Reaming after pre-boring

[DaveTooley]

why wouldn’t the core drill have the same problem as wander/flex as any normal spiral stub drill? Even carbide and colbalt drill bits flex

Fully supported radial cutting edges not to mention the precision of the grind. It's called a drill but in essence it's an aggressive reamer.

 

[Alex Wheeler]

The core drills work well. I did go back to preboring though. Too many different chambers to have core drills for and they can still get off track. Boring is always concentric to the spindle. I tried most of the floating reamer holders out there. I'll never stop holding the reamer in my hand. I could not get the same results with a floater. Everyone has different methods and things they look for. Through trial and error you will find a method that produces what you want with consistency. Thats the big one, you should not have chambers that dont turn out right. They all should be on size with concentric throats. If thats not the case, keep trying different processes.

 

[dnellans]

The core drills work well. I did go back to preboring though. Too many different chambers to have core drills for and they can still get off track. Boring is always concentric to the spindle. I tried most of the floating reamer holders out there. I'll never stop holding the reamer in my hand. I could not get the same results with a floater. Everyone has different methods and things they look for. Through trial and error you will find a method that produces what you want with consistency. Thats the big one, you should not have chambers that dont turn out right. They all should be on size with concentric throats. If thats not the case, keep trying different processes.

In your hand? Are you using something like a mars ii stop collar to control depth?

 

[Alex Wheeler]

A pusher of my own design. No need for a stop, just measure and cut.

 

[FireMedic]

The core drills work well. I did go back to preboring though. Too many different chambers to have core drills for and they can still get off track. Boring is always concentric to the spindle. I tried most of the floating reamer holders out there. I'll never stop holding the reamer in my hand. I could not get the same results with a floater. Everyone has different methods and things they look for. Through trial and error you will find a method that produces what you want with consistency. Thats the big one, you should not have chambers that dont turn out right. They all should be on size with concentric throats. If thats not the case, keep trying different processes.

You say the core drills can get off track. Do you think more so then just using a finish reamer from start to finish? I was thinking about ordering a core drill to try.

Ive always felt that if I can get the first 4” of barrel (length of my indicator stylus) running perfectly concentric to the lathes spindle bore, the reamer/core drill will want to go to the center as long as it’s not influenced otherwise.

I’ve had good luck with a JGS reamer holder. I tried the bald eagle pusher and I couldn’t fall in love with it.

 

[Alex Wheeler]

I have reamed plenty of chambers the whole way. Theres a noticeable difference in reamer life. When you have a hummer reamer you want it to last as long as possible. They are not all the same and a good one is a good one. The core drills work well. Try one. Theres different reasons why a drill or reamer will go off center. Hardness variation in the steel will make a drill wander. Boring is a sure thing. It just gives me more consistent results.

 

[tobnpr]

I'm lost on the "theory" behind using the core drill.
My assumptions:
The reason for dialing the throat area concentric is to align that specific area- with the operating theory being the bore behind it may not be...
Drilling as a first step does not align the first couple inches of barrel to the throat, as the drill will follow the bore.
Boring is to remove that runout- if it exists. We know we're talking about tenths here at most on a quality barrel.

I do not see how using a tapered core drill changes that. It's still a form cutter, and it's still going to follow the bore. If you don't skim with a boring bar after, I fail to see what has been accomplished. Core drill follows the bore, so does a roughing reamer, and I'm seeing very little if any practical difference in what both of these accomplish- which is saving reamer wear. Tell me what I'm missing...

 

[Walt Krafft]

The JGS piloted core drills I get use pilot bushings just like the reamer. You are correct in that they are used to save reamer wear and with the pilot the chamber is concentric as it would be if you just used the finish reamer. These core drills cut just as fast as a regular drill where a roughing reamer only cuts as fast as a finishing reamer. If you have 15-20 barrels to do the speed and wear saved on the finish reamer is well worth the money. If you only have a couple of barrels to do, use a finish reamer and drill and bore if you want.

 

[skeeljc]

I cut my first chamber using the Gritters method 100%. Pre-drilled and straight bored with a carbide boring bar. Used the GTR reamer holder. Made sure the tailstock was aligned first. Chamber came out fine.

I cannot imagine doing the whole chamber with the finish reamer stopping every .050" to clean chips.

 

[Carl S]

The core drills work well. I did go back to preboring though. Too many different chambers to have core drills for and they can still get off track. Boring is always concentric to the spindle. I tried most of the floating reamer holders out there. I'll never stop holding the reamer in my hand. I could not get the same results with a floater. Everyone has different methods and things they look for. Through trial and error you will find a method that produces what you want with consistency. Thats the big one, you should not have chambers that dont turn out right. They all should be on size with concentric throats. If thats not the case, keep trying different processes.

I have reamed plenty of chambers the whole way. Theres a noticeable difference in reamer life. When you have a hummer reamer you want it to last as long as possible. They are not all the same and a good one is a good one. The core drills work well. Try one. Theres different reasons why a drill or reamer will go off center. Hardness variation in the steel will make a drill wander. Boring is a sure thing. It just gives me more consistent results.

