Ever cut a chamber with a boring bar?

[goodsteel]

OK don't have a cow, I'm just asking, why, if the barrel is running true in the lathe withing .0005, cant you use a boring bar to cut the chamber? Is it a finish issue? Maybe most gunsmiths aren't shop savvy enough to use a boring bar? Just curious why I'm having to shell out so much money for a reamer I will only use once, when I have a perfectly good boring bar and I am confident that I can make the right cuts.

[elk hunter]

I know it has been done and for a bottleneck cartridge at that. I just can't remember where I read about it. I do remember that it required a throating reamer, couple of special boring bars that the author made and at least two dial indicators to accurately track the location of the boring bar tip. It was an interesting read and I thought it would be a useful technique to chamber barrels and make dies. Never have tried it though. I have used a boring bar to straighten up a chamber when the reamer started to chatter, but only enough to get the hole straight enough for the reamer to cut properly.

If I were going to try it, I would select an old piece of barrel that I could fit to the action and practice on it and then fireform a case in the chamber to see what it looked like before I chucked up a new expensive barrel and started cutting.

Try it and let us know how it works.

[waksupi]

Cheaper to rent than own. Call Elk Ridge Reamers, 1-888-777-3252.

[KCSO]

Depends on how many chamber jobs yo do for a caliber. Once you have done 3 jobs the reamer is paid for so if it is a popular caliber I buy a reamer. Now to the question at hand I have cut 9MM 380 and 45-90 with a boring bar and had pretty good luck but I use a D reamer to finishe the last couple of thou. I do rough cut my chambers with a boring bar for rifle calibers but I am no Howe so I haven't trield to finish cut one.

[S.R.Custom]

I don't see why you can't... if you're that good.

If I were to try, I believe I'd do things differently than I do with a reamer. Mainly, I'd cut the chamber first, deeply, and thread & face afterwards, so as to adjust headspace that way. But you've prolly already sussed those things out.

Sure is going to make indexing for sights a real pain, if trying to use existing...

[deltaenterprizes]

DRO on both axis would be a big help.

[goodsteel]

Check er' out! I tried it out on a scrap piece. the neck area was cut with a regular chucking reamer that I modified to have a floating pilot.

http://castboolits.gunloads.com/imagehosting/thum_177714dc0af9814a28.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=755)http://castboolits.gunloads.com/imagehosting/thum_177714dc0af9806b84.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=754)

I think this will work just fine. The only trick I can see is that you have to be able to figure out your head-space mathematically and use precision when doing the cutting. I had no problem doing this but it is definitely not something that a novice would feel comfortable doing.
By the way If you ever have to do something like this in a pinch and your lathe has a DRO, do yourself a favor and take a cleanup cut on the outside of the barrel about .100 deep. Measure and record the diameter produced, and this will give you something to touch off with your tool to locate the cutting tip from one tool/angle change to the next.

[S.R.Custom]

Looks good. And if a fired case has less than .001" runout, you're hired!

[goodsteel]

.001? in no way could it have that much run-out. Heck I tweak the barrel until it is lined up to .0002 . The geometry is what gave me the most trouble but it was all because I could not see what I was doing. You have to be stone cold confident that everything is setup perfectly and go on faith, but I was pleasantly surprised by the fit and finish that was produced when I cut the test piece in half.http://castboolits.gunloads.com/imagehosting/thum_177714dc0af9814a28.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=755)http://castboolits.gunloads.com/imagehosting/thum_177714dc0af9806b84.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=754)

[rbertalotto]

There a couple of record holding, 1000 yard shooters that are cutting their chambers with CNC machines using boring bars. And they were cutting Weatherby type chambers that are very intricate.

Cutting a 45-70 or like chamber would be child's play for a CNC turning center.

[enfield]

I cut chambers in 2 Lee Enfield barrels using a 11/32" bit and 21/64" bit to make 32-20 chambers and they both work fine so I would say a reamer would be o.k. Ya just gotta experiment once and a while. one is on an old hopkins & allan and the other is a #4mk1 LE.

[jerry_from_ct]

OK don't have a cow, I'm just asking, why, if the barrel is running true in the lathe withing .0005, cant you use a boring bar to cut the chamber? Is it a finish issue? Maybe most gunsmiths aren't shop savvy enough to use a boring bar? Just curious why I'm having to shell out so much money for a reamer I will only use once, when I have a perfectly good boring bar and I am confident that I can make the right cuts.

Looks great.

