Tech Force TF79 / AR2078A Upgrades--Part 9

Some quick notes about what's coming in the semi-near future: I've got one of Frank B's Feinwerkbau 124Ds to overhaul with some Maccari parts--and I may use that as an excuse to take a break from the Tech Force. Also, I have a lost post from August of 2009 that I started to write, then shelved, on a stock modification for a BAM B26-2. I liked the concept, but I wasn't happy with my sketches or the first prototype. (We call them prototypes when it all goes wrong) Anyway, I've got a better(?) way this time around, so that's back towards the top of the project que. Right now, I'm checking back in with our slowest airgun project to date: The TF79. With the holes drilled for the adjustable cheek piece, it was necessary to add two more additional holes in the side. I'll make threaded aluminum inserts for these holes that will house screws to lock the cheek piece in position. Yeah, there was layout to find the locations for the holes. The 1/2" holes allow for easy insert manufacture from a piece of stock aluminum rod.

Many chemical strippers have a shelf life and my old can of Strypeeze was apparently done. It barely softened the finish.

Got a can of Dad's Easy Spray and it did the trick on the heavy Tech Force finish. I'm guessing that it was an acrylic. Whatever it was, it was excruciatingly difficult to remove. Sanding it all off was out of the question due to it's thickness as it instantly loaded the sandpaper.

Some thin stain left behind. That was straightforward to sand out. Sanding drums, the Dremel tool and a lot of time reshaped and blended the adjustable cheek piece into the body of the stock.

Here it is, sitting at 100 grit. Needs to go to about 220 or so to be somewhat respectable. There's a few tiny areas that still need the factory stain sanded off. Probably another two hours of work before it's ready for some color.

Happily surprised to find zero wood filler. From all the airgun article I've read over the years, I was led to believe that massive amounts of wood putty was mandatory for China made rifle stocks. Maybe in the past, maybe on some, but not here. The only filler present is the small amounts of epoxy that I added when fitting the slot for the accessory rail. I'm tempted to make a slightly flared maple grip cap to get some extra length on the short (for me) grip. Since it's taken this long already, I'll probably do it. Assuming that the dark areas are mineral streaks. I've no idea what kind of wood this is. Hope it stains well. Let me rephrase that. I hope it stains well the first time, as I have no desire to sand it out and start anew. More soon.

Tech Force TF79 / AR2078A Upgrade--Part 8 Adjustable Cheek Piece

With the adjustable butt plate ready for installation, I went back to the stock for an additional change. Wanted to make a relatively simple adjustable cheek piece. Didn't have a bandsaw available and didn't want to bother anyone for a single cut. What's the worst that can happen? Taped up the stock and just made the cut with a scroll saw. Had to do only a minor amount of truing up the cut surfaces. Just to make things even easier, the rear of the piece was cut at an angle. With the thickness of the saw blade as well as the clean up on each piece, there was a gap. Found a piece of maple and the Gorilla Glue... and clamped it up. Trimmed the maple back a bit. Glued up a second piece of maple to the angled rear cut. In a huge fit of stupidity, I elected to use blind holes for the adjustment rods in the stock and cheek piece. Had I any sense, I'd have drilled from the bottom of the stock upward into the cheek piece before cutting it off. That would have aligned all the holes--but left two visible holes in the bottom of the butt stock. Blind holes require drilling four holes in two pieces and get all of them correctly aligned. As I'm working on this in my free time, it took a couple days to work out how to make this happen. After marking the butt stock, I center-punched the marks. Set a 1/8" ball bearing into each marked hole. Aligned the cheek piece and seated it firmly into the stock. The two ball bearings transferred small dimples to the cheek piece to mark the hole locations. Used a bubble level to align the bottom edge of the cheek piece. Drilled the holes with a 1/2" forstner bit. These are the holes in the cheek piece that the adjustment rods will be glued into. I didn't get any pics while drilling the butt stock. My fixture was too horrific for pictures. Essentially, I leveled the flat section in a similar manner to the above pic and drilled the holes. Uh, essentially. Cut off a couple pieces of 0.500" aluminum rod. Faced then beveled the butt stock ends The cheek piece ends were test fitted, marked for seating depth, then grooved for the eventual glue that will hold them in place. It took an evening, but a test fitting proves the cheek piece holes all line up and it slides up and down. Need to make a couple fittings to hold the cheek piece in place, then refinish the stock. Astonishing sidebar: This is the 550th posting for the blog. Congrats, Nick. As always, more soon.

Tech Force TF79 / AR2078A Upgrades--Part 7 Finishining up the Buttplate

Back at it. With the baseplate done, I can finally attach the buttplate to the rifle and shape and adjust as required to get a good fit. First wanted to take the corners off the shoulder blocks and add a curve. All three blocks got the same treatment. Not going to show it all here, but tried to carry the curve through the three pieces. The scratched up aluminum look wasn't going to cut it. I wet a piece of 500 grit emery cloth with some WD40. Any light oil would probably work just fine. The trick is to keep the piece flat and sand gently, but briskly in the oil. A slurry of aluminum dust and the abrasive is created. This puts a fine scratch pattern on the piece--a nice matte gray. Sanded each piece, each side. Also finished the accessory rail to match. The cohesive finish will help tie the gun together aesthetically and keep it from looking like a hodgepodge collection of parts. Tried assembling the plate to the base, but using separate mounting nuts wasn't going to work. The stock has a groove cut in the butt from the factory. Regular nuts just spin on the mounting bolts. I'd have to take off the baseplate each time I made a vertical adjustment. Making a single nut that's close to the groove width and depth solves the problem. Started with this nasty, rough cut, out of square, piece of steel scrap. Could've milled or fly cut but I chose to just face both ends in the lathe. Then cleaned up the wide flats, then the sides. Here it is next to the baseplate. It's trued up to within a few thousandths. More than good enough for a nut. Transferred the hole spacing to the piece, spotted and through drilled. Tapped each hole M6 x 1.0mm. OK, I started the holes. Couldn't finish them by turning the chuck by hand. Clamped the piece in aluminum jaws and finished with a proper tap handle and some cutting fluid. Rounded the top off on the belt sander to match the groove in the stock. That lets the piece slide slightly further upward. It's pretty thick. Wet sanded the piece like the aluminum. Serious overkill for something no one will ever see once installed. I test fit everything and wanted more purchase on the buttplate. Some grooves on the shoulder piece will help and add some visual impact. Did the layout then mounted a pointed indicator to center. Traded the point for a 3/16" center cutting endmill. Arbitrarily set the depth and made a single pass. Barely stopped myself in time. Had to remove the endmill holder with the cutter and replace it with another to hold the pointed indicator to center for the second groove. If I'd pulled the endmill, I'd have lost the location it was seated to in the holder and each groove would be a slightly different depth. Tedious, but there were only five grooves. Did some clean up. Leaving the grooves as milled. I like the cutter marks. The rest of the piece was wet sanded again to fix the matte finish and remove burrs. Final test fit to the baseplate. Blued the steel hook and main rod with Van's cold blue. The custom nut. Got some stock work to take care of next before this all comes together. More soon.