Rail placement for TAPCO AK flat

[thud]

I'm to the point that I need to mount the rails on my almost complete TAPCO AK flat. With the center support in and the rail locations locked because of the support, I'm about .036 inch below where ACE Arms says I should be. Now, I've installed the hammer and trigger and put in the bolt carrier (with the bolt), and everything seems to work just fine. So, how critical is the placement of the rails (as long as they are parallel to the top rails). I've moved them from .236 to .275 away from the top rails and there doesn't seem to be any difference.

To reiterate, ACE calls for the rails to be a lettered drill bit C away from the top rails; I'm using a lettered drill bit J. Am I going to shot myself in the foot if I leave then there?

[7.62x39]

That is my tutorial from my AK47.net thread, that Ace is using(with my permission) on their site.

If you read all the text, I pointed out that the final determination of lower rail placement should be double checked with your bolt and bolt carrier.

There are too many variables, including upper rail thickness, for that trick to be perfect in every receiver type now available.

That said, most will work using the C bit and bending the lower rails slightly up or down for correct alignment.

But stepping up the drill size for your particular receiver is the best way to go. Using the drill bit ensures you are parallel to the upper rails.

If your's lines up correctly with a J bit, then that's the one to use.

[thud]

I just finished welding the rails on and I used the "C" drill bit clearance. I had to do some adjusting of the hole locations to get it to work, especially the hole for the hammer. In my case, I found that the magazine ran into the ejector rail when it was placed in original position (.277" below the upper rail). When placed at .242" below the upper rail, the mag just cleared the ejector extension.

For the hammer pivot hole, I welded over the old hole, redrilled, and reheat treated the area. It should work fine; welding was the easiest way I could come up with.

And, thanks for the tutorial. It was very helpful. Now, if I could just see a few different barrel presses.

[Makman]

What is the best way to bend the top rails if they should need adjusting?

[butteco@att.net]

THUD;

Please inform me how you welded your lower rails into your receiver? I have a just purchased a wirefed mig welder and am anxiously awaiting my receiver flats and stamping dies expected in 2 days. I was wondering the best way to weld in the lower raills? Should I puddle weld from pre-dilled holes? or just use the existing lower rail holes? Or is there a different alternative?



ALSO DOES ANYONE KNOW WHERE TO FIND A BUTTON-HEAD SCREW SET for the AK47?

[Rhino_66]

Some links for those who wish to use the screw together method:

http://www.thread-rite.com/unbrako/button.htm
http://www.fastener-express.com/subcat.asp?0=207
http://www.mjvail.com/holokrome/dd_bhcs_metric.html
http://www.midwestsocket.com/socket-head-cap-screws.htm
http://www.microfasteners.com/catalog/products/SSCSBA.cfm
http://www.earnestmachine.com/cap_screws.htm
http://www.circlebolt.com/socket.htm
http://fastener-warehouse.com/Fastener%20Warehouse/SOCKET%20HEAD%20CAP%20SCREWS/button_head_socket_cap_screws.htm
http://www.nutty.com/bsc.html

Also check your local hardware chain store in the specialty fastener aisle. You can pick up a box of 1/2" 10-32 button heads for a few dollars.

[thud]

butteco@att.net, et al

The existing holes in the rails are for the center support and the hammer pivot pin. To mount the rails, you will need to spot weld in 4 or five places on each rail, or you can plug weld (rosette weld). You can also use cap head screws and small nuts (see ACE Arms in their resource section on how cap head screws were used).

When I setup the rails, the existing holes did not match to the holes on the reciever. I had to weld over the pivot pin hole and redrill it for it to align properly. The center post holes I filed to fit.

I drilled four 0.20 holes through the receiver for the ejector rail and five for the other rail. I did not drill the rails. I built a jig to center the MIG gun perpendicular to the reciever, very close to the hole, and centered. I then turned the power up and the wire speed down. I used a weld time of 3 seconds. Of course, all the settings will be unique to each setup, and you NEED to practice before you try it on the reciever. Check the web for plug welding techniques; GM has a couple of good procedures listed.

[butteco@att.net]

THANK YOU FOR THE INFO!

[butteco@att.net]

Thud,

Could you tell me why the following is occuring?


I HAVE A TAPCO KIT AND AM BUILDING AK47 (amd63)

I have the ejector rail mock fitted right now, held in with a pair of vice grip pliers through magwell. I lined up the holes for the hammer pivot and put the bolt and carrier in and slid it back, but the bolt hits the ejector?

It is the rear part of the bolt it is hitting, specifically the outer firing pin casing, the round hotdog shaped piece which mates to the larger front end.

DO I NEED TO TRIM MY EJECTOR LIP DOWN A BIT?

[thud]

butteco@att.net

I had to trim the ejector by at least 0.020. I also had to do A LOT of trimming on the upper rails. Look a lot, trim a little. You will get it to work. The TAPCO flats need a lot of adjusting before they everything lines up.

[allesennogwat]

I just bent a Tapco flat and the predrilled rails ended up needing a 19/64 drill bit to be parallel with the top rails.AGI's video recomends a 17/64 drill bit.A letter J drill bit is pretty close to 7mm I think.

[erikk]

Why screw around...Just go buy a 5mm & a 7mm HSS bit. I got mine from ACE Hardwre and saved myself a whole lot of grief. Works first time, everytime...16 & counting

[allesennogwat]

I think he was using the J drill bit to line up the lower rail with the top rail.That's where I used the 19/64 bit.I do have metric drill bits for drilling the holes.