I think the problem would be "any" flex in the bar, chamber reamers run true to the bore and provide throat. using the bore as a guide removes any possibility of an off cut.

Have you considered renting a reamer ?, just a thought.

http://www.reamerrentals.com/


Judging from the pics with your machining abilities, why not cut your own reamer.

[longbow]

While I have not used them for chambering reamers, a friend told me his grandfather was a gunsmith for BSA and that many years ago he used D reamers for cutting chambers.

They are very easy to make in whatever shape you want with no special tooling or grinding fixtures required.

I've made and used D reamers for reaming push out bullet moulds and other things. So far I have used them on brass, aluminum, bronze and mild steel with no problems.

I am sure they wouldn't last as long as a standard multi flute reamer but who cares if you are only cutting a couple of chambers. They are much easier to make.

Longbow

[goodsteel]

I cut the chamber with the boring bar. Went perfectly.
http://castboolits.gunloads.com/imagehosting/thum_177714dc6bd185d416.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=792)http://castboolits.gunloads.com/imagehosting/thum_177714dc6d5f27edb4.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=795)http://castboolits.gunloads.com/imagehosting/thum_177714dc6b9183f5b7.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=790)
pulled the two circled in red.

[jerry_from_ct]

If it works correctly and works for you, that's all that matters.

Congrats............

Well Done.
Jerry:drinks:

[EMC45]

Nice job.

[goodsteel]

Here's a chamber slug from the finished barrel.
http://castboolits.gunloads.com/imagehosting/thum_177714dcebeabd9ddb.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=842)

[JIMinPHX]

I've always figured that a boring bar would be a good way to cut a chamber, especially for a straight wall case. Thanks for confirming that.

[Rio Grande]

I'm an Inspector in a moderate-sized machine shop. After reading the posts above I asked an first-class lathe machinist there what he thought, and even showed him chamber reamer drawings.
He replied there was no difficulty involved in lathe turning ('single-pointing', I think it's called) a chamber of any kind on a CNC, programmable, lathe.
Piece of cake. We do more difficult lathe jobs every day.

[leftiye]

So how bouts sending me one a them there CNC lathes? They grow on trees, right? I can program one, just cain't afford one.

Getting the angles right whilst setting up a lathe for case taper, and shoulder angle can be muy problematical. Impressive job Goodsteel! I've had instructors from gunsmithing schools brag to me about how they singlepointed a given chamber, but I am in no way contemplating doing it.

Any pointers on how you got a good finish?

[justashooter]

for those of us with less accurate and expensive lathes a dutchman tool would be a better option. take a round blank of 0-1 tool steel and turn it to your chamber dimensions plus a chucking extension on base and a bore follower at the neck, then grind it thru the exact centerline in the areas it will be cutting in. do not grind past exact centerline, or less, or it will cut poorly and tend to wander. works best on moderate tapers. some wear on leade is inevitable. best to drill sub-dimensional cut if removing a lot of stock before using dutchman. make a long leade follower if you do this.

[goodsteel]

