Gunsmithing how do you indicate a barrel in a lathe when ....

[skog]

How do you indicate a barrel in a lathe for chambering when the head stock of the lathe is longer than the barrel and you cant use a cat head? I have heard to use a masking tape bushing on the muzzle end to center it the best you can and prevent wobble, center the breech and use a floating reamer holder. Is that sounding right? The floating reamer holder will allow the reamer to follow the barrel if it is slightly off center correct?

Thanks
skog

 

[chpprguy]

Re: how do you indicate a barrel in a lathe when ....

I am a "tinkerer", by no means a professional...

My clausing spindle is too long as well...

I typically make a bushing from aluminum that slip fits into the spindle id, and seats snug to the od of the barrel close to the muzzle...
If I am worried about the finish on the barrel, I will put one wrap of tape on the
barrel, then seat an oversized bushing (od oversized) and turn the bushing od to size with the barrel between centers........

I have no experience with a floating reamer holder,
FWIW
Andy

 

[Keith Johns]

Re: how do you indicate a barrel in a lathe when ....

I dont have a good answer because I dont understand why you cant put the front 80% in a 4 jaw, then put the rear centered in a steady rest. Steady rests arent the best option, but its better than tape.

You cant hope it's centered. You have to indicate it and make sure there's zero runout. Even then, you will get some.

Does your spindle stick out the rear of the headstock enough to drill and tap four holes in it? Or do you have a big enough spindle bore to make and insert a spider? Youd need about a 2.5" spindle bore but you could insert a steel spider, with atleast a 1.5" hole and 4 brass tipped screws protruding to use as a spider to center the muzzle end. Then of course use an indicated 4 jaw on the chamber end.

Just some ideas
I'm sure someone much more experienced than me will chime in with better help.

 

[skog]

Re: how do you indicate a barrel in a lathe when ....

dont have a steady rest. not sure about building a steady rest into the existing spindle, never though of that. I will check it out. That bushing idea isnt sounding too bad either.

thanks
skog

 

[BLAWTON]

Re: how do you indicate a barrel in a lathe when ....

Best thing for you to do is make a aluminum collet that will slide into you spindle and cut the id to match the barrel.

 

[Keith Johns]

Re: how do you indicate a barrel in a lathe when ....

What lathe do you have?

 

[sinarms]

Re: how do you indicate a barrel in a lathe when ....

I run my barrels all the way through the headstock except for the last 2-3" of the chamber end. Use a 4 jaw chuck and use a .0005" indicator to true up off of a proper caliber range rod. On the back side of the head stock I have 4 screws to support the back side of the barrel. easy to do and very accurate. I also use a floating reamer holder.

 

[chpprguy]

Re: how do you indicate a barrel in a lathe when ....

I am not sure how long the op's spindle is,
mine is ~34" plus the chuck thickness...
this makes the "spider" on the back unusable for me, hence the use for a collet/spacer....

 

[eddybo]

Re: how do you indicate a barrel in a lathe when ....

Here is what I am planning on doing in the future, right now I just use aluminum bushings that fit tight in my spindle bore and on the outside diameter of the barrel.
I am going to make a bushing that fits tight in my spindle bore with a .500 hole in the center. I am going to use a 1.250 inside diameter bushing that fits tight in my spindle bore on the breach end and chuck the muzzle in the chuck like I am going to cut a crown. Then I am going to indicate the barrel in and turn down about 3/4 inch of the barrel to fit my .500 bushing. Then using the barrel with the .500 inside diameter fitted on the shank turned concentric with the bore I am going to reverse the barrel and indicate it in as close as I get to the throat as I can.

I do not think there is anything wrong with using the bushings on the outside of the bore without the extra step, I have had good luck doing it this way, and know many who do it this way. But if an extra step may help, I may as well do it. If barrels were 100% straight then I think there may be more of a benefit to indicating the outboard end. But then again if barrels were 100% straight the inside and outside diameters would probably also be perfect and we could do them all in a 3 jaw without having to indicate anything.

 

[JJones75]

Re: how do you indicate a barrel in a lathe when ....

I kow a very well know rifle builder (in the BR and F-class world) that uses a 3 jaw true set chuck and a brass bushing that fits the ID of his spindal bore because the headstock is so big. He uses range rods to get the bore close then fine tunes the chamber end with a .0001" indicator with a long tip , he reaches into the barrel around where the throat would be and indicated off of the grooves. I hold this mans work in the highest reguard and when I saw him do this the first time I thought "this guys is a quack" but after shooting some of his work I'll say it second to none and if I were going to try to set a world recond he is who whould do the build as he has severl to his name !!

Barrels are rarely strait so indicating off the muzzle end and the chamber end while they are both strait and dead nuts will leave you with a bow in the barrel , granted we maybe only talking about .0002" but it will be their.

