Spanner Wrench for a Watch Case





Introduction: Spanner Wrench for a Watch Case

My watch has a screw- in back on the watch case. It is possible to order a universal spanner wrench for around $10 US. I wanted to make my own spanner wrench so I can replace the battery without needing to get to a store that can change it for me.

In the photo you can see the indents for the spanner wrench so it can unscrew the case back.

Step 1: Use a Mending Plate

I used a 1/2 x 2 inch mending plate. These are available in any hardware store. Any thin piece of steel would work, too. (The photo is from Google Images.)

Step 2: Mark the Area to Grind

I like to make markings for cutting or grinding steel on masking tape. The markings are easier to see. Cover the mending plate with masking tape. Mark the edges of the spanner wrench indents.

Step 3: Rough Grinding

Grind away most of the steel that will need to be removed, but do not go too close to the marks for the indent edges.

Step 4: File to Fit

Use a good file to remove the amount of steel required for a very precise fit on the back of the watch. Check your work frequently.

Step 5: The Wrench on the Watch Case

If all was done properly, your new spanner wrench fits the indents very neatly. Remove the tape. Grasp the spanner wrench between your thumb and first finger. If the case back is on very tightly, you may need to grasp the mending plate spanner wrench with a slip-joint plier. Hold the watch firmly with your other hand and twist in a counter-clockwise direction.

Step 6: The Back Is Off.

Here you see the back of the watch case removed. Replace the battery. Be sure to get all gaskets, etc. back in place. You may want to turn the back of the case counter-clockwise until you feel the threads fall in so you do not jamb the threads by cross threading.

Step 7: Easy to Carry

The last time I changed my watch battery I slipped my spanner wrench in to my wallet and changed the battery immediately after purchasing it at a store that does not change batteries for customers.

You can also see that I cut a second profile on the other edge for a watch with a different size back. Now my one wrench allows me to change the battery in a second watch I came to own.



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The one problem with changing your own battery is that the "O" ring seal may need to be replaced. If it does not seal properly, perspiration may get into the watch and create other problems. Having the battery replaced by a shop means you will have a functioning "O" ring. So, there is that to be considered, too.

Wow, although I already have the correct tool I am going to make one of these anyways. A fantastic idea

Here's a short video I made:

This worked!!! I used a thick board and heavy gauge finish nails. I flattened out the end of the nails with a hammer, and put the watch in a vise to keep it from moving. Just saved me a couple bucks! Thanks!

Very good. Thank you for sharing.

Good 'ible Phil.

A word of caution though:

Do not touch new battery contact points with your fingers. Handle battery with a cloth or paper towel. Your fingers are coated with natural body oil, which can cause a bad connection when installed. Really, this applies to all batteries in flashlights, toys, etc.

great idea, too bad I already bought the watch tool from harbor freight.

Maybe this is here on site, but.. A Vietnamese watch repairer outside the train station near my house did thousands of batteries on watches. For commuters in a hurry. His tool of choice? A metal vernier caliper measuring tool. A lot of people here will have one in their workshops! Multi adjustable of course.. Unless a watch was xxx tight he could unscrew and replace a battery in about 45 seconds! Always puffing air into back of case first to clear any dust. The good quaility eg Mitutoyo verniers with a screw lock are ideal You can lock them in place. Load on them is negligable in the scheme of things. He always sat his watches on a sandbag/ soft support. For xxx heavy watchbacks he had a real watch undoer as a backup. Seldom he used it! Like I say he did thousands.. Pic uploader not working for me... will try a pic send for you guys later!

Thank you for this brilliant tip.
Con Peters, Netherlands.