Cutting a .222 Remington Chamber

[Lucky Shooter]

Butch. .
I've thought about a no-pilot job a lot and then get
stopped by the feathers on my legs.

I think of the pilot as holding the front end of the reamer
on-center until the reamer body cuts enough surface to
help hold the rear of the reamer on-line.

You are right about the no-pilot if the compound is set
somewhere between damn good and perfect.

As usual when Butch says "think", we should start thinking.

A. Weldy

 

[butchlambert]

Whether you taper or straight pre-bore as long as the reamer pilot engages the lands before the body engages the pre-bore you should be good.

Why? If I indicated the throat and taper bored to that indication, I would want my reamer to follow the taper bored hole without any influence from the bushing.
Guys, If you have a little basic machine shop practice you will understand some basic reasons to machine a certain way. First you need to understand a bore that is not straight is not an arc or curve. Think about that. When you deep hole drill the barrel is turning and the cutter is pushed through the material. How can you make that cut in a flat curve?
Sorry I'm coming off as I am and I'm not the Jackie Schmidt of machining, but several years in a job shop in the "olden" days `was very valuable to me.

 

[X Count]

Butch I think there is a lot of us who understand and agree with the theory but are just to $#!+ scared of ruining a reamer or a barrel to give it a go. When your new to the game and only have one reamer and one barrel there isn't any room for trial and error.

My main concern would be chatter. I run a ptg floating reamer holder and I make sure the pilot is engaged at least half its length before starting or stopping the lathe. Without a pilot how do you start and stop without the reamer bouncing around in the tapered hole? I wouldn't have thought doing a start / stop with pressure engaging the reamer on the taper would be good for the reamer and would create an initial "bite" at each flute that may continue to propergate?

I struggle to get my head around parallel boring. I know people say the reamer will follow a straight hole but just mechanically there is not much to support or guide that reamer. A holder that exerts any type of pressure or even slight chip build up or an uneven grind are going to make things worse than just using a pilot. I know people will say "well you shouldn't have those things" but this is real world and they do happen.

Most people think that they can do a near perfect job with a pilot vs without a pilot it's going to be perfect or an absolute failure that may take months to obtain replacement barrels or reamers

Doing a lot of work with 304 and 316 stainless previously I thought turning and reaming a barrel was going to be a dark art. Once I touched the tool against a piece of 416 and with using a flush system for reaming it was way easier than expected . . . . .maybe taper boring is the same

 

[spitfire_er]

Here's a question to ponder. All else being equal and concetric. When cutting the whole chamber with a finish reamer, and a non-stressed reamer setup.

Once the reamer starts cutting, is it held in the centerline more from the pilot or more from the leade and neck cutting down the bore followed by the neck/shoulder junction cutting down the reamed neck taking the path of least resistance?

This of course assuming you are not using a 6 flute in a 5R.

I would argue that there is more force holding the front of the reamer in center from the reamer cutting into the bore than the pilot holding it centered.

With this method, after the shoulder starts cutting, I would bet you could cut the pilot off and you'll get a good chamber.

I would also argue that a non concentric throat is the product of the bore being a minute or two of a degree in the opposite direction that the reamer is traveling. If you reamed deeper, it would work to self correct that.

Pre-boring for us that do it takes the entire bore out of the equation until you get to that last portion of the chamber where ether the pilot engages your zeroed out bore section or your reamer starts cutting the dialed in portion of the bore.

I bore all the way and have never had chatter issues. I uses really sharp reamers and a flush system. Takes no time at all.

 

[X Count]

Spitfire. What diameter do you bore to? Some are saying -20 tho but are you suggesting splitting the difference between the neck diameter and the shoulder diameter so there is more surface to centralise the reamer?

 

[spitfire_er]

No, my example was based on not pre-boring. I have gone anywhere for 20-40 thou under shoulder body junction measurement. 40 is getting to be alot of extra cutting especially if you are not running a flush system.

 

[skeeljc]

Why? If I indicated the throat and taper bored to that indication, I would want my reamer to follow the taper bored hole without any influence from the bushing.
Guys, If you have a little basic machine shop practice you will understand some basic reasons to machine a certain way. First you need to understand a bore that is not straight is not an arc or curve. Think about that. When you deep hole drill the barrel is turning and the cutter is pushed through the material. How can you make that cut in a flat curve?
Sorry I'm coming off as I am and I'm not the Jackie Schmidt of machining, but several years in a job shop in the "olden" days `was very valuable to me.

Because I am using a floating reamer holder (Bald Eagle/PTG type). I am concerned the reamer will not start in line with the indicated bore just by the shoulder contacting the pre-bore and the back end of the reamer allowed to float.

 

[butchlambert]

If you indicate a flute of your reamer and adjust your compound you will have the correct angle. I don't understand the reamer being loose and chattering. I suppose I've been lucky. It would be minor, but if your bushing takes off a little in the wrong direction. What happens-it may turn your reamer into a flycutter and make the base of your chamber larger.
I have a feeling I've not explained it well enough. Just do it in a way that leaves you feeling warm and fuzzy.

 

[skeeljc]

If you pre-bore does it depend on the type of reamer holder you are using?

If you use the Bald Eagle full floating holder the back of the reamer is not constrained at all.


If you use the following PTG floating reamer holder omly the radial alignment is allowed to float. The axial alignment is controlled by the tailstock.

 

[skeeljc]

If you indicate a flute of your reamer and adjust your compound you will have the correct angle. I don't understand the reamer being loose and chattering. I suppose I've been lucky. It would be minor, but if your bushing takes off a little in the wrong direction. What happens-it may turn your reamer into a flycutter and make the base of your chamber larger.
I have a feeling I've not explained it well enough. Just do it in a way that leaves you feeling warm and fuzzy.

