AM3 Key blank for impressioning question

[WolfSpring]

So I'm filing down my AM3 key blank to start an impression just to make the top smooth and I notice something I notice every time I smooth out my keys, two distinct marks that look like pin marks, but they are not. I just ordered calipers so when they arrive I'll measure to see if they happen to line up where the pins would, but these have a habbit of throwing me off and I can't keep smoothing out or the key will not be cut right, well it could be but still.


KeyBlankEditWeb by xpakratx, on Flickr

The key has not been put in the lock these marks appeared as i filed it down a little to get a smooth look. Anyone else come accros this?

[Raymond]

You can verify the spacing by comparing to another working key or to the cylinder itself. If, as you said, the key has not gone into the lock yet when the marks appear, then the most likely cause is directly related to your file or how you are filing.

I measured a factory key cut to '1' and found it to be .280". I measured a blank and found it to be .310". So in preparing the blank for impressioning you can obviously cut the blank down a full .025" and watch for a heavy dent if the cut is actually a '1'.

I have used a method of smoothing the blank where I file down to the near starting depth and then slide my file sideways. I move the impressioning file from side to side and and near the tang of the file where the edges are fresh. This only burnishes the blank and doesn't cut anything.

[WolfSpring]

I am using a flat file to prepare the key and the marks are showing up under the blade and no where near the edge, i have already got this key going into cuts so the next one I will do I iwll put the plug against it, don't know why my mind blanked on that idea, i do that when I get my first set of marks sometimes if I"m not sure.

[raimundo]

Have you tried any black marker on the edge?

there are some things including a very small deposit of luberication that can appear to be marks but can be wiped off with a piece of paper towel,

[WolfSpring]

I experiemented with sandpaper and that didn't even take it off but I did file one down a little ways, I'm not a knowledged person in this but it did appear to line up with the plug, is there any chance it is a manufactureing detail to assist in cutting a key, a weeker portion that will cut first to help guide a cutting wheel? I'll have to play around a little more, got plenty of blanks right now and all my locks have two keys. Will get back to you all on my findings, but I highly doubt this was done on purpose.

[raimundo]

The really blank, blanks, on which keyblanks are cut, are stamped out on punch presses so this top edge is just a cut/break edge
usually with a lot of fracture showing, the dies must be loose in tolerance to make this edge without many stria from the cutting, done to speed the process,

the keyway grooves on the sides are of course milled, and you can get an idea of the diameter of the tool bit by looking toward the bow of the key where the cutter stops cutting.
this is also an area that you can examine when comparing two keyblanks to see if they are the same, the difference are more obvious there than looking at it end on, when the difference is quite subtle.

Often one can get hold of some blanks that have the work of other locksmiths on them, these two marks may be index marks that for some reason were part of a project that was not completed, or excess from one that was.