Wednesday, March 23, 2022

A New Bolt Handle for the Tech Force TF79 / AR2078A

Since it was still in pieces,  the TF79 upgrading continued.

Wanted to try something different from the factory cocking handle. 

Thought I'd make a bolt stem and attach a separate ball handle.  I started by sourcing a 1" diameter rubberized ball handle with 1/4-20 female threading.  Got it from McMaster-Carr for about $4.  They're sold as replacements for machine handles.

Much better than I could make for four bucks.

This should be an easy project.  The TF79 bolt has an 8mm hole.

Found a piece of 8mm stainless rod as well as a piece of 5/16" drill rod.  Something like 0.002 in difference, I think?  Close enough that either will work.

The stainless rod looked to be spot on already for length, so I went that route.  I dusted a couple thousandths off one end to round it up.

Skimmed the face and broke the sharp edge.

Test fitting already.  Guess I'm almost done.

Got the set screw hole location and diameter from the original bolt handle.

A little magic marker and the caliper scratches the location.

Need to hold the rod to drill the hole.  A 5C collet block is easy.

The stem in a 5C collet

Into the milling vise and picked up the edge. 

Dialed over to center then picked up the scratched line.

Spotted then drilled.  Size?  Dunno, it was the drill bit that just fit into the original part. 

Like so.

And it was test fit #2 time.  Made sure the set screw locked the handle to the bolt.

Then back to the Taig lathe.  Turned the opposite end down to about 0.248"

Found my 1/4-20 die and the Taig tail stock die holder.

The holder fits on the tail stock drilling attachment and aligns the die to cut threads concentric to the work.

Threaded, trimmed the thread to length, and a quick polish.

Screws right on.

Looks like its a go.

Installed in the breech.  Feels better than ever.  Honing the inside of the breech really did the trick.

And put the TF79 back together.

Soft grippy bolt knob. 

It's good.  I like it.  This rifle is all about options and adjustments, so what else?

Back to McMaster-Carr.  $5 this time around! 








1" diameter polished aluminum ball.

With 1/4-20 threads.

Seconds later. 

Pretty slick.  I think either of these are better than the factory bolt handle.  The old Tech Force is coming along.

More in a couple days.