Key Cutting

Thanks Richard - PM sent.

Thanks Michael, that makes sense. If I measure the four Chubb keys I have in my possession the majority of the cut depths are (after selecting a suitable base for zero) approximately integer multiples of 0.508 mm or 0.015". They are 4,5,6,8,9,10,12,13 & 14. There are a couple of anomalies (one cut is 0.5 and one 13.5) but close enough to suggest the steps you found.

Perhaps from Richards measurements and my worn keys I can establish the same sort of pattern.

Thanks again to all

.

I think someone other than me deserves that ‘Thanks’

... My contribution has been negligible.

... perhaps a Moderator would be so kind as to change the name for you

MichaelG.

Here you are, Michael. They were my working notes, not intended for others to understand, but I think they contain the information you want.

There were nine different detainers (not seven as I misremembered), each with a notch in the leading edge. They were called D1 to D9 by Chubb, so I was able to purchase them by that name. I didn't take any measurements off the detainers as they were mainly used as supplied. When I needed to add a notch for a master key, I laid the appropriate detainer on top, marked the new notch and filed it out.  The hole was probably designed as 7/32".

The key measurements were taken from new or known good ones. My comments about the lands may need explaining a bit. The key has nine lands for the five detainers - one in the middle and four outwards in each direction, so the key can operate the lock from either side. The average width of these is 0.063", which gives a nominal key width of 0.567". Where a land is cut deeper than its neighbours it needs to have a bit more width to prevent adjoining detainers from snagging , so the width I measured for the deepest lands was 0.069", the extra 6 thou being taken equally from its taller neighbours. Not easy to explain in words - I hope it's clear.

It was quite an installation - sixteen different locks, thirty-plus keyholders for the entrance door, and two levels of master key all to be maintained and kept track of. Fortunately I knew the locksmith well, and he trusted me to cut my own keys on his key-cutter!

George B.

Edited By Georgineer on 11/01/2021 20:46:35

Excellent, George

Many thanks

MichaelG.

Just an update, and thanks to everyone, especially Richard whose measurements were very helpful.

The key blanks arrived today, and after a bit of experimenting to work out how to hold the blank in the mill (two 2" toolmakers clamps held in the vice was the final solution), the keys were cut.

I left the first a bit (0.2mm) wide, not realising that that was as important as the cut depth, but a bit of judicious filing sorted that. The other two worked straight off the mill.

Thanks again for the help. Some of the posts were most enlightening.