A bad lock picker never blames his tools

[DB_Cooper]

I have had no trouble with all the padlocks and locks that I own. Five or six pins presented no problems whatsoever. But I had made up a lock board and was having real difficulties with one I had re-pinned with three pins and the one with four pins.

That didn't make sense. Why was I having so many problems with the three and four pin locks. They would rake sometimes but would never open with spp and I couldn't work out why.

I read my literature again, this site and everything else I could find but still couldn't work it out. I then was browsing through another simpletons guide and the advantages and disadvantages of various picks and it struck me.

I have been using a small half diamond and a couple for rakes for everything (since I realised that all of the rest are just rubbish for regular pin tumblers) but I had not been using a hook as I have never been happy with any of the hooks that I had made.

You've already guessed what the problem was, haven't you? Reach. The small half diamond was not reaching the right places in my repinned cylinder. I had repinned them with short pins at the back of long (to make them harder) and the small half diamond just couldn't get there.

Sterling, the lock manufacturer, obviously do not pin their locks with the smallest behind the longest (there are only five pin sizes). This is why the OEM locks were not presenting a problem but I hadn't checked this when I took them apart.

Obviously I still haven't got feel sorted but I'm getting there.

Moral of the story, always check the obvious first.

Security pins next (I'll probably make my own with my existing pins).

Hello by the way.

[sandplum]

yep, I know what you mean

and... hi

[3-in-1]

By design, lock makers have what are called MAC's Maximum Adjacent Cuts. For example, you would not as rule see a no.1 pin behind or in front of a no.9 pin. There is the required fixed angle ramping between the key cuts that is necessary to push the pins up as the key enters and leaves the cylinder plug. This ramping can wipe out the seating area of a very short pin when it is next to a very long pin.. However, it is not so much how many pin depths there are, as it is the distance between the cut depths. In a lock with 9 depths, you may find that the MAC rule is a 7 depth difference, meaning 1-8, 8-1 and a 2-9, 9-2 pinning sequences are the maximum allowed. So when re-pinning a lock without knowing the MAC rule for that particular lock, setting it to a 1-9 or 9-1 sequence may be making it tougher than it would normally be from the factory.

[sandplum]

So when re-pinning a lock without knowing the MAC rule for that particular lock, setting it to a 1-9 or 9-1 sequence may be making it tougher than it would normally be from the factory.

3-in-1, do you ever come across cylinders in the field where the locksmiths have violated MACS? Especially in the last chamber? Knowing how to work with the added challenge is a useful skill.

[DB_Cooper]

Thanks for that 3-in-1. A very concise description of MACS. Since your post I have read Graham Pulford's description in his High Security Mechanical Locks book.

However I am a little surprised that the Sterling lock that I am working with could have a MACS of 8, although all of the keys would confirm this. 8 would be the the highest possible MACS with the five pin sizes available when pin one and pin five could not be used together. A MACS of 8 would reduce the possible key combinations from 3125 to 625, minus the other constraining bitting rules, 00000, 11111, 33345, 32323 etc, thus reducing this number further to a couple of hundred. This seems extremely low, even for a very low security lock. Or Possibly not.

I've now made up a short hook which seems to have solved the picking problem, MACS or no MACS.

Many thanks.

[3-in-1]

MAC is a physical limitation of the cuts that can be applied to the key, so attempts to go beyond that, while possible when pinning a lock, will not result in being able to cut a properly working key. But I am confused, if the total factory number of pin depths available for a lock is only 5, the MAC possible cannot be greater than 4. Meaning a 1-5 or 5-1 sequence could be possible, depending on certain dimensional factors of the lock core, spacing and the key itself. There could also be cases where only a 1-4, 4-1, 2-5, and 5-2 are possible in a lock with only 5 pin depths.

[unjust]

not necessarily. you could have a 3 depth pin variation with a mac of 1. think of it this way. the mac is less the number of differs but the maximum distance between any 2 points, as defined by the angle between those points.

so, if you're only going to pin a schlage with ONLY 1, 5 and 9 depth pins, you've got a mac of 1, but if you say were to add in additional pin depths to a total of say 18 (1.5, 2.5 etc added), your mac for the same lock would be 14 (or 7 halves)

macs depends on how far apart each pin stack is, and the acceptable maximum ramp angle, and this is actually a distance, which happens to be usefully represented with the regular depth changes between pins within that particular lock. e.g. for schalge you're looking at around .205" with a mac of 7 (assuming i did my math right, which is rarer and rarer these days) the actual acceptable variance may be say .210" but a 7.3 mac isn't communicating any more useful information because you don't have a .3 height pin to swap in.

were you to decide to custom pin a lock with a random assortment of custom pins, you'd want to know the actual mac distance, not the pin #.

