Its a simple process to setting up a vertical milling machine to accurately cut slots that has to be x thousandths from one side by x thousandths from one end by x thousandths long by x thousandths wide by x thousandths deep, and accurately duplicate that slot on more than one part.

The first step in the process is to know what the dimensions are for the part to be made. Lets say we have a blueprint outlining the details for the part. We see that the slot is .500 from the side, and starts .250 from the left end, 3.250 from the starting point to the end of the slot, and the depth just goes all the way through the part, with a .250 diameter cutter.

Now that we know what were making the next step is to make sure the milling machine has everything all lined up. First check that the head on the mill is it zeroed in? it has indicator marks in degrees in two places that need to be set to zero. The first set of marks are for the back and forth tilt of the machine head loosen the bolts and move the head to the zero mark, and tighten the bolt down. The next step is the side to side tilt of the head loosen the bolts and dial it to the zero mark, and tighten the bolts back down. Now we have the head lined up vertically to mill straight down.

Now that we have the cutter end of the machine dialed in we turn our attention to the vice that will hold our part firmly for milling. We will need a precision indicator that fits in a collet where the cutter is held into the head, the indicator needs to be what I call a side indicator where the spring loaded button is on the side when held in the machine collet within the head.

We need to open up the vice all the way and move the bed in both directions to get the indicator to rest against the back jaw of the vice the jaw that doesn't move. The button on the indicator needs to face the back jaw of the vice and ride along the top portion of the vice jaw just slightly below the top of the vice. Move the bed until the indicator is at the top right corner or left corner of the vice jaw. Now use the cross feed and feed into the indicator until it starts to move the needle of indicator then move it about ten to fifteen thousandths, into the indicator.

Now that we have our indicator resting against the vice jaw we need to dial the indicator into the zero position by just turning the ring around the top of the face of the indicator. Now move the bed of the mill so that the indicator is at the other end of the vice, if its lined up the indicator will still read zero if its not lined up lets say it moved a few thousandths from one end of the vice to the other. What we need to do is loosen the nuts that hold the vice but not completely leave it snug so that the vice can be taped with a hard rubber mallet and moved, and what ever the difference is from one end of the vice to the other you want to just move the vice half that back toward zero then run the bed back to the other end of the vice and if it didn't move you can lock the vice back down, but after locking it down check it again sometimes it moves when locking it down you may have to repeat the process.

Now the machine is setup to cut a accurate slot. Next we need a new tool called an edge finder it has spring loaded ends that will float, one end is for finding the center of a hole, and the other end is for finding an edge. You put it into a collet in the head of the mill where the cutting tool goes. We need the edge finding end its the straight end. The hole finder is pointed. Put the hole finder end into the collet and lock it into place.

You want to put a precision parallel into the vice and let it stick up a quarter inch or so out of the top of the vice. Next move the bed of the mill so that the parallel is in front of the edge finder and that only the small end of the edge finder will touch the parallel. Move the floating end of the edge finder so that its slightly forward toward the parallel. Now start moving the bed so that the edge finder touches the parallel and keep moving until the floating end looks as though its allmost back in line with its shank. Now you need a set of one inch micrometers. Mike the edge finder at the point where the two peaces of the edge finder come together it should mike .500 a half inch, to be the size of the shank of the edge finder. It should mike slightly over so move the bed how ever many thousandths its over when the edge finder mikes .500 thats the true edge of the vice. Make sure you only feed the bed into the edge finder you don't want to over shoot and feed the bed in the other direction because most mills have some play in the bed screw and you want the bed moving in the direction you have to move to find the center of the slot.

We now need to check the blue print and see how far over the slot needs to be for our new found edge. First we don't really have the true edge yet because we need to move the bed half the thickness of the edge finder tip that was touching our parallel so mike the small end of the edge finder and move the bed half that thickness. Next the blue print says the center of the slot is one half inch over from the edge so crank the handle of the mill .500 and lock the bed so it can't move in that direction anymore.

Now we need to setup a stop for our blank part to rest against so we can have each one placed at the same spot each time we finish milling one and place another into the vice. They need to be placed accurately each time one is placed into the vice. There's several ways to setup a stop we drilled and tapped a hole into end of our vice to bolt on an adjustable stop but there are stops that clamp to the top of the bed the important part is to setup a stop that will position the part evenly and so that the slot will be centered into the vice.

Next place parallel's into the vice to place the blank part on top of. Place a blank part on top of the parallel's and slide it against the stop, and lock down the vice clamping the part into the vice.

Use the edge finder at the left end of the blank part and line it up as before but this time on the edge of the part its self. Then move half the diameter of the edge finder like before. Now our blueprint calls for the slot the start a quarter inch from the left end of the part so move the bed .250 now that's not our starting point that's just the center of the cutting tool so we check the diameter of our slot and find its a quarter inch so move half that distance more .125 that puts the outside edge of our cutting tool a quarter inch from the end of our blank part. Now lock the bed into place so it can't move.

Next we need to have a way to insure we find that same starting point quickly with the next blank part so we setup a stop on the front of the milling table loosen the nut on the stop and slide it all the way over to the stop, and tighten back down. Now we have our starting point setup.

Next we want to setup our stopping point as we did for our starting point except we don't need the edge finder anymore. Our slot is 3 and a quarter inches long so we need to subtract half the diameter of the cutter from 3.250 that would be 3.125 move the bed of the mill 3.125 and lock the bed so it can't move. Now set the other stop on the front of our milling table by loosening the nut of the stop and slide it until it stops and tighten it back down.

Now the mill is setup so all you have to do is put one blank in against the stop, move the bed to the starting stop, and slowly plunge the cutter into the metal and start cutting your slot until it reaches the other stop remove the blank and repeat to quickly and accurately duplicate as many parts as you like just check one every few to ensure nothing has moved.