Chamber Reaming.

[CentrePunch]

Hi all,
I am about to cut my first chamber so i hope this does not sound like a dumb question.
Do you start your reamer into a revolving barrel or do you start the pilot and then switch on?
Also, do you switch off before withdrawing the reamer or withdraw with the lathe still running? Thanks

Ian.

 

[Cheechako]

Ian

Always, I mean ALWAYS, have the work turning while both inserting and withdrawing. One of the best ways to snap off a reamer is to insert and then turn on the power. Not as bad as when withdrawing but, almost.

Ray

 

[tightneck]

There are a whole boatload of opinions on how to properly chamber a barrel. You would be wise to get a good video on Chambering from Greg Tannel, Richard Franklin or AGI. Everyone has an idea of how it should be done but seeing it done is very helpful. I've watched some excellent gunsmiths chamber barrels and I use different ideas from different smiths. Mike Bryant's website has some excellent write-ups on precision barrel fitting as well.

 

[CentrePunch]

Hi,
I have watched videos by Darryl Holland and Richard Franklin, both use different methods, with Richard starting the reamer into the bore, before switching on his lathe.
I have a Dave Manson floating reamer holder and will be chambering using the steady method.
It seems logical to just start the front of the pilot into the bore, swith on the machine and feed the reamer in, rather then feeding in the reamer and allowing the bore to pull the reamer onto centre.
Any more thoughts?
Thanks

Ian.

 

[kaferhaus]

I always start the lathe with the pilot already in the hole.

I always fully stop the lathe before withdrawing the reamer.... otherwise you're likely to get a chip fall in behind it...

I've seen some outstanding BR smiths start and stop their machines with the reamer fully but "lightly" engaged with the blank....

 

[tightneck]

start and stop their machines with the reamer fully but "lightly" engaged with the blank....

I'm certainly no expert but this is the method I have adopted after seeing it done in this manner, as well as taking the advice of some excellent gunsmiths. I drill out most of the chamber and then use a boring bar to true up the hole to just under shoulder dimension. Always make sure my reamer is engaged when I start the lathe or stop it. I haven't cut as many chambers as most but so far it has worked for me. Very little TIR, and a chamber that needs little polishing.

 

[lazylabs]

So when you start the reaming process the pilot is not in the bore of the barrel? The reamer is just using the shoulder to center on the hole you drilled/bored? I can see where drilling out the majority of the material would save a LOT of work on the shoulder of the reamer but what is guiding it when you start the reaming process?

 

[kaferhaus]

So when you start the reaming process the pilot is not in the bore of the barrel? The reamer is just using the shoulder to center on the hole you drilled/bored? I can see where drilling out the majority of the material would save a LOT of work on the shoulder of the reamer but what is guiding it when you start the reaming process?

Sure it is... the reamer is much longer than the finsihed chamber... there's still plenty of length to get the pilot into the bore before the reamer ever starts to cut.

Most smiths drill/bore the chamber just short of the eventual chamber and about .020 or so narrow of final dimension.

This saves a lot of wear on your finishing reamer and eliminates the need of a roughing reamer.

 

[techshooter]

I too have tried to figure out how this pre-boring operation could work. Please let me know what I am missing with the following analysis:

If you look at a 6 Dasher reamer,from my reamer drawing, Dave Kiff, see my web site http://www.the-long-family.com/images/6mm%20Dasher.jpg), there is about 1.2" of body from base to shoulder. There is another .675" from there to the end of the throat, including the leade. The pilot is about 0.5" long, making the total distance forward of the shoulder about 1.175". That still makes the front of the reamer about 0.025" short to engage the pilot in the bore before the shoulder part of the reamer starts cutting. I am assuming that the bored starter hole is a bit less than the 0.460" shoulder diameter of the Dasher, say 0.430". How could I be sure that the reamer would cut on center accurately enough that once the reamer has advanced by that 0.025", the pilot would slip right into the bore, and not get hung up? This would be even worse with a longer case, like the .308, etc.

I really like the idea of boring a starter hole to save wear-and-tear on the reamer, but I can't get by the image of an off-center reamer pilot trying to jam into the bore. How do you all do this out there? A very loose pilot? No pilot? Or is there no issue as the reamer will cut close enough?

Very curious...

Cheers,

 

[Wild_Bill]

Hi if you look after your reamers you will get a lot of chambers out of your Finishing reamer. I dont like to pre bore the a hole into the chamber because it does not have a pilot so it can go off centre very easily.

If you have a lot of chanbers to cut purchase a roughing reamer to do the job. if you have an old reamer you can also get it reground undersize to use as a roughinf reamer to keep your Finishing reamer in top condition. I would not worry about it if you are only going to be using it for yourself you will likely only cut 5 or so chambers in a few years with it so their is not problems using the Finishing reamer.

