Pacific tool uni throater necker kit sizing .30

[mackeral5]

I am interested in purchasing tooling to assist me in creating/modifying .30 barrel chambers.  I found this kit at Pacific tool. 

http://pacifictoolandgauge.com/throat-and-neck-reamers/5266-17-cal-uni-neck-and-throater-kit.html#/1209-specify_reamer_caliber-30_cal_300_cal_308_cal_762mm_782mm

The kit is customizable for neck diameter, which I believe translates to chamber diameter. 

I hope to be able to use the same kit for .30 and .308 barrels, assuming this is possible. 

What neck/chamber diameter should I specify ?
If there is a better path to take here, please let me know.  My goal is to be able to create .30 and .308 chambers/leads in raw blanks and adjust existing chambers/leads, using a system such as this that does not require machine tools.

[BigBird]

I am interested in purchasing tooling to assist me in creating/modifying .30 barrel chambers.  I found this kit at Pacific tool. 

http://pacifictoolandgauge.com/throat-and-neck-reamers/5266-17-cal-uni-neck-and-throater-kit.html#/1209-specify_reamer_caliber-30_cal_300_cal_308_cal_762mm_782mm

The kit is customizable for neck diameter, which I believe translates to chamber diameter. 

I hope to be able to use the same kit for .30 and .308 barrels, assuming this is possible. 

What neck/chamber diameter should I specify ?
If there is a better path to take here, please let me know.  My goal is to be able to create .30 and .308 chambers/leads in raw blanks and adjust existing chambers/leads, using a system such as this that does not require machine tools.

Wondering abpout such a tool myself.  I was thinking I saw someone here who makes custom reamers.  I might be interested one for a .458 if my back woods bubba tools don't work.

Looking at it further I dont think this is adjustable for .300 bore.  It is adjustable for freebore depth.  Youd have to order one for .300 if they make it.

[rsterne]

The reamer is not adjustable for diameter, it must be made for whatever chamber diameter you require.... A .300 cal airgun barrel will require a smaller reamer than a .308 cal PB barrel....

I don't know if these reamers cut a tapered leade on the rifling at the same time as they machine the chamber or not.... Your best bet would be to contact the company and describe what you need.... When making my own chamber reamers, I use a tapered leade angle of 1 deg. per side, ending in a parallel chamber 0.001-0.002" larger than the groove diameter of the barrel.... They have a pilot that is 0.002" smaller than the land diameter to guide them straight into the bore....



and before you ask, I don't make them for others, sorry....

Bob

[mackeral5]

Thank you for the replies.  As I understand it the throat cutting portion cuts a 30 degree lead on the rifling.  I did end up sending Pacific tools an email, I will share info once I hear back from them.

[rsterne]

A 30 deg. leade angle will require that you cut the chamber to precisely the correct length for a given slug.... Too shallow it won't chamber without excessive force, and too deep the slug will get a running start before it hits the lands.... If you are chambering the barrel for pellets, this is much less critical....

Bob

[luge007]

Unfortunately it appears the Premium Uni-Throater / Necker Kit besides being expensive, is designed for use in powder burning, necked cartridge chambers.  From what I read in the description, there is a 'dummy' chamber that goes into the barrel that is already chambered for a given cartridge, then you can adjust the free-bore or the lead-in area in front of the chamber for a given bullet.  I do not believe it will work for airgun applications, you'd be better off bribe'n Bob with the similar amount of cash as Pacific Tool & Gauge wants.

M

[mackeral5]

Understood.....  I will call them and ask of they have a product to offer for airgun chamber/lead  purposes. 

The price may seem high, but if it performs as designed the value is there, IMO. 

[luge007]

Hopefully you will post what you find out from PT&G about airgun chamber reamers, I am sure they will cut anything you wish for a price.  I would like to know since I am staring down the barrel of a chambering project myself and not looking forward to making and heat treating my own reamers.  I am sure it is no big deal, but I am betting the first one is the toughest with lots of errors along the way.  I may just cut them and pay a knife maker friend to do the heat treating for me since he has the proper oven and knowledge to do it.

Nothing ventured, nothing gained,
M

[mackeral5]

Hopefully you will post what you find out from PT&G about airgun chamber reamers, I am sure they will cut anything you wish for a price.  I would like to know since I am staring down the barrel of a chambering project myself and not looking forward to making and heat treating my own reamers.  I am sure it is no big deal, but I am betting the first one is the toughest with lots of errors along the way.  I may just cut them and pay a knife maker friend to do the heat treating for me since he has the proper oven and knowledge to do it.

Nothing ventured, nothing gained,
M

I called, the right guy was out of office until Monday.  I will call back monday.  I plan to ask about changing the 30 degree angle to X degree---I'm curious what the ideal angle would be. 