I did not use a CNC, I dont even have a digital readout! You have to cut the chamber in two steps. Three if it's a belted case.
1. figure out exactly how far it is from the barrel face to the shoulder of the cartridge. This was easy for me because I was cutting a chamber for a rimmed case.
2. Figure out what the difference is between the base diameter and the shoulder diameter.
3. Divide this value by 2
4. Mount a piece of strait, smooth stock between centers and run the length of it with an indicator in on the apron to insure that it is strait, adjust the tail-stock until the test piece is parallel.
5. Set up your indicator on the compound crank and set the compound close to parallel to the test piece. Set a zero on the compound and set your indicator to zero also. Crank the compound dial until you have moved the length of step 1. Adjust the compound angle until your indicator reads the value that you had in step 3. Take care to make sure that this value is perfect.
6. lock your compound in place and dont move it!
7. Remove the test piece and set up your barrel as you normally would to ream a chamber.
8. Use a normal RH tool to true up the face of the barrel
9. Install a sharp boring bar and take all necessary precautions to make sure that it is aligned properly.
10. return your compound crank to the zero that you set in step 5 and touch off the face of the barrel.
11. set a stop for the apron or an indicator or something so that you can always return to that spot exactly.
12. using the cross slide and the compound crank only, extend the tool into the bore and use the cross slide to move it back and forth as you move the cross slide to you a little at a time, until you touch-off.
13. Withdraw the tool with the compound and move the cross slide towards you about .010 inches (just enough to clean out the rifling.
14. use the compound to push the tool onto the bore, being mindful of the depth of the cut.
15. Finish the cut and withdraw the tool as slowly as you inserted it. (listen for chatter, if the bar starts to chatter or wine at any time dump some RPMs until you hear a smooth cut. Use plenty of cutting oil and go slow.)
16. Back the apron out of the way and carefully measure the edge of the cut with your calipers. Continue making .010 cuts until you have reached the diameter of the cartridge where it enters the bore.
17. Reposition the compound to the desired shoulder angle, and align the boring bar again. Re-set the zero on the compound only this time as it is being reversed instead of as it is being advanced.
18. Touch off the face of the barrel again only this time set an indicator on the ways to measure cut depth in the normal way.
19. Use the cross slide to touch off the tool on the very edge of the bore that you just cut.
20. place an indicator on the apron, touching the tool post so that you can read the cross slide movement exactly.
21. Move the cross slide in until the indicator reads the value in step 3
22. Move the apron in until the indicator reads the value in step 1
23. You should hear the tool start to touch the bore about .005-.010 befor you get to depth. dont worry about it, this is tool push-off being loaded. Continue to insert the tool until you hear it touch the place you stopped cutting in the previous operation. It should be within .005 of your indicator reading, when this happens, very slowly and deliberately move the compound crank in order to cut the shoulder. Once the tool stops removing material, reverse the direction of the compound and return to zero.
24. At this point it is critical that you use the apron to remove the tool slowly from the bore.
25. Use your piloted chucking reamer to cut the neck portion of the chamber.
26. Use your piloted and tapered chucking reamer to cut the throat.
27. Wrap some 400 sandpaper around a pencil and polish the bore.
28. Crack open a beer, you just saved yourself $70!!!

[Rio Grande]

So how bouts sending me one a them there CNC lathes? They grow on trees, right? I can program one, just cain't afford one.

Getting the angles right whilst setting up a lathe for case taper, and shoulder angle can be muy problematical. Impressive job Goodsteel! I've had instructors from gunsmithing schools brag to me about how they singlepointed a given chamber, but I am in no way contemplating doing it.

Any pointers on how you got a good finish?

I work around so many of those CNC machines, I guess I forget they are unaccessible to some folks. They do simplify things. And there are used bench models that are not that expensive.
Like y'all, I wanted to emphasize that practically, reamers are not necessary, and it's something I've been thinking of.
It's very impressive also that you manual lathe guys can 'git 'er done' with the tools you have.
Especially with the more complicated tapered and bottlenecked cartridges.
Some of the manual machinists I work with, lathe and mill, well, to them it's more than a profession, it's an art.

[JIMinPHX]

Goodsteel, I admire your perseverance. That's an easy job to loose with a single mismatch of boring bar moves. It takes a steady hand & a focused mind to get that to come out right.

My compliments to the chef.:drinks:

[goodsteel]

I'm a little OCD so it wasn't a problem. The test barrel helped a lot to build confidence and I would recommend it to anyone wanting to do a chamber like this. As it turned out, the barrel came out so close to the mock piece, that the fire-formed brass fits perfectly in the cavity. I cut a total of 3 chambers 2 mock chambers, and one in the rifle. After doing all that I feel very confident that I could do almost any chamber this way, providing that the cartridge in question is not too long and skinny.
cutting chambers this way is scary to think about but once you do one or two your confidence goes way up and it doesn't seem so bad at all.
Grab a piece of steel and give er a try, what the heck.
If you're like me, I'm short on patience, time, and money (mainly money[smilie=b:) but necessity is the mother of invention.

[drhall762]

Nice to see a machinist who still uses indicators. I do as well. While I have never cut a chamber with a boring bar I think after reading this I will give it a try. Seems as with all machining, don't get in a hurry and pay attention. Pays off.

While I haven't used a boring bar I have EDM'd a few but that is another story.

[John Taylor]

for those of us with less accurate and expensive lathes a dutchman tool would be a better option. take a round blank of 0-1 tool steel and turn it to your chamber dimensions plus a chucking extension on base and a bore follower at the neck, then grind it thru the exact centerline in the areas it will be cutting in. do not grind past exact centerline, or less, or it will cut poorly and tend to wander. works best on moderate tapers. some wear on leade is inevitable. best to drill sub-dimensional cut if removing a lot of stock before using dutchman. make a long leade follower if you do this.

