- Joined
- Jun 2, 2003
- Messages
- 23,591
Some of you may have wondered about what this thread was. I have decided to chronicle the whole picture intensive project for your pleasure (or aggravation). I'm not on a schedule, so finishing this project may take a while, months, maybe even longer.
The Project:
Modernizing and making 100% functional an old military compass (No, it's not French, but the one in the picture was made for the French army. Mine was made for an English speaking market). Why? Well, because it's a fun project of course! Also, this type compass had a few features that set it apart from other, more typical compass designs. Unfortunately, the compass itself wasn't a fluid-filled compass, and as such the needle was not dampened. This made this compass comparatively slow and cumbersome. What to do? Fit a modern fluid-filled compass with a "global needle" in the old unique housing, what else?
My old compass is very similar to this model (not my picture):
Step 1: MAKING A NEW DIAL
This is the adjustable metal circle cutter ("General" brand, "Made in China") that I used. It's pretty well-built and doesn't seem to be cheaply made. It's at least sufficient for my needs. Both, the drill and cutting blade are replaceable. I removed the 1/4" drill bit and replaced it with a short length of steel tubing, because I did not want to use a drill press for this delicate job.
I took a 3"x1" piece of bass wood and drilled with my drill press a perpendicular 1/4" hole.
I drilled an 0.2" hole in a piece of 0.032" thin sheet aluminum. I used a precision drafting compass to scribe the two circles that would function as a guide when setting up the metal circle cutter. I scribed the circles on both sides of the sheet.
I used drill bits of increasing size in my drill press to widen the 0.02" hole to 1/4." I was worried the hole might not be sufficiently centric to the scribed circles, but it worked out just fine.
I tested the following procedure successfully during a trial run with a piece of 0.02" sheet styrene to make sure the tool was set properly and that it would cut the piece exactly right:
I placed the aluminum sheet on the piece of wood and inserted the steel tubing of the circle cutter. I clamped the metal to the wood. With the steel tubing (remember, there used to be a drill bit?) firmly inserted into the wood, I could now turn the cutter by hand, allowing me to use just enough pressure to gently cut the metal, following the scribed guide marks. The cutting blade was angled, so it was important to to rotate the blade depending on if I was cutting an inner or outer circle.
I needed about twenty trips around to cut about 1/3 of the thickness of the metal. I guess I spent two minutes on that. I did that with the inner and outer circle. Then I flipped the sheet metal and cut the inner and outer circle (Remember, I scribed the circles previously on both sides) in alternating steps until I could tell that the "donut" was about to pop out. That took me about 5 minutes, because I was working slowly.
For the close-up freaks:
The edge was pretty rough, but the size was where I wanted it: outer circle oversize and inner circle undersize by about 1/25 mm.
Not shown: I smoothened both sides of the donut on a flat diamond hone by hand to remove any rough edges. Next I taped the donut to a thicker aluminum sheet. I sanded the surface by hand and gave the donut a brushed finish. I removed the donut with dental floss, so I wouldn't bend it, from the aluminum sheet. I then sanded the outer carefully edge until totally smooth.
Here is the compass insert that has to fit into the hole of the donut. Let's call the donut a dial from now on.
As you can see, the compass has to fit tightly into the dial, because all that's preventing the compass from falling through the hole in the dial is that narrow edge formed pointed out by the red arrow.
It seems to fit tightly enough! I did have to widen the hole a little with sandpaper. I think I spent about 5 minutes with 400 grit sandpaper. I didn't care about the finish on the underside of the dial. It's ugly but it won't be visible.
The dial with the compass had to fit into this brass bezel. The dial is not completely done. I will cut a little window into it that will be filled with glow paint. This will make the pointer, which allows reading headings and bearings, stand out in the dark.
Money spent:
- one old compass: $35
- one new Swiss made compass with global needle (cannibalized!), $49 (heavily discounted)
- sheet styrene for mockup parts and testing, $2.99
- aluminum sheet, $4.99
- metal circle cutter, ~$20 with shipping
--------------------------------
~$112
The bezel with the compass will eventually be installed into the compass housing. Before I get to this, I will have to cast a spacer that allows mounting the compass in a secure but removable manner inside the bezel. I'll need another long weekend for that! After that, a bottom cover will have to be fashioned. I also will need to source, or fabricate, some very small metric brass set screws.
