We go Metric — Boatworks

After consultations with Björn, my machinist friend, we came to conclusion that silver steel is not appropriate for making keel bolts.

Initially we’ve chosen this steel as it is one of few which comes in 3/4 inch diameter. However it is high carbon, tool steel, with carbon amount of 0.9%. Too much.

To use mild steel - low carbon steel with carbon amount less than 0.5% - we are limited to diameters 18 and 20mm. One could turn 20mm into 19 but with so long bolt it will be lots of work so instead I’ve decided to re-drill holes into 20mm.

Implications are:

floor timbers should be wide enough to accommodate thicker bolt and still have enough oak around to carry loads
drilling through iron ballast keel might be tricky

For the first point - I’ve already decided to make thicker floors. I make floor #3 now, the other two I will make either this winter or next autumn, depending on time left after other repairs pending.

The second point -if re-drilling iron would become too tedious - would be dodged by tempering last decimetre of the bolt to nominal 19mm diameter.

Having all that figured I rushed to boatyard for “drilling adventure”.

To my surprise it became really quick job! After all, it is only 500 micrometers on each side and Bosch D20mm metal drill handled that with no complaints.

So we go metric!