What you have described is called a "D" reamer. I have made a few many years ago when I was to cheep to buy a real chamber reamer. I was taught to grind just short of half way. They do cut OK if you take your time and use plenty of cutting oil, remember there is only one cutting edge instead of six.
I did cut a chamber with a boring bar one time. It was for a 32 S&W on a rifle and it worked OK.

[justashooter]

What you have described is called a "D" reamer. I have made a few many years ago when I was to cheep to buy a real chamber reamer. I was taught to grind just short of half way. They do cut OK if you take your time and use plenty of cutting oil, remember there is only one cutting edge instead of six.
I did cut a chamber with a boring bar one time. It was for a 32 S&W on a rifle and it worked OK.

we always called them dutchmen, prolly because dutchies have a habit of doing things for themselves, rather than buying factory.

one cutting edge is right. speed of rotation and advance must accommodate. in any case, i'd rather use a piloted reamer, for sure. dutchies are best for simple cases where there is not a lot of stock removal, like 45-70 and 32-40 (which can be well made from any old 8X57 barrel). more reliable on any lathe that has any backlash in the transits (like mine, guess i need to re-build them).

trouble with chamber reamers is that they are often not marked. some i have inherited are real puzzlers. FE, i have one set that looks sorta like 25-25 stevens, but seems just a hare too big. nothing else in my reference is close, so i will never be able to use them.

[goodsteel]

You know, I keep thinking that one way to get around the weakness of the dutch reamer would be to use a boring bar to remove most of the material and follow up with the dutch. Concentric is concentric, might not work with an old battle barrel, but with any modern blank, the outside of the blank should run perfectly true with the bore. The pilots are nice just to be on the safe side but honestly, whats stopping us from using pilot's on the dutch reamers?

[uncle jed]

Hello, Goodsteel. What rifle is this and what caliber is it rechambered to? Thanks, Uncle Jed.

[goodsteel]

The rifle started out as a No.4 Mk1 brittish enfield in 303British. I loved the action but the barrel was no good. As long as I was going to rebarrel the action, I decided that I would like to turn it into a wildcat with a .358diameter barrel. I cut the chamber in such a way that I could fire form the brass to the new configuration. I still use 303British brass, but I straitened the side walls, gave it a 45degree shoulder, and opened up the neck to accept a .358 paperpatched boolit. Since I could find no information on another cartridge like this with a 45degree shoulder, I called it the 358 Malcolm. After much wrangling and agony, I got the rifle to feed 8 rounds of this ammo from the magazine, and it holds a 2" group at 100 yards with iron sights. It has light recoil, hits like a sledge hammer, and is all around a joy to shoot, especially offhand.

[lmcollins]

First: The Wolf Publishing Company has a book called something like "Gunsmith Tips and Tricks." It has a good article in it on boring a rifle chamber. It has been years since I looked at it, but I think that they had to make their own boring bar to get one the correct dimensions. You should check it out.

Second: If you've ever played with a barrel blank from even one of our best makers you know that it's outside is not true with its inside. Before I even try to cut and thread I set them up on centers with a dog and do a truing cuts. I then cut the thread stub, and thread on centers. If you've ever played with a barrel spinner and a good belt sander you'd know what can be done to correct small problems.

An experienced hand would know all of these things. I chamber either through the steady, or the headstock - but I always use a floating holder with a lot of float and a piloted reamer.

I think it might be appropriate to start with a drill bit (undersized) and then bore with a small boring bar to be true to the bore" if you don't have a roughing reamer so that your finishing reamer pilot pickes up the "bore" without giving you an oversized or out- of-round chamber.

Chuck up a barrel between centers, and play with some indicators....

[goodsteel]

I guess I must have gotten lucky, my barrel blank ran almost perfect between centers. less than .0002 on the muzzle and on the breach ends with only .0018 deviation in the very center. This is not surprising since I believe that the contour was cut/ground between centers. I did have to pay close attention to the run-outs after I chucked up the muzzle in the 3 jaw though, because it was inducing torque on the barrel that resulted in .010 run-out in between the steady and the chuck. I solved this by removing the chuck jaws and only gripping the barrel by the last 1/4" of the muzzle.
I agree that careful preparation and indicating is crucial but I am surprised that barrels that cost 3 times what mine did, would have that much run-out. Mine cost only $89.95 and I was very impressed by its precision and accuracy. My one gripe would be that the internal finish was not as good as a Shilen or a Douglas, but a few hundred paper patched boolits have fixed that right, good, and proper.:bigsmyl2:

