Andy221
Cast Iron
- Joined
- Mar 13, 2013
- Location
- moorhead mn
What do you guys think about using a collet to hold a barrel?
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Barrel holding
- Thread starter Andy221
- Start date
- Replies 20
- Views 5,029
GGaskill
Titanium
- Joined
- Feb 14, 2001
- Location
- Central AZ
All right if you have the right size collet, but there is no guarantee that the bore is concentric with the OD, and usually you want to index on the bore. A collet doesn't allow you to deal with an off-center bore while a 4 jaw chuck does.
thermite
Diamond
- Joined
- Sep 21, 2011
I don't have that specific need, but for "similar things" it is where I'd use my plate-mount ER-40 held in a 4-J... so I could "dial in" the work to pick-up on a "feature". Bore.. or even an existing chamber - in this case.
I do have a D1-3 direct-mount as well, but the plate-mounts have lots of uses, too, not all of them even on a spindle at all.
Same again, 5C in an "unmounted" key-operated nose-closer that can as easily be a fixture for bench, grinder, or mill. And then there are both hex and square collet "blocks" in both 5C and ER40.
PS: Any of those "separate" collet'ish goodies can also be tilted, sine-bar style, as well as/instead of/in addition-to being intentionally offset from a centre of rotation.
You bought "a" set of collets? Let them "moonlight" in multiple mounts at a second or third job to save time and hassle to better earn YOUR crust!
2-or-more-approaches-worth.
Andy221
Cast Iron
- Joined
- Mar 13, 2013
- Location
- moorhead mn
Yeah, thanks thermite, i was thinking along those lines too.
Illinoyance
Stainless
- Joined
- Aug 24, 2015
You must have King Kong turning the chuck key.
I work between centers and collets are all I use on whichever end is held at the headstock- but always and only after trued to be concentric to the bore.
Working directly at the collet as you are, you should true the shank by turning between centers and taking a skim cut.
Working directly at the collet as you are, you should true the shank by turning between centers and taking a skim cut.
300sniper
Hot Rolled
- Joined
- Nov 14, 2006
- Location
- Greenwood, Ca
Dunham makes a nice concentricty adjustable collet chuck. Been using one for years.
Or the measuring machines to see what amount of distortion. Thermites setup idea would work with a faceplate and some type of collet holder. I use to center reamers or other tools on a Hardinge Conquest. If you have any doubt that threads can't distort metal, then why do engine rebuilders use a torque plate? I do not know what effect this has on accuracy.
Andy221
Cast Iron
- Joined
- Mar 13, 2013
- Location
- moorhead mn
Can it be adjusted radially and conical(if that is what you want to call it)?
thermite
Diamond
- Joined
- Sep 21, 2011
Nah. He's off teaching scraping classes.
Andy221
Cast Iron
- Joined
- Mar 13, 2013
- Location
- moorhead mn
Here's a little bit bigger picture
How much distortion? As for collets, we played around with setups to see effect on accuracy. Built a 300rum in a 3 jaw with a piece of wire to allow for a pivot point and a catshead. The bore had .007 tir. Shoots as well or better than the others that were done with other methods. Best of luck
Is this that the muzzle end was held in a 3-jaw and the chamber end was held in a collet at the catshead?
TIR and distortion can be two different things. With a 3-jaw chuck, there might and probably is three 'lobes' on the roundness of the chamber. Not sure if this would have anything to affect accuracy. I think HK has splines or serrations in their chambers.
thermite
Diamond
- Joined
- Sep 21, 2011
It only matters how well the projectile is aligned with - and started on its way into - the bore.
Chambers? ISTR CETME was ahead of H&K w/r flutes to retard unlocked-breech blowback, and that they were managing full-power battle-rifle rounds even if there didn't seem a lot of POINT to it vs roller-locked gas-operated designs not really at any sort of disadvantage anyway?
Generally a welcome feature is they not rupture cases and leak gases. If even they HAVE "cases" involved. Doubt one can even MEASURE the residual effects of a puny lathe chuck's jaws on a chamber meant to resist the propellant forces without "undue embarrassment".
Mind, its "boom-sticks:, so few limits exist on creativity, ergo there will always be the odd... umm.. shall we say "extremes"?:
Dardick tround - Wikipedia
Some chamber reamers are draw through. I'd have to check the correct term. So, as the barrel is threaded or otherwise in the action, the chamber reamer is pressed forward by the bolt. Also turned by a rod that goes through the barrel. Its not a cheap setup. I think the Army Marksmanship Unit developed it, or at least uses it.
GGaskill
Titanium
- Joined
- Feb 14, 2001
- Location
- Central AZ
Some chamber reamers are draw through.
I think those are usually called "pull-through" reamers, although that is a complete misnomer since you never pull on the through rod with significant force, it is only used to turn the reamer.
They are typically used on rifles like the M1 and M14 which do not have clear chamber access from the rear. You start with the barrel installed and indexed on the receiver. The rod is put down the bore from the muzzle and the reamer is inserted into the short chambered barrel and the rod is screwed into the reamer. The bolt is then moved forward into the locking recess and gently pushed down to push the reamer forward while it is being turned with a tap wrench on the rod end sticking out of the muzzle. When the bolt lug reaches the bottom of the locking recess, the forward motion and the cutting stops. You are typically cutting the chamber .030" deeper, give or take. The reamer has a bushing shank at the rear and a bushing that bears on the bolt face and controls the depth of cut.
I think those are usually called "pull-through" reamers, although that is a complete misnomer since you never pull on the through rod with significant force, it is only used to turn the reamer.
They are typically used on rifles like the M1 and M14 which do not have clear chamber access from the rear. You start with the barrel installed and indexed on the receiver. The rod is put down the bore from the muzzle and the reamer is inserted into the short chambered barrel and the rod is screwed into the reamer. The bolt is then moved forward into the locking recess and gently pushed down to push the reamer forward while it is being turned with a tap wrench on the rod end sticking out of the muzzle. When the bolt lug reaches the bottom of the locking recess, the forward motion and the cutting stops. You are typically cutting the chamber .030" deeper, give or take. The reamer has a bushing shank at the rear and a bushing that bears on the bolt face and controls the depth of cut.
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thermite
Diamond
- Joined
- Sep 21, 2011
Great example and explanation, but the need dates from several forms of falling block, rolling block, and lever guns a great deal older and carried-forward that needed more finesse, yet.
Removing the barrel was almost certainly more common, that era, if not also "still yet, today". Might not be far wrong to class that an in-the-field "armorer's reamer", IOW a necessity rather than a preference?
