I have a nice oil-tanned leather strap that is too thick for the fixed spring-bars on my Lemania HS9. The maker suggested I get some sandpaper and thin out the rough side of the leather. Has anyone ever done this before? Is there some technique to it or do you just sand until it's thin enough?

 

I do believe the process is known as Skiving and there are tools for it. Me thinks the Skiving tool would produce a uniform and much cleaner reduction over the sandpaper.

 

You're right on that score, but a skiver takes off too much at once--they're designed for working with thicker leather, while this strap is already pretty thin. I need to take it from 3mm to about 1.5mm.

 

I would use a sanding block then, maybe the foam type with a finishing end - fine grit.

 

If I understand correctly, you have, for example, a 20mm lug-width strap, and need a 19mm one. Sanding with fine sandpaper will do. Put painter’s tape on the surrounding section that you don’t want to accidentally sand, and sand on a level surface with very very light pressure. Just take your time. When you have the fit right, lightly dampen the sanded area, and use some canvas or the inside cuff of your denim pants to very lightly rub the sanded area. You want friction, not pressure, or you can weaken the fibers. This step is called burnishing, and will lay the fibers down after the sanding, and give it a finished look. If the strap is made with vegetable tanned leather, this will work fabulously. If it is chrome tanned, it will work but much much less so. A high quality strap should be vegetable tanned, as chrome tanned can attack metal after a while, and cause skin reactions.

 

That's an excellent method for making a strap narrower, to be sure, and that's a more complicated process since you really want to make get an even line. In this case, we're trying to make it thinner though--it's a 3mm thick trap, but the space between the fixed spring bars and the case is only about 1.5mm. So I am trying to take some material off of the inside of the strap. The width is fine (20mm).

 

Ah, Got it. A photo would help, and @Duracuir1 can maybe advise. I think sanding with a light hand would work for what you describe, but photos first?

 

Curved spring bars? Or a thinner spring bar not from a bracelet?

 

Of course, and many thanks for the advice. It's a lovely strap, and I am trying to do my best not to ruin it in the process!

 

Looks like you'd have to sand down the top and bottom. Just sanding the bottom makes it seem you'd go right into the middle layer.

Personally, I wouldnt do it.

 

A skiving tool takes far, far less than 1.5mm. More like .2mm similar to a piece of thin cardboard.

 

I'd buy either a new strap for the watch, a new watch for the strap or maybe even both. Anything else seems like just too much hard work.

 

Tough. On a day to day basis, and only while making straps (not after they are finished) I use a hand held skiver (looks like a razor). I also use my belt sander with 120 grit, and if all else fails I have a monster machine (see pics). If your leather is oily though it does not always work well. It may be easier to try to pound it with a hammer. This may compress it enough to let you slide it through before it expands again. These fixed lug straps are next on my to do list. (For trial and error)!!!

 

Very helpful indeed. I've experimented on a spare (lower-grade) leather strap, and the sandpaper seems to be working. We'll see . . .

 

Alas, fixed spring bars are standard on these old HS9s. They can be a pain to deal with, but are an integral part of the piece!

 

It sounds like you've succeeded already, but how much are you trying to reduce the strap width by in mm? If its 1 or 2 mm I'd go with abrasive paper and gently rub the strap down a bit at a time holding it with two hands to keep it straight and taught. You might need someone to hold the paper flat and firm while you reduce the straps width.