OSI 1911 Jig User's Guide
Finally, a one stop shopping tool kit for finishing the 1911 frames available from Tannery Shop. This includes the jig, slitting saw, and slide fitting file. All you need is a milling machine (even a small tabletop model like is shown here) or a good drill press with a sliding table or if you are really hard up, a coordinate vice.
The OSI 1911 finishing jig is the result of about a year's worth of part time research and protoyping. This new jig system is about as idiot proof and user friendly as I can make it. If you follow the directions here and are halfway careful, you can have a usable 1911 frame within hours. In addition, the jig has relief cuts which will allow for fitting the slide rails even after you have installed the grip screw bushings or plunger tube. This will make it possible for a non-FFL gunsmith to fit parts on a 1911 frame and transfer it to a customer without cutting the slide rails and the end user can use one of these jigs to finish out the slide rails.
Here is a new style 1911 jig positioned in a small milling machine. It is important, but not critical, to periodically check the level on both the slitting saw and the jig rails. This will ensure a good even initial cut. This also is important to reference any settings on the milling machine that may wiggle off when the machine vibrates.
The level of the slitting saw and the desired rail should match. If not, adjust the position of the jig in the vice, the frame in the jig, and or the tilting head on the milling machine.
The new 1911 jig has enough "wiggle room" in the plates to allow for minor adjustments to make sure the frame sits even in the jig. I generally line it up with the casting lines that are already in the jig, and then match the four corners of the frame with the same elevation off the top plane of the jig. This will ensure an even cut when you get to it with the slitting saw. The slitting saw blade is a high speed steel which is not much harder (if any) than the stainless steel frame I cam cutting here, so it is very important to go very slow and take shallow cuts. Check your measurements a few times in the operation just to make sure nothing has jiggled out of place.
Lining up the slitting saw is very simple. Gently lower it down to where you get minimal contact with the top plane of the jig and maybe .005 contact with the 1911 frame. Make your first contact with the frame somewhere behind the front edge, not on the edge. Work your way first to the edge and then back accross the length of the rail you are cutting. Make the initial cuts shallow as the slitting saw will develop a "track" that will keep it aligned as you continue cutting. Go at a slow cutting speed until you get closer to your last finishing cuts where you will take fast shallow cuts at a high bit speed to wipe out the machine marks.
The cutting operation in action. You can see the cutting oil dripping from the work piece. The saw will chatter a bit and try to walk out of alignment, but if you keep a gentle downward pressure on it, you can make sure it stays in contact with the jig and rides the plane evenly enough to track an even cut as you gently feed the milling table from side to side. If the frame is not held in a jig at this point, it will easily snag and drag out of the narrow vice jaws. The weight and strength of the jig keeps the work piece in the vice, but you should check the vice from time to time to make sure it remains clamped tight and is not working its way loose or onto an angle.
Here are frame rails that are nearly finished. I am using a pretty trashed old slide for comparing the fitting instead of bringing one of the nice slides into the workshop where it can be scratched up. Once the frame rails are closer to where you want them, it is time to finish up with the slide fitting file. The 3/32 slitting saw is set up to give you slightly narrow slide rail cuts so that you will have enough material left to fit any available 1911 slide to your Tannery Shop frame.
After a lot more parts fitting work, you will be well on your way to a home built 1911 pistol that will give you the pride and experience of doing it yourself. Here is an example of my first 1911 built on a Tannery Shop frame using Chip McCormick internals with a SARCO parts kit to produce a unique and functional pistol. The ambi safety is fitted to function perfectly. External finish is black baked on epoxy over Parkerizing. This solved the aesthetic issues involved with using parts that have a mismatch finish. The pistol frame you see being machined above will be left in a natural stainless steel finish.