Rough chambering a barrel?

[Wolfer]

On the three rifles I've built I used short chambered, pre threaded barrels and set the headspace with a finish reamer.
I see finish reamers for sale all the time but I don't ever see a roughing reamer. In one of my machinist books he talks about using different sized drills at different depths to hog out most of the metal before finish reaming. This appears to me that it could get off center.
I've read somewhere that some cut the entire chamber with a finish reamer. I can see that working but isn't it hard on reamer life?

How do you guys do it?
Thanks, Woody

[MattOrgan]

I've never used roughing reamers or drill bits, always have used finish reamers. If used carefully with plenty of cutting fluid, removing chips from the chamber and reamer frequently, and never turning it backwards, don't drop them and they will last for many barrels. I have a .338/06 reamer that has chambered 6 or 7 barrels and is ready for the next. I have a friend who barrels a lot of rifles for a living and only uses finish reamers. I once borrowed a .300 H&H reamer that he said he'd had since the early 60s. He did not know how many chambers that had been cut, but it was a lot. Running a twist drill without a pilot seems like a risk I wouldn't want to take with a new barrel. Renting reamers is always an option too.

[MBTcustom]

I take a lot of care to line up barrels perfectly.
When I line up a barrel, it all starts with the first spider I tighten.
I make sure that the barrel is running true within .001 when teh only thing affecting it is that rear spider.
Then I slip my drive collar on and tighten the bolts.
The front spider barely touches the barrel with enough force to keep it in place through all the threading and reaming procedures, and again, the barrel is lined up till the needle on my .00005 indicator just quivers and shows no preference for a high or low.
I hog out most of the material with a standard HSS twist drill (you're right, it does get off center).
Then I follow with a boring bar almost to final size.
Finally, I check alignment one more time (making sure that the bored chamber is perfectly concentric with the bore of the rifle) and I ream with a truly floating reamer holder of my own design.
Once the chamber is cleaned up inside, but not nearly to full depth, I check the bore and the chamber for concentricity, then I slip the reamer into the chamber and indicate the shank to see if it is truly running perfect (Usually it is. If it isn't, then the whole process starts over again)
The reamer plunges about .050 and only needs to remove about .010 off the ID of the chamber.
If there's a way to achieve more perfect alignment, I don't know what it is.

[B R Shooter]

I've never understood this short chambered concept. Unless you have the same reamer to finish with, things can be very different. To me, a better way would be to long chamber a barrel, then back up the shoulder and tenon to headspace.

[John Taylor]

The problem with roughing a chamber is the pilot of the finish reamer may not be in the bore when it starts to cut.

[MBTcustom]

The problem with roughing a chamber is the pilot of the finish reamer may not be in the bore when it starts to cut.

Its not a problem at all with a bottle neck cartridge. Also, the purpose of preboring the chamber close to finish dimension and perfectly aligned, is to insure that the reamer follows the path of least resistance and the pilot is passed accurately to the bore.
I was trying to get it so that I could get a brand new reamer to cut a perfectly tight chamber, tight and parallel and I found that it was in fact possible if I prepared the barrel correctly.
I tell you one thing, it was absolutely Impossible till I made a truly "floating" reamer holder.
Regardless, if anything went wrong, an indicator on the shank of the reamer after it has been slipped back into the chamber tells the tail. Either it was right, or it wasn't.

I have had smiths argue with me that it is impossible to cut a chamber with a floating holder and have both a tight chamber, and one that will show nearly zero runout when the reamer is indicated after the cambering is completed.
It is very possible (albeit a little like herding cats), but only if unconventional methods are used in the setup.

Does it matter? Only to me, but I'm convinced that it gives a noticeable edge shooting cast lead fast and accurate. In fact, the only chambers I have found that were cut truly concentric to the bore, parallel, and tight, were cut in my shop (not that I have followed any other smiths work of course. So no offense to anyone in the world is meant here)
There's nothing magic about this. Anybody can do it if they have an indicator and like to use it. I've built special fixturing to help me get the same results faster, but I proved the concept with nothing more than my standard setup.

All that said, I only posted this for educational purposes, and just because it works for me on my equipment means absolutely nothing outside of that environment. The most accurate tool you have in your toolbox is the one that sits between your ears. Keep it sharp, and understand accuracy, and you can get the same result with any setup. (heck you might get there with a lot less headbanging than I do on a regular basis! LOL!)

[B R Shooter]

Once again Tim, we all bow to your infinite, and "my way is the only way" wisdom.

[swheeler]

Once again Tim, we all bow to your infinite, and "my way is the only way" wisdom.