[3-in-1]

I am not sure what you are referring to when you say "Not necessarily". Sure it would be possible to have a lock with 3 pin depths and a MAC of 1. But when you speak of pinning a Schlage to factory depths, the MAC doesn't change regardless of what pins you use. Note I said factory depths. As it is entirely possible to use you own custom pins depths and thereby increase the MAC number or decrease it, depending on the number of depth changes you use. You could even drill the pin chambers deeper into the plug and use deeper cuts than standard. But as you say, it is the distance between the pins and the ramping that will always determine the maximum pin length available between adjacent pins. But more to the point, are we talking about locksmithing or trying to pin up a tough challenge cylinder. Pinning cylinders beyond the factory MAC may make for a tough picking session but are not realistic challenges. Usually it is necessary to verify that you have a working lock by producing a functional key. Safe and lock maker Joseph Hall challenged lock maker James Sargent (Sargent and Greenleaf) to open one of Hall's own combination locks, the "Victor". After failing to open it, Sargent wisely demanded that Hall open his own lock with the proper combination. The lock wouldn't open. Go figure.

[DB_Cooper]

Having re-read Pulford's explanation and reading Tobias' (simplified) explanation in LSS+, it would seem that both of you are correct although coming at MACS from different perspectives.

The formula used by the manufacturers to determine the MACS of any lock includes pin spacing (D), the cut depth increment (d), the cut angle (θ), and the cut root (or pin footprint) (δ)

MACS=(D-δ)/(d tanθ/2)
ie MACS = (pin spacing) - (cut root) / (cut depth increment) tan(cut angle/2)

The number we get as end users (locksmiths, repinners, hobbyists etc) is always the difference between the maximum acceptable height and the lowest for adjacent depths of cut.

I was wrong as the MACS for my Sterling lock is indeed 4 and not 8 (I had assumed wrongly that MACS was always out of a constant figure and I had assumed that was 10).

Thanks again

[unjust]

3-in-1 i think you misunderstood my use of schlage as an example. the point was not those specific factory depths, but that the functional mac for any lock may not actually be the basic x a mfg tells you. e.g. if you're master keying a system using a standard spacing of 2, then you've functionally halved not only your variation in pins, but also your practical mac.

in working on a lock that we haven't set up, we need to assume that it's entirely possible that someone did something nonstandard in the setup of it.

i have a lock that exceeds mac, but works just fine, in part because i didn't have a way to cut a factory key for it at the time, and didn't wish to change the pinning when i got it, so, since the initial key was hand filed until it worked smoothly (impressioning wasn't working as the key would stick, so it was shimmed and filed with the core disassembled) copies could be made that looked odd, but also worked.

[3-in-1]

DB and unjust, this is a little struggle for me as I have not done any pin tumbler lock work for over 20 years, so I am trying hard to get the facts straight in my mind. I am not getting how the MAC would change at all when pinning a Schlage, masterkeying or not, as long as the factory depths are adhered to. The keys (masters and changes) don't care whether there are master pins installed. It is only the limitation of how deep one cut can be next to a shallow cut before the shallow one is wiped out. Now going outside of the factory depth of cuts and the number of depth changes you want include, can alter the MAC. But this would generally not be recommended practice for several reasons. Just as making the ramp angle more extreme to accept a greater difference in pin length is also not accepted practice. Now that is the locksmith view, based on the fact these accepted practices are the result of many years of the manufacturers experience. Regarding hobby ,sport and challenge picking I guess anything goes. Traditionally though, a lock must be functional. Meaning it has to work with a key, comb whatever. Pinning a lock high low high beyond which a key would function might make for a good challenge but if a working key can't exist for it, that removes it from the real world of picking functional locks.

[unjust]

i think we're looking at it from a more theoretical standpoint.

going back to my example, if you only use 1, 5 and 9 pins the MAC is still 7, and that means you can't have a 1 next to a 9. so *functionally* you have a MAC of 1x, where x=4. since 2*4>7 _and_ we've limited our pin selection, the factory MAC is still 7, however when you're pinning up that lock, going from any one cut to the next, you can only shift 1 space (of 4). likewise, were we to switch to kwikset pins in a schlage core, the mac would not necessarily be either the schlage or kwikset mac because of the differ in spacing as well as cut depths.

now, lets assume you don't know anything about a lock that you come across. by measuring the spacing of the pins, and assuming a standardish ramp angle, you can determine the maximum distance differ between any two pins, which gives you the "mac distance" which by then measuring the differs between pins, which one hopes are regular, you can determine the MAC for that particular lock. all of that said, you still don't know that it wasn't pinned outside of MAC. as i noted above, i've a very functional lock that i'm certain is outside of MAC, but is functional because i could create a pretty silly looking key that operates the lock smoothly, but can not be direct code copied, and as such remarkably more difficult to cut a functional copy from a photo which is an interesting unintended security boost.

likewise, lets take a look at a well used lock that is still functional, but has it's pins and key correspondingly worn for years of use. while it originally fell within MAC, it may no longer, and may work just fine, and since it's so worn, the pins are no longer factory depth, so repinning it to stock depths could make the operating key no longer function. because of the changes in pin depth, the standard mac may no longer apply.

you're right in that with factory pins and factory cuts, a mac is always the exact number, but in practice the mac that will determine what operates in any one lock, given any number of installation or wear creativities and parameters may be very different.

is that any clearer, or have i added more mud?

