Metric Bolts

[Captain Smollett]

A recent automobile repair has got me to thinking: is it 'better' to have everything on the boat metric?

My wife's Saturn decided to give up its water pump about the time my kidney stone hit.  After dealing with the stone, I finally got to work on the car (which, by the way, means boat stuff, too, since I drive her car to the boat   :D ).  But alas, the three bolts that hold the sheave on the pump were totally siezed.

Much abuse with a 190 ft-lb impact driver would not budge the bolts, so I decided to simply grind of the heads to remove the pulley.  That DID work, but of course left me with trying to replace the bolts - on New Year Day at that.

While I drove around the greater Columbia, SC area attempting to locate both the replacement 6 x 1.25 mm bolts and a replacement 10mm socket (that impact driver took its toll), I got to wondering about "what if this were a boat project in a remote port??"

Would metric bolts be easier to locate in remote locales?  What say you guys that have BEEN to remote locales?

Would it be better if we 'converted' whatever imperial system bolts/nuts we have to metric, "just in case?"

CJ, you've said, "1/4-20 taps" but what of metric sizes?  If in New Zealand or the South Pacific, would that be an accessible tap/bolt size, or would it be better to think "world view" metric?

Just some winter land-bound ponderings, as I contemplate my spring haul-out and the next trip (that is, US SE Coastal trip)..

[Fortis]

Well, for a start, you won't be able to covnert EVERYTHING even if you wanted to and were demented enough to persue the goal with vigor.

We tried, it just can't be done.

In part the reason is that metric bolts come in a very limited selection of sizes. It is simply sometimes not possible to tap out an existing boilt hole in a casting so that it ends up with metric threads. You either end up with a hole slightly too large apart from the existing threads or you end up drilling away at too much of the casting (those lovely threaded tangs that stick out of engines for alternator attachment and similar). Even if all that could be overcome...you would nto in truth believe how many bolts you have in your boat *somewhere*.

I find that even here in the very metric australia, getting imperial threads in stainless is still much easier (even all four major flavours of imperial threads) then getting metric, especially in 316 instead of 304. You can, make not mistake....but it is easier to go imperial.

Alex.

[CharlieJ]

John, If I were heading out long term, I'd have those taps and dies aboard. And should something occur "out there" I couldn't handle, I'd deal with it then. I try hard to limit my usage to a few standard sizes so I don't need a full set of them.

All the bolts and nuts on our Yamaha are metric, but all the rest on the boat are SAE, and we carry a small stock of SAE bolts screws and nuts in varying sizes.. Not a lot, but some- like a peanut butter jar full. I can usually scrounge whatever I need from my supply aboard. Not always, but usually.

I also carry both metric and SAE sockets and wrenches aboard always. And add ones we find we need. For example, Laura found we didn't have a metric wrench ( we had the socket) to fit something on the engine. We'll buy one and put it aboard before the next trip

[AdriftAtSea]

I think it'd be almost impossible to swap all the fasteners on a boat over to either metric or imperial units.  There are just too many fasteners on a boat.  Part of the problem is that it depends on where the item was made, and in some cases what market it was made for.  I've seen two almost identical parts that were different only in that one had metric fasteners and the other imperial.

Alex's point about there being far more limited a size selection in metric fasteners is also a good one. I think some of the larger bolts I have on my boat would be very difficult to find in metric. 

I think you'd be better off carrying spare nuts and bolts, and the proper tools to fit them, rather than trying to convert the boat.

[Captain Smollett]

I find that even here in the very metric australia, getting imperial threads in stainless is still much easier (even all four major flavours of imperial threads) then getting metric, especially in 316 instead of 304. You can, make not mistake....but it is easier to go imperial.

Alex.

Thank-you, Alex.  You answered the question underlying my question: how AVAILABLE are imperial bolts outside the US? 

Really, I was not considering trying to convert the boat; I just wanted to know who had even thought of this potential problem.  "I broke this dern 8-32 bolt here in {$NON-US_COUNTRY_POSSIBLY_THIRD_WORLD), now what do I do?

Even with a can of spares, there's a CHANCE the one needed will be missing.  It's just something I thought about while spending my New Year's Day driving around trying to find three bolts for the wife's car.  Ace had exactly what I needed, but they were closed yesterday.

[CharlieJ]

You could have come to the ACE where Laura works. THEY were open yesterday. She was there from 0800 til 1900.

Long drive though ;D

They are ONLY closed on Christmas day.

[CapnK]

Well, for a start, you won't be able to covnert EVERYTHING even if you wanted to and were demented enough to persue the goal with vigor.

and:

We tried, it just can't be done.

Very revealing.  ;D :D ;D

[Fortis]

Yeah, I admit it. It was not on my boat, it was the jester project. The owner got all enthuisiastic about swapping out all the bolts as part of the upgrade (we knew we needed to do close to two hundred, anyway...)

On one factory built boat we had UNF threads for most rigging related stuff (chainplates, mast fittings etc), for hull-to-deck join we had a few hundred UNC system, MOST everything on the engine is sae, but the engine mounts and exhaust all use metric. Internal furntiure is mostly UNF, though a later owner seemed to be fond of metric too. Bolt that holds the rudderhead onto the shaft is UNC, bolt that allows the tiller to pivot up is Metric. Bolts holding down the headsail tracks were mostly UNC. The traveller is NOW metric, and was a mixture of stuff.

Winches...I cannot even remember. Deck hardware like cleats seemed to be a mix, sometimes the two bolts holding the one cleat not being the same.

Shifters and locking grips are your friend when disassembling a boat! Socket sets are effette idealistic devices that barely conect to the real world. They are fortunatly useful for putting things back together with new standardised bolts.

We figure that we have now replaced maybe 30-40% of the boltage on Jester, and it involved total strip out. The keelbolts....Still UNF.


Sasha