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| Article by Rob Summerhill (RapidRob) | |||||||||
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There are several methods that are available for you to use to attach the lower rails. (The ejector/guide and the bolt/magazine guide). I have found that drilling holes and back filling into the rails using a TIG or MIG type welder works; but there is much clean up to be done, grinding, sanding and the good chance of warping the frame or rail. Screws also can be used to mount the rails, or even rivets if need be. This method will allow later replacement of worn or broken parts, but the sleek looks of the receiver are changed. I have found that it is hard to beat the spot weld method. It’s fast, relative clean and very easy to do. I’m using the 120-volt Harbor Freight Spot Welder part # 45689. |
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This welder can be bought on sale for less than $ 110.00 but normally runs for around $150. Do be aware of the fact that this welder draws lots of current during the weld and should be on a circuit that is not all ready loaded down with lights or other electric devices. You will also need to modify the bottom electrode arm and tip. The reason being that the welder needs to ride inside of the receiver two side walls to make the welds. You can make the modifications to the lower arm yourself or buy one all ready done from a member on another web site. Here the two welding tips have been ground down to finer points and a thinner profile to allow easier access to the rails during the welding process. |
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| The welder basically clamps the two pieces that need to be joined by the welding tightly together. The two tips will cause a very localized electrical pathway that will short together generating heat and weld the two spots together. Hence, a “ spot weld “. | |||||||||
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The force needed is a trial and error effort on your part. There is a table that list the force needed in Kg per CM/Sq that we cannot check even if we wanted to do so. A “feel” of the jaws holding the parts is like a firm handshake. So, what you want to do is use a force on the two welding tips that will ensure a good contact of both parts and not burn through or arc so badly as to burn and splatter the metal parts. The time required to weld the parts together is a fast count to 3. You have total control of the welding time via a thumb switch that you activate after you are happy with the clamping force and alignment of the two rails. There are two adjusting nuts just behind the welding arms that allow the clamping force to be set. It is very important that the two welding tips are perfectly aligned with one another. |
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Both rails will be mounted at slightly different heights on each side of the receiver sidewalls. Buy using drift punches to help keep both holes in the rails centered into the holes of the receiver sidewalls. You will now hand fit the front barrel trunnion. The rails are used to guide the bolt/carrier assembly into the breech area and allow the bolt to lock into the breech. Once you are sure the parts will line up as required to allow smooth operation, you now need to use a guide to help keep the rails aligned during welding. Drill bits are you best option and will also prevent the rails from tipping during the welding process. The diameter of the drill bits will be determined by the height of the rear end of the barrel trunnion and where the ejector is riding in the bolts face. |
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While this process sounds very complicated, it is in practice very easy to do. After you are satisfied that the two rails will align with the barrel trunnion, you are now ready to do the spot welding. Use small clamps, such as the two inch C-clamps sold at Harbor Freight. These clamps will hold the parts in place for the first or second spot weld. Once the welds have “tacked” the parts in place you may remove clamps to allow easier movement of the spot welder. |
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| O.K., what you should now have is one of the rails clamped in place, the drift punch has the holes aligned, a proper drill bit is allowing the rail to trunnion measurement to align for smooth operation and you have the welder plugged into a good power source and you are sure the clamping force will cause a good contact between the two parts for welding. Double check every thing once again to make sure all are still aligned. Removing a spot weld is no fun, take your time and do it right the first time. | |||||||||
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| You now are ready to do the welds. As you bring the spot welders pinchers down to clamp the parts, make sure no parts are shifting under force. Now with your thumb, or trigger finger, move the switch to either side. You will hear the welder hum, and may see some small sparks. The trick to good welds is clamping force and speed. You should see the steel being welded glow cherry red. Remember not to forget to count to 3 fast! If you don’t you will get large, ugly spot welds or worse, a burn through. | |||||||||
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Your welds should look like a BB gun shot the steel parts, a nice round dark dent. This is the weld and is very strong. Where you place the welds will depend on your welders tip size, the part being welded, and how many welds you want to use on the rails. I prefer to use at least four per rail. It’s up to you to add more or less. |
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Once you are done, hand fit the barrel trunnion back into the receiver and verify the rail to trunnion line up. If all is well you are good to go on. Now do the other rail. Be aware that one of the rails is also the ejector. The ejector is made over size to allow the same ejector to be used with all calibers of the AK-47 type rifles. It is in fact made to fit .223 Remington, as it would have the smallest base of any of the cartridges. It is very important that the drill bit you are using will allow the bolt head free movement into the barrel trunnion and not strike the lower left portion of the barrel trunnion as it moves forward. Also, the ejector must ride in the groove milled into the face and guide rod of the bolt head. After you have welded the ejector make a mental note that unless you are building a rifle in .223 you will need to trim the ejector down with a hand held grinder. We will go though this step and other hand fitting steps later on. |
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You now have spot welded the two rails into place. The next step is to rivet in the barrel trunnion, front spacer and the rear trunion. The trigger guard will also need to be riveted into place. Most of the receiver flats will all ready be drilled for these parts at the factory. You need to do a hand fit at this time to make sure the hole will align with all parts. The receiver will now be cleaned of any welding splatter, and cleaned. You may wish to paint the areas where the trunnions mount to prevent rusting. Next: Part 4 Riveting the Trunnions and Part 5 a Full Screw Based Build. |
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| Article by Rob Summerhill (RapidRob) | |||||||||
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