Dial/Drive cam tightness and how it affects manipulation

[mdc5150]

So the last safe I manipulated open I got lucky and got to take the lock home. (It was purchased cheap so we could re-sell and we put on an electronic lock) I have mounted that lock on my practice door at home and have struggled for two weeks. I couldn't get it to tell me a damn thing. Finally today I decided to try something out. I had mounted it the way I have always been taught with just a slight forward/backward play in the dial. But I remembered that as it was mounted on the original safe it came from it was tight. So I tightened it down one turn and found that to be just like it was before and now it seems to scream the numbers at me. Has anyone else messed around with this?

[MartinHewitt]

Nope, not I.

[femurat]

A loose dial gives inconsistent readings. You can try to pull it always the same way when you take the readings. But a correctly tightened dial is the best possible thing.

Cheers

[safecracker33]

I would have expected it to be the other way round with a tighter dial disguising the contact readings, a loose spline key would be a problem, but if that is good then a nice free spinning loose dial feel I would normally consider to be a good thing.

[femurat]

I said correctly tightened

Of course it's better a bit loose than over tightened. But if it's too loose it's not easy to always read the same way.

Cheers

[castle 2]

Has anyone else messed around with this?

I have messed around with this problem, but it seems to be determined to mess right back at me; at ONE torque stiffness, it seems to be looser than a hooks back door, (just as information ,and in case it's of importance, this is on RH configuration. ..),yet when I turn the complete revolution necessary to be once again at the RH position, it seems tighter than my Grandad just after Christmas time. ..

Any pointers?

[MartinHewitt]

My first combination lock I mounted on a wood board. Tightened like your Grandad just after Christmas time it was AFAIR a quarter turn beyond RH. A quarter turn back to RH it is nearly as tight as your Grandad, which is too much to use it. Another turn more and it is rather wobbly, but ok for manipulation. Perhaps I automagically push it it when I manipulate it.

[castle 2]

By 'a quarter turn past RH',are you referring to VD?lol I have always been taught by everyone that mounting your lock in the correct orientation is of PARAMOUNT importance to prevent any Wile E Coyote + ACME rocket -style unfortunateness involving my loved ones. ..?

[MartinHewitt]

Sorry, yes, VD. I never mounted a lock different than RH, so I haven't really looked at the other positions.

[madsamurai]

To get a proper fit, you'll need to adjust the thickness of the door/board you're installing on with some shims. The process I use (which I read somewhere but can't find now) is to screw the dial into the cam until it stops (using light tension, don't torque it). Ideally this will end up about a quarter turn (90 degrees) past the spline slot you're aiming for, give or take a bit for preference. If it's landing at that spot, you should be pretty good, just turn it back to align it with the slot and install your spline key. If it stops past the quarter-turn mark, you'll end up loose and wobbly. If it stops before the quarter-turn mark, you'll be tight. To fix that, you'll need to add some shims either behind the dial where it meets the door/board, or under the lock between the lock body and the mounting surface. S&G and LaGard (and I assume many others) use a 5/16" x 40 tpi thread, so using that as an example we can calculate that each full turn tightens or loosens .025" and each quarter turn is then ~.006" so you can use that to determine how thick your shim needs to be by how far past the quarter-turn mark it goes. On my practice locks I've used paper and also thin mylar washers successfully as shims. I've recently started using threaded brass inserts on my mounting boards, and that can allow some adjustment either by turning them in/out or filing them down after they're installed. There's a sweet spot where the dial will spin smoothly and also not wiggle at all, and it may be slightly different for each lock due to differences caused by manufacturing tolerances, so it may take a bit of tweaking to get it dead on, but knowing the thread pitch and using this technique it's generally pretty quick.

Of course this creates an ideal practice situation, and seems to me to be a rare thing on production safes (at least the cheaper ones I have access to) and only slightly more common on safes where aftermarket locks were installed by locksmiths. So practicing with dials that are either too loose or too tight might be a good idea if you're doing real-world work, I would think.