmission flange.

I figure I've got two choices.

1. Find a way to drill out a hole for the set screw to sit in. I'm thinking that without something to keep the drill centered It'll be difficult to drill a clean, straight, perpendicular hole. I should be able to sink a second set screw in the same hole.

2. Use the set screw hole to guide a drill bit through the shaft and the other side of the coupling. I'd need to drill straight through the other side, or I'd have no way to remove the pin once assembled. Then..that's a heck of a pin. I was thinking of using 1/4 inch bronze rod I could cut to length. It would be 3.5 to 4 inches long.

I don't know why Vetus recommends a pin over a set screw. My guess is that a pin would be more secure ultimately.

Open to any suggestions, concerns, criticism, or better ideas.

[DaleH]

You could buy this self-centering drill jig from Northern Tool for $19 and cut off a 1-2" length as needed for this job. Then I'd tap drill the jig itself for the bit size you need, maybe even throw in a bushing, and would then strap the jig in place to the shaft with large hose clamps or even el-tape. They call it the Wel-Bilt Self-Centering Drill Press Jig.

Many, many, many years ago, before cordless drills were even on the market, my Dad fabricated such a jig (for a shaft application) out of laminated pieces of angle aluminum, into which he forced-fitted a hardened drill guide, ground on the shaft end to match the shaft OD. Same principle, just the Rube Goldberg method - haha! Believe me, it was a looooooooong process drilling that monel prop shaft by hand! But ol' Rube works well, albeit a tad slow ;) .

[Oscar]

it was a looooooooong process drilling that monel prop shaft by hand

Oh man......

Use the set screw hole to guide a drill bit through the shaft and the other side of the coupling.

I don't think that would work. The shaft is a lot harder than the coupling, and I bet you money the bit would start eating sideways and widen up the hole in the coupling. Plus it's waaaaayyyy overkill. (Even Zach wouldn't go THAT far......)

So there's a set screw hole with a thread in the coupling but no hole in the shaft. I would take a bolt that fits snug in the the hole and grind a point on it. If you have friend with a lathe you can get it perfectly centered. Then put it in the hole and whack it. Now you have the exact center of the hole. Then I would drill it very shallowly with successive sizes of drills starting small. Just deep enough to put a "v" in it. When you get to the drill size you need you should be centered. Buy a GOOD set of drills for this. (You can NEVER have too many GOOD drill bits.)


I would also consider grinding a point on the set screw and stopping when you have the right sized "v" to match the "v" in your shaft. It should settle and form in there. It doesn't need much.

Finally, make sure there's a hole in the head of the setscrew and safety wire it. Very important. They can work their way out. Locktite is not enough. Don't ask me how I know this.

If I'm way off base, someone will put me straight, but I think you need to not over engineer this.

[preserved_killick]

Finally got to talk with someone at Vetus today. They say drill and pin. They even have the pin, lucky for me the last one in the country!

The trouble I may have, is that my crude measuring (holding a tape measure to the shaft) tells me the shaft is 7/8 inch. Vetus says the coupling requires a 25 mm shaft. With a mis-matched shaft, the pin will quickly shear due to a stress riser where the pin enters the coupling. I'm hoping my measuring is wrong. One thing in my favor is that the coupling feels very snug on the shaft. I can barely turn it. Surely I would notice a nearly three millimeter gap..unless the shaft is bent.

Anyway, I've got the pin coming and I'll measure the shaft & coupling with a micrometer. If they are correct, I'll drill using the coupling as a guide. I'm hoping the bronze shaft won't be too bad. Not sure if I'll have shore power or not. I may give it a go with 4 charged batteries and a cordless drill.

[Oscar]

I'm hoping the bronze shaft won't be too bad.

Aaaah, here I was thinking it was hardened something......bronze, piece of cake, cut it like butter.

[Tim]

That has to be the most unnecessarily complicated coupling I have ever seen. My head hurts just thinking of having that on my boat.

[Oscar]

Agreed. To it's credit, it is also a rubberized limited universal joint, which should help with vibrations and small misalignments whether over time, or instantaneous after, say, whacking a log with the prop.

[preserved_killick]

Well, here's the follow up.

Went to the boat this weekend prepared, which took some running around. Vetus sold me what might be the only two pins in the country. I needed an 8mm drill bit. I never knew how difficult it was finding a metric drill bit, no hardware stores carry metric drill bits, nor do the big box stores. I ended up at a small machine shop, and they had one 8mm bit in a closet they were willing to sell me. Metric bits can be found on-line, but I was short on time.

I took it apart the coupling, figured out where the coupling needed to be mounted, braced the shaft with some wood and drilled the hole. The hole drilled easy. Getting the pin in was not. The pin is actually two parts, a split sleeve, and the solid pin that goes inside of that. I can't imagine getting this pin out without drilling and making a mess. And the pin had better last..it feels like some type of low carbon steel. Thinking back, I wish I had smeared some grease on both ends.

Putting it back together, I had a 26 inch length of steel with two holes drilled that I bolted to the coupler to keep it from turning when closing the lock ring. And, that damn lock ring. How does vetus expect anyone to get that much leverage on the ring once inside a boat? The ring has 4 notches in it. I figured I'm lucky in that I can hang upside down over the back of the engine and hold the spanner wrench (they don't stay put unless two hands are holding) while someone stands on an extension bar that protrudes through a cockpit locker. The trouble is, there's just four notches in the ring, so when you reset the wrench it ends up moving 90 degrees, and does not fit.

At this point, the pin is in and the locking collar is as tight as I can get it. I hope it lasts. I agree with Tim, this is too complicated and difficult to work on.

[Zach]

Oscar... Hehehe!

Good to hear you got it all fixed up.

For future reference, drill bits are sized wacky... as the hole for taps to cut threads are different from any standard... so take a caliper, micrometer, or dial indicator... and measure your pin.

8mm is .315... an O drill bit, is .316

Size chart: http://bobmay.astronomy.net/misc/drillchart.htm

The machine shop I worked in had one hanging on the wall, along with the tap sizes to go with it. One of those things that shooting for precision, you end up measuring the drill bits anyway... 2-3 thousandths is a slip fit if the pin measures dead nuts .315 it'd slide right into a .317 or .318 hole. Drilling by hand it'll wander enough to take up the slack. When we wanted an absolute press fit, where the hole was the same size as the pin we used a straight fluted reamer to square up the hole.

Anyway, next time you need a funky sized drill hopefully you won't have to look as hard. Fastenall and Fastener supply houses are generally the go to places for quality drill bits of weird sizes... they keep a lot of them... and the taps to go with them.

Going the opposite way, you can use drill bits as pin gauges to figure out what size a hole is... on those smaller than what you can fit a measuring tool inside... helps if they are new though!!

Zach

[Rachel]

Going the opposite way, you can use drill bits as pin gauges to figure out what size a hole is... on those smaller than what you can fit a measuring tool inside... helps if they are new though!!

Ooh, good tip! I'm going to remember that one for future reference - could come in handy.

Rachel

PS: Frankly I'm amazed you can type a coherent response at all on ...what is it ... Day 3,250 of The Great Grinder War of 2009?