 

[eddybo]

Re: how do you indicate a barrel in a lathe when ....

same boat here. Jet 16x40 with the big through hole has a looong hole....but the inside diameter spins dead nuts.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chpprguy</div><div class="ubbcode-body">I am not sure how long the op's spindle is,
mine is ~34" plus the chuck thickness...
this makes the "spider" on the back unusable for me, hence the use for a collet/spacer.... </div></div>

 

[eddybo]

Re: how do you indicate a barrel in a lathe when ....

JJones you were right about that thick stuff you sent me. If you ever have a reamer that is chattering try it then and you will be really impressed. Thanks again.

 

[JJones75]

Re: how do you indicate a barrel in a lathe when ....

No problem , and it doesn't smell as bad as "best oil" does , best part is that you can cut it to suit your needs

 

[300sniper]

Re: how do you indicate a barrel in a lathe when ....

how much too long is your spindle? if a couple inches shorter would work, you could make a spider chuck to replace your 4 jaw. i did this and saved about 2-1/2" of length.

another option for dialing the bore in dead nuts with a range rod and two indicators is to make a bearing spider that rides in a steady rest. i saw some pictures posted somewhere of this setup and it makes a lot of sense. i think there was some question of the quality of bearings used in the setup though.

i have also used my action truing jig to precision thread a 12" 10/22 barrel. using this same principle, a piece of heavy wall tube say 12"-18" long could be drilled and tapped for a spider at each end, driven by the chuck and supported by a steady rest would work also provided you have enough bed length.

this is the spider chuck i made to shorten up my overall through the spindle length:

 

[NBLongRanger]

Re: how do you indicate a barrel in a lathe when ....

Very nice piece of custom work there 300sniper

 

[skog]

Re: how do you indicate a barrel in a lathe when ....

Lathe is a JET 1340. Front of chuck to back of spindle is about 26" so it is close but tooo oong none the less. What do we think of making a cat head for the end of the spindle and then turning down and threading the muzzle to say 1/2 x 28 or 5/8 x 24 and then screwing on a tube that has matching threads and using that to hold an indicate in. then cutting off the threads when you crown because the first 1" of barrel junk anyway.

 

[300sniper]

Re: how do you indicate a barrel in a lathe when ....

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: skog</div><div class="ubbcode-body">Lathe is a JET 1340. Front of chuck to back of spindle is about 26" so it is close but tooo oong none the less. What do we think of making a cat head for the end of the spindle and then turning down and threading the muzzle to say 1/2 x 28 or 5/8 x 24 and then screwing on a tube that has matching threads and using that to hold an indicate in. then cutting off the threads when you crown because the first 1" of barrel junk anyway. </div></div>

i'd drill and tap the rear of the spindle instead of making an add-on spider. i'd also make a spider chuck like i posted earlier. this should give you enough space to thread and chamber a barrel blank. also make a 6" long tube id threaded 1.062"-16 on one side and 1.072"-16 on the other. after you do the chamber work and want to cut the barrel to finish length, you can thread the tube on to your barrel tenon to make it long enough to work on the muzzle end.

 

[AKA-Spook]

Re: how do you indicate a barrel in a lathe when ....

I thread the end of the barrel back 3/4 of an inch and screw an extension on that reaches through the cat head. Typically you need to remove the last inch of the barrel anyway. Takes about 10 minutes.

 

[GasLight]

Re: how do you indicate a barrel in a lathe when ....

Here is an idea that one could use to center the bore in a 'too-long' head stock. Hopefully I can explain this well enough to make sense, I don't have any pictures just an idea:

You could turn a piece of solid stock until it was a very snug fit inside the spindle bore. On this piece of solid stock you can turn it down so there was an extension that was the same diameter as the floating pilot bushing interior dimensions the PT&G uses. This way you can use the same piece of stock for multiple cartridges, you would only need to find an appropriate bushing for that particular barrel, and this would hold the bore very close to center of the spindle bore... just something I have been thinking about myself as I am facing the same problem with my headstock being longer than practical for most through-the chuck barrel work.

DD

 

[300sniper]

Re: how do you indicate a barrel in a lathe when ....

the more i think about it, an 18" long piece of 2.25" diameter, .375" wall dom tube with a spider drilled and tapped into each end, held by a chuck at one end and supported with a steady rest on the other would work great. the only problem i can think of is if you like to index the muzzle high point up, it would be near impossible to locate that high point. i think you are going to have a hard time doing that any other way where the muzzle end doesn't daylight out of the back of the spindle though.

 

[skog]

Re: how do you indicate a barrel in a lathe when .

I am going to make fixture to hold the barrel tenon while crowning. I would like to drill and tap the spindle but after looking at it today not sure how to. There isnt very much room to get a drill in there. Dont have an angle drill and dont really want to drill through the front of the lathe. Got any more ideas?

Very nice piece there 300

skog

 

[TCA4570]

Re: how do you indicate a barrel in a lathe when .

300. I see, and have to say thanks!
We could switch out both for a 5-C in the same time.
Or pads.