Gunsmithing Question about why to use a reamer holder

O

OnyxSkyDV

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Nov 5, 2009
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#1
Forgive my question that comes from ignorance, but in talking to my friend who is a machinist by trade, he was asking why a floating reamer holder or one of the fancy morse taper mounted reamer holders was needed, as opposed to ensuring your tailstock was properly aligned (both vertically and horizontally) and just using a tap handle braced against the carriage?

When I mentioned that it might be of help when retracting the reamer to peck at the chamber, he stated that we probably should have roughed the chamber via drilling then boring to within a very close tolerance of the final dimension in order to save wear on the reamer, and that with the flush coolant it shouldn't be pecked, but done to almost finish dimension, measured, and finished.

Since I didn't have a good answer, I thought I would ask here where someone would surely know, and my dumb questions might provide some humor at the same time.
smile.gif


Onyx
 
#2
Re: Question about why to use a reamer holder

If you can get your tailstock in perfect alignment there is no need for a floating holder. Most tailstocks are a little high. The best builder I know uses a tap holder. His guns shoot lights out.
 
#4
Re: Question about why to use a reamer holder

I agree with his comments regarding drilling and preboring the chamber. I would also agree that an accurate chamber can be cut with a center in the tailstock pushing the reamer. On some lathes it can be difficult to get the tailstock perfectly aligned with the spindle bore, and alignment can change as the tailstock ram is extended or retracted from the original position resulting in a potentially oversized chamber. I use a floating reamer pusher, similar to a Bald Eagle Holder
 
#5
Re: Question about why to use a reamer holder

Thanks for the input guys. From your responses I gather the floating reamer holders help to allow the reamer to self center when you are unable to get your tailstock aligned in all dimensions.

Thanks!

Onyx
 
#7
Re: Question about why to use a reamer holder

When holding the reamer with just a lathe dog or tap wrench, I worry about it applying more pressure to one side because of how its being held. Like using a lathe dog and letting the handle rest on the carriage like you mentioned. I worry that since the carriage is holding it, or the smiths hand, that it could be torquing it to the side or up or down while its cutting.

Dont know if its anything to worry about but its gone through my head every time.

Ive chambered 7 rifles that way with no problems.



About pre-drilling and boring before you start the reamer... when you do this, are you able to still get the pilot in the bore before the reamer starts cutting the sides? I cant picture how you would. And I dont like the idea of the reamer cutting even for a second unpiloted.
 
#8
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Like using a lathe dog and letting the handle rest on the carriage like you mentioned. I worry that since the carriage is holding it, or the smiths hand, that it could be torquing it to the side or up or down while its cutting.
</div></div>

Keith,
If the tail stock center is holding the back of the reamer, and the pilot is guiding the front, then how can any side forces cause the reamer to move laterally at all.

It would seem that the torque that you are concerned with would have to move the tail stock center, the pilot or actually bend the reamer to get the effect you are worried about?

I've had no issues either and that is certainly the way we were taught.

But the engineer (spelled geek) in me is always interested in understanding the physics and mechanics of how these things work, and don't work.

I had the same question WRT the pilot.
I've only used finishing reamers thus far so that was not an issue.
But if it comes a time to chamber lots of barrels, then I'd planned on buying roughing reamers.
 
#9
Re: Question about why to use a reamer holder

I have chambered many times without a holder with good results. I now use a manson holder. I have more control with the reamer holder. When you hold the reamer with a wrench and tailstock there is some chater caused by the cushioning from your hand on the wrench. Thats just my experience. It is money well spent.
 
#10
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mark Housel</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Like using a lathe dog and letting the handle rest on the carriage like you mentioned. I worry that since the carriage is holding it, or the smiths hand, that it could be torquing it to the side or up or down while its cutting.
</div></div>

Keith,
If the tail stock center is holding the back of the reamer, and the pilot is guiding the front, then how can any side forces cause the reamer to move laterally at all.

It would seem that the torque that you are concerned with would have to move the tail stock center, the pilot or actually bend the reamer to get the effect you are worried about?

I've had no issues either and that is certainly the way we were taught.

But the engineer (spelled geek) in me is always interested in understanding the physics and mechanics of how these things work, and don't work.

I had the same question WRT the pilot.
I've only used finishing reamers thus far so that was not an issue.
But if it comes a time to chamber lots of barrels, then I'd planned on buying roughing reamers.