Thanks for posting Goodsteel

[MBTcustom]

Heck it's a FORUM. We're free to give an opinion.
I never said it was the only way, but it's my way and it might work for you if you care to try it. If it doesn't work for you, then its no skin off my back. At least Im not hording my methods and trying to get rich off of secrecy or something weird like that. Feller asked for an opinion so I gave it, then I backed it up with more information. I'll probably modify my method even more as time goes on, and I'll be glad to tell anybody who cares to listen how I do it.
I don't appreciate the information being thrown in my face though. It's not like I'm using my knowledge to troll people and build empires like some on this forum are want to do. I'm here to help and to get people to think. This is my area of expertise, so I have very entrenched views on how I do things, but I'm still learning too and I'm a long way from "being there".
It was not my intention to demean anyone with my remarks here.

[Sweetpea]

Bite the helping hand...

[B R Shooter]

Go read your post Tim. When you write "it was absolutely Impossible....", what you are clearly saying no other method will work.

Nobody wants to limit means and methods others use, but the arrogance and narcissism isn't needed.

[enfield]

O.K lets all get along here, I like reading anybodys ideas about this kind of thing because I like trying to build stuff myself. the only reamer I ever used was a 22 hornet finish reamer and I had no idea it was such a slow process ( not my reamer so I didn't want to hurt it ). on a crude note I have now made 5 32-20 barrels out of old 303 L.E. barrels by chambering with 2 drill bits that I have a depth stop on ( actually a piece of rubber gas line that is pushed on the drill bit ) 21/64 and 11/32. after drilled it takes some polishing with emery cloth on a wood dowel to finish it until a round will chamber. they actually turn out pretty good even though it sounds like I'm making a mess. I'm sure these guns wont win any match shoots but they are all surprisingly accurate a the lyman 115 gr gas check boolit works very well.

[Wolfer]

Tim, I certainly appreciate your input. Since I'm not a machinist and my lathe is a 1894 Porter machine works that was converted to electric via a model A transmission some of what you said may have been over my head. I did get the general jist of it though.
Thanks for confirming that the drill would get off center.

I don't have a project going at this time. I was just setting here on a cold winter day wondering how most did it. It appears that several methods will work. If I was to do one at the currant time I'll probably just rent a finish reamer and tell him I'm going to cut the whole thing with it.
I've always rented from 4-D and he has been very square with me so I certainly would be square with him.

I had considered building a D reamer slightly undersized and then finish ream. I don't know if my skill level, equipment is up to that though.
Woody

Enfield
While Tim's method may have been over my head yours was not! Evidently we think outside the same box and that's why it made sense to me. Woody

[KCSO]

I use the James Howe method and use a boring bar on the lathe to take out most of the chamber, then finish with a reamer.

[country gent]

Another thing to check and look for is how strairght true the tail stock on the lathe is setting. Most are adjustable side to side to remove taper when turning long work. Hieght is is the real issue as normally there isnt any means to adjust for this. Put a mandrell ( known to be straight and venter) between centers and with the carriage indicate down the side and top of it for the working length of it. A barrel indicated in straight and true dead on wont cut straight if the tail stock isnt straight also. The reamer floats will help with this condition. There are many issues getting a true chamber, drill imporperly ground slightly off center will lead off, a dull reamer may not follow true, Chip build up can push a cutter off, and last is heat build up. I have end mills relieved on the back for truing a hole up after being drilled. But for the truest roughing a boring bar is most accurate for location and true. Why presiccion holes are roughed in the lathe and then bored and ground, or roughed in the mill, jig bored and then the jig grinder for finish. Set up is everything at all points in the set-up. I agree with Tims method of indicating front and back of barrel this [puts barrel on center in a truly flat plane allowing for centerline to be true and straight. If the myzzle is running out and the chamber is true its in the machine on an angle. If the tail stock isnt true its inducing an angle to the cutter.

[rbertalotto]

I hog out most of the material with a standard HSS twist drill (you're right, it does get off center).
Then I follow with a boring bar almost to final size.

I do my chambers the same way. Much less stress on the reamer and a much nicer finish. I never have used a roughing reamer.

[oldred]

Tim I also appreciate your input (I have been following this discussion with much interest, just not posting) and I think what you said makes a lot of sense, I did a quick sketch to help me visualize what you are describing and I think it's an excellent approach. To expand on your proverbial cat phrase, there's more than one way to skin a cat!

[mrbill2]

Most people don't use a roughing reamer because they don't want to spend the extra money, not because they think they have a better way. Same with go and no go gages. Some brass and some tape works for them.

[Marvin S]

Post 15 makes good sense. I dont really do chambering but work in a job shop. Would not end mills and core drills be better than standard two flute twist drills. One thing for sure in machine work is that there is always more than one way to set up.

[country gent]

Marvin, In the tool room we all had reground end mills that were ground .010 under nominal they were standard length and "long" length with about 1/4" at dia and relieved behind that. A pilot hole and then a quick pass with one of these made a very straight true hole on location. The flat cutting face didnt want to follow the existing hole but trued it up. From there it was heat treat and the jig grinder. A reamer is notorious for following the existing hole so set up and straight and true is important when reaming. The most accurate machine I ran for holes was a cnc edm the electrode never touched anything to move it off location. Its readouts were to .00005. I always wanted to make an electrode set to cut a bullet mold with it. Never got around to it.