Acrylic Crystal help

[easthammer]

I have a watch that I cant find the right acrylic for.

It has 30mm Diameter but I have tried an Inner Height of 3.7mm but it just causes friction. Can anyone point me into the right direction on what I need and where to find it? 

I have looked on cousins and the highest inside height i can find is 3.7.

[jdm]

Can you find by how much the pinion impinges on the crystal? What about a thin wire round on crystal base to raise it a bit, once you apply cement it should stay put and invisible.

[easthammer]

6 minutes ago, jdm said:

Can you find by how much the pinion impinges on the crystal? What about a thin wire round on crystal base to raise it a bit, once you apply cement it should stay put and invisible.

Very good idea but only issue is that the movement is removed from the front. I will look into this idea though, I only believe that there needs to be only a slight increase (preferably 0.3mm to start testing). 

 

also anywhere i can get a brass 30mm gasket? (If there is such a thing )

[jdm]

1 hour ago, easthammer said:

also anywhere i can get a brass 30mm gasket? (If there is such a thing )

https://www.aliexpress.com/item/32983330241.html

Probably not at the hardware store, craftsmen manufacture that sort of thing, which can be time consuming. That's why I suggested wire.
 

Edited May 3, 2020 by jdm

[AndyHull]

Probably not applicable to this particular use case, but I thought I'd post this here anyway.

A trick for making thin metal washers (superglue, acetone, some skill, and a drill press, or more preferably a lathe required).

Cut squares of sheet  metal of the desired thickness, and the size of the outside diameter (plus a little extra). 
Superglue the squares together to form a block of reasonable thickness. Clamp them, using a couple of squares of baking sheet  or plastic on the outside, while waiting for the superglue to set up. This will ensure a secure bond, so they don't simply fly apart during the subsequent operations. The baking sheet will ensure you don't glue them to the clamp.

The more washers you make, the thicker the block, and the easier it is to turn/finish. To make one washer, you may need to make 20, simply to make the process easier.

File the block roughly round, allowing some material to let you finish to your desired diameter.

You can of course file to some other shape, or add tabs or notches if you have a need for odd shaped washers.

If making circular washers, finish the roughly round stock down to the desire diameter in the lathe, or using the drill press (much more tricky).

Drill/cut out the centre to leave the washer, and finish the block by hand. If you need internal features, like a square centre hole, or internal notches, this is the time to add them.

 
Soak the finished ring of stacked washers in acetone to break the washer block down into individual washers. This may take some time, as the acetone needs to dissolve the cyanoacrylate (superglue), so patience is required. Pop the whole thing in a small jar, screw on the lid, and come back in the morning. Warming the acetone may help, but remember it is a major fire risk.

This is not an easy task to get right, and would be particularly tricky when making a washer where the inside and outside diameters are relatively close to each other. Making a 30mm OD and a 28.5mm ID would be a challenge. It is also tricky when the washers are relatively thin.

There is a reason why industrial manufacturers don't mess about like this, but instead stamp these out of sheet metal with steel stamping dies.

You can also etch washers from sheet metal (brass, copper etc), but that is a whole 'nuther story.

Edited May 3, 2020 by AndyHull

[CaptCalvin]

Why not try a teflon gasket? Or even a shim cut from transparency film(or multiple if more height required)? You can probably cut one out yourself and it would really be invisible.

Edited May 3, 2020 by CaptCalvin

[AndyHull]

4 minutes ago, CaptCalvin said:

Why not try a teflon gasket?

That is a good idea. Plastic sheet can be cut with a compass style circle cutter.

These are available in craft shops and on ebay. Cut out the inside diameter first.