Introduction: Top Cap for a Razor
This Instructable will show how I made a pretty decent top cap for my three piece Merkur 23C safety razor. The original top cap is still in new condition. But, I have been reading a lot about Zinkpest, or the crumbling rot of the zinc alloy used to make most razors once the chrome plating cracks or flakes and allows water to come into contact with the zinc alloy (zamac). The photo shows my Merkur 23C with the top cap I made from simple materials with relatively simple tools.
Rationale: The screw threads on the top cap seem to be the most vulnerable part of a zinc alloy razor. Muhle/Edwin Jagger 89 heads have excellent chrome plating, but there are frequent complaints that the screw on someone's 89 head rotted and broke off. The handle is stainless steel, but the baseplate is also zinc alloy. The baseplate could rot, especially if damaged by falling to a hard floor. But, it seems the top cap is most likely to fail. I wanted to see if I can make my own top cap.
- 1/8 x 1/2 inch steel bar
- 3/16 inch steel rod
- A 10-32 screw (or an M5 x 0.8 screw)
- T bevel (angle finder)
- Digital caliper
- Spring clamps
- MIG welder
- Center punch
- Screw tap
UPDATE: I have since developed a way to make a baseplate as well as this top cap, and it works very well. You could make an entire 3-piece razor you can customize for the degree of aggressiveness you prefer in a razor. See that Instructable here. It includes links to this Instructable and some other helpful things.
Step 1: Base Plate Blade Angle
The photo shows the baseplate from my razor wrapped in a towel and held in a vise so I can use a T bevel angle finder to get the angle on the two baseplate flats that push the blade into its proper angle. I determined the angle is very close to 152 degrees.
Step 2: Sacrificial Steel Plate
I used a piece of scrap steel for a welding form. I put the steel into a vise and used a hammer to bend it. I checked it regularly until the bend in it fit the T bevel angle finder.
Step 3: Weld Pieces of Steel Bar
I cut two pieces of 1/8 x 1/2 inch steel bar to the length of the baseplate's width. These two pieces welded together will be the main part of the top cap. See the drawing in the second image. The gray smudges represent the weld bead. Grind the weld bead sections flat for starting a hole with a drill.
Remove a little steel from each side of the welded assembly with a hacksaw. File to smooth the sawed edges and to narrow the assembly to match the original top cap. Try to keep the edges a uniform distance from the center seam very visible from the underside.
Step 4: Drill the Screw Stud Hole
The seam down the center makes locating the screw hole easier. I drilled a hole undersize on a drill press. I used a reamer to enlarge it slightly until a 10-32 tap would catch and thread the hole. Thread the hole.
Step 5: Locate and Drill the Other Two Holes
Properly locating and drilling the other two holes can be tricky. Everything must align and tolerances for error are very small. Put a screw in the threads and use the baseplate to mark the hole locations with a thin center punch. Drill a very small hole for each. Make it big enough to pass a miniature round file. Compare the location of the hole with the baseplate. Use the miniature file as necessary to "move" the center of the hole by filing more on one side of each hole. When ready, drill each hole out to 3/16 inch.
Round the end of a 3/16 inch rod with a bullet nose. Cut a short piece about 3/8 inch long. Push it into a hole in the top cap. Weld it in place from above. Do the same with the other hole. Test fit the top cap to the baseplate. File the outer circumference of the 3/16 inch rod pieces to make the top cap fit smoothly onto the baseplate while the screw is in place.
Step 6: Grind to Contour
Grind the top cap to the necessary contour. Be careful not to remove so much weld bead that the 3/16 inch rod pieces fall out.
Step 7: Ready to Shave
This photo shows that the blade alignment is pretty good on both sides. I did grind away a little too much on the lower right corner as seen in the photo. That does not seem to affect how it shaves.
Most razors are designed and constructed to tolerances measured in hundredths of a millimeter. Those that are machined rather than molded are done on very precise CNC machines. I used very crude tools by comparison, yet, this new top cap on my razor gives a good shave. There is excellent audio report so I can hear the razor sing when whiskers are yielding to the blade. I can feel a little more blade exposure than I feel with the original top cap, but I usually shim my Merkur 23C a bit to make it more aggressive, anyway. I now have a few months experience with wet shaving and am able to compensate for a few things to make the razor cut well. I just shaved growth from a day and a half with it and got a BBS shave ("baby's bottom smooth"), even if I did give some extra attention to trouble spots.
I did clean and coat the top cap with clear spray enamel to protect it from rust. I will watch when changing the blade for early signs of any rusting. I may try making a baseplate too. If that works, I will enjoy using a razor I made enough to stave of RAD ("razor acquirement disorder"--the temptation to buy yet another new razor) Steel may have a tendency to rust, but it does not rot like zamac and does not cost as much as an aluminum or stainless CNC razor.