Throating reamer selection

[Rich S]

When selecting a throating reamer is it recommended to go with the same free bore diameter or slightly over/under? I'm thinking a few ten thousands under would allow finding the start of the throat easier.

If extending the throat at the time the chamber is cut, is it better to go with a standard throat reamer and push it with the tail stock like a chamber reamer? Or is the uni-throater a better set up?

 

[Dusty Stevens]

Uni throater is a better setup. Be careful itll cut before you feel it. Id get the reamer recut if it was mine.

 

[DaveTooley]

I use regular throating reamers. I use a very short holder on the reamer. Very seldom can I feel it cut the cylinder section which isn't really what we're trying to do anyway. I hold it in my left hand for sensitivity and set my zero when I feel it start to cut the leade angle. I use a dummy round or a bare bullet like a HS gage. I make a partial cut then get a final measurement and repeat the process to depth. It takes some getting used to so as not to over shoot your number.

 

[dnellans]

Dave, how close can you get to a desired depth typically? let’s say you start with .060 FB and you’re shooting .104 - within 5 thou either way of the target?

I’m not sure I follow what you mean holding with your left hand. A unithroater or a tailstock pushed throater and you’re touching it for feel?

 

[DaveTooley]

Probably +/- .005". I err to the short side most of the time. Most of my throaters came from Manson/Cylmer. He ran Cylmer before starting his own company. They are short. I made extensions for them. I use a Sinclair case holder that is designed for turning necks. It's a very short tap holder. You could make a ring with a set screw as a holder. The extension is smaller in diameter than my normal reamer holder so I use a drill chuck cracked open just enough to get a little clearance on the extension and push against the Sinclair case holder. I hold it in my left hand and can feel it engage the lands as I feed it in. Like I said I do it in two steps. The first step is to get a feel for how the reamer is cutting and to get the matching profiles. That makes the last pass more precise. Attached is a pic of the same Sinclair holder where I extended one side for use with chamber reamers.

 

[Rich S]

Thanks for the replies. I ended up ordering a reamer from Manson yesterday He talked to me when I placed the order. He is very knowledgeable and helpful. Waiting for a bolt also so it may be awhile before it gets used.

I have a small tap handle similar to Dave’s picture. I’ll use it or make a small round grip from aluminum like I use on my chamber readers

 

[tobnpr]

7/16" to 1/4" adapter, used with the same micrometer reamer stop for chambering:

 

[Will Henry]

I also use standard throaters. I have throaters from Clymer, Manson, JGS, PTG, and Henriksen. For 5 groove barrels, I prefer spiral fluted throaters since straight six flute reamers will often not cut true in a 5 groove barrel. Interestingly, I have never had a problem with 7 groove barrels, only 5. I feel that I can definitely hit within .005" of my intended depth. WH

 

[Rich S]

After waiting for parts and then getting through long hours at work I finally got a chance to chambered the barrel. Extending the throat was uneventful and went well. I stopped the chamber short and did a practice run just to get a feel for it. I had to extend it 0.090 so had plenty of margin to pick up the lands and determine where I was. I ended up with a Manson reamer and made an adapter to hold it in a Bald Eagle holder, It was pushed with the tailstock the same as for a standard chamber reamer. It came in just fine.

Thanks for all the input.