pre boring reaming

Jay,

True we are not talking about target rifle chambers, but we are talking metal working fundamentals. Much of the process is similar, the hydraulic ports and valve spool chambers still must be to an exact size, in an exact location and most importantly not be "egged".

We used to run undersize spade drills and end mills in to remove most of the stock before porting and pre setting shoulders and such. At one point we were even going in with tiny carbide boring bars but the end result after porting still required excessive honing to make the tolerance. For a period of time last year, the hone department couldnt even hone the egg shape out and stay in the dimensional tolerance over the entire valve bank. You know if the hole is honed out to size and the left side sits further left than its supposed to, it is still non conformant. Dang those iso and military inspectors.

The question that I'm asking is: if you increase tool pressure on the reamer by making it work in a 100% cut rather than a 10% cut, is there a chance the reamer would have a greater affinity to follow the pilot hole, meaning the rifle bore?

I don't have the answers other than to say that a process changed at work has drastically improved the quality of the stuff I been making.

Thanks Wayne Shaw,

different way of looking at the whole relationship between shop activity and range results, although related, I agree the outcome is likely too small to be quantified.

Mike
 
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I have started pre-boring chambers per advice of some benchrest gunsmiths. I check the throat, neck and chamber after reaming and it has been dead on so far with both methods. I cannot see a difference so far.

I have only been drilling to 80% of length, so I guess...the reamer is loading up anyway at the end. And in my mind, it's only the last bit of reaming that matters...within reason.

I have noticed that it takes me 3 light passes with my boring bar, to get the hole concentric enough so I cannot see it on the indicator before reaming. I'm using a soldered carbide bar. Maybe I need a different tool, or will grind one with more rake?

I will continue to pre-bore since I still feel like it is easier on my reamers.

Going by feel.....I'm getting less chatter/squeeking by taking light cuts, removing, cleaning, oiling with moderately high feed rates.

I let the tool tell me how much and fast.

Ben
 
I rough rifle chambers primarily to save time. I rough just deep enough that the pilot can still engage; then I push the reamer pretty hard until the neck starts cutting. Then I do it again until the shoulder starts cutting. So, if I was able to rough 1 1/8" deep, the reaming takes two steps, maybe three. The reamer is loaded pretty good.
When I was doing hydraulic valve work, I did it much the same as I would a chamber. I bored to about .015" under the smallest part of the port, then let the form reamer do the rest and held it just like I do a chamber reamer. Of course, this was for "one off" valve bodies using Sun cartridges, not a production run. If it was a bore for a spool, it was bored and honed. Regards, Bill.
 
Rustystud said:
Mickey:

With the cure of chatter behind us now. I have a second issue I would like for you to cure for me. I high speed ream chambers and my pilots like to sing. With 35-125 psi of coolant flushing between the pilot and the reamer I still get singing pilots.

Nat
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Nat,
You flatter me in asking me something. I'm far behind you in machining knowledge. I would do as Ben suggests. Makes a lot of sense to me.

The waxed paper does work, though. :)
 
Amazing

I have explained quite a few times why, as a Mchinist, I prebore chambers that are intended for exrtreme accuracy use, but I can tell by many of these post that there are those that do not have a clue as to the concept.
That being said, I will repeat what I have stated many times. It makes absolutly no difference which methods you use, the only thing that counts is results.

Many of you need to get out of the concept of simply leaning how to do things, but learn the concepts as to WHY you do things. Untill you do that, you are simply painting by the numbers...........jackie
 
Mickey,

Thank you for the wax paper tip!! You know, its funny how a metal ring hung on a long shaft or a pipe clamp with a rubber strip tightened up on a boring bar will change harmonics and eliminate chatter.

Sorta reminds us all how important the harmonic effect really is, especially with BR and bullets escaping into free air. Specifically, bullets escaping into free air in the micro-second that the barrel is in transition harmonically, and about to make it's next move.

My mind is made up, I'll take a face cut and ream 100% from the start.

Thanks for the info guys, Mike

Jackie,

I appologize for not being aware of your previous post/posts. As stated, the thought occurred after some of the manufacture process was changed at work concerning the multiple holes in our valve banks. There were similarities in that the holes were becoming irregular; irregular due to a number of suspected reasons. There is a time that for reasons unknown, a chamber hole might become irregular. I was trying to find out if not removing chamber material was practiced and if so, what was it a preferred practice? I learned to drill and bore but the above situational outcome at work prompted some rethinking.

I'll go in search of your posts on chamber prep and reaming.

Sorry to ruffle any feathers with old topics, but consider that it wasn't new for me, again sorry.

Mike
 
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Noob wants to speak.

Normally I stay out of these discussions, but let me toss this out there.

this is meant more for those who thread/chamber in one set up using the through the spindle method.

Ok, take an indicator and stick it in the bore right at the edge. Indicate it as best as you can.

Now move an inch, did it change? Diiiiiid iiiiiittt? Be honest.

Now move another inch, where is it now?

Keep going until you get to the point where you can't go deeper (hmmm, should I be using an indicator with more depth or reach) or you get to where the throat ends up when the barrel is chambered to HS dimension.

