Gunsmithing Barrel runout
- Thread starter Snuby642
- Start date
How are you holding the barrel on the machine?
How are you dialing in the bore?
Is the run-out you speak of the outside diameter of the blank relative to the bore?
How are you dialing in the bore?
Is the run-out you speak of the outside diameter of the blank relative to the bore?
The bore should be dialed to the center line of your lathe to less than .001" . Ideally it should be less than .0005". If you're new to chambering than it can take some time and patience.
Concentricity of the outer contour to the lathe center line is not really important, although most gunsmith's will clock the barrel so the high point is in the 12 o'clock position.
The bore of most barrels will not run concentric to the outer contour along it's entire path.
If you're measuring .01" and .006" from the bore of your barrel you need to spend some extra time dialing things in.
Concentricity of the outer contour to the lathe center line is not really important, although most gunsmith's will clock the barrel so the high point is in the 12 o'clock position.
The bore of most barrels will not run concentric to the outer contour along it's entire path.
If you're measuring .01" and .006" from the bore of your barrel you need to spend some extra time dialing things in.
A little info.
My son is in gunsmith school.
This is his first chamber to cut.
He is building a traditional hunting rifle, stock from a blank truing action ect.
It was mandated to be hunting contour and stock.
I'm not sure the competence of instructions or if being hung out in the wind to figure it out for himself.
He is trying to center the bore but it is not concentric with od.
I don't have a lot of lathe experience I like mill work better.
I will ask about what jaws he is using I imagine 3 jaw .
He is a dv and working hard at this and I help all I can.
I have made a lot of tooling fixtures from stock on a manual lathe but that is about it. Most of it was using collets.
My son is in gunsmith school.
This is his first chamber to cut.
He is building a traditional hunting rifle, stock from a blank truing action ect.
It was mandated to be hunting contour and stock.
I'm not sure the competence of instructions or if being hung out in the wind to figure it out for himself.
He is trying to center the bore but it is not concentric with od.
I don't have a lot of lathe experience I like mill work better.
I will ask about what jaws he is using I imagine 3 jaw .
He is a dv and working hard at this and I help all I can.
I have made a lot of tooling fixtures from stock on a manual lathe but that is about it. Most of it was using collets.
He should be using some sort of 4 jaw chuck or what some call a "spider" to adjust each contact point independently from the others. A traditional 3 jaw chuck isn't going to get him close to where he needs to be since the the jaws don't usually adjust independently of the other two.
His goal should be to get the bore of his barrel to have less than .001" run-out at two locations along it's length. Where he measures those two points is completely dependent on his fixture methods and the measuring tools he's using. Definitely more than one way to skin that cat.
Buy a pair of these with bushings. 4 Jaw chuck on the headstock, barrel through the headstock, spider on the opposite end of the headstock, dial both ends in to less than .0005", ignore OD.
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I think it's 4 jaw as mentioned as he was getting frustrated trying to dial it in. I forgot how 3 jaws were connected.
I will be reminding him of 12 oclock up position.
Reminds me why I would install the collets on the lathe for my work.
He is good on revolvers pistols and shotguns. His stock work is good with the exception of substandard checkering. Needs more practice on that.
I will be reminding him of 12 oclock up position.
Reminds me why I would install the collets on the lathe for my work.
He is good on revolvers pistols and shotguns. His stock work is good with the exception of substandard checkering. Needs more practice on that.
I don't undestand why he is not provided the grizzly rod guides?
Makes perfect sense to me.
I made a rough version of that for working on some aircraft parts that were built on a mandrell with composites and the od was rough as hell. Not good at well over mach speed.
Makes perfect sense to me.
I made a rough version of that for working on some aircraft parts that were built on a mandrell with composites and the od was rough as hell. Not good at well over mach speed.
So yes a 4 jaw .
I sent him this video that looked right to me.
4drentals.com
I sent him this video that looked right to me.
#1 Range Rod (Gordy Gritters/Grizzly) - 4D Reamer Rentals
Gizzly Range Rod by Gordy Gritters
4drentals.com
Most Bartleins I've done are .003-.006" out, ID to OD. I've seen better and much worse (.02-.03). One Bartlein was straight through, nearly perfect. Within .001 on each end, and within .0005" in the middle when I cut to length. That doesn't happen very often IME.
Other than visual appearance if it's really shit, matters not how close the OD of the barrel is to being concentric with the bore.
This is true, whether chambered between centers, or through the headstock as all the replies above indicate.
A rifle with "hunting" accuracy can be easily chambered between centers/with a steady rest, and is the only way to do it if the headstock won't accommodate the barrel.
This is how it was taught for decades at Trinidad and other schools, and may be how he is expected to do this one- which would be why no Grizzly rods (which is just one of several ways to indicate the bore, if working through the headstock). Suggest he consider picking up the following book, great info on basics and theory behind "what" and why".
www.brownells.com
This is true, whether chambered between centers, or through the headstock as all the replies above indicate.
A rifle with "hunting" accuracy can be easily chambered between centers/with a steady rest, and is the only way to do it if the headstock won't accommodate the barrel.
This is how it was taught for decades at Trinidad and other schools, and may be how he is expected to do this one- which would be why no Grizzly rods (which is just one of several ways to indicate the bore, if working through the headstock). Suggest he consider picking up the following book, great info on basics and theory behind "what" and why".
JOHN HINNANT THE COMPLETE ILLUSTRATED GUIDE TO PRECISION RIFLE BARREL FITTING | Brownells
John L. Hinnant. 8½" x 11". Revised third edition 304 pages. Self-covered. Not fancy but a very well illustrated, well written, in-depth analysis that provides both the advanced and beginning student a complete and informative shop manual. Covers ...
www.brownells.com
It's very possible that @Wannashootit
Has hit the nail on the head.
I expect this was how the instructor was tought and feels the need to pass on.
Old school is how everything in that class has been taught.
Frustrates my son but he may actually be better for it in the long run.
I appreciate all the input and will have him read this thread.
I wish I were more help to him but only have a narrow experience with lathes.
Has hit the nail on the head.
I expect this was how the instructor was tought and feels the need to pass on.
Old school is how everything in that class has been taught.
Frustrates my son but he may actually be better for it in the long run.
I appreciate all the input and will have him read this thread.
I wish I were more help to him but only have a narrow experience with lathes.
My son dropped by and has varified barrel dialed in to .0005 to the bore so that is good.
He messed up about an inch or so of barrel and had to start over. Lol
The guys didn't teach him how to set up the stop thing that kicks it out of gear on the leed screw.
I'm not much on a lathe but I know about that gadget.
Any of you have experience with one of these?
I'm used to much larger equipment.
www.grizzly.com
He messed up about an inch or so of barrel and had to start over. Lol
The guys didn't teach him how to set up the stop thing that kicks it out of gear on the leed screw.
I'm not much on a lathe but I know about that gadget.
Any of you have experience with one of these?
I'm used to much larger equipment.
12" X 36" Combination Gunsmithing Lathe/Mill - Grizzly Industrial, Inc.
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