ar 15 80 tutorial drill press

8/12/2019 AR 15 80 Tutorial Drill Press

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UT Arms 80% Billet Lower Completion on a Drill Press

This tutorial will cover the process used to complete a UT Arms 80% lower using only a drill press andthe fixtures from UT Arms. A drill press is designed to drill vertically, not mill horizontally. Due tothis fact, extra care must be taken. Be sure your chuck is secure and check it often. It has the tendency

to come off if you put too much side load on it. This can cause serious injuries. This tutorial is forinformational purposes only and all normal shop safety precautions must be followed.

Tools Required:- Drill Press- Allen Wrenches- 1/8 Drill Bit- 3/8 Drill Bit- 7/16 Drill Bit- Drill Bit- Drill Stops- 3/8 Endmill- Calipers- Fixture and Receiver From UT ArmsNew drill bits are recommended, but not required. Many of the drilling operations involved aretedious and the drill bit will try to walk out of position. New, good quality drill bits will helpminimize, but not eliminate this walking effect.


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1

stOperation: Mount Receiver in Fixture.

The fixtures from UT Arms make this simple. Simply align the side plates on each side so that thepins align with the front and read take down pin holes. Squeeze them together, and then place thesupplied bolt through the magazine release hole. Thread the bolt into the other side and tighten with anallen wrench.

Mount the top plate with 36 small holes in it to the side plates using the 4 supplied hex cap screws.Make sure the plate is flush with both of the side plates and tighten.

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Operation: Spot Drill (36) 1/8 Holes

Using a 1/8 drill bit, spot drill each of the (36) holes. Just drill down about 1/16 into the receiver.After all holes are spot drilled, remove the top plate and finish drilling the holes to a depth of 1.245.By removing the top plate, you are saving wear on the holes in the fixture and your fixture will lastlonger. Be sure to drill the 1 indicated hole all the way through to locate the trigger slot.

The easiest way I have found to get this depth is using a drill stop. Place the stop at the correct depthon your drill bit so you will know when to stop drilling. Just check it occasionally to make sure ithasnt moved.


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Go slow when drilling these holes and remove the chips from the drill bit often to prevent walking andpossibly breaking the bit. Using a lubricant will make drilling these holes esasier. These holes aretime consuming, but if you rush you could damage your receiver or break a drill bit off in one of theholes.

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Operation: Drill (14) 3/8 Holes

This is the most vital and most difficult step of the process. It can be difficult to keep the 3/8 drill bitfrom walking off course. Just take your time and be extra careful. You will be pretty good at it by thetime you finish.

Switch to a 3/8 drill bit and drill the (14) holes indicated on the template to 1.245. These holes canbe hard to drill because after the first one, the holes begin to overlap. I have found its best to drill thefirst row, and then drill every other row, and then come back to the ones you skipped. They are stilltricky, but this leaves the same amount of material on each side for the bit to cut. The drill bit will tryto walk. Keep a really firm grip on the fixture and go really slow. This process will remove most ofthe material in the fire control pocket.

Here you can see how I skip a row and the small portion of material left between. When you go backto drill the skipped rows, go slow and try to keep the drill bit from walking, especially towards theoutside of the receiver. If it walks towards the center of the receiver you can clean it up with theendmill, but it walks toward the outside, it will leave a groove.


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Operation: Drill (1) 7/16 Hole

Switch to a 7/16 drill bit and drill the 1 hole indicated on the template to 1.245.

Now you should have a rough fire control pocket that looks something like this. If you look close, youcan see the bits of material left on the sides by the drill bits. The next step will clean most of this up. I

took this picture before I drilled the 7/16 hole, but you can get the idea.

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Operation: Mill the Front Portion of the Fire Control Pocket

Attach the plate to the top of the fixture that has (6) 1/8 holes in it. Be sure it is centered as before.