I prefer obtaining that warm and fuzzy feeling from being taught by someone that knows as opposed to expensive trial and error type learning.

 

[X Count]

I prefer obtaining that warm and fuzzy feeling from being taught by someone that knows as opposed to expensive trial and error type learning.

Totally agree! Ruining things isn't warm and fuzzy!! Hahaha

Butch what I mean by loose is even if the taper between the reamer and the bored hole are perfect matched... . . .at some point that reamer needs to go from not touching to touching a rotating surface. I'm concerned about the moment in time when the reamer first engages in the tapered bore and starts bouncing from one sharp flute to another until it loads up evenly and starts following the tapered hole. If that jump / chatter is bad enough it could damage the pre bored hole enough that the it won't correctly align the reamer for the remainder of the cut. That's what I'm picturing is going to happen, am I missing a step or are you saying it just slides into the taper and starts cutting with no jump or chatter?

With a pilot the reamer is relatively centralised so starts cutting evenly on first engagement so doesn't have a chance to bounce around the tapered hole

 

[skeeljc]

Totally agree! Ruining things isn't warm and fuzzy!! Hahaha

Butch what I mean by loose is even if the taper between the reamer and the bored hole are perfect matched... . . .at some point that reamer needs to go from not touching to touching a rotating surface. I'm concerned about the moment in time when the reamer first engages in the tapered bore and starts bouncing from one sharp flute to another until it loads up evenly and starts following the tapered hole. If that jump / chatter is bad enough it could damage the pre bored hole enough that the it won't correctly align the reamer for the remainder of the cut. That's what I'm picturing is going to happen, am I missing a step or are you saying it just slides into the taper and starts cutting with no jump or chatter?

With a pilot the reamer is relatively centralised so starts cutting evenly on first engagement so doesn't have a chance to bounce around the tapered hole

If your tapered pre-bore is close enough to the final size the reamer pilot bushing will engage the rifling before the reamer body engages the tapered pre-bore. If the pre-bore is even closer to final body dimension the lead, freebore and neck of the reamer will be cutting before the body begins to cut. It should be just like starting the reamer with no pre-bore.

 

[X Count]

Why? If I indicated the throat and taper bored to that indication, I would want my reamer to follow the taper bored hole without any influence from the bushing.

skeel. This sounds like Butch is not using a bushing at all

 

[butchlambert]

I give up guys and no I care not about a bushing.

 

[skeeljc]

I give up guys and no I care not about a bushing.

Don't give up, we just want to understand.

So when starting a reamer without a bushing in a trued taper bore how do you hold the back end of the reamer?

 

[spitfire_er]

Don't give up, we just want to understand.

So when starting a reamer without a bushing in a trued taper bore how do you hold the back end of the reamer?

I know Butch has talked about this a lot in the past and explained his methods on this site several times.

Shouldn't matter what your holding the reamer with. With proper pressure and a good setup it should ride in there and straighten itself out real quick.

Think of a chucking reamer. You set a piece up in the mill or lathe to drill a hole, drill it undersized with a twist drill, then you run the chucking reamer in to get to size. That chucking reamer has a very slight taper on the front of each flute to center that reamer up. That little angle does a pretty good job of keeping that reamer on the centerline.

Ill add that the whole purpose of a floating holder is to allow freedom of movement to follow a bore. Whichever bore you are using.

 

[Will Henry]

As long as the reamer is ground properly, it will follow a bored hole; tapered or straight. If straight though, the rear of the reamer has to be supported. If supported by the tailstock center, the center must be truly centered. Once the body of the reamer is well in, the rear can be allowed to float. WH

 

[X Count]

I know Butch has talked about this a lot in the past and explained his methods on this site several times.

Shouldn't matter what your holding the reamer with. With proper pressure and a good setup it should ride in there and straighten itself out real quick.

Think of a chucking reamer. You set a piece up in the mill or lathe to drill a hole, drill it undersized with a twist drill, then you run the chucking reamer in to get to size. That chucking reamer has a very slight taper on the front of each flute to center that reamer up. That little angle does a pretty good job of keeping that reamer on the centerline.

Ill add that the whole purpose of a floating holder is to allow freedom of movement to follow a bore. Whichever bore you are using.

Ive read his and Dave Tooly's posts about taper boring in the past but have only recently become a forum member to ask specific questions myself. I have a lot of respect for people that have done this 100s or 1000s of times but it's a bit like one of us trying to teach a absolutely green shooter. Sometimes what we do on the fly as muscle memory is a 5 minute deliberate thought process and act for a new shooter. Sometimes it becomes so engrained in the sub conscious that it becomes hard to describe what it takes to actually "just do it"

What I see as different to a chucking reamer is the front face loads up and starts centralising before the side flutes make contact. A chamber reamer is tapered so the majority of the reamer is in the hole before it engages steel so it starts cutting on 6 flutes say 1.25" long all at a similar time.

Ok so my specific questions how your start the reamer.

Hole taper bored to match the reamer angle. Yes

Pilot removed. Yes

Floating reamer holder? (PTG / JGS)

Lathe running and feed reamer in?

OR

Engage reamer into tapered hole and start lathe?

To remove reamer. Maintain pressure and stop lathe before withdrawing reamer?

OR

Withdraw reamer and turn off lathe?

 

[skeeljc]

Starting: move the reamer in until it contacts, start the lathe, feed reamer in.

Stopping: stop feeding, let run for a second, stop lathe, withdraw reamer.