In this hobby we all have capabilities and constraints.  We are able to use our capabilities to identify workarounds for our constraints.  Sometimes the only workaround is $$.  Unfortunately for me, this is one of my constraints that will require $$ to solve.  if Pacific Tool and Gauge can make a tool that allows me to rough drill a chamber, then precisely finish the chamber and lead or simply modify an existing lead with repeatable precision, without machine tools/skills, they can have my $$.  If they can't, then I learned a bit more about the topic but didn't lose any $$ in the process.

I'll keep the thread alive as I learn more.

[rsterne]

I have made chamber reamers with a 1 deg. angle per side (from the C/L) and also a 2 deg.... The shallower angle allows a much longer tolerance in overall slug length and shape to be chambered without excessive force, and still engage the tapered leade to some degree.... It also reduces the force required to chamber a slug, because the very shallow taper on the land is more easily pressed into the nose (or front driving band) of the slug, engraving it to whatever depth is required to chamber so that the base is forward of the barrel port.... Here is an example of several slugs that have been chambered in my .257 cal, all to the same depth to the base.... This chamber was cut using a reamer of 1 deg. per side for the leade….



All seven slugs engage the leade to some degree.... The shortest slug on the right barely touches it, while the longest slug on the left is engraved to the full depth of the lands at the back edge of the nose.... and in fact the marks would have been quite a bit further back on that slug, if it were not for the recessed midbody, which is designed to prevent that, and reduce the bore drag.... The slug to the right of it is the same....

The back of the leade, where the parallel chamber starts, is just behind the front of the drive band on the right hand slug.... In fact, if you look closely at the bullet to its left, you can see the mark from the leade extending to the front of the forward lube groove.... and marks from the back of the leade in a similar location on the middle three slugs....

Incidently, there is a classic example of a poorly cut sprue, damaging the base of the slug, on the one third from the left.... You can see that the gas check stub is clearly bent to the left in the photo.... the base is rounded on the right, and bent out and pointed on the left, from the force of cutting the sprue.... Either the lead had not cooled sufficiently, and/or the hole in the sprue plate is too large....

Bob

[mackeral5]

Bob, thank you for the post.  I can see where reducing the angle allows for a much more broad range of length/weight slug. 

[rsterne]

Here is a generic drawing of the way I make my reamers.... this example is for a .22 cal airgun barrel....



The leade starts in the recess immediately behind the pilot, and continues at a 1 deg. taper until it meets the chamber diameter.... The cutting occurs in the area marked as "Leade".... Here is the cross section, with dimensions in calibers....



The dotted lines are if you wish a single flute reamer instead of 3 flutes.... It is plunging the mill slightly past the centerline (~5% of caliber) that forms the cutting angle.... A professional tool company will have their own ideas, this drawing is just FYI....

Bob

[luge007]

Woah, Thank You Bob!  That was exactly the 'type' of drawing I was looking for.  A specific drawing for .257 would have been more helpful, but (LOL) it will be easy enough to extrapolate a proper drawing for my needs from your illustration.  I had attempted to make a cutter about a year ago but the geometry was wrong and it didn't cut.  knowing about twice as much as I did a year ago I can see now that I should have gone past the centerline a little bit.  Would it also be possible to take a 7 degree cutter and make the flute cuts ON centerline and have a similar effect?

Cheers,
M

[rsterne]

Not sure what you mean by a "7 degree cutter".... I assume you are not talking about the taper of the leade, but the angle of the cutting edge of the flute, in cross section?.... Would it surprise you to know that if you plunge the mill 5% of the diameter of the cutter below the C/L, you end up with a cutting angle of 5.75 deg?

Think about it this way.... Look at my drawing, and notice that there is a rectangle between the horizontal C/L and the depth of the flute.... It is 0.05 cal high, and 0.50 cal wide.... ie the ratio of height to width is 1:10.... If you now draw a diagonal from the center of the circle to where the edge of the flute is, the sine of that angle is 0.100, right?.... That works out to an angle of 5.75 deg.... If you want to increase the flute angle to a full 7 deg. then you would plunge the mill slightly deeper.... The sine of 7 deg. is 0.122, so multiply that by the radius of 0.50 cal and you would get 0.06 cal (ie. 6% of the caliber).... The deeper you plunge the mill past the centerline, the more aggressive the cutting angle of the flute.... so the reamer cuts faster, but the surface finish is not as good....

I have settled on 5% of the caliber as a nice compromise.... If you hone the edge with a diamond hone (on the flat where the end of the mill cut, NEVER touch the outside of the circle)…. when turned slowly and advanced slowly into the bore, you get fine shavings of metal as it removes the lands.... I use 28 RPM on my lathe, and advance the reamer very slowly, maybe 0.010" every 10 seconds.... Once I have advanced it 0.100" (nearly 2 minutes), I remove it and clear the chips, relube it and repeat.... Here is a photo of the reamer just after removing it from the bore....



