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. 

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Quick Recrown and Deburring for the Tech Force TF79 / AR2078A Barrel

Picking up when I left off with the TF79, figured it was time to give the barrel some attention.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The original muzzle crown.   We've seen much, much worse.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

And since it's out of the breech block, here's the aft end of the barrel.  The o-ring grooves and the dimple for the barrel retaining set screw are a bit sharp and bitey.

 

 

 

The pics didn't come out as well as I'd hoped.  Not enough light.  Some aluminum sheeting was used as chuck padding for the barrel.

Skimmed the face.

Recessed, then cut an 11 degree angle.

Flipped the barrel around and knocked down the high spots.  Just softening edges.

Like so.

The crown--before going back to polish.

Some new o-rings for the breech end of things.

A final pic of the muzzle after some polishing and a re-blue.  

I did end up making a new bolt handle.  Really just to try something different.  Try to get that posted in the next few days.

Thanks for reading.

Breech Honing the Tech Force TF79 / AR2078

Got three or four airgun projects in process right now.  Thought I'd get a quick post up with one of the happenings.  I've been shooting my old Tech Force TF79 target rifle, and while I've reworked the stock, the mechanical parts have been left almost untouched.   I did try to smooth out the bolt loading mechanism a few years ago.  Trued up the bolt body.  It's been straightened, polished and deburred.  When cocking, the bolt mechanism feels like it's full of sand and gravel.  It originally felt like it was full of rocks--so at the time this was an improvement!

Thought I'd give it another go and smooth out the inside of the breech this time around.

 

Removed the breech and took it into the shop.

 

Yep. Tech Force.  Is that brand name still around?   Pretty much identical to the AR2078A CO2 rifle--or QB78, or QB79, or Crosman 160...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Found a few 1/2" diameter silicon carbide Flex Hones from Brush Research.   These are also sometimes referred to as "Ball Hones" or "Cylinder Hones"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This particular flex hone is pretty worn.  I'll start with it and see how it does.  I really only want to knock off the high spots.  If this doesn't work, I can always hone the ID on a Sunnen horizontal machine and really get the gouges out.

 

 

 

 

 

 

Simple.  Chuck it in a drill, flood the tube with oil and hone away.  Keep the hone moving.

 

I cheated and got some honing oil from one of the Sunnen machines.  The used oil works great with flex hones because it's charged with very tiny particulates (micro pieces of grinding stones and ultra fine metal dust) from the honing process.

Still see some rough machining marks.  As long as the high spots and sharp edges are gone, this should be OK. 

Didn't bother with the very front of the breech where the barrel fits.

Fixed?  Dunno yet.  It occurred to me that while the gun was apart, this is a fine time to re-cut and crown the muzzle. 

Are the remaining scratches in the tube a problem?  Doubtful.  If it was a mirror polish, I'd have honed the tube to intentionally put some scratches in there.  The scratches retain lubricating oil.  

Anybody got a favorite grease/oil for the QB bolt mechanism?

More in a couple days.