Chamber reamer tool life

I sold one of my lathes to a young man who graduated from the gunsmithing school in Trinidad, CO. We got to talking after the machine was loaded and the subject of chambering reamers came up. He remarked that most reamers didn’t last more than two jobs, and that the students would usually grab an old one for the rough cut then use a new one for the finish. He said the school didn’t buy both rough and finish cutters - the only difference was new or used.

I didn’t question his comments, but this level of tool life sounds extremely low to me, so long as the tool is being utilized properly. My gut instinct would be in the range of 40-50 barrels but maybe I’m way off base.

I don’t chamber rifles, but I’m curious what is a reasonable life for a reamer?

I switched to carbide reamers over 30 years ago. That being said proper methodology, speeds, feeds and lubrication maximizes tool life.

Using a finish reamer to do the roughing greatly reduces the tool life. Normally I rough drill than bore till I am close, but I have used damage or out of spec. reamers for roughing.

Most people don't have the setups that will allow them to exceed the maximum tool speed, but lots don't feed fast enough to prevent work hardening of the material. SS is more of a problem.

I also use a high pressure through the bore flush coolant system.

Even with my HSS I've never sent one back for sharpening. Judicial stoning helps. HSS used solely as a finish reamer 40-50 barrels is very doable. I can not give you a solid answer since even the lathe rigidity comes into play.

"He remarked that most reamers didn’t last more than two jobs" Something is very wrong here.

A good borescope inspection of the freshly cut throat and leade angle will indicate when the reamer is getting dull.

https://rifleshooter.com/2015/04/chamber-reamers/

https://bisonballistics.com/articles...rifle-chambers

Gunsmiths and gunsmith courses/schools only cover limited machining. Most gunsmiths are not good machinist. The majority of the highly acclaimed benchrest and long range accuracy rifle smiths have a heavy machining background and moved into precision gunsmith later.

When you are not the one buying/paying for the tools it is easier to just grab a new one ??

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Originally Posted by BLAHUT

When you are not the one buying/paying for the tools it is easier to just grab a new one ??

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That could certainly be the case - he also said the students have to draw file barrels for a grade, then they go out to the parking lot and bang up the barrels on the asphalt. The next group of students have to remove the damage with more draw filing - eventually the barrels get pretty thin.

In production we used a 3-flute core drill to do initial stock removal. Next a 4-flute rougher, tools being high speed tool steel with TiCN coating and work immersed in oil with heat exchanger. Semi-finisher was 6 straight flutes also in TiCN coated tool steel. Finish reamer was full carbide 5 flutes left hand spiral for right hand cut with oil holes. Carbide finisher cost $1000 in 1987 and would hold size for a full shift without tool changes and maintain 32 microinch RMS surface finish. Either roller burnished to 16 RMS or electropolished if barrels were to be hard chrome lined.

So..Outpost75 what does all that mean in terms of how many jobs per reamer?

I had considered going to that school at one point n my life. Now I can see hat maybe I did OK n not going. I don't know what their paying for reamers, but in private practice, one reamer per job, all the expense goes to one job - passed directly to the customer. A needless expense I think.

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Originally Posted by Outpost75

In production we used a 3-flute core drill to do initial stock removal. Next a 4-flute rougher, tools being high speed tool steel with TiCN coating and work immersed in oil with heat exchanger. Semi-finisher was 6 straight flutes also in TiCN coated tool steel. Finish reamer was full carbide 5 flutes left hand spiral for right hand cut with oil holes. Carbide finisher cost $1000 in 1987 and would hold size for a full shift without tool changes and maintain 32 microinch RMS surface finish. Either roller burnished to 16 RMS or electropolished if barrels were to be hard chrome lined.

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That many tools? Doing the work on a multi-station machine? Or some sort of CNC turret lathe?

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Originally Posted by Outpost75

In production we used a 3-flute core drill to do initial stock removal. Next a 4-flute rougher, tools being high speed tool steel with TiCN coating and work immersed in oil with heat exchanger. Semi-finisher was 6 straight flutes also in TiCN coated tool steel. Finish reamer was full carbide 5 flutes left hand spiral for right hand cut with oil holes. Carbide finisher cost $1000 in 1987 and would hold size for a full shift without tool changes and maintain 32 microinch RMS surface finish. Either roller burnished to 16 RMS or electropolished if barrels were to be hard chrome lined.

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I haven't seen a full carbide spiral cut chamber reamer with thru the reamer body oil holes.

PTG later produced and still offers USR oil groove 5 flutes left hand spiral right hand cut solid carbide for Winchester/Browning and possible others. The USR oil groove bushing is longer than standard bushings and it has grooves for thru the bore high pressure flush. Since no oil holes are required in the reamer body they are much cheaper.

