Checked on the progress of a rifle I am having re-barrelled and was told they had to send out their reamer to be sharpened.

Is there any advantage to using a "just sharpened" reamer? Somewhere I have heard that it is not good to have the first chamber from a new or sharpened reamer. True or false?

The sharper, the better. Sounds like you're in luck, as long as the sharpening job is done correctly. Unfortunately, that's an easy one to screw up. Hope it works out for you.

I'm with triggerguard. I'll take freshly sharpened every time, thank you.

You do have a slight risk of a bad grind job leaving a bad chamber, as you will be the "crash test dummy", but it's well worth it. Just test fire when finished, check the fired brass for obvious ridges, grooves, chatter marks, etc, then do a fine measuring job to ensure all is within limits.

Have fun with your project!

Absolutely not true. You WANT a freshly sharpened reamer(assuming it was sent back to the original maker like JGS).-Rob

One of the mysteries of the machining arts---

Why does a reamer cut the smallest hole when it's at it's biggest?

It IS explainable.

OK Jack I'll take a stab at it....

A sharp reamer (or drill bit) cuts a smaller hole than a dull one because it CUTS the material cleanly. A dull tool RIPS the material out and in doing so takes extra material with it.

How's that????

Because the reamer is at it's sharpest, and thus doesn't heat up as much, thereby expanding and cutting a bigger hole?

I have no clue. My idea of machining is to use my drill press and a file as a lathe.

Curious question though. I would like to know the answer.

Brent

Jack what do you mean "when the reamer is at its biggest"?

Brent reamer should NEVER EVER be allowed to get hot.

This must be another one of those Zen-gunsmithing things. Life is a mystery,Grasshopper.
I have always sharpened reamers by hand when necessary. Sometimes it has been necessary to retouch reamers when they were brand new in order to get them to cut smoothly. I set the reamer between centers and set up a .0001 dial guage to monitor size reduction (that sounds pretty technical eh!). Then I rub on it with a ceramic stone (not quite so technical). Regards, Bill.

Or better (worse) yet, why does a reamer cut a different size when using a different cutting fluid? Huh?

I bet its because a sharp reamer doesnt get any build up of material on its edge thus making the "tool" larger....thats also a possibility if you dont use enough coolant. A sharp one with cut cleanly like a sharp knife slices a peice of paper...but a dull one will tear and so a dull reamer will get resistance along the cutting egde, and you can get tearing of the metals and "welding" of the material on the cutting edge of the tool......it may be happening even though it is not that obvious to the naked eye....or it may be the elevation!!!!! ha ha..bob

It was described to me as 222blr says.......and all of the above.... Less edge build-up, less heat, AND less deflection of the tool while under load.

Machinery Handbook has a blurb about sharp reamers making a smaller hole than a dull one of the same diameter.

Machining of any material with any type of tool requires that the tool be resistant to deflection and heat. The surest way to accomplish this is through the use of a sharp tool that will cut cleanly and provide a good quality chip. By making a larger chip, more heat is drawn away from the tool and into the chip. An excessive feedrate can also cause tool deflection and oversize holes, as well as too slow of a feedrate. That is why it is important that you use correct speeds and feeds when doing any machining. Reamers tend to cut better when they are pushed on feedrate to their upper limits. This produces cleaners holes, or chambers, and provides good chips that carry the heat away from workpiece and tool.