The big pile of shavings sitting in the flute is from a single insertion of 1 turn of the handwheel on the tailstock, which is 0.100".... You can see by the shiny mark on the side of the flute just below the shavings where the cutting action occurs.... on the last part of the 1 deg. taper, just before the parallel section of the chamber.... As you can see, you must NOT keep going with your cutting, or the flute could clog up.... I remove the reamer and blow off the chips and relubricate every 0.100" of chamber depth.... This also gives you the opportunity to blow out the bore and check the fit of the slugs as you make the chamber deeper, so you know when to stop.... You MUST know where you want the base of the slugs to be when you are finished, of course.... I actually use the end of the reamer to push the slug into the bore a bit past where it stops by hand.... You can get a "feel" for how tight they are in the leade, and where you need to stop the chamber, for the selection of slugs you want to use.... You just knock the slug out from the muzzle each time with a cleaning rod.... If you have to pound on it, you forced the slug into the leade too far.... 

Bob

[luge007]

Bob, wow I had to read that one twice just to make sure I got it. 

Sorry, my reference to using a 7deg cutter was incomplete.  It is in the 'dovetail' cutter family but only puts a 7deg taper on your cut, and is a common relief angle for cutting tools.  Then you hit us with "Would it surprise you to know that if you plunge the mill 5% of the diameter of the cutter below the C/L, you end up with a cutting angle of 5.75 deg?"

I completely understand the concept now that the 'trig' was spelled out so amazingly well.  However I would like to request some clarity  with your wording in the following description.  You mentioned  "......The deeper you plunge the mill past the centerline, the more aggressive the cutting angle of the flute."  Just so we are clear, are you lowering the cutter in the 'Z' axis with the quill (or raising the knee of the mill) to make the cut deeper with the tip of the endmill as opposed to moving the 'y' axis to make the cut deeper with the side of the endmill?   I guess it depends on the orientation of the part in the mill as to which cutting edge you intend to cut deeper with.  Which 'endmill cutting surface' makes a better cut for building a reamer?

I think I speak for everyone reading this thread, thank you for educating us on this topic, we appreciate it greatly.
M

[rsterne]

If you look at the photo of my reamer in Reply #2, you will see that it is the END of the mill that is past the centerline, so that the cutting edge of the flute is straight, from end to end.... If you use the side of the mill, then due to the radius of the tool, both ends of the cutting edge will arc upwards.... which means you have to increase the LOA to get the same flute cutting length.... I don't think that is the best way to make the reamer.... Having the cutting edge of the reamer a straight line also makes it much easier to hone with a diamond stone, IMO....

Additionally, using the side of the mill can cause a difference in the depth of cut depending on if you are "climb cutting" or cutting the other direction.... and if the end mill itself (or the reamer) flexes at all, it can chatter.... Although the end of the mill tends to leave circular marks, those aren't really an issue, and can be honed out before hardening, if you wish....

Incidently, when I install the reamer in the tailstock chuck, I put one flute groove on the top, to hold a large puddle of cutting oil (I also squirt some down the bore).... I use "Cool Tap" cutting oil, and it seems to work well for this application.... It comes in a small (4 oz.? ) squirt/dropper bottle, and I have had that one bottle for over a decade.... 

Bob

[Hobbyman2007]

I have ordered throat reamers from pacific tool and they have all worked very well. I believe the taper is 1* just like Bob uses but I do t have the tooling to actually measure it accurately. I’m presently waiting on a .172 throat reamer. I should mention it again that all you need is the throat reamer , the others are for cutting chambers for powder burners.

[mackeral5]

I have ordered throat reamers from pacific tool and they have all worked very well. I believe the taper is 1* just like Bob uses but I do t have the tooling to actually measure it accurately. I’m presently waiting on a .172 throat reamer. I should mention it again that all you need is the throat reamer , the others are for cutting chambers for powder burners.

Thanks for the info Denis.  I started out the new year with a cold so between rest and staying caught up with work I haven't taken the time to call Pacific tool yet.  I hope to get in touch with them this week.  I guess I misunderstood the tools and how they would work for us.  I was thinking the necker would finish ream/size the chamber (slightly diameter than bore) then the throater would ream the tapered lead? 

As I get more information I'll update the thread...

[rsterne]

I most cases, in a PB, the neck of the cartridge is significantly larger than the caliber, because the bullet fits inside the neck of the brass.... The exception is the .22 rimfire, where the base of the bullet has a smaller that caliber "heel" that fits inside the case, and the case OD is virtually the same as the bore....

So yes, you want a throat reamer, not a neck reamer....

Bob

[dyotat100]

A cheaper way to do it is buy a reamer of your caliber. Take it to a tool grinder. Have them grind a pin on the end and put a 1 degree taper on it. Then make a bushing that fits your bore.

I do this for calibers I know I'm not going to do more then once or twice. My tool grinder will make one out of carbide for $135 though.