Wierd bump key phenomenon

[mrhappy]

I made a bumpkey today to see if it would actually work. To my suprise it actually did, fairly easily in fact. Just not in the way I was expecting.

Here it is, sorry for the low image quality but i was using my cell phone camera which is my only digital camera at the moment.

Anyway, i tried the standard twisting and knocking with no avail. Then I tried bumping while pulling the key out. That did it! It looked like it was being pulled out almost one tooth in fact. This does work though almost invincibly every time. I was thinking that maybe i didnt take enough off the shoulders and top so i filed down a bit more. Still the same problem persisted. I'm wondering why this is. I only have one lock at the moment to try it out on so it could just be an anomily with the lock. I'm trying to think why this is working as opposed to the other way.

[p1ckf1sh]

Anyway, i tried the standard twisting and knocking with no avail. Then I tried bumping while pulling the key out. That did it! It looked like it was being pulled out almost one tooth in fact. This does work though almost invincibly every time. I was thinking that maybe i didnt take enough off the shoulders and top so i filed down a bit more. Still the same problem persisted. I'm wondering why this is. I only have one lock at the moment to try it out on so it could just be an anomily with the lock. I'm trying to think why this is working as opposed to the other way.

Do you know what kind of pin configuration the lock has? After successful bumping and rotating the lock a little bit, can you pull out the bump key? When you put the bump key in all the way, and push it in to the point where the filed down shoulder touches, does the lock push the key back out a bit?

It could be that the valleys are not precise (distance and/or depth) enough and leave one pin untouched. With the pull back method you get this untouched pin as well, but if there is a lock with long keyway pin (deep cut on the key) this method might push the long pin past the shearline.

I'd take the lock apart and see if you can find any traces in there that might explain this behaviour...

[raimundo]

from the look of the photo, you cut this with a triangular file. there are different depths to the cuts, but all of them are at a steeper angle than the 45 degree angle that is common in keys. This could eventually become a problem of the nature of a key stuck in the lock and un removable, if that happens, before you use any aggressive force, shoot some kind of lubricant from a pressure can into the lock. force will tend to make a dent along one of the slopes, which will make the problem intractable, but lube will help greatly. because you put a steep angle under each of the pins, it cams the pins up quickly as long as friction is not a factor, friction will eventualy become a factor, and theres where the problems will begin. Your key does not appear to have full 9 cuts on each of the places, so it cannot open a lock that requires the really deep cut. Also, if you look a the other bumpkeys pictured in this forum, you will notice that the bumps do not emphasize height, each of them only comes as high as a 6 or 7 cut. the concept is to launch the pin, not to actually carry it upward. but what you made is an interesting varient, I will experiment with the idea, making one with the front slopes steep, perhaps requiring a lifting tool to insert it, and the backslopes at 45 degrees to avoid the retraction problems. Thanks for showing us your bumpkey.

[mrhappy]

Do you know what kind of pin configuration the lock has?

Seems pretty high and even. Could be why pulling it out was needed.

After successful bumping and rotating the lock a little bit, can you pull out the bump key?

Yup, pulling it out was no problem at all. In fact when it successfully catches the key frequently pops right out because I am pulling on it.

When you put the bump key in all the way, and push it in to the point where the filed down shoulder touches, does the lock push the key back out a bit?

Yup, it moves in and out about 2 milimeters.

It could be that the valleys are not precise (distance and/or depth) enough and leave one pin untouched. With the pull back method you get this untouched pin as well, but if there is a lock with long keyway pin (deep cut on the key) this method might push the long pin past the shearline.

I tried to make the cuts as even as possible but its hard to be super precise with a file .

