Sunday, July 31, 2011

TF79 Upgrades --Part 1 Fitting an Accessory Rail

After shooting the TF79 a bit, there were a few modifications to the stock I thought would be helpful. (Note that this rifle is also known as the AR2078A.)

I had some accessory rail left over from the Haenel 303-Super project.

Yeah, pretty much the same job.

A few issues immediately arose. Where the Haenel forend was relatively square and blocky, the TF79 stock tapers on the bottom as well as the sides. Didn't have a way to fixture the stock to cut the slot.

Traced the outline of the rail then added some vinyl tape to act as guides.

Gonna freehand the slot with a trim router and a nice sharp bit.

Well, there's no turning back now. I consoled myself by noting that Archer Airguns sells reasonably priced replacement stocks for this rifle.

Multiple passes and slowly adjusting the depth of the cut

Almost there.

A few really small tear outs along the edge. The stock will be stripped and refinished, so those shouldn't be a huge problem.

Finished the slot with various wood chisels and scrapers. Was a relatively difficult slot to cut, as it had to be parallel, centered, the correct depth...

Test fit. Decided to fix the tear outs now while there was still sawdust on the bench for filler.

Scrounged up some shoe polish and clear epoxy.

The sides and bottom of the rail got a coat of shoe polish. The epoxy won't stick to the polish--it acts as a release agent.

Waxed rail installed.

Mixed the epoxy and added sawdust from the stock.

Pushed the epoxy into any and all gaps along the sides of the rail. Overfilling is preferred.

Pressed additional sawdust into the epoxy.

Gave it a few hours to dry then scraped off the excess.

Still need to fit the ends of the rail to the forend. A half-round at the rear and an angled cut up front would best match the stock lines.

Hogged out most of the curve on the drill press with a milling cutter. Just used it like a drill bit. The benefit was that it doesn't need center contact like a drill bit to feed into the work. The edge cuts efficiently even with overhang. I repeatedly moved the work int he vise, moved the vise, moved the table until I had a passable curve.

This was close enough to finish on a small sanding drum (not shown).

Pretty OK match to the curve for the mounting bolt.

It's not perfect, but it'll look just fine once the stock is finished. Sanded the epoxy filled edges to blend them into the stock.

The front of the rail just needs cut to match the angle of the forend. Marked it with a precision Sharpie. A hacksaw did the trick.

A bit of filing, but it'll be easier to sand the front as one piece later.

Lot more work to be done on this one. I'll keep the replacement stock from Archer bookmarked.

Check back soon.

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