I much prefer the carbide USR oil groove reamers. For non-CNC machines the straight flute version are easier to use. The spiral flute requires fairly aggressive feed rates.

https://castboolits.gunloads.com/sho...-reamer-needed

I have a 6PPC reamer that I can't count the number of barrels it has cut. I pre-drill the barrel about .050" short of the shoulder. I go in and check/dial in the barrel as close to zero runout as possible. then bore the hole to .010" smaller than shoulder diameter. The finish reamer does the rest. I use a flush system that has cutting fluid pumped in from the muzzle, so a reamer is constantly lubed. Never had it sharpened, but I do check for chip weld by running a triangle shaped stone in the flutes that rides on the cutting face.

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Originally Posted by HWooldridge

I didn’t question his comments, but this level of tool life sounds extremely low to me, so long as the tool is being utilized properly. My gut instinct would be in the range of 40-50 barrels but maybe I’m way off base.

I don’t chamber rifles, but I’m curious what is a reasonable life for a reamer?

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Using a finish reamer for the entire chamber cut, they don't last long. I've cut a few chambers into Redman liners in .22LR. Just using a finish reamer, after the 4th chamber it needed to be cleaned up. Was then able to cut a few more. It will be relegated to a rougher, and a new finish will be purchased for the next chamber.

In .22LR, not much needs to be removed. If a bottleneck chamber needs to be cut, it definitely needs metal removed prior to final reaming.

OTOH, in .45 ACP, when final cutting the chamber depth to set head space, it isn't too bad. Not much is removed and that reamer is as good as new. Also used it in a couple of barrels that didn't have a leade cut (between the throat and rifling). Those no longer lead like crazy.

45_Colt

The first chamber reamer I owned was a used Manson 9mm NATO reamer that suposedly came from storm lake barrels. Said it should be good for a few barrels. You could see the TiCN coating was getting lighter colored at the case mouth step. Still cut a chamber in spec. I finally replaced it last year after well over a dozen barrels plus however many storm lake did with it. I replaced it with Mansons 9x19 marked reamer with the TiCN coating. Manson said set up correctly they'd expect at least 60 chambers with it before it needed sharpened. Bottleneck cartridges I'll generally get a rougher, but straight walled cartridges I just get a finisher as you're really not removing much metal. Not sure how many chambers my 223, 308, 762x39 and other reamers have cut, but it's more than 2 and they still look new. If the kid is only getting 2 chambers before wrecking a reamer he's doing something wrong.

Makes me wonder if the students at the school were running the reamers dry - or maybe turning them backwards on removal (that would certainly wreck an edge).

No telling - this young man has his lathe now so hopefully he can do some gunsmithing work on it.

another factor in reamer life is the actual barrel material, Stainless steel, steel also make a big impact on reamer life. Black Star (???) barrels were sold as tougher material to resist erosion and wear a few years ago. Had several guns smiths tell me they would not do them do to reduced tool / reamer life.

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Originally Posted by country gent

another factor in reamer life is the actual barrel material, Stainless steel, steel also make a big impact on reamer life. Black Star (???) barrels were sold as tougher material to resist erosion and wear a few years ago. Had several guns smiths tell me they would not do them do to reduced tool / reamer life.

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The issue with 416 SS is surface work hardening from underfeeding.

I only done 4 or 5 BlackStars. I've read they were hard on HSS reamers but my carbide reamers had zero issues with them. They are long since out of business. Rumor was BlackStar got their barrels from Lothar Walther and did additional processes for a taper and smoother finish. I've never chambered a Lothar Walther blank so no comment other than what I've read.

I'll not tell you how many bottle neck chambers I've cut with only a finish reamer and no predrilling/boring because I'll likely get accused of lying.

Let's just say more than 2.

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Originally Posted by Hannibal

I'll not tell you how many bottle neck chambers I've cut with only a finish reamer and no predrilling/boring because I'll likely get accused of lying.

Let's just say more than 2.

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Not from me. I've never done it that way but I know a couple of full-time rifle smiths that have told me they get 25 to 30 chambers with no predrilling/boring on competition long range match rifles before they have them sharpened. I know one other full-time smith that does hunting rifles in volume. Accuracy is not his or his customers number one priority. Quick turn around and price is. He does a lot more than 25 or 30 per reamer.

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Originally Posted by BLAHUT

When you are not the one buying/paying for the tools it is easier to just grab a new one ??

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probably this

When I was taught chambering at CST, we were told we should be able to get 40 to 50 chambers from a good reamer. They stressed using dark cutting oil, low speed/heavy feed. and clearing chips often. That was in 1977 and at the time I had heard very little about benchrest and it was not mentioned at all by the instructors. Stainless barrels were also not mentioned.

I got chewed out for wanting to use the power downfeed on a Bridgeport for a 5/8" diameter hole in a trigger guard I was making. Was told to "Do it how you are told" with no explanation that the power downfeed had weak components and could only handle boring cuts reliably. Trigger guard turned out quite well. It was a streamlined version of a Krag that I used on a blind box Mauser 98.