[DB_Cooper]

Mud's good. It hides a multitude of things.

You are absolutely right 3-in-1 and you say nothing that I disagree with. You are taking a much more pragmatic/locksmithing approach to MACS. As a locksmith, MACS is there in order that locks are installed and used within allowable tolerances. unjust is taking a more theoretical approach.

On the theoretical side, I do not see that you can change the MACS for a particular lock from what the factory has dictated unless the lock is altered in some way or different pins are inserted that do not adhere to the oem specs. The MACS is set by the manufacturer for the purposes of keying that particular lock.

The end user can drill it, use different pins or do any other modification they wish and the MACS will alter for that particular lock and the end user can dictate what the MACS is for that lock using whatever formula they wish, or not using a formula at all and deciding 'their' MACS by way of any other means. But I would suggest that this is not a MACS at all and won't be unless the above formula is used to calculate it. That is what the formula is for and that is what makes a MACS a MACS.

The end user can decide that the manufacturers MACS is a little on the safe side and could pin their unmodified lock in accordance with their own idea of what the MACS should properly be. This does not alter the original factory MACS that was calculated for that particular unmodified lock.

you're right in that with factory pins and factory cuts, a mac is always the exact number, but in practice the mac that will determine what operates in any one lock, given any number of installation or wear creativities and parameters may be very different.

unjust, using the formula that the factory use, MACS is not in fact, an exact number but the decimal point is always rounded down in order to leave leeway on the side of workability.

If a key and pins are so worn that the MACS was radically altered, then I should imagine that the lock would require re-pinning and a new key cut.

Oh look I'm all muddy again.

[3-in-1]

unjust, there is no doubt in my mind going outside the realm of standardization might result in an increase of security for a particular lock. As a student of the history of locksmithing, I see that demonstrated time and again. Customizing a lock from standard definitely has its advantages, as long as it remains functional. On the other hand, due to economics and convenience, there is usually a trade off and things like reproducibility by code and factory MAC rules become important in the real world of locksmithing. Can you post a picture of your strangely cut key and how far off from standard is it pinned? Or is it actually being used, in which case I can understand why you would not post it.

[unjust]

it's theoretically in use, so i'd rather not post a pic, but i can describe the situation. (i say theoretically, as it's used to secure a door that is rarely if ever locked.) discussing the vulnerability won't functionally endanger the security of the room though.

i took over management of locks in a new space, which had several existing 5 pin mortise locks. the landlord did not possess keys for them, and gave me permission to create keys for them, but wanted the original faces to remain (quasi historic/aesthetic value). i tried to impression the first of (4) locks, and was consistently getting binding all over the place, and the key was starting to get very difficult to remove/insert due to some steep ramping between cuts. a friend suggested that i instead shim the locks, and then cut the keys, which while less of a practical practice in impressioning, was a great practice in shimming which i hadn't tried before.

it turned out that what i'll call lock #1 had the equivalent of a 919 biting in it on a sc1 keyway. interestingly i was getting binding marks on the other (2) pins that had caused me to file them lower than their actual biting, although i hadn't yet gotten (1) of the 9's to full depth yet. the other (3) locks had much more normal biting, what i'd expect to fall comfortably w.in mac for any lock.

so, having filed a key that at least accepted the pins for #1, and judging by wear on the door that it had at some point actually been in use, i figured the original pinning must have actually worked, and worked the shape of the key until it operated the lock, and slid in and out easily. i'd been using a 1/8" chainsaw file to cut the depths, and this resulted in more of a waveform for the key than the saw tooth with flats that is typical.

this has the detriment of very little forgiveness in copying the key as any minor shift off of the shoulder, which would normally be accommodated by the width of flats and the ramp and key pin taper clearance, no longer exists, as the wave is actually hitting precise points. this makes copying a bit of a pita, as you want to copy a few thou tall, and impression the last little bits as odds are good a copy will have at least one point that's just too low.

the advantage of this however, is that in a group with access to key machines, it's significantly harder to simply copy a key one has access to for a few seconds to gain working access, and a code cut key extrapolated from measuring the biting carefully won't operate, as the 1 cut's flat is too small to accurately engage the pin. it also makes picking the door rough as the 1 cut is a very high lift that due to keyway warding almost certainly means the bow side 9 will be overlifted.

and again, the rich irony is that this door is almost never locked as it's to a semi-public space.