Sunday, September 18, 2016

Upper, part 1

Still need to blue and engrave lower, but it is done and functional. Still need to find missing sight. May rob a scope off of the one of my other AR's to use. Just don't want to have to sight it back in as it is set perfectly for the rifle it is on.

I figured it was nice out, so I wanted to play in the garage. I started machining on the raw upper casting. Had to think about how to approach it. I figured, looking at the blueprint, most dimensions come from the center of the hole, so, I figured, square everything up so I can hold on something. Next up, find the center of the thread boss and drill a precise hole, followed by, drilling a hole through.

After several attempts, I came up with this one to hold part while making first cuts. I did the top first.

Here, I did the front of the thread boss, the rails, as well as a cleanup cut on the back face. I figure this trues up three of the four sides so I can rest on any surface to machine another side. I am not finishing anything at this time, just squaring things up so I can grab them in a vise, or clamp to an angle plate.

 Here is the clean up pass on back side of upper.

Now, I was able to flip it, put it on parallels in a vise and cut the panel on the other side. This pic doesn't show it, but I also did a clean up pass on the top and front of the two nubs so as to square them up if I should need to clamp on them later.
I clamped the part to an angle plate, using a second angle plate and a parallel to square part up and support it for drilling operations.
I center drilled the part, followed by drilling through with a 1/8 diameter drill. I drilled about half way through, when I needed more clearance for flutes of drill. I ran a bigger diameter drill down most of the way, leaving some of the 1/8 inch hole for the drill to follow. In the end, it did walk off center, which I pretty much expected, but hoped against. It only walked about .060 to one side (but did stay centered up and down). So, plan B.
I clamped it the other way and used a center cutting end mill to center things back up. I used my extra long 3/8 end mill from the lower project. I followed this up with a 1/2  end mill. I will do the same on the other side. My new plan is to use a 1/2 dowel pin on each end to use for indicating center of hole to use as a datum point.
This is the other side also opened up and ready for the dowel pin. This should not have been such a long job, but my mill is extremely primitive. I have little travel on the ram and have to move the head up and down frequently for height changes, which is a real PITA. I really want to upgrade my mill. I believe I am going to buy myself a Christmas present this year. I know what I want, and the travel on it is a lot more, plus it is built a lot sturdier than this one. Plus, it is variable speed. I bought the one I have now off Craigslist, which is probably how I will get rid of it when I upgrade. The new one will be a table top model again, but bigger. It is also upgradable to CNC.

I am hoping on moving next year so as to get a bigger garage. Am watching a house about a mile down the road. It has possibilities, if the price drops. It only has a 1 1/2 car garage, attached, but, it has a bit over an acre of land. Plenty of room for a pole barn and/or garage. In that case, the attached garage would become the shop. I would then be looking for an actual Bridgeport at some point down the line. The new table top mill at that point would turn into a CNC at some point. Only reason I am really hesitant on that house is, school is back in session. I need to sell this house to move. This subdivision sells immediately during summer break. It is a perfect family subdivision and people tend to move more in the summer when school is out. There are a few houses for sale in my neighborhood now, and they aren't moving. During the summer, average time on market in this subdivision was a few weeks. If he drops the price on the house, I may have to go for it. It does have hardwood throughout and a walk out basement. House itself is fairly small, but the property would make up for it. A garage would be built immediately at time of sale as I would have it in the mortgage. I love my house, I just hate having to pull the car out to do anything. During winter, it is hard to pull the Vette out and get it out of the way. I could definitely get a lot more done with more room.

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