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 Post subject: Chamber Reamers
PostPosted: Fri Feb 01, 2019 7:37 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8934
Location: Coalmont BC
I started on the Chamber Reamers for my new .172 cal and .224 cal TJs barrels today.... The first step was to turn the pilot and chamber sections, and then next was to turn the 1 deg. taper between them, which actually does the cutting.... Here is the .224 reamer, mounted in my lathe, while I was turning the taper....

Image

The taper starts about 0.010" smaller than the pilot, and the taper runs out to the chamber diameter about 1" behind the nose of the reamer.... The actual cutting occurs in the last half of the taper, just before the chamber portion.... After polishing, I milled the flutes, and the turned down the clearance portion between the back of the chamber and the shank.... Here are the two fully machined reamers, ready for heat treating....

Image

Wow, that .172 cal reamer is REALLY tiny, I hope I don't break it when cutting the chamber.... ::)

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: Chamber Reamers
PostPosted: Sat Feb 02, 2019 1:29 am 
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Joined: Wed Oct 17, 2007 3:27 am
Posts: 2545
Location: Winnipeg, Canada
Always been interested in this.

Let us know how you make out. Good luck with the heat treating.

-D.S.

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 Post subject: Re: Chamber Reamers
PostPosted: Sat Feb 02, 2019 1:40 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 5878
Location: P.G. B.C.
Well done, Bob. Small diameter reamers are quite fragile. I broke my first .17 Rem. reamer & had to buy a new one.
Picked up a chip and before I could let go of the handle - 'tink'

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 Post subject: Re: Chamber Reamers
PostPosted: Sat Feb 02, 2019 3:40 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
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Location: Coalmont BC
I use a 5C collet to hold the shaft of the reamer, with the collet in a Hex block.... I can turn that in my milling vice 1/3 turn per flute.... but yes, eyeballing would be close enough, and there are those that say staggered uneven spacing prevents chatter.... Here is my setup (no collet in place in the Hex block)…. I have a square block as well, really handy for drilling valve screw holes and the port all at 90 deg. to each other.... 8)

Image

Here is a photo of the two reamers after hardening....

Image

The .172 cal has been polished, the .224 cal is just the way it came out of the cold water after the hot oil quench.... As you can see, the soap does a pretty decent job of keeping them bright and reducing the scale buildup.... I'll polish the larger one, and then temper them....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: Chamber Reamers
PostPosted: Sat Feb 02, 2019 3:50 pm 
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Location: Coalmont BC
I tempered the reamers in my wife's oven at 470*F (I think it is actually 480 at that setting)…. I did the .172 cal for 40 minutes and the .224 cal took 50 minutes to achieve the nice even brown colour I like to see.... In theory, that indicates 500*F, which is on the upper end of the temperature range for reamers (tougher but not as hard)….

Image

I wish I knew more about tempering O1 drill rod.... Hudson steel say 1hr. per inch of thickness, but then turn around and say a 2 hr. minimum.... ??? …. Most guys that use O1 say to temper something the thickness of a knife blade for an hour.... Other places just give a temperature and don't specify a time.... while others say 8 min. per mm of thickness.... which interestingly ended up being what gave me the colour I was after....

Anyone REALLY know how long I should cook reamers when tempering them?....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: Chamber Reamers
PostPosted: Sat Feb 02, 2019 6:13 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8934
Location: Coalmont BC
I chucked up the .224 cal TJ's barrel, blew out any dirt, lubed it and the reamer, and reamed the chamber.... These may just be the best reamers I have ever made.... 8) …. They shaved the rifling off like a hot knife through butter.... Once the chamber portion was entering the barrel, after that I only went 0.10" at a time, but the way the reamer was cutting I probably could have done the whole thing at once.... The danger in doing that, of course, is that you collect too many chips, and if one jams, you will shatter the reamer.... Here is a photo of the amount of chips that collect from removing just 0.10" depth of rifling....

Image

The chips are sitting right at the part of the reamer that does all the cutting.... Forward of them, the flutes don't touch the lands, and behind them the reamer is parallel, the diameter of the chamber, so no real cutting occurs there either.... You can see that rather than "dust", these reamers are producing actual "chips" or "slivers" of steel as they cut.... which is why they are cutting so nicely.... For the first time, the barrels were not even getting warm to the touch, another indication that I am shaving off metal, rather than wearing it away....

The .172 cal reamer cut just as nicely, in fact you could barely feel the reamer bumping as it removed the four shallow lands in that tiny bore.... I am absolutely DELIGHTED in they way these cut, and the smooth finish they left.... 8)

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: Chamber Reamers
PostPosted: Sat Feb 02, 2019 6:32 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 5878
Location: P.G. B.C.
VERY nice indeed - seem to cut as well (same chips) as my $150.00 (U.S.) chambering reamers.
I chamber about 3/8" then extract, clean re-lube, blow out the barrel, then cut another 3/8".
That seems to work with all chamber sizes(calibres and cases).
The commercial reamers have 6 flutes in all sizes and will cut 10 chambers before needing sharpening.


custom sizes as well. Most of my reamers are from Dave Kiff, at PTG.

Pacific Tool and Gauge throat and neck reamers, .20 to .45 cal.

http://pacifictoolandgauge.com/throat-a ... -only.html

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Daryl


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