Put a 3/8 endmill in the chuck and make sure it is as tight as you can get it. The drill press is notdesigned for side loading, and the endmill will have a tendency to slowly work its way out. Check itoften.

I use a 3/8 endmill with a cutter length of 3/8 from MSC Direct. Cutter length is the length thecutters come up the side of the endmill. Long cutters make it difficult to mill the pocket withoutdamaging the fixture. Just make sure the endmill you choose is center cutting.

For the first pass you will have to go really slow as you will be milling deeper to avoid damaging thefixture. Adjust the drill press table so that the smooth shank of the endmill is at least below the topsurface of the milling plate. Failure to do this will damage the fixture.

Lock down every adjustment your drill press has. Mine has a locking screw on the table heightadjustment and on the column where the head swivels left and right. You want everything to be stilland stable. Its best to leave the chuck all the way up and use the table to adjust your depth. Just besure to lock it back down each time.

Use plenty of cutting fluid during this entire process and keep the chips cleaned out using a shop vac orother means.

Keep a tight hold on the fixture and mill in a clockwise direction using the milling plate as a guide.The smooth shank of the endmill should ride against the milling plate. The first pass will vibrate a


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good bit as you take a pretty deep cut. Slow and steady is the key. This pass is the most difficult andthe most likely for something to go wrong. Stop a few times and make sure your chuck is secure andthe endmill is still tight. Also make sure you are deep enough and the endmill is not cutting into yourmilling plate.

After the first pass, drop down about .025 (25 thousandths of an inch) and make another clockwisepass. This one should go much easier. Be sure to keep your chips clean and the cutter lubricated.

Continue to mill going down .025 with each pass and go in a clockwise direction until you reach adepth of 1.25. Depending on the length of your endmill, you may have to remove the milling plate asyou get near to full depth. Just make sure that at least of the smooth shank on the endmill is belowthe top of the receiver. Use the area on the receiver that you have already milled as a guide just as youused the milling plate as a guide before.

Be sure to lock down all adjustment points on your drill press each time.

The last little bit of depth is a little deeper than the holes you drilled. This will get rid of the dimplesleft in the bottom by the drill bits. This is where a center cutting end mill is important.

Be sure to check your chuck and endmill often to make sure nothing is coming loose. Using the drillstop is optional here, but I would recommend using it because the endmill will want to work its wayout of the chuck. This can cause you to go deeper than you wanted without knowing. If you dont useit, stop often and check your depth. Check you depth after every pass when you get close to 1.25.

Dont worry too much if the sides of your fire control pocket are not perfect. You can sand themsmooth with a file or dremel after you are finished.

After the milling, I had some grooves left in the side of the fire control pocket where the drill bitwalked off a little. This can be smoothed out with a dremel when everything else is done.

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Operation: Drill (6) 1/8 Holes

While you still have the milling plate attached, put a 1/8 drill bit in the chuck and spot drill the (6)1/8 holes as indicated on the template. Remove the milling plate and finish drilling the holes to adepth of .625 using the same process as before.


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Operation: Drill (2) Holes

Put a drill bit in the chuck and drill the (2) holes as indicated on the template to a depth of.625.

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Operation: Mill the Shelf

Reattach the plate with (36) 1/8 holes and mill the rear shelf to a depth of .630 using the sameprocess as before. Some of the shorter endmills are not long enough for the drill chuck to clear tobuffer tower. Due to size differences in different chucks there isnt a universal length. If the endmill

you have is too short, just do as much as you can and finish the rest with a dremel. I was lucky andhad a longer endmill so I just used it.

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Operation: Drill Fire Control Holes

Using a 5/32 drill bit, drill the holes for the hammer and trigger pins through each side of the fixture.Drill each side of the receiver separately. Trying to drill all the way through both sides of the receiverat one time will cause the drill bit to walk, and your holes may not be in the correct location.


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Operation: Drill Safety Selector Hole

Using a 3/8 drill bit, drill the safety selector hole using the same process described in operation 9.

