Gunsmithing Looking at action truing fixtures for chambering work? Which one?

[BenY 2013]

Right now the only two that I have seen are the Viper and PTG. In you're experience which is better suited for chambering barrels or is there another? I worry that I may get chatter with that much handing out of the chuck, any experience here? I decided instead of looking for new lathes now I would get one of these and use with the lathe at work or my friends house, one day however I will have my own. Just wanted to know the thoughts of the guys who use them here! Thanks

Ben

 

[STR]

The cuts you'll be making will be so light that there shouldn't be any chatter. However, if you want to be close to the chuck, take a look at what William Roscoe uses, which he made him self. I have done the same and highly recommend it. It is simple to use, and easy to make. I think there are pictures of it on his web page. Take a look for yourself. William is an awesome rifle builder, and this is what he uses.

Louisiana Precision Rifles, LLC - Precision Firearms - A list of custom reamers we use to chamber barrel blanks

 

[Gene Poole]

PTG sells the Viper rig now as their only truing fixture don't they? Do they have another I don't know about?

I have the Viper rig and it works OK. I do have a few things that I would do differently: make it cylindrical (no flats), and make it shorter. The flats on it make it really difficult to true up with a dial indicator. You could chop 3 inches off the length and still get the adjustment needed for long or short actions by using the set screws between the jaws on a 4-jaw instead of putting them in line with the jaws and having to stick it out past the jaws to adjust it.

 

[LRI]

Might consider this as well when pondering a fixture. Especially with supporting a heat treated receiver with a hand full of brass tipped screws.

For those with the equipment, conduct a simple experiment if your so inclined. Throw a piece of material in your lathe, something similar in hardness to a receiver if possible. With an insert carbide turning tool, take a .025" depth pass and see what finish you get. So long as everything is right, pretty good I'd bed. Really good if your speeds and feeds are correct.

Now, same tool, take a .001" depth of cut and repeat. Is it just as good? I'm betting no.

Why?

Tool pressure, machine rigidity, and style of tooling.

Repeat with a threading tool and see if results are similar. I'm betting yes. (would not advise a .025" DOC with a threader though) Now switch to HSS with some cobalt and try again. So long as you don't cook the tool it'll prolly cut really nice on a light pass. Why? HSS is sharp where's carbide inserts generally aren't. Less tool pressure although you give up efficiency due to loss of hardness.

Various grades of carbide come sharper than others. If your taking light cuts, consider a harder grade as it'll likely have a sharper cutting surface. Know though that it'll break down sooner as the radius feature on the cutting edge and shallower rake angles on softer grades helps direct heat back into the chip instead of cooking the insert. The softer grade is "tougher" and withstands the abrasion longer. Hard carbide is more apt to be brittle and prone to chipping. This however does reduce the tool pressure. Bounce a tool lightly across a surface and it'll want to sing like a choir. Load it and it tends to shut up. Properly adjusted gibs and tight machines go a long way towards producing nice finishes. So does a more solid form of work holding and this is where Roscoe's fixture is really advantageous over the pipe and screw contraptions.

Hope this helps someone next time they run into this stuff.

 

[BenY 2013]

I really appreciate the input guys! Sounds like you may have saved me some headache! I love when professionals join in to weigh their opinions! Only here on the Hide!

Ben

 

[jscandale]

It's an expensive option, but the True Bore Alignment System from Straight Shot Gunsmithing is like the Cadillac of apparatus for truing actions and threading short barrels.

JS

 

[rigmaster10]

I like the ptg kit. Simple and easy. Forget the action spyder.

 

[Killswitch Engage]

cut it off and turn a section of the flats off in your lathe if you want to indicate it easier. better yet, get yourself a spare chuck and just leave it in there.

PTG sells the Viper rig now as their only truing fixture don't they? Do they have another I don't know about?

I have the Viper rig and it works OK. I do have a few things that I would do differently: make it cylindrical (no flats), and make it shorter. The flats on it make it really difficult to true up with a dial indicator. You could chop 3 inches off the length and still get the adjustment needed for long or short actions by using the set screws between the jaws on a 4-jaw instead of putting them in line with the jaws and having to stick it out past the jaws to adjust it.

 

[Terry Cross]

The flats on it make it really difficult to true up with a dial indicator.

You could chop 3 inches off the length and still get the adjustment needed for long or short actions by using the set screws between the jaws on a 4-jaw instead of putting them in line with the jaws and having to stick it out past the jaws to adjust it.

I don't run that type fixture but.....

Couldn't you indicate the fixture into your chuck by going just inside the I.D. at the front?
The fixture's through hole is prolly bored at the same setup as the O.D. and should be concentric.


I also agree about whacking the length way back.
Sticking things that far out of your chuck is never good. Because the fixture O.D. can't actually slide into the through hole of the chuck and sits against the face of the chuck, you will only be catching the fixture with the outboard 2/3 of the jaws. This takes away a large portion of their effective clamping force. I know you will be taking small cuts and not running high RPM but I still don't like it.

 

[Gene Poole]

I don't run that type fixture but.....

Couldn't you indicate the fixture into your chuck by going just inside the I.D. at the front?
The fixture's through hole is prolly bored at the same setup as the O.D. and should be concentric.

I usually will rough mount the barrel or action in the fixture before I put it in the chuck so I don't have the option of using the ID. It's a bit easier that way, but maybe you're right and the time saved by premounting doesn't offset the time needed to get it trued up.