[Blanket]

Great job and yes I have bored complete chambers but only on straight taper chambers, no bottleneck. I normally rough out chambers with a boring bar before reaming anyway, As to barrels being concentric to the bore, you would be suprised how far off even premium barrels are. I set up and turn between centers to give true areas for setup or if the barrel is a rework or finished press a sleeve over them and turn the sleeve to acheive a concentric setup area. Modern cnc lathes would be a snap to do a lot of chambers by boring and I don't think the finish would be a problem. The Haas cnc we have at work would do a great job although it does not have a toolpost capabile of multiple tool setups. Again great job on the work...Russ

[Willbird]

One thing that puzzles me.

If we drew a triangle for the case taper, you moved the compound the distance from the shoulder to the barrel face, this is the base of our triangle, you then swung the compound an amount equal to the height of the triangle.

The base of our triangle became the hypotenuse when we swung the compound ?

I have no doubt it worked, but the taper I am willing to bet was not exactly what you were planning on ? For a shallow taper maybe the error is tiny ?

[Willbird]

Also depending on where in the travel your compound is the amount moved over will create a different angle. The compound has a fixed pivot point, but we can move the tool or indicator to different locations from that pivot point, in effect changing the length of our sin bar.

[goodsteel]

That is very true, but the difference in this case between the hypotenuse and the base of the triangle was very slight. Also when I set the angle on the compound I did so by measuring how far the tool moved inward for a given distance on the compound. This is the most accurate way to set an angle on the compound. As it was, when I had moved the tool in 1.75" the exact difference between the base and the shoulder was .005 inches. So it was an easy matter to reset the compound for the shoulder angle, touche off the tool at the base of the cut, move the cross-slide in .005, and simply move the tool towards the shoulder until I heard it start cutting. I was not to concerned if I missed dimension to the shoulder of my cartridge by .0005 inches.
You see, if you know the deflection that a given angle produces over a given distance, then when you need to pick up that corner with your tool all you need to know is how far off what you cant see is from what you can see.

[Willbird]

My point if there is one, is thinking about these kinds of things. that trick might work with an Ackley ctg, but will it work with say a 7.62x54r ? For making Morse tapers cranking the tailstock over with a long travel indicator will get you CLOSE, but not dead on. And indicating taper masters straight on an OD grinder, again close, but not perfect. Due to most tailstocks not being the perfect height, and the indicator not being right at the height of the cutting tool or the grinding wheel.

[goodsteel]

Well, you are right that it wont be perfect, but it doesn't have to be. It was my understanding that making the chamber concentric with the bore was paramount, followed by chamber dimensions, which need only be held to a comparatively loose tolerance like +- .002 inches.
I still believe that indicating the linear deviation of the compound slide against a known parallel cylinder, that is running true to the axis of the lathes rotation, "where the distance moved by the compound is considered the hypotenuse of the triangle, and the indicator reading is considered side (A)" is the most accurate way to set up the compound slide to a particular angle. The only way to improve beyond that is to use layout blue and a cylindrical standard of angle to lap in the last few ten-thousandths per foot.
This is my understanding and so far it has not failed me. Especially when I am cutting a bore for a rifle that I intend to neck-size the brass for. What ever the chamber comes out is what the brass will be. However I must say, that upon casting the chamber, the slug measured exactly right in every dimension.
All that being said, the margin for error is enormous when cutting a chamber in this way, and the only reason I did it was because I was and am, broke as a duck. I could not afford the reamer rental fee because I had spent my last hundred on the barrel blank. If I had had the money you better know that I would buy a reamer! Of course when you are doing R&D on a new wildcat cartridge, you better have deep pockets cause its going to cost you another $150 every time you change your mind on the design. I just thought that If a fella was forging ahead with a cartridge that has not been made before (ie. a true wildcat) he might like to know that there is a way to find out how his idea will perform and make quick changes as needed, without dropping a lot of money.

[smokemjoe]

I made a barrel for my TC in 357 Max. from a rifle barrel to shoot up alot of cast 35 bullets, I used a boring bar and its perfect,

[Ronbo256]

I used a boring bar to finish cut a .40 smith 1911 barrel on a Hardinge tool room lathe with dual DRO, but I couldn't muster up enough courage to cut the leade/throat and bought a used Manson 10mm reamer from Storm lake for 27.50 shipped to do the leade. I used a gauge pin to measure the diameter and depth.