Diameter of Mortise keys?

[Engineer]

I'm used to seeing gages in metalworking, but am puzzled by Mortise keys being available in gages like 4.5 and 5.5.

Can anyone tell me the diameter of these fractional sizes? Only I can find no referance to them in all the usual engineering literature.

I can't even find the diameters in my key supplies catalogue - I get either the diameters OR the gage, but no apparent way to cross-referance them...

Thanks very much for any help anyone can give!

[straightpick]

I assume you are talking about bit keys. The round tip of a bit key is called the post. Sometimes they give it as a gauge number, but the gauge they are refering to is a bit drill chart. This gives the bit size (gauge), size in inches and size in millimeters. Not sure how to post a scan so I can't show you the chart. For example:


Bit Size Inches Millimeters

1 .228 5.79
2 .221 5.61
3 .213 5.41

The dimensions are approximate. They go from #1, the largest to #44 the smallest

[Engineer]

Hi Straightpick!

I really appreciate you trying to help. I spent this afternoon looking through my book of drill tables as I had never considered them.

Yes, I did mean bitted keys, they are known as Mortice keys here.

The drill charts looked promising at first, but proved to be way off. I have an old "Mancuna Mortice Cabinet Key" guage and got out one of my digital calipers and did some measurements.

They definately correlate to SWG (Standard Wire Gauge), not AWG, ISO or drill. The only problem is that my Mancuna only gives gauges 1-12 and I was wondering if anyone knew the correct sizes for the fractional ones, like 3.5, 4.5, etc.

I ended up going through my stock of bitted keys with the caliper and even those results are confusing as they are a mixture of metric, Imperial and Gauge now of course, as the newer designs do seem to be metricating.

Thanks again for the help, that really came at me from left-field, as I'd never considered drill gauges!

[Jaakko]

A liitle offtopic, but this thread shows why it is just easy to refer to diameters with the exact diameter and not to use gauge measures.