How do keyways get into plugs?

[mh]

Hi there,

I'm new here, and I hope this is the right forum to place this question. I did search for the answer but was not successful so far.

My question:

Looking at the plug of a "normal" pin tumbler lock, I always wondered: How do lock manufacturers make the keyways?
For some thin keyways I can't think of any shape of a tool that cuts them.
Or do they use a casting process?

Anyone who knows how they do that?

Thanks,
mh

[keysman]

The method is called ' broaching',
Please don't quote me on this but I believe they draw a "negative" of the keyway through a piece of brass stock

maybe one of the machinists here can enlighen us a little more

[mh]

Thanks, I looked up 'broaching' and found e.g.
http://en.wikipedia.org/wiki/Broach_(metalwork)

But is that really the method used to make keyways?

And how exactly?

I guess that for simple keyways one could use a broach like a thin saw and just 'saw' back and forth from the top of the plug, just like you would do with a jigsaw. But it would take very long, and the tool (the broach) would probably wear off quickly.
Or do they mill a rough shape first?

Cheers,
Michael

[Shrub]

Well a casting process would be entirely possable but the numbers made and required do somewhat lend theirselves to broaching, the surface finish on casting would also not be acceptable.

In the instance of key ways i would suggest that a hot piece of rod is passed through various dies that each remove mor material with the end one being the final key form, if you look closely at a plug you will see the tooling marks are all lengthways and straight which supports this also there is a cut on the bottom of the plug which is where the tooling/die will be held to the machine.

The first die may remove a slot in the bottom, the second may remove the next sereis of bends and the next the full form with a final one being the finished sizes.

A die can be any thinckness imaginanable to get the strength, a die that is 2mm thick would just bend and cut nothing but one that is 2" thick would be little resistance to a rod of bras kept at near melting point.

The brass will be gradualy cooled as it gets worked and the process will work harden the material on the last few passes.

I am only summiseing as i have only seen how Dudley combo locks are made but the above seems the most cost effective way of doing things in my opinion unless ive not thought of somthing.

[Shrub]

Just to add the rods will be long not the length of a few together, off the top of my head unless it is reeled off drums i would guess they will be 6 metres long each.

The cuttings are also probable smelted down and reused for pins or somthing.

[mh]

Thanks,
*hot* broaching makes sense to me.
The references I found before that talked about chipping cold metal, and I thought that would be rather ineffective.

But passing *hot* material through dies makes perfect sense.

Thanks again,
mh

[Shrub]

Well im only guessing hot as cold would do just as well.

[raimundo]

think of something like a hacksaw blade, with profile of the keyway, and the teeth cut on at an angle, so that when the plug blank first meets it ,it is only high enough to cut the open slot at the bottom of the plug, but as the plug goes along its length, it becomes higher and cuts the first ward just because the shape of the saw is like the keyway. As the plug is passed along this saw, it gradually puts the keyway shape all the way to the center of the plug, then if you are wondering why such a saw dosent fill up with chip, think of it in segments with chip clearing holes between.

[Omikron]

think of something like a hacksaw blade, with profile of the keyway, and the teeth cut on at an angle, so that when the plug blank first meets it ,it is only high enough to cut the open slot at the bottom of the plug, but as the plug goes along its length, it becomes higher and cuts the first ward just because the shape of the saw is like the keyway. As the plug is passed along this saw, it gradually puts the keyway shape all the way to the center of the plug, then if you are wondering why such a saw dosent fill up with chip, think of it in segments with chip clearing holes between.

I'm still having a very difficult time understanding how this method would be able to cut tight wards. How thin is this "saw"?

[Einzee]

According to Encyclopedia Britannica, "The configuration, or shape, of the keyway is also almost unlimited. This shape is broached, or cut, into the lock cylinder plug and a corresponding shape milled into the blank brass stock that constitutes a key."

That exerpt was taken from the online version.
^^^^^^^^^^^
(wanted to mention that for copyright purposes)

[mh]

I also assume that the 'broach'/'saw' needs to be modular to some extent:
if you think of masterkeyed systems which rely on different shapes of the keyways, I guess it wouldn't be very economical to make new broaches for each keyway.

So there's still some mistery for me around this, and I would highly appreciate if someone who actually has seen the production process could solve that

Thanks,
mh

[mh]

I also assume that the 'broach'/'saw' needs to be modular to some extent:
if you think of masterkeyed systems which rely on different shapes of the keyways, I guess it wouldn't be very economical to make new broaches for each keyway.

So there's still some mistery for me around this, and I would highly appreciate if someone who actually has seen the production process could solve that

Thanks,
mh

[Shrub]

Well to be honest my posting is prety much the way its done to be hoest, yes there may be someone who has seen the process o here still but for now thats going to be the best youll get.

If a company churns out 30 locks a minute i dont thing the tooling cost for a set of dies on a differant keyway is going to be a majour issue, in the days of cnc almost any form can be made quickly and easily without even having to contract the work out.

There is no saw it is a piece of metal in the shape of the keyway, it will have an angle on the face on each side so it creates a cutting edge but as for teeth and such like no thats not what a die does, imagine those play clay (play doh, plastercine etc) kids things where you place some of the clay a plastic holder pull a lever and the stuff gets pshed through a star shape leaving you with a long sausage with the cross section of the said star now instead of having a mass of material behind the star 'die' imagine there was a series of dies the clay was pushed through maybe 10 and that the star was actually not a hole but a solid shape and the clay needs to be pushed around that shape to make a hole through the clay in the shape of a star so you have a tube with a star shape as the hole through the middle, you may start with a circle then the next mould would be a circle with cuts in which over the following few 'dies' turns the circle into a star shape with the last die or two being a rightly sized star shape the hole is required to be.

Now the only query is if the material is pushed through heated up (which isnt the thing wanted really as when it cools it will alter the shape) of whether the material is kept cool and is heated between dies due to being worked.

Image gradulary scrapeing away at a woodern desk lid with a knife that has a wiggly edge, you would start by marking the wood with the most outward points of the blade edge, the more you scraped in the same place the grooves would get bigger until eventually you would have a groove across the table in the form of the edge of the knife blade, if you soak the table in water first then of course it will scrape easier but once cut and then dryed out the wood will shrink and you would no longer have the right shape of grove to match the blade,

To get around this you can either not wet the table or wet the table then dry it to do the last scrape or you can wet the table and use a bigger knife so when it shrinks back once dry it shrinks to the correct size,

I the case of keyways i would image due to the toleranceing the material is cooled down at each pass and inbetween and the sections are cold formed with no shrinkage at the end of the process.

I hope this clears up any worries you may have, it would not be easy to create/cut a keyway at home and almost impossable to make a producion run.

[horsefeathers]

Its really quite simple. It involves three companies at work here.

One company makes a solid plug. One company makes the keyway 'hole'.
And a third company joins the two together with rivets....

I've had a long day. I will go and sit in the corner.....

regards

[Shrub]

Well yes the question should have been
'How do they get the brass around a keyway?'