Key cutter problem

[sharpfire]

I purchased a used key cutting machine about a month ago and have been very happy with it so far. I have cut several keys and most seem to work fine. I was reading through the instructions to see if it is adjusted properly. When doing the test to check the depth adjustment I found a problem. The blade scrapes a small amount near the tip of the key and then has a very small gap near the shoulder. I read in the instructions that after many keys have been cut there may be a slight angular displacement. It says that the carriage shaft bearings should be replaced to fix this problem. Does anyone know where I can purchase these bearings and I was also wondering how they would be replaced. There are no screws so it seems like they have been pressed in. The key cutter is a Simplex 6210MK II. Thanks for any suggestions.

[Jaakko]

Ball bearings usually have a code lasered to the side, for example "6082 2RS". That can be used to buy new bearings, the problem is just uninstalling the old ones and getting new ones in.

[zeke79]

Be sure your vise jaws are clean. Seems remedial but a large brass shaving between the vise and the key blade can put you several thousandths off from one side of the blank to the next.

This can also happen for various reasons. The machine being dropped and one of the vice jaws or the carrage guide rod bending slightly worn out bearings and or bushings. You never said what kind of machine you have which would help us get things lined out.

The "bearings" they are talking about in the carrage are most likely bushings. Some machines even use bushings instead of bearings in the head of the machine that the cutter shaft rides on which wear quickly. Machines designed this way are the lower cost machines designed more for intermittent use such as a hardware store that duplicates the occasional key and not a lock shop that does many duplications daily.

The benefit of machines that use bushings instead of bearings is the fact that if you cannot find replacement bushings you can have them made cheaply out of bronze by driving the old ones out, measuring them and then having a machine shop turn some new ones out. The advantage of this is you can pull the machine apart and measure shafts on the machine for wear or bends along with the bushings. If your guide rods, shafts etc are worn then replacing with standard replacement bushings will still leave problems in the machine. Having the new bushings made with your measurements ensures that the machine is nice, tight and straight. The only problem you might have in doing this is that you will need to ensure proper tolerances and interference fitting etc which finding actual engineering specifications for your machine will be hard if not impossible. This information is not required as long as you use common sense when you order the custom bushings. You would want the carrage bushings to be tight on the guide rod but not so tight that the carrage binds or is hard to move.

[sharpfire]

Thanks for the for the replys. I have cleaned the vice several times to be sure that was not the issue. The key cutter is a Simplex 6210MK II. Since this machine has two different layers in the vise i decided to try the deeper layer. It seems to improve the problem but does not fix it completely. Any suggestions on how to see if the vise is or carrage shaft is bent. Im assuming that it will not be easy to notice a problem with them since it is such a slight distance.

[Wizer]

If your clamp is turnable so you have different vises, check wear under the clamp. If the vise wiggles when loose, you could tighten the key inclinated.
I´ve seen this happen. When swiching to another side of vise the screw wasn´t loosened enough, and spring pushed the vise down causing wear.

[zeke79]

To see if the shaft is bent you could take it out and roll it on a level surface. This should show any major bends. To check it further the only thing I can think of is to chuck it up in a lathe and put a dial indicator on the end and roll the chuck by hand. While doing this the dial indicator will show runout in the shaft. I would say that if you are only a few thousandths crooked towards one end then you'll not see that small amount of runout by rolling it on a level surface now that I am thinking about it.

[Jaakko]

To see if the shaft is bent you could take it out and roll it on a level surface. This should show any major bends. To check it further the only thing I can think of is to chuck it up in a lathe and put a dial indicator on the end and roll the chuck by hand. While doing this the dial indicator will show runout in the shaft. I would say that if you are only a few thousandths crooked towards one end then you'll not see that small amount of runout by rolling it on a level surface now that I am thinking about it.

The problem is chucking it to the lathe accurately. Basic 3-jaw chuck has a TIR (total indicated runout) of 0.05-1 mm when you chuck something to it, so it ain't coaxial with the lathe spindle ever. You would need 4-jaw chuck and a few minutes to dial it up.

The level surface, like black granite surface plate will show even a 0.01 mm err in the axle, when you place an intense light behind it and look for light between the axle and the plate.