Now, if it's running concentric at the breech but isn't running concentric where the bullet first touches the barrel what does that say to you?

And if it says what it should be saying WHY ON EARTH would you want to use a drill that is going to follow what ever hole is there in the same direction its going? Never mind that a reamer is going to do the same thing.

Single point tooling is a beautiful thing.

Ok, noob is done speaking.

Cheers,

Chad
 
lathe set up?

hi my job is building lathes (cnc and manual ) there some fact that most people miss the head and tail stock are not on the same alinements ! buy this i if you set up a test bar between centers and set the tail stock and head stock enf both reading zero (as most gun smiths do )

you 'll find that if you set a test bar in head stock and tail stock you'll find that the test bar both piont to the center of the bed , if you know clock on both test bar s you 'll find the if the laths is set up correctly they should both read .010 mertic micron to the appron side of the bed , this is to compensate for tool push when truning ! now here the problem if you drill a barrel or bore on out with this set up the cuting tool run of the bore line ! and as any engineer now you cant force a ream to true a off center hole !

please feel free to ask me any questions !
 
What does the tailstock have to do with it?? Drill the hole to allow your indicator to reach in and indicate the throat. Taper bore your hole. Ream with a pusher and you won't care how far out your tailstock is at this time.
Butch
 
tail stock to do with it

well where your reamer held? the tail stock , the bold egel reamer hold is only one that eliminate the tail stock ! and as the tail stock quill advanes it the end of the ream moves to wards the apron ! this is uselly within .005 to .010 (or .0002'' to .0004'') so it you pre drill a chamber the head stock and tail stock work agianst each other and as resulte the resulting bore well not be true to the bore line of the barrel ! you could get away with singel piont truning (boreing using the tool post )

so the tolal error between the head stock and tail stock is .010mm to .020mm ( .0004'' to .0008'' ) please bear in mond that a ream well follow the primary hole as long as it is floating, if they not floating then they well bore on 1 or 2 flutes
 
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Mr. Enfield, a carbide boring tool in the compound will bore the hole concentric to the lathe bearings. My pusher tool is similar to the Bald Eagle. It has a small polished radius on the rear inorder that the flat in the tailstock tool will not influence it's direction. I also have a little longer handle on mine. I do not use a tight reamer bushing. I want the reamer to follow the tapered bored hole.
Butch
 
yes you are right butch

yes you bang on but the axis of the headstock bearing are not on same axis as the sadle or tail stock as all lathes are set up to compensate for tool push off !and your tool cut on its axis, if you look at the attached coyp of the standerd for a small maunle lathe and look at the g7 this is how the head is set in realtion to the salde movement and the tail stock mirois this ! so and drill (with the use of floating holder ) or boreing a rough chamber out will resulut in a missalinment in the chamber , which is why i will touch a chamber with any thing other than a reamer ! ( there are exption like rechembering a factoy barrle with a badly missalined chamber )
 

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Jackie & Butch,

I think, after much reading on this topic both here and over at 6BR.Com you guys are saying, correct me if wrong that:

Removal of the bulk of material allows the pilot to become the frontal guide much later or deeper in the barrel; this situation encourages the reamer to start doing it's job or locating on a more critical surface, the neck and throat region.

I agree, just because that was the same way I was taught.

As stated, there were procedures changed at work that seem to have cured a chronic problem in holes and deep chambers that had to be right, in all three X,Y and Z. Tooling change was to eliminate removal of material, no more spades, no more end mills. We were going in with finish reamers and JIC port tools at higher feed rates and achieving good results.

For whatever reason, when bulk was removed, we experienced greater tool drift which ultimately led to the hole being off center and true, on center and oblong or a combination of both. It could be tested by going back in with the probe and probing X,Y and Z on the finished hole. We post probe all of this type of part because the customer QC department is real tough.

There is one conclusion that I am comfortable with though, that is, if the pilot hole or bore leads off, and secondary tooling passes over the lead off point, the tooling will also lead off.

As prefaced before, I thought about this at work and said, " Hey, thats kinda like some of the problems we run into in rifle barrels."

Thanks, and again sorry for chapping anyone about an old topic. It was the changes at work which prompted me to share thoughts.

Mike
 
yes there well be a taper
but if you take a few spring cut the the taper is gone and you have 2 cyclinder the roughed out chamber and bore which are not true(squre) to each other on there independant axis

there as just reaming with a floating holder ther is on chance of misalinmant ,

butch thanks you are good to talk to hope to talk more on other topics
 
Hey i think i am following this thread ---but i feel like a ping pong ball, lol. joe
 
His statement is, I believe...:

On a manual lathe, the headstock is factory aligned so the saddle (ways) are not aligned to the axis of the spindle bearings, it is intentionally skewed for tool push.

So, if you indicate a BBL in headstock, and then drill and bore, the you are creating a bored hole on a different axis than the bore.

I do not believe this is a problem, since the barrel indication point is the throat.
 
Ben,
I understand what he said about misalignment, but you are still boring to the axis of the spindle bearings. It may be a taper and a very small one, but it will meet at .000000 in the bore at some point. I believe we are just exercising our brains and not making more accurate chambers. It's like looking for the bogieman and he ain't there.
Butch
 
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