[mrhappy]

from the look of the photo, you cut this with a triangular file. there are different depths to the cuts, but all of them are at a steeper angle than the 45 degree angle that is common in keys. This could eventually become a problem of the nature of a key stuck in the lock and un removable, if that happens, before you use any aggressive force, shoot some kind of lubricant from a pressure can into the lock. force will tend to make a dent along one of the slopes, which will make the problem intractable, but lube will help greatly. because you put a steep angle under each of the pins, it cams the pins up quickly as long as friction is not a factor, friction will eventualy become a factor, and theres where the problems will begin. Your key does not appear to have full 9 cuts on each of the places, so it cannot open a lock that requires the really deep cut. Also, if you look a the other bumpkeys pictured in this forum, you will notice that the bumps do not emphasize height, each of them only comes as high as a 6 or 7 cut. the concept is to launch the pin, not to actually carry it upward. but what you made is an interesting varient, I will experiment with the idea, making one with the front slopes steep, perhaps requiring a lifting tool to insert it, and the backslopes at 45 degrees to avoid the retraction problems. Thanks for showing us your bumpkey.

Wow... I'm suprised you could make out the type of file i was using with the quality of the images. I was guessing at the depth of the valleys. Looking at my original key for the deepest cut and making it deeper than that. It was really eyeballing. I havent found anything on what the exact measurments are so i had to do it this way.

Thanks for the advice about getting the key stuck. Hopefully I wont have to use it. This was my first key so I was just guessing on heights and depths. Going from a couple pics I googled and a video I downloaded. After hearing your suggestions ill probably try another with deeper cuts and shorter tops. I will pick up a file that has a 45 degree angle on it too. I'm not going to modify the one I have just for postarity sake .

[p1ckf1sh]

Seems pretty high and even. Could be why pulling it out was needed.

Yup. I see two explanations for this thing... either you put too much tension on the plug when bumping normally, so that the pins have too much binding friction to overcome or one or more pins do not get any energy because of the cuts, therefore they don't move and the lock stays shut.

Yup, pulling it out was no problem at all. In fact when it successfully catches the key frequently pops right out because I am pulling on it.

Wait, you are pulling back on the key and you hold the pull force when bumping? How deep does the key go when you bump? All the way into the lock and then you pull it back or do you just get a minimal movement into the lock?

I tried to make the cuts as even as possible but its hard to be super precise with a file .

You don't have to tell me... I know that

[mrhappy]

Yup. I see two explanations for this thing... either you put too much tension on the plug when bumping normally, so that the pins have too much binding friction to overcome or one or more pins do not get any energy because of the cuts, therefore they don't move and the lock stays shut.

You are right, in fact I have actually successfully bumped the door in the 'proper' way today. I was using waaay to much tourqe. Like 4X to 5X to much. It is still faster (if you consider 7 seconds as opposed to 13) to use the pulling method though. I was so suprise the ease at which I could open my front door. I think I will be picking up a better lock soon. Either that or hope that ner-do-wells do not have the advanced filing technology I have.

Wait, you are pulling back on the key and you hold the pull force when bumping? How deep does the key go when you bump? All the way into the lock and then you pull it back or do you just get a minimal movement into the lock?

Yup, I pull back while i was bumping. I push the key all the way in then pull it slowley out. It usually shifts back about half-full tooth length before the lock would open.

[raimundo]

if you are trying to file with precision and duplicate it five times, remember to count the strokes, use constant pressure each time, and keep the length of the stroke also constant. thats probably how the guy who made the antikathera mechanism did it. a bumpkey made on a code key machine will have seats at the bottom of each cut, but the key to knowing you did it with a triangle file was that yours has no flats at the bottom of each cut.

[jimb]

a bumpkey made on a code key machine will have seats at the bottom of each cut, but the key to knowing you did it with a triangle file was that yours has no flats at the bottom of each cut.

Is it best to have flats at the bottom of the cut or better to have no flats?

I have only made one bump key. I did cut it by machine with a V shaped cutter and just eyed the cuts into an existing key since I did not have a spacer key. This made my bump key with no flat spots???

[p1ckf1sh]

Is it best to have flats at the bottom of the cut or better to have no flats?

Check this: viewtopic.php?t=12226

[timelord]

More posts on bumping: http://tinyurl.com/rtqhp

[Mutzy]

Pdf File on bumping: Bumping