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Key Cutting

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Peter Cook 611/01/2021 15:50:33
462 forum posts
113 photos

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

Michael Gilligan11/01/2021 16:28:30
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23121 forum posts
1360 photos
Posted by Peter Cook 6 on 11/01/2021 15:50:33:

[…]

Thanks Michael, that makes sense. […]

.

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.

Georgineer11/01/2021 20:43:38
652 forum posts
33 photos
Posted by Michael Gilligan on 11/01/2021 12:36:40:
Posted by Georgineer on 11/01/2021 11:07:15:

I worked on Chubb 5-lever locks for a local, and very large, church in the 1980s. I still have my technical notes somewhere, but from recollection there were seven different levers available (I don't think they're actually called levers) and they differed by 0.015" from each other. I can dig the notes out if anybody thinks it would be helpful.

[…]Yes please, George yes

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.

chubb keys.jpg

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

Michael Gilligan11/01/2021 20:56:48
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23121 forum posts
1360 photos

Excellent, George

Many thanks yes

MichaelG.

Peter Cook 613/01/2021 18:56:39
462 forum posts
113 photos

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.

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