Cheers Bill
Australia

 

[techshooter]

I am using all finish reamers right now. I had Dave Kiff re-work my 6.5-284 reamer after about 7 chamberings. It was cutting fine, but not as smooth as when new, so for the cost of $50, I got back to Kiff perfection. A great value for peace of mind. I figure that a really sharp reamer will cut a rounder and straighter hole with less TIR. The pre-boring thing is just a curiosity for me.

Cheers,

Chris

 

[WayneShaw]

The theory is, you drill out the chamber to just shy of the shoulder, with a drill that is smaller than the shoulder diameter. Then, you have to use an indicator that can reach up to where the new throat will be, and indicat the barrel in there. Given the fact that barrels aren't drilled straight, you probably will see a difference. Once the throat area is set to zero, you use a boring bar, and bore the drilled hole true. From that point, the drilled hole will be concentric with the throat. The reamer will follow the drilled hole, and the pilot will follow right in. There is definite advantages to saving the reamer from cutting so much, but the real reason is to get the chamber centered where the throat will be, regardless of whether the barrel is straight or not.

 

[SamLS]

Wayne is correct I have never had a reamer not follow the concentric bore. The advantage of boring comes when you realize the end of the barrel is where someone reversed an abrasive lap about 100 strokes or so and unless you cut about an inch off and recenter you are inducing error into the chamber by starting a pilot there. You only have to pre bore about an inch or so and if your concerned just do it in steps so your pilot is always engaged.

 

[kaferhaus]

I think the guys that haven't done this before are making a mountain out of a mole hill so to speak...

Once the barrel is indicated in, all operations on the chamber and shank are completed with the same setup.... there is no need for "re-indicating" anything.

When "pre-boring", you're not getting any closer than .020 of the side walls of the chamber and I usually stop .040 or so from the shoulder / body junction.

On most reamers the pilot extends at least .5 forward of the throat.... that's plenty of room to engage the pilot before the reamer ever starts to cut.

The only exception being chambers that have a lot of body taper.... for most "target" cartridges such as 6PPC, 6BR, 308 etc with little body taper this is child's play.

If you want to "test" this, just take an old barrel, cut a stub off of it, bore it and then section it.... lay your reamer into one of the sectioned halves and you'll see immediately what I'm refering too.

Nothing complicated about it...

Using this method, I can usually finish 20 or so chambers before the reamer needs a regrind. Unless I'm chambering 17h4 stainless,Lothar Walther)...... then you'll get maybe half that life.

 

[tightneck]

As Wayne eluded to, indicating at one spot in the barrel doesn't mean the entire bore will be running true. After pre-drilling my hole, I do re-indicate where the throat will be. I ALWAYS have to make some adjustments to get the throat area running true if I first indicate near the end of the shank. I always indicate off the lands and grooves. The reason for all this is to get the bullet started on as strait a course as possible when it first enters the rifling.

 

[lazylabs]

Now explain the prebore idea with a large cartridge like a 300 Ultra. Say I drill/bore a 1/2" hole 2.250 deep, how do you get the reamer started? The large cases are where reamer wear really matters to me. One Ultra chamber is 3 times the reamer wear of a BR size case.

 

[Rustystud]

All that pre- drilling/boring is unnessary if you use a good flush system and the correct cutting fluid. In fact it most likely stress the chamber end of the barrel. Drilling and boring creates lots of heat. My barrels and reamers never even get warm to the touch. They turn at cutting speeds recomended by the manufactures. If you contact any of the modern reamer makers they will tell your high speed, hi presure coolant flow is far less wearing to the reamers and less stressful to the barrels. Reamers are made to cut not scrape or grind. Drilling or boring may also tend to work harden the barrel. Moderm reamers are cut with a geometry for faster speeds. Snug fitting pilots and floating reamer holders with barrels maounted in the rigid headstock with and outbound spider is a much better option when it comes to chambering. I know this will draw some aguement but it only took me 35 years to realize I was wrong before.
Rustystud

 

[tightneck]

Rustystud, There are lots of ways to come to the same end result. I'm sure that the way you are doing it now works great but I for one don't see the need to invest in a flush system simply because I don't cut that many chambers. As far as pre-drilling and boring prior to finish chambering goes, you are arguing with a great deal of success.

 

[BillK]

The muzzle flush system is worth its weight in gold so far for me. I have tried with it and without and found it is much easier to chamber with it. The finish seems to come out much better too!!!

 

[Rustystud]

Tightneck:

I cut chambers the same way you are doing for 30 plus years. Excuse the phrase, I have seen the light. I have also talked with every major reamer maker and they all agree cut and flush in a high speed set up is the best.

Rustystud