I have found out that when I dial the muzzle and throat in perfect.drill and prebore also I take a wafer thin cut on the final pass with the boring bar so there is no tool deflection.i check with the DTI and everything is right.i no my tail stock is spot on as is the rest of my lathe.ino then everything is as perfect as can be before i start to ream.it works great for me and the chambers come out excellent.i think if you're set up is slightly out you can be fighting it from start to finish.some of you guys do and have chambered alot more barrels and no alot more about it than me.in any machining application set up correctly finish correctly thats how I've always was taught.

 

[AckleymanII]

I indicate the barrel in where the new throat will be and muzzle, then cut the chamber, check for run out, then cut the shoulder and thread, then check run out. Hard to get .0003 run out on this method, and most of the time it is .0000-.0001. I use the smallest drill possible, then a carbide boring bar, cutting to within .015 of reamer dimension. The reamers cut very small chips. Reamers should last my lifetime.

I feel like having .0003 and LESS on a finished chamber gives a guy the very best chance of getting the best accuracy out of a barrel with the largest spread of powder charge in the Tuned load.

 

[FireMedic]

I have found out that when I dial the muzzle and throat in perfect.drill and prebore also I take a wafer thin cut on the final pass with the boring bar so there is no tool deflection.i check with the DTI and everything is right.i no my tail stock is spot on as is the rest of my lathe.ino then everything is as perfect as can be before i start to ream.it works great for me and the chambers come out excellent.i think if you're set up is slightly out you can be fighting it from start to finish.some of you guys do and have chambered alot more barrels and no alot more about it than me.in any machining application set up correctly finish correctly thats how I've always was taught.

I guess it depends on how you indicate your barrels, and what you think is important.

I know a lot of guys dial at the throat and the muzzle. This has never made sense to me. For me I want the chamber concentric and on the same plane as the bore at the breech end. I believe this gives a bullet the straightest start down the bore.

For me I indicate the Barrel from I” of the breech to 5” in (longest my long reach indicator will reach). And do that portion as fine as I can get it. What The muzzle end is doing matters not to me.

Like many others I do clock them at TDC and never notice any windage problems or barrel channel misalignment. Barrel to barrel poi is within a few inches.

 

[Carl S]

I guess it depends on how you indicate your barrels, and what you think is important.

I know a lot of guys dial at the throat and the muzzle. This has never made sense to me. For me I want the chamber concentric and on the same plane as the bore at the breech end. I believe this gives a bullet the straightest start down the bore.

For me I indicate the Barrel from I” of the breech to 5” in (longest my long reach indicator will reach). And do that portion as fine as I can get it. What The muzzle end is doing matters not to me.

Like many others I do clock them at TDC and never notice any windage problems or barrel channel misalignment. Barrel to barrel poi is within a few inches.

I think most people do things slightly different and what makes one happy with his finished chamber is key.i am always interested in how other people do there work.i never stop learning and valuable advice is worth it's weight in gold and there is lots of it on this forum.ive tried different methods with excellent results,but my current one gives me the most consistent results,straight concentric chambers barrel after barrel.

 

[FireMedic]

The JGS piloted core drills I get use pilot bushings just like the reamer. You are correct in that they are used to save reamer wear and with the pilot the chamber is concentric as it would be if you just used the finish reamer. These core drills cut just as fast as a regular drill where a roughing reamer only cuts as fast as a finishing reamer. If you have 15-20 barrels to do the speed and wear saved on the finish reamer is well worth the money. If you only have a couple of barrels to do, use a finish reamer and drill and bore if you wa

The JGS piloted core drills I get use pilot bushings just like the reamer. You are correct in that they are used to save reamer wear and with the pilot the chamber is concentric as it would be if you just used the finish reamer. These core drills cut just as fast as a regular drill where a roughing reamer only cuts as fast as a finishing reamer. If you have 15-20 barrels to do the speed and wear saved on the finish reamer is well worth the money. If you only have a couple of barrels to do, use a finish reamer and drill and bore if you want.

Do you prefer the HSS or Carbide Core drills? I’m gonna order one for one of my more common reamers to try out. The carbide is spendy!

 

[Walt Krafft]

High speed steel. I am not at all a fan of carbide drills and reamers.

 

[FireMedic]

High speed steel. I am not at all a fan of carbide drills and reamers.

I prefer the HSS reamers as well. I wasn’t sure if the core drill would be worth buying carbide for tool life. What speed do you recommend drilling with?

 

[Walt Krafft]

With the coolant I use, I drill and ream between 250 to 350 rpm.

 

[DaveTooley]

I use HSS also. I get the other side of 300 barrels with this. Speed is limited to the strength of the holding fixture. Depending on caliber 250-300 rpms with a .005- .006" feed rate. I do like carbide finish reamers. Not necessary but I like the finish.

 

[Clark]

1) I drill for 1/2"
2) I boring bar for 1/2"
3) I push the reamer 1/2" with an arbor in the tailstock and a tap wrench on the reamer.
lather, rinse, repeat, lather, rinse, repeat, as Robenz says.
Only 1/2" at a time as I want to keep the reamer pilot engaged.

 

[Edd]

Can someone confirm what I think I remember reading.

I think I read where Chad at LRI said he reams a 308 size chamber with a finish reamer in under 2 minutes.