Chamber reamers & spring back

[TAJ45]

A bit of back ground - I'm a retired toolmaker. Had a good 4 year apprenticeship but only abt 20 yrs shop time. So, I've spent a lot of time with chips and prints.

Like many guys new to the wonderful world of wildcats, new chamberings, long range records, I dream of a "gee, what if design" for a cartridge that will accomplish X, Y and Z with a little something extra to feed the angels that dance on the heads of pins.

When it comes to reamers, folks that "run them in short" plus other techniques, the one foundational aspect that is escaping me is how the same reamer can be used to finish a chamber as well as cut the FL die. If ea hole is size to size, how is spring back accounted for?

I've tried to reconcile/ picture how running same reamer in a bit more or a bit less would help or hurt the situation. I found out in the later apprentice years when making a tang for a # 4 Morse taper, that taking off a couple of thou on the OD will let the the shank go in what seemed like a disproportionate amount further.

Then we get into the small base dies or Paul's honed rings to redux the bases. Spendy but I've made similar items, heat treated then honed them out.........time CONSUMING, therefore co$ts. Not disparaging Paul Becigneul at all. Take something down to a three tenths toleranceor less and see how many you can whip right out before lunch.....after buying the measuring instrument and the hone and the heat treat furnace and build the quench tank. Sorry, the above paragraph just about hijacks my own thread.

Let the discussion and polite comments begin - I'm here to read/listen, sift, analyze and learn.

 

[Dusty Stevens]

the same reamer doesnt cut the chamber and sizing die. it can cut the seating die

 

[TAJ45]

My thoughts exactly. Maybe I'm misremembering what I thought I'd ingested on that.

How much would you want FL reamer to be under? .003 - 4 in and in what areas or if easier, in all but what dimensions?

 

[Erik Cortina]

Resize reamer cut chambers ~.004" undersized.

 

[Dusty Stevens]

theyre diferent sizes in different places not just a set amount. a reamer maker knows where to shrink it and how much. kiff can do it for any of his reamers and they are perfect everytime.

 

[Erik Cortina]

theyre diferent sizes in different places not just a set amount. a reamer maker knows where to shrink it and how much. kiff can do it for any of his reamers and they are perfect everytime.

Kiff I believe does .003" at the body/shoulder junction and .0035" at base.
JGS does .004" everywhere.

I a set of reamers (finishing and sizing) and they were not perfect. I had to make a small base die to deal with click on brass after two firings.

I now prefer the reamer to be undersized about .005" at the base because I can polish it out until I'm happy.

 

[shortgrass]

My thoughts exactly. Maybe I'm misremembering what I thought I'd ingested on that.

How much would you want FL reamer to be under? .003 - 4 in and in what areas or if easier, in all but what dimensions?

No, your probably not 'misremembering'. I've seen the chamber reamer can also be used for the size die reamer posted on forums several times. Just more mis-information being spead by those who don't know and don't "get their hands dirty'. AHHHHHHHHHH! The wonder of the internet!

 

[Eddie Harren]

Call JLC Precision. He knows how to make a sizing die with the chambering reamer. Some of you could learn a lot from Jim.

 

[LHSmith]

Is a JLC Precision FL sizer made from a chambering reamer a viable alternative? performance-wise, cost-wise, availability-wise ? Is it do-able throughout the spectrum of cartridges?

 

[Eddie Harren]

Smitty, I don't know if it's viable or, cost effective. Personally a Whidden or a Harrell's would be my first choice. I was just tired of hearing a few "Experts" tell people that what JLC can do, can't be done.

 

[Dusty Stevens]

I cant see how even Jesus himself can ream a hole with a reamer and make it end up smaller than the reamer itself. But hey I sure dont know everything. I wish I did know so i wouldnt have to spend all that extra money on resize reamers anymore.

 

[shortgrass]

I cant see how even Jesus himself can ream a hole with a reamer and make it end up smaller than the reamer itself. But hey I sure dont know everything. I wish I did know so i wouldnt have to spend all that extra money on resize reamers anymore.

+1 here! Someone's blowing smoke! You cannot drill a 1/4" hole with a 17/64"" drill bit, basic physics. Maybe they cut the chamber over size and then use the same reamer to cut the die to size (like the chamber should have been!).

 

[rockrat]

Way out it left field, but


Could you take the size die blank, use the chambering reamer, but short chamber it, maybe to where the neck area would start to be cut. Then, chill the reamer in the freezer overnight and warm the die blank to maybe 150 degrees or so, then finish reaming? the blank would be a bit oversize and the reamer undersize, but when finished and the now "chambered blank" cools off, it would shrink enough that the combination of undersize reamer and "chambered blank" be enough to have a useable size die?

Just a thought

 

[Eddie Harren]

I realize that it is difficult to ask others, when you are sure you know everything, but you really should contact JLC Precision and ask. You might learn something. God forbid!

 

[LHSmith]

IIRC, ( big "if" ;D) , a particular steel alloy is used for the die blank and upon heat treat (after machining of course), the ID shrinks the appropriate amount?

 

[shortgrass]

Eddie, you need to do a bit more research. Here's the link www.6mmbr.com/CarstensenJLC01.html Scroll on down, near the middle of the page and read "Dies Made from Chambering Reamers-Why They're Not a Good Concept". And written by Carstensen, himself!

 

[Eddie Harren]

I guess I got my hat handed to me. Jim told me face to face, at the super shoot one year, that a man could make a sizing die with a chambering reamer, if he knew how. I took that to mean that he did. I apologize if I ruffled your feathers.

 

[LHSmith]

shortgrass- that Daily Bulletin is dated 2004. I could have sworn I heard JLC developed a method as Doc ED claims and as I posted earlier.

 

[clowdis]

You can use a chambering reamer to make a sizing die to set the shoulder back on a case. But any sizing you get on the diameter is insignificant.

 

[butchlambert]

I didn't take the time to read all the post. I have an extra reamer that is .002 smaller at the shoulder and .003 smaller at the base. This is based on my chambering reamer specs.