Machining a Para TTR Gas block

[Duc]

Old coworker has been looking for a Para TTR gas block to finish off a build for a few years. The parts used to be at a few different sites but those are long gone. I happen to have a Para TTR AR15 rifle. Took awhile to build the solidworks model to machine the two parts from. Hopefully I trade some 1911 custom work for building this.

Material: 4140 PH
Machine: Fadal 4020
Cam software: HSMworks plugin for solidworks

Going to be alot of pictures.


Lower bracket

Material was oversized for both parts due to cost and what was on mcmaster

3D profiling the .75 Diameter for the barrel. Roughed out with a 3/8 endmill before finishing off with a 3/8 ballnose with a .003 step over

Flipping over to remove the bulk of extra material

Finishing off one side of the lower bracket

Flipped back over to finish off the lower bracket

Upper Bracket
The upper bracket was going to be a bitch compared to the lower bracket.

Rough machining the top of the upper bracket. 3D profiled the angle into the wings and left some extra material for the hard part. Section to the right of the blue mark.

Pucker factor drilling 2 holes 2.7in deep hole using a 1/8in drill bit. Calculates out to about 22x the diameter for the bit. I found a dewalt 12in 1/8 drill bit from home depot for $11 that I could cut down to 5inches overall length. 760 RPM .083 IPM with a peck every .100 so I could clean out the chips and relube with tap magic. My heart rate was spiked during this operation since I didnt want to lose the part.

 

[Duc]

Finished off the other features of bracket before changing orientation for next op. Chamfer is used to clear the radius in the barrel profile when it changes from .750 to ~.850in I think. 8-32 tapped into the top hole for a set screw. Lower hole drill to .22 for .400 for the gas tube.

Section view on how the block works

Barrel setup. A small spacer goes into the barrel and upper part of the gas block.

Removed the extra material before drill and tapping the holes for the bracket. Holes were hand tapped to 6-32 to avoid breaking tap into hole. Used a spring center tap guide.

Profiled the tube into the bracket using the same settings as the lower bracket. 3/8 ball nose endmill with .003 step over.

Cleared more of the bracket

I still have a few more things to machine on the upper piece. Maybe tomorrow or Tuesday

Test fit of both brackets on the spare barrel

 

[Duc]

Finished off the machining to the gas block but still need to make the barrel spacer and rail plunger that sits in the gas block to hold the rail into place


Showing the bottom hole for the barrel gases to enter the gas block. I need to machine a spacer thats roughly .25x.150in with a .80 hole thru it.

Drilled the .078 cross hole for the plunger and .062 to pin the gas tube. I should have drilled these holes first but the old coworker can finish off the .062 hole when the gas tube is in place. Drill bit wont drill thru the cross hole.

 

[Brokenxj]

That is great work, amazing skillset

 

[carslut]

looks like some killer work! ...... now go test it and report back

 

[Duc]

That is great work, amazing skillset

Thank you

looks like some killer work! ...... now go test it and report back

Parts will be shipping off soon to the buddy otherwise I might.

Finished off the last small parts for the build. The plunger piece and a barrel plug to interface between the barrel and the gas block