KiDD Rear Tang Install

[azguy]

I have recently picked up some of these KiDD Rear Tang kits and installed one on my "Inletting/WIP Receiver". This is an older receiver I use for trial fitting and such. These Rear Tang Takedown kits come from KiDD and are top notch quality, as to be expected:

In the package you receive the Rear Tang itself, 1/4-20 SHCS takedown screw, takedown escutcheon, and a #8-32 Torx pan head screw (#20 Torx Bit) for securing the Tang to the rear of the receiver:

The Tang is aligned to the reciever by a register fit on the back that needs a slot in the receiver to alloow for the installation of the Rear Tang:

More to come:

 

[azguy]

I spent some time trying different setups and decided on one that allows me to set up the receiver relatively quickly. I clamped one of my slotted angle blocks in the mill vise and dialed it in so it was true within +/-.001 in all axis. That became the base line for the setup. I then took some jig stops that were in my router table stuff and took one and trued it to the angle plate:

I also added a clamping screw for later. Then I took and placed the receiver in the setup jig up so the side of the reciever was against the trued jig stop and the bottom rails were tight against the angle plate face. I took the second jig stop and slid it up against the other side of the receiver and locked it in place to keep the receiver from "Twisting" sideways during milling. The clamping screw I used to place a hold-down clamp on the receiver top that holds the receiver tight against the angle plate face:

I know most dont have a mill, but you could do something similar in a drill press.

 

[azguy]

I then took a "Edge Finder" and used it to locate the exact center of the reciever from side to side and also to find my '0' on the DRO for the bottom of the receiver. The DRO allows me to set my zeros and then make any cuts and such from those '0' reference points. The bottom of the Tang on a KiDD Supergrade receiver is .250 from the bottom of the receiver. On these kits the top of the tang is square to the sides. The top of the receiver is rounded (about a 4" radius). That means the tang can either stick up above the rear of the receiver just a bit o the corners of the tang OR you can adjust the location to keep the tang even with the receiver radius at the corners and below the top of the receiver radius in the middle. That entails moving the tang bottom down to about .240 from the receiver bottom rail.

Heres the "Edge Finder". It works by moving the smaller end out of center (it is spring loaded) and as you move it closer to the edge it touches and starts to be recentered. Once it has reached center alignment if you move it anymore it will "jump" to the side. That point at which it "jumps" is the edge of the piece you were trying to find. Finding the opposite edges gives you the total width of something within +/-.0005. Divide that in half and you have the center point between the edges. An invaluable tool for sure:

The tang register is .0625 from the bottom of the tang. This register is .250 wide and .625 long and extends out from the tang assy about .050. I have noted all the locations and the relevent tooling centers so I can repeat this process readily. The slot in the receiver should be a touch deeper so that the tang rests tight against the receiver back and not held "out" by this register copntacting the bottom of the slot. I milled the slot about .065 deep:

 

[azguy]

Once the tang slot was milled I need to locate and drill a clearance hole for the screw that secures the tang to the receiver. The screw threads have a .164 diameter so I used a .1875 end mill to machine the thru hole:

Now obviously I used end mills for this work. You could do the thru hole with a 3/16 drill bit of course. As for the slot itself, if you have a cross slide table on your drill press I don't see any reason you could not do this yourself. I ran the end mills at 1000 RPM and you can get that speed on your drill press. I usually run faster but I wanted to see how the aluminum machines at a drill press speed. No problem, just take your time and don't rush it. With the mill I can be extremely accurate. Does this need to be spot on? Not really, if you are going to bed the rear tang anyway. The important thing is to keep the tang assy as square to the receiver as possible. If it is tilted one way or the other you stand a chance of locking your reciever into your stock when you bed the rear tang. Off-center is not an issue other than the looks. but tilted off axis top to bottom (vertically) will cause you issues.

The next step was to countersink the tang mounting screw hole so the screw doesn't interfere witht he trigger group installation. If the screw isn't flush, with the inside wall of the reciever, it will not let the trigger group go in properly. One issue on the tang is that the mounting screw location is even with the V Block screws and thus you cannot simply set the receiver vertical and use the barrel hole to access and do the countersink. I played with the set up a bit and found if you set the receiver at about 5 degrees off vertical you can access the location for the countersink.

Then I took a 12" long, 3/8 drill bit, and set it up in the mill, along with the receiver.