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Operation: Trigger Slot

Turn the fixture over and locate the 1/8 hole that you drilled all the way through in operation 2.

Option 1: Drill a second 1/8 hole .365 toward the front of the receiver from the center of this hole.Then use a 5/16 drill bit to enlarge both holes. You can then use a file or a dremel to remove thematerial left between the holes.

Option 2: Drill a second 1/8 hole .365 toward the front of the receiver from the center of this hole.Use a 3/8 drill bit to enlarge both holes. Then use the 3/8 endmill to connect the holes. You canclamp some guides such as a 2x4 to your drill press table to help you keep a straight line.

Measure forward .365 from the center of the 1/8 hole and scribe a line.


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Then find the center line of your receiver by measuring the width and dividing that in half. My halfmeasurement was .455. Yours should be very similar. Scribe a line there intersecting the otherscribed line.

Drill the second 1/8 hole at this intersection, and then enlarge both holes to the size depending onyour option chosen. Ill be using option 2, so I enlarged mine to 3/8.


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Heres a picture of my make shift guide. You can also see how the (2) 3/8 holes just barely connectand leave material between them. I clamped a wooden slat to the drill press table as guide. Lower the3/8 endmill into one of the holes, then slowly move it to the second hole.

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Operation: De-burr the Trigger, Hammer, and Safety Selector Holes

This is an optional step, but I have found it the easiest way to create nice looking holes.

Remove the receiver from the fixture.

The holes you just drilled probably created some burrs on the outside of the receiver. You can sandthese off, but this creates variations in the finish of your receiver, especially if you are going to anodize

it. Take a large drill bit and just barely tap the holes. This will quickly remove the burrs and provide aslight counter sink. Just tap the drill bit on the hole lightly once or twice until you are happy with theresult.

Attach one side of the fixture plates at a time to the side opposite you are drilling. This will give you aflat surface for the receiver to sit on.

The size of the drill bit is not important as long as it several sizes larger than the hole. Just usewhatever you have. You will have to use a different size for the safety selector hole because a bit bigenough to deburr that hole will hit near by features of the hammer pin hole.


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Operation: Smooth Fire Control Pocket

Now you will probably need to smooth out imperfections in the fire control pocket. You will get better

at the milling process the more receivers you do and eventually can skip this step. The quickest thingto use is a dremel with assorted sanding drums. Keep the drum moving all the time and dont take offtoo much material. You want to smooth it out, but once your gun is assembled, you wont see most ofthis. So dont sand so much that you have thin walls on your receiver because you tried to smooth outsomething that you will hardly ever see. The width of the pocket should be .690. You can be a fewthousandths over this, but too much will cause slop in your trigger and hammer. In extreme cases, thiscould be dangerous.

Here is the finished fire control pocket. This is probably best looking pocket Ive done on a drill press.You learn by your mistakes and each time you will pick up something that you could do different to

make things a little easier.

Now you are ready to test fit your receiver. Install the trigger, hammer, safety selector, and pistol gripand make sure everything functions as it should. Be sure to check the function of the safety. You maynot want to install the pivot and take down pin detents until you apply the finish to the receiver.Sometimes they can be difficult to remove once installed.


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Hopefully this tutorial has been educational and helpful. I make no guarantees, but this is the process Ihave used and it has worked doing several receivers, and they all functioned just fine. The fire controlpockets on the first ones were not perfect, but you never see that once the gun is assembled.

I would also suggest upgrading to a small milling machine if you plan on doing several receivers. If

you ask around, several of your friends may be willing to split the cost of the fixtures, and maybe evena small milling machine if you get enough of them together. Just remember they must complete theirown receivers in order to comply with regulations. Small milling machines can be purchased new foraround $500.00 from Harbor Freight and Grizzly. They are table top models and are perfectly capableof completing lower receivers. They drastically reduce the time involved and its easier to achieve abetter finish on the fire control pocket.

ar 15 80 tutorial drill press

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