True Bore Alignment System

[BuffaloBill]

My first point, on a 4 jaw, is where the pivot point is. Second is another 1.5 inches or so inward... but with the TBAS your pivot point is adjacent from where you will be dialing.

Could you help me understand what you mean by adjacent?

 

[BuffaloBill]

Measuring the pivot location:

I chucked a length of 1 1/4” bar stock in the ER-50, adjusting the TBAS to make it tram parallel to carriage movement. For simplicity of calculation I set the dial indicator mounted on the carriage to read 0.6250” (the centerline of the bar stock) against the bar stock (the X axis on my DRO). Then adjusted the TBAS to angle the bar stock to nearly as much as the radial adjustment screws allowed, and took X dimensions at two points along the spindle axis. One at 0.250” outboard of the collet face and the other at 5.250”. This data allowed calculation of the angle and ultimately the pivot location.

Edit for typo: I find this location to be 2.250” behind the collet face.

One source of error in my measurements is that I only eye-balled the squareness of the indicator to the spindle axis. Another is eye-balling to position a pair of radial adjustment screws perfectly vertical. I went and dislocated my right shoulder Sunday so am down to mostly one hand at the moment. But at some point will revisit this, insuring that indicator is square and the pivoting plane horizontal.

This depth is too deep to reach with the 312b-15 when the blank sticks out of the collet enough to cut a tenon. So will use the Gordy rod & bushing again next time. I would hope to find that dialing the axial adjustment measured at this location, would eliminate most of the interaction from radial adjustments. I imagine the bushing having length will prevent a perfect indication at the pivot point? It would have been nice if this calculated pivot point was within reach of the Interapid.

 

[Ksracer]

I believe this is the general idea of what you're describing. My initial impression when I got mine was that a larger radius Ball and Socket on the radial adjustment would have moved the pivot point forward so that it could be reached with a long stem. Maybe I'm wrong.

 

[BuffaloBill]

I believe this is the general idea of what you're describing. My initial impression when I got mine was that a larger radius Ball and Socket on the radial adjustment would have moved the pivot point forward so that it could be reached with a long stem. Maybe I'm wrong.
View attachment 1691616

Yes, I had the same thought.

 

[Ksracer]

I went and dislocated my right shoulder Sunday so am down to mostly one hand at the moment.

I completely dislocated mine 4 separate times before I was 30. I had a labrum repair done in my late 30's to fix some of the damage. It doesn't slip out of socket any more but my mobility is pretty bad on that side.

 

[DSMWerks]

I would not use a 3d printed collet on the chamber end of coarse and there is no need but for the muzzle end it is easier than making them out of aluminum. I modeled some up for barrels I have around and will try one next time. I made one master blank. I measure the two diameters 1.500" apart on the barrel in the area I want to hold it and extrude them into a solid and subtract it from the Blank. I put some dimples on the muzzle end of the sleeve so I can identify it easily. I can't attach an STL file but if any one want them PM me and I can send it. I don't have any barrels right now or this would be a post about trying this out.

 

[urbanrifleman]

I would not use a 3d printed collet on the chamber end of coarse and there is no need but for the muzzle end it is easier than making them out of aluminum. I modeled some up for barrels I have around and will try one next time. I made one master blank. I measure the two diameters 1.500" apart on the barrel in the area I want to hold it and extrude them into a solid and subtract it from the Blank. I put some dimples on the muzzle end of the sleeve so I can identify it easily. I can't attach an STL file but if any one want them PM me and I can send it. I don't have any barrels right now or this would be a post about trying this out.

Nice design.

 

[BuffaloBill]

A brief update on my TBAS experience:

I dialed in a barrel for the second time the other day. This time using a long-reach Interapid rather than the rod & bushing. Although I couldn't reach all the way in to the radial pivot point, the process didn’t take near as long as my first attempt, to reach a dead needle at the two locations. I’m very pleased with the TBAS w/ER-50 collet chuck.

