Safety Razor Bolt/Top Cap Threading
Standard (10-32) vs. Metric (M5x0.8)
Some info about the differences between these two common thread sizes used in 3-piece DE razors (most of which I've gathered from various internet sources)...
There's a 5% difference in diameter and a 1% difference in thread pitch between the two.
Since M5x0.8 is a little larger, a handle threaded for it will often work with the smaller 10-32 bolt on a top cap.
However, there are cases where a maker will not follow exact tolerances, which may cause an improper fit. I have had cases where the 10-32 head feels too loose in a metric handle. I do not like to use that in shaving, because I feel there is too much pressure on too few threads.
You can use a metric tap (a machinist's tool) to enlarge #10-32 threads to make a handle likely to fit more heads.
- Muhle (older, but heads were plated, which enlarged the bolt some, it seems)
- Vintage Gillettes
M5 X 0.8
- Blackland Razors
- Charcoal Goods
- Maggard Razors
- Muhle (Modern)
- Vintage Gillette 3-pieces
M4.5 x 0.75
M5 X 0.9
- Gibbs (French)
- Gillette Travel Tech (some models)
Unknown So Far
- Feather AS-D2