I then was able to cut the countersink required. Subsequent to doing this first one i ordered a reverse countersink that will enable me to do the countersink from the outside in the same jig setup.

More to come:

 

[azguy]

Here are some pics of the finished receiver. This particular receiver is one I use for testing things out so it is pretty roughed up and old. Obviously a new receiver would be protected from any damage.

All in all looks pretty good IMHO. Now the rear of the receiver is not as flat as it looks. With the tang installed there is about a .002 gap at the top. You can barely see it unless you are looking for it. The fit to the rear on this receiver is about 85%. I could take a cut to true the back but it would show at the top center of the receiver. You could also move the receiver up and try and sand it to fit the rear radius on the receiver exactly. Guess it's up to y'all. Would I attempt this without the mill? If I had a drill press with a cross slide table, probably. You could do it without the cross slide table but it'll be tough going to be real accurate. If you do that, just make REAL sure the tang is parallel with the sides of the receiver and not tilted off the vertical axis. I plan on doing this to several of my old builds. The rear tang takedown with a front bedded pillar gives you a rock solid platform! Hope this didn't bore y'all. Take care.

 

[JFB]

thanks for the detailed discription and the reasons.
having to set the reciever 5 degrees off to access the location for the screw hole seems like a mistake on Kidds part. looks like they could have placed in higher on the locating fit.

I was real impressed with your setup UNTIL I saw the "carpenter's" protactor.
let me suggest a http://www.grainger.com/Grainger/STARRETT-Protractor-Head-2ZUT6

 

[azguy]

Actually everything was checked using a final word, or test, dial indicator during the set up and then re-checked afterwards. I first set up everything with the indicator (mounted in 3/8 R8 collet). And then re-set the jig stop, for the side of the receiver, using just the machinists (not carpenters) square to see what the difference was. Subsequent checking with the final word dial indicator revealed a difference of less that .0015 which is more than repeatable enough for the work at hand.

I plan on machining a more permanent jig stop that will square itself to, and run parallel, with the sides of the angle plate, as the time becomes available. For now this works very well.

 

[Richbaker]

Nice... Where are you in AZ?
Gunsmith?

 

[9x19]

Now obviously I used end mills for this work. You could do the thru hole with a 3/16 drill bit of course. As for the slot itself, if you have a cross slide table on your drill press I don't see any reason you could not do this yourself.

A couple words of caution in trying to use a drill press as a mill - side load.

A mill is built to handle the stress of cutting side to side, a drill press is not.

You can ruin a drill press pretty quick trying to turn it into a mill.

Please, be careful.

 

[azguy]

Nice... Where are you in AZ?
Gunsmith?

Actually live in NW Tucson. I make custom stocks and do some gunsmithing on the side. More of a self-sustaining serious hobby.

 

[azguy]

Now obviously I used end mills for this work. You could do the thru hole with a 3/16 drill bit of course. As for the slot itself, if you have a cross slide table on your drill press I don't see any reason you could not do this yourself.

A couple words of caution in trying to use a drill press as a mill - side load.

A mill is built to handle the stress of cutting side to side, a drill press is not.

You can ruin a drill press pretty quick trying to turn it into a mill.

Please, be careful.

Totally agree. But in this case you are dealing with a small slot and usually 6061 aluminum. I woulod NEVER try this on any steel or other hard material. But yes, BE CAREFUL. Never rush it. If I was doing this in a drill press I would plunge cut first by using the drill press like a drill press with a drill bit in it. Set a stop on your spindle or carefully run the end mill (MUST be a square end, centercutting, endmill) down the distance you need. About 1/16 or more. Move over a bit along your centerline and do it again and again until you have your slot. On the last cut, if you have a cross slide table, you could clean up the sides with by locking you spindle at the cut depth and milling the sides to clean them up. You would not be cutting much and the side loading on your spindle would be greatly lessened.

But obviously using a mill is the ay to go. Luckily I have a mill that I use for small parts and such and also for all my stock inletting. Was a natural to go to doing this as well. If someone wants this done just get in touch with me. I plan on doing this to my 10/22 rifles and my Chargers.

 

[Richbaker]

Nice... Where are you in AZ?
Gunsmith?

Actually live in NW Tucson. I make custom stocks and do some gunsmithing on the side. More of a self-sustaining serious hobby.

I'm mid-town, we should do some shooting together. There are several other Tucsonites here, as well.