 

[DSMWerks]

I had a buddy print a tapered sleeve for this fat Shilen barrel. It's the same length as the 31mm ER50 collet and100% fill. I will give it a try soon

 

[BuffaloBill]

I don’t mean to dilute this TBAS thread with extra stuff. But I convinced myself this is somewhat related:

Today my BIL shot for the first time, the 6BRA I just put together for him. This was the first barrel chambered by me using the TBAS. And although I struggled a bit (that first time) to achieve a perfect dial-in, the results seem pretty great. So if someone is apprehensive about the TBAS with ER-50 collet chuck for precision barrel holding, this one example points towards it working just fine.

We forgot to note on the target that it is a 3-shot group. This was shot after two fouling shots, after cleaning the barrel, after a few sight-in rounds. Bullets seated .008” into lands from touch point (Wheeler method). Shot off of concrete bench & Seb NEO, not the bipod shown in pic. We did have wind but were shooting between two cornfields, without wind flags.

Kauger CRS II
Krieger HV .237 7.5T finished at about 28 1/4”
6BRA Wheeler #1 reamer .268NK .104FB
MTD ACC chassis, bedded at tang & recoil lug area with MarineTex gray
Leupold Mark5 HD 7-35X

 

[Sniperhandle]

I don’t mean to dilute this TBAS thread with extra stuff. But I convinced myself this is somewhat related:

Today my BIL shot for the first time, the 6BRA I just put together for him. This was the first barrel chambered by me using the TBAS. And although I struggled a bit (that first time) to achieve a perfect dial-in, the results seem pretty great. So if someone is apprehensive about the TBAS with ER-50 collet chuck for precision barrel holding, this one example points towards it working just fine.

We forgot to note on the target that it is a 3-shot group. This was shot after two fouling shots, after cleaning the barrel, after a few sight-in rounds. Bullets seated .008” into lands from touch point (Wheeler method). Shot off of concrete bench & Seb NEO, not the bipod shown in pic. We did have wind but were shooting between two cornfields, without wind flags.

Kauger CRS II
Krieger HV .237 7.5T finished at about 28 1/4”
6BRA Wheeler #1 reamer .268NK .104FB
MTD ACC chassis, bedded at tang & recoil lug area with MarineTex gray
Leupold Mark5 HD 7-35X

View attachment 1694532View attachment 1694533

Nice Job.

 

[BuffaloBill]

Nice Job.

Thank you!

 

[urbanrifleman]

I had a buddy print a tapered sleeve for this fat Shilen barrel. It's the same length as the 31mm ER50 collet and100% fill. I will give it a try soon

Those are so cool.

 

[Nbmonte]

Anyone have any contact info for Straight shot gunsmithing? I’d like to order a TBAS, but can’t get the website to work.

Thanks

 

[Sniperhandle]

Anyone have any contact info for Straight shot gunsmithing? I’d like to order a TBAS, but can’t get the website to work.

Thanks

Try his Fakebook account.

 

[urbanrifleman]

I would not use a 3d printed collet on the chamber end of coarse and there is no need but for the muzzle end it is easier than making them out of aluminum. I modeled some up for barrels I have around and will try one next time. I made one master blank. I measure the two diameters 1.500" apart on the barrel in the area I want to hold it and extrude them into a solid and subtract it from the Blank. I put some dimples on the muzzle end of the sleeve so I can identify it easily. I can't attach an STL file but if any one want them PM me and I can send it. I don't have any barrels right now or this would be a post about trying this out.

Send me the whole set and I will print them up.

What is the OD?

 

[LVLAaron]

Send me the whole set and I will print them up.

What is the OD?

I posted some code earlier so you can make your own. OpenSCAD isn't too difficult to figure out. If you measure things well, you don't really need to make the "collet style" - I printed some that are solid PLA and just give them a good whack onto the barrel and they're snug as a bug.

 

[DSMWerks]

I made the taper muzzle end 3D printed collets with a 1.216 straight OD so they fit 31mm ER50 collet real nice. These budget 3D printers just amaze me how they can hold tolerance. No where near I can on my CNC machines but still amazed.