 

[BenY 2013]

I think I am going to make one of the short ones mentioned here. I am thinking like 2-3" long and 8 brass tipped screws. I also think I may put flats on it but just 1/2" the length of the fixture so the OD can still be indicated on! Thoughts on this?

Ben

 

[Killswitch Engage]

When I want a quick and dirty set up on my fixture I put my bullnose live center in my tailstock. Run it up into the bore hole on the fixture and run my chuck jaws in til they all make light gripping contact. Start indicating from there and it's much much quicker. I don't know if I get why you're installing the barrel before you mount the fixture gene? That just seems like a good opportunity for the barrel to get damaged to me.

 

[LRI]

If it were me:

Drew this up as I'm pounding out a Subway sammich during our little spring opener blizzard (meh) as trying to explain it would just suck. The principle advantage being full radial contact where the machining is going to be done. The back half just floats in space. Stick your bushings in the action, slip the mandrel into the bushings, captivate in the collet (1-23/64 16C), slip into the inner hub, mount in a buck chuck, align to parallel with spindle, then indicate. (or vise versa)

Easy, rigid, no more little screws that beg to slip, no distorting the action to get the answer you "think" you want.

Assembled.

 

[JJones75]

So this system would "gimble" and the axial alignment would be done via their 4 bolts holding the pieces together?

Looks fairly easy to make and as you said way less likelihood of slipping

 

[338RUM runner]

Chad, Nice idea, where do I get the 16C collets. Google found them.

 

[woodsy]

It's an expensive option, but the True Bore Alignment System from Straight Shot Gunsmithing is like the Cadillac of apparatus for truing actions and threading short barrels.

I bit the bullet a year ago and bought one of Nate's TBASs. It wasn't cheap but works great and beats the long jig that I was using before. I'd buy it again.

 

[jscandale]

I bit the bullet a year ago and bought one of Nate's TBASs. It wasn't cheap but works great and beats the long jig that I was using before. I'd buy it again.

Have you made any mods or additions to the TBAS? I made an aluminum alignment hub as an interface between the back plate and 6 jaw chuck that helped out a great deal. I wrote a lengthy review of the TBAS over on the AccurateShooter forum. The bottom line is that I like it very much.

JS

 

[woodsy]

Have you made any mods or additions to the TBAS? I made an aluminum alignment hub as an interface between the back plate and 6 jaw chuck that helped out a great deal. I wrote a lengthy review of the TBAS over on the AccurateShooter forum. The bottom line is that I like it very much.

The only thing that I did was make a jig for bolts similar to what Nate shows on his site. This allows me to dial the bolts in using the TBAS speeding up the process of cleaning up the rear of the lugs and face.

My only complaint about the system is that I wish he would have machined the back plate so I could actually use the adjust-tru chuck as designed.

 

[jscandale]

Why would you want to use a the adjustment feature of a set-tru chuck when the TBAS itself has a set-tru feature built in?
The aluminum hub that I made for mine was 2 1/4-8 tpi on one side and a close tolerance fit on the other side to accept the recess in the 6 jaw to keep the back plate in perfect alignment with the chuck. It also was very useful when using a transfer punch to to make 6 holes for the mounting bolts that the Gator semi steel chuck uses. As a result, I can zero the chuck and spin it at 1200 rpm with not even a pulse as a result good balance. Here are some pics.

JS

 

[jonaddis84]

Wasnt the OP asking about chambering barrels, not truing actions?

While I agree, and personally use the roscoe style for action truing, it can't be used for chambering unless you make a bushing for every contour barrel. The old style action jig is also not ideal for chambering, but if you aren't allowed to make an outboard spider on the lathe you're using, or the head stock is too long, it will work.

Galaxy S3 on tapatalk

 

[BenY 2013]

Wasnt the OP asking about chambering barrels, not truing actions?

While I agree, and personally use the roscoe style for action truing, it can't be used for chambering unless you make a bushing for every contour barrel. The old style action jig is also not ideal for chambering, but if you aren't allowed to make an outboard spider on the lathe you're using, or the head stock is too long, it will work.

Galaxy S3 on tapatalk

Yes this will mostly be for just barrel chambering. All of the lathes that I have access to have a headstock that is much too long to fit a 16" barrel(my personal favorite length) between chuck and outboard spider. So I have to figure out another way to do it. I think I am going to make one like roscoe uses for now. I may eventually try and make something like the drawing Mr. Dixon put up. It took me a bit to understand how that worked, but I understand it now and seems like it would work very well! I have a feeling I might could even do some CNC lathe work with something like that!

Ben

 

[xringaccuracy]

$10 and an hour of your time will make one like William and myself use. Just sayin'

 

[Killswitch Engage]

I would leave you blank at full length until you've chambered it then chop it off and put it in the fixture and crown/thread. I doubt your buying 18" or shorter blanks?

 

[BenY 2013]

I got most of one built today! Was all going smooth until I snapped off a tap in one of the holes, decided to call it a day. But it's mostly done! I'll try and get pics when it is all finished!

Ben

 

[JJones75]

Question for you guys turning your own indicator rod.
are you using a follow rest when doing this?
I have made some pretty tight tolerance pump shafts using a follow rest and turning between centers bit we are talking a 1"+ shaft over a 18"-24" span

 

[Killswitch Engage]

Question for you guys turning your own indicator rod.
are you using a follow rest when doing this?
I have made some pretty tight tolerance pump shafts using a follow rest and turning between centers bit we are talking a 1"+ shaft over a 18"-24" span

i assume you meant this to probably go in gene poole's bent action truing rod thread?

 

[JJones75]

Dammit thats where it was supposed to be