This is a basic question, but I am having trouble getting the crown gasket on the screw-down crown of a Seiko H357-5200. The gasket opening is very small, and I was able to get the gasket around the stem and all the way down to the beginning of the crown tube. But, using two pairs of tweezers to try to open the gasket enough to slip on the crown tube, I only succeeded in breaking the gasket. I was using the correct gasket for this caliber. Can I use a larger diameter gasket safely? The gaskets are a bit expensive, so I was wondering what technique to use to put this type on. I did not see how to take the stem out of the crown, either. Thanks,
Pete

Peter,

I've done this two ways. The first way is like yours, but once I got the gasket to the crown I used a dental pick and slipped it under the gasket and carefully lifted (not too far!). Then I took another pick on the opposite side and did the same thing and worked it over the crown post. The crown/stem is in a pin vice and then clamped in a bench vice to do this operation. This was very tedious.

The other way is to find a tube (brass, plastic, whatever works) that will just fit over the stem and up against the crown post. Get the gasket onto the tube. Slide the tube over the stem and roll the gasket onto the crown post. It helps to have the gasket lubed beforehand.

The real trick is finding a suitable tube. Sometimes empty, plastic ink pen tubes will work but you may have to turn it down a bit.

I found that you can stretch a gasket like this without harm as long as it is done evenly and not to far. The other way I mentioned above has the disadvantage of stretching it in one direction(actually two directions) and it will often break the gasket.

It still takes a little practice not to break them though. Make sure to lube the gasket before doing any of this. Dry ones break easier.

As far as using a larger gasket... who knows, it might work. I tend to stick with what the manufacturer recommends.

Tim,
Thanks very much for your help. I will follow your instructions and try again.
Pete