To be continued...
The Project:
Modernizing and making 100% functional an old military compass (No, it's not French, but the one in the picture was made for the French army. Mine was made for an English speaking market). Why? Well, because it's a fun project of course! Also, this type compass had a few features that set it apart from other, more typical compass designs. Unfortunately, the compass itself wasn't a fluid-filled compass, and as such the needle was not dampened. This made this compass comparatively slow and cumbersome. What to do? Fit a modern fluid-filled compass with a "global needle" in the old unique housing, what else?
My old compass is very similar to this model (not my picture):
Step 1: MAKING A NEW DIAL
This is the adjustable metal circle cutter ("General" brand, "Made in China") that I used. It's pretty well-built and doesn't seem to be cheaply made. It's at least sufficient for my needs. Both, the drill and cutting blade are replaceable. I removed the 1/4" drill bit and replaced it with a short length of steel tubing, because I did not want to use a drill press for this delicate job.
I took a 3"x1" piece of bass wood and drilled with my drill press a perpendicular 1/4" hole.
I drilled an 0.2" hole in a piece of 0.032" thin sheet aluminum. I used a precision drafting compass to scribe the two circles that would function as a guide when setting up the metal circle cutter. I scribed the circles on both sides of the sheet.
I used drill bits of increasing size in my drill press to widen the 0.02" hole to 1/4." I was worried the hole might not be sufficiently centric to the scribed circles, but it worked out just fine.
I tested the following procedure successfully during a trial run with a piece of 0.02" sheet styrene to make sure the tool was set properly and that it would cut the piece exactly right:
I placed the aluminum sheet on the piece of wood and inserted the steel tubing of the circle cutter. I clamped the metal to the wood. With the steel tubing (remember, there used to be a drill bit?) firmly inserted into the wood, I could now turn the cutter by hand, allowing me to use just enough pressure to gently cut the metal, following the scribed guide marks. The cutting blade was angled, so it was important to to rotate the blade depending on if I was cutting an inner or outer circle.
I needed about twenty trips around to cut about 1/3 of the thickness of the metal. I guess I spent two minutes on that. I did that with the inner and outer circle. Then I flipped the sheet metal and cut the inner and outer circle (Remember, I scribed the circles previously on both sides) in alternating steps until I could tell that the "donut" was about to pop out. That took me about 5 minutes, because I was working slowly.
For the close-up freaks:
The edge was pretty rough, but the size was where I wanted it: outer circle oversize and inner circle undersize by about 1/25 mm.
Not shown: I smoothened both sides of the donut on a flat diamond hone by hand to remove any rough edges. Next I taped the donut to a thicker aluminum sheet. I sanded the surface by hand and gave the donut a brushed finish. I removed the donut with dental floss, so I wouldn't bend it, from the aluminum sheet. I then sanded the outer carefully edge until totally smooth.
Here is the compass insert that has to fit into the hole of the donut. Let's call the donut a dial from now on.
As you can see, the compass has to fit tightly into the dial, because all that's preventing the compass from falling through the hole in the dial is that narrow edge formed pointed out by the red arrow.
It seems to fit tightly enough! I did have to widen the hole a little with sandpaper. I think I spent about 5 minutes with 400 grit sandpaper. I didn't care about the finish on the underside of the dial. It's ugly but it won't be visible.
The dial with the compass had to fit into this brass bezel. The dial is not completely done. I will cut a little window into it that will be filled with glow paint. This will make the pointer, which allows reading headings and bearings, stand out in the dark.
Money spent:
- one old compass: $35
- one new Swiss made compass with global needle (cannibalized!), $49 (heavily discounted)
- sheet styrene for mockup parts and testing, $2.99
- aluminum sheet, $4.99
- metal circle cutter, ~$20 with shipping
--------------------------------
~$112
The bezel with the compass will eventually be installed into the compass housing. Before I get to this, I will have to cast a spacer that allows mounting the compass in a secure but removable manner inside the bezel. I'll need another long weekend for that! After that, a bottom cover will have to be fashioned. I also will need to source, or fabricate, some very small metric brass set screws.
To be continued...