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chambering and polishing

robbor

When chambering any of you guys actually measure how much over reamer size a chamber really comes out? I hear talk of runout and only seems logical that if there is runout then chamber is a tad over reamer size. Second question is should polishing with flitz open up the chamber at all,.0001-2)? I bought a few pin gauges to check but am not ready to chamber yet.
I bought a tight 22lr reamer,.2242 at largest diam) and would like it to end up atleast .2245. I still need to to get an inside threading tool and build my spider. I can understand it would be difficult to tell exactly being as though reamers are tapered.
When talking to other machinists they said that with normal reamers and thicker oil that you get a tad larger hole over thinner water based fluid flooding. I will using pressurized coolant through the barrel.
 
Robor,
A reamer will cut to any size that you will permit it to do whether it be smaller or larger. "Runout" pertains to eccentricity in two different diameters that are supposed to have the same center but don't. It's derived from TIR which is always derived from double the amount on an indicator. This is for rounded surfaces only but TIR has an important role to play in a flat surface too. Any of the reamers I made have a failsafe stop built in so I would not go oversize, it's not too hard to do this. You state other machinists, so I assume you are a machinist yourself and posess all this knowledge. Using more viscosity does not always make a reamer cut larger than nominal. Many dispute this. Polishing,burnishing or even lapping) can be attained either by a fine grit stone ground as a finishing reamer and if you want a high polish,and knowing you own a lathe, turn up a chamber slug and charge it. It will produce a fine lapped ID finish at about no cost. Yes the ID walls will also be charged but it is not a working surface subjected to constant motion and will not affect any accuracy. If you own any of these chinese lathes,Some are real junkers) make sure the head and spindle are in alignment with the bed and carriage with a set of set up tapers to be sure it's all parallel to each other . LOL
 
Thanks sjk, much appreciated. Im not a machinist. I am taking a machining course and have a lathe. When I have questions that my teacher doesnt address to my satisfaction or at all I usually ask over on the practical machinist forum. I have learned lots from many knowledgeable forum people and gunsmiths sites.
 
robber--
you don't want the chamber highly polished, it needs to be able to grip the case when it's fired, and your back thrust will go out of sight if highly polished and the possibility
of getting a close up look at the back of your bolt could happen.....
 
Ditto Butch in your entirety.
The main thing about not gripping the walls of a chamber is some oil or sizing lube left on the case or the chamber itself. This will cause undue pressures on the bolt locking system whatever case you may have. To be a little more specific on finishes, you cannot get a V4,mirror like) finish on softer materials. The lapping will charge the softer metals. The best you can attain is a V32 or V 64 with lapping of any kind. The grit will impregnate to the softer metal ALWAYS. Lapping to obtain a mirror like finish can only be accomplished when the base metal has either a .001 or so of case hardening, Chrome or metal that is hard all the way through as in a RC 60. Grit will not impregnate the casing and very fine finishes can be had right down to a V4. A flash chromed chamber can be lapped to mirror like, but opening up yet but another can of worms is the fact that chrome has its own lubricating qualities, so be careful if you even want to do this or not. This is one of the times you do not want a mirror finish on this type of chamber. Otherwise a V64 finish is wery adequate on metals like 4140 and the only true way you can check this is with a profilometer, not visually. Just some more .02
 
butchlambert said:
A highly polished chamber will grip the brass!
Butch
Click to expand...

I have a number of highly polished,mirror smooth) chambers, and there is no problem. and the fired cases look new with no tool marks.


.
 
Cat Shooter, I don't recall saying that it would mark your cases or be impossible to extract. It is the same reason as stated before that barrel makers don't polish the inside of barrels. They copper foul more so. A polished surface has a higher coeffecient of friction.
Butch
 
butchlambert said:
Cat Shooter, I don't recall saying that it would mark your cases or be impossible to extract. It is the same reason as stated before that barrel makers don't polish the inside of barrels. They copper foul more so. A polished surface has a higher coeffecient of friction.
Butch
Click to expand...

I don't agree, and it makes no sense. Things are polished to lower friction... rough surfaces have higher coefficients friction.

But I'm not going to argue about the obvious.

But consider this.

If a case sticks to the walls of the chamber and the head is not firmly planted against the bolt face, how does that 0.05" of brass protect that big-assed piece of ordinance steel.

We all know that if the case is not against the bolt, the case will stretch in front of the web, cuz the case can't support the pressure.

So how does the wall of a case, that is weak brass ring, ~0.05" thick, protect a bolt made of ordinance steel that is about eleventy million times stronger?

It can't... whether the case head is off the bolt because it is stuck to the walls, or whether it is in contact with the bolt because the case has minumum,or minus) headspace, the case whacks the bolt face with a few thousand pounds of pressure...

... mull it over.


.
 
Cat Shooter, It is pretty simple. A polished surface has more surface area to grip with. Also the 50,000-60,000PSI explosion will fill the chamber from the shoulder to the bolt face. After the case is formed it will fill the chamber fully and a polished case will lessen the load on the bolt lugs. I think we are arguing about different things. I don't believe that I stated that the case would not touch the boltface. I did not state that you don't have pretty cases.
I stated that a polished case would grip the chamber walls. Have you heard of Dave Tooley? He has forgotton more about shooting and smithing than most of us on the forum have known. If you like, I will do a search and show you he "polishes" his chambers with 240 sandpaper.
Butch
 
butchlambert said:
Cat Shooter, It is pretty simple. A polished surface has more surface area to grip with. Also the 50,000-60,000PSI explosion will fill the chamber from the shoulder to the bolt face. After the case is formed it will fill the chamber fully and a polished case will lessen the load on the bolt lugs. I think we are arguing about different things. I don't believe that I stated that the case would not touch the boltface. I did not state that you don't have pretty cases.
I stated that a polished case would grip the chamber walls. Have you heard of Dave Tooley? He has forgotton more about shooting and smithing than most of us on the forum have known. If you like, I will do a search and show you he "polishes" his chambers with 240 sandpaper.
Butch
Click to expand...

You're kidding right??

You are trying to bate me into a cat fight... PLEASE say you are - because if you aren't, what you just said is off the scale in all areas of mechanics and engineering to the point of being ludacris.

.
 
This discussion is way to deep for me, and I wouldn't make a pimple on a machinists rear end, but on the question about chamber runout, I don't have a good way to check it. After turning the shank O.D. concentric with the bore, I set it up in the chuck and fiddle with it until I have <.001" T.I.R. on the O.D. of the shank.,I use a floating reamer holder) As soon as the reamer has cut the neck, I stop and stick a last word in the newly cut neck and turn the barrel by hand. This won't tell me if the neck is out of round, but will tell me if the reamer is tracking the bore, in which case the chamber is off to a good start. After that, I just put my left hand on the reamer shank to feel for any movement when the pilot engages the bore and the reamer starts to cut again. This can't be the best way, but it works for me.

On polishing, I've been afraid to polish on the belief that the very best chamber possible is the one cut by the reamer in the lathe, and anything I do after that might degrade the chamber.

Just my opinion without a trace of scientific evidence.

Tom
 
CatShooter said:
You're kidding right??

You are trying to bate me into a cat fight... PLEASE say you are - because if you aren't, what you just said is off the scale in all areas of mechanics and engineering to the point of being ludacris.

.
Click to expand...
CatShooter

Think about how hard it is to separate two panes of glass. I had a similar reaction to this but I'm try to remain willing to learn something new. Here is the evidence of what is being discussed:
 
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