survey: what is your total length of reamer use ?

C

CMaier

Guest
How much metal do you cut with the chamber reamer ?
Total , not steps or final cut.

I have little gunsmith exp,(more machine exp) but saw where jackie said something that got me thinking.
His chamber cut is very short due to his pre-bore / tool design.
 
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I usally do entire chamber with finish reamer. I use a hi pressure flush system and have over 100 chambers on one PTG .308 reamer.
 
We're rarely use carbide roughers. Instead we pre-drill removing a conservative amount of metal. Example - on the PPC we go in with a 23/64” (0.359”) bit and stop 0.100" short of the shoulder. Then we cut the chamber with our finisher.

-Lee
www.singleactions.com
 
.010" radially on the entire body and full form from the shoulder forward. I'm holding my reamer rigidly though so the pilot does not need to make purchase in the bore at the beginning to start straight.
 
Use a twist drill then set the taper atachment on my heavy 10 and bore body profile to with in .005-.010 under reamer size. The shoulder on my reamers do all the hard work.
 
It appears everyone is ignoring the most important part of any reamer. The throat from the lead angle back to the end of the neck. The most important and most used section unless you have a roughing reamer with smaller diameter neck with no throat. The body and neck can cut a lot of chambers. The throat not so many. It's pretty easy to see the edge breaking down on the throat. The freebore gets tighter and seating depth can change drastically in just a few too many chambers. YMMV
 
Dave Tooley said:
It appears everyone is ignoring the most important part of any reamer. The throat from the lead angle back to the end of the neck. The most important and most used section unless you have a roughing reamer with smaller diameter neck with no throat. The body and neck can cut a lot of chambers. The throat not so many. It's pretty easy to see the edge breaking down on the throat. The freebore gets tighter and seating depth can change drastically in just a few too many chambers. YMMV
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Makes sense. I used to believe that I would get the best and most concentric chamber by using a single finish reamer. Lately, I have been using a short throat reamer and lengthening the throat with a throat reamer. I do seem to get a nice, crisp throat by doing this. I once used a .280 reamer to recut a chamber that I set back one thread a couple of times and it became dull right at the end of the neck. None of my other reamers have needed resharpening after the relatively few chambers I have cut.

I pre-bore to get the straightest chamber possible, and I assume it also reduces wear on the neck portion of the reamer.
 
Compared to using the finish reamer to cut the whole chamber it does. I use core drills caliber specific and stop .050" short. That's the body only. The throat starts cutting at the end of the shoulder so you have the neck length + .050". That takes a toll after awhile.
 
One caution. Most of the reamer manufacturers recommend running their high speed steel in the 250-275 RPM speed range. That is in the carbide speed range.

Look up the recommended CUTTIG speed for your barrel material and your cutting tool type.

RPM=SFM x 3.82 / Dia

SFM=RPM x 3.82 x Dia

Dia is the average diameter of your reamer in the chambering situation (about 0.3 for a PPC/308 reamer). Dia would be the diameter of the workpiece in the turning situation.

SFM is simply how fast, in Feet Per Minute, the tool and the work are passing by each other.

The major tool wear problem occurs, in reaming, when you pause the operation. i.e. The barrel is still spinning and the reamer is against but not cutting the barrel. This gives the material a chance to work harden, so when you go back to cutting the very first bite is into work hardened steel. Practical solution, when you stop feeding the reamer, IMMEDIATELY back it off, if just for a few thousants.

BUT, upon reaching the finish depth let the barrel spin a FEW more turns to improve the finish. This is one reason why reaming in the 250-275 RPM range the reamer spins too many times.

Generally, when chamber reaming, with a high speed steel reamer, about 70-90 RPM is best.


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What is the recommended surface speed for HSS in 416R? I'm away from my machinery's handbook. Off memory, the reamer manufacturer's recommended speeds are pretty conservative from a sfm perspective. I typically use carbide now but I do run HSS reamers faster than their numbers and I've tried carbide way faster but still nowhere near what the sfm calc out to.

I am able to program my dwell to controll how many turns are at each peck depth. Even on a manual machine, I never found much issue from work gardening of 416.
 
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If you have a HS reamer why would you not run at HS speeds? That is the lesson I received from the Old guy at JGS. I am going to assume he knows.
Bill
 
r44astro said:
If you have a HS reamer why would you not run at HS speeds? That is the lesson I received from the Old guy at JGS. I am going to assume he knows.
Bill
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Simple. There are different sets f parameters for determining cutting speeds for metal removal. Single point metal cutting has one set of parameters since the contact area is minor. Chamber reaming is a forming operation where a large area of contact exists between the cutting tool (chamber reamer) and the workpiece. Reamer grinding folks, while being very competent in what they do, are not by default machining experts.

Theoretically, a particular cutting material will have an optimum relation with the material being machined based on the metallurgical elements of each material. In reality these relations vary depending on the factors of what the tool to workpiece relationship is.

In theory, you could run your reamer to full depth and make one revolution of he workpiece and end up with a finished chamber, in reality it just doesn't work out somehow.


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dave
couple questions. On your core drills. do they cut slightly under final chamber diameters? Also do you get them from dave manson? I know you like his tooling.
I have a 338 Lapua to do here pretty quick. I haven't yet cut a chamber that large. The core drill idea appeals to me. thanks Lee
 
skeetlee said:
dave
couple questions. On your core drills. do they cut slightly under final chamber diameters? Also do you get them from dave manson? I know you like his tooling.
I have a 338 Lapua to do here pretty quick. I haven't yet cut a chamber that large. The core drill idea appeals to me. thanks Lee
Click to expand...

Skeet, just a simple jobbers length twist drill that is slightly under the chamber shoulder diameter is what is commonly used. I'd go about 1/32" under on the drill size. You can't put back metal when you have taken too much.

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lee if you go look at jackie's chambering, he regrinds to shoulder angle on the drill bit.
 
Skeet yes they are under size. I get them from JGS. They are made for production work. Not 1, 2 or even 10 chambers makes economical sense.
 
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