</div></div>

i wouldn't assume the reamer itself is completely rigid. i also wouldn't assume the tailstock/lathe bed is completely rigid on most sub 2k lb lathes.
 
#11
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">
i wouldn't assume the reamer itself is completely rigid. i also wouldn't assume the tailstock/lathe bed is completely rigid on most sub 2k lb lathes. </div></div>
Certainly there would be <span style="font-weight: bold">some</span> movement in the tailstock but how much flex would it be reasonable to expect in a reamer? That would also seem to be caliber related?

What magnitude movement would be reasonable to expect in a decent tailstock that isn't run way out under the sorts of force we are talking about?

I'm trying to get a handle on the theory vs reality.
Do these sources of movement really cause a measurable change in the chamber, and if so, enough to actually make a difference.
 
#12
Re: Question about why to use a reamer holder

Do you guys normally just use the finish reamer to hog out the entire chamber, without pre-boring at all? I thought I had heard of people doing that, but my friend reacted like that was akin to running a bus full of orphans and nuns off the road just for fun.
smile.gif


If so, what kind of life do you get from your reamers?

Thanks!


Onyx
 
#13
Re: Question about why to use a reamer holder

I hold my reamer solid in a GTR holder, more or less the same as using a dead center and pushing only it had adjustable collar to hold the reamer from turning and in alignment. NO floating, I've only chambered about a dozen barrels but I've never experienced reamer chatter or getting fat or of center chambers either. Also have it in the tool holder as apposed to the tail stock, works very good and much easier than hauling the tail stock around and torquing it and I have a good feel for the feed and can remove, clean and oil the reamer and advance it with a faster cycle time.
 
#14
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Onyx</div><div class="ubbcode-body">Do you guys normally just use the finish reamer to hog out the entire chamber, without pre-boring at all?</div></div>

Every time so far.

Might be tough on the reamer but if I get 20 chambering out of a reamer, thats money well spent.

And I'll get more than 20. Maybe double.
 
#16
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">When holding the reamer with just a lathe dog or tap wrench, I worry about it applying more pressure to one side because of how its being held. Like using a lathe dog and letting the handle rest on the carriage like you mentioned. I worry that since the carriage is holding it, or the smiths hand, that it could be torquing it to the side or up or down while its cutting.</div></div>

+1....This is a valid concern and certainly something anyone should be mindful of when chambering. The weakest part of the reamer is right behind the pilot, so any appreciable lateral movement at the back of the reamer will snap the reamer just behind the pilot, especially in the LA/Magnum calibers.

I've never been a fan of tailstocks, so my setup is a bit different. The tool I use to push my reamer is indicated true to the bore/lathe ways so I have no lateral runout at the back of the reamer (although I still hold my reamer by hand).

For the time being, my chambers are first cut with a roughing reamer and then finished with the "finish" reamer. My CNC setup will be a little different, but the finish cuts for the chamber will still be completed manually, as I hate to give up the personal "feel" of cutting my chambers.
 
#17
Re: Question about why to use a reamer holder

I do like feeling my reamer with my hand while cutting. I dont see myself letting the handle rest on the way or the carriage any time soon.

I see us going to a floating reamer holder soon to at least try it.


The more I learn and see, I believe that a great rifle can be built a few different ways. Some ways might be theoretically better than others but in practice, when done right, they both create a rifle that shoots under half minute with good ammo.
 
#18
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">I do like feeling my reamer with my hand while cutting. I dont see myself letting the handle rest on the way or the carriage any time soon. </div></div>

Exactly. When it comes to resting the handle on the way or carriage, there are those that have broken a reamer and those who will break a reamer. It's just a matter of time (not to mention the runout in the chamber).

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body"> I see us going to a floating reamer holder soon to at least try it. </div></div>

Of the floating holders out there, the one from Gre-Tan is probably the best....as long as the tail-stock is dead nuts....
 
#19
Re: Question about why to use a reamer holder

The floating holders still allow gravity to pull the reamer down slightly. I use piloted reamers and a floating pusher cup that never contacts the reamer and only pushes against a small tap handle. The tap handle was machined on both sides of the handle while it was attached to a spud I made in a four jaw.

I've used commercially manufactured holders in the past and all of them required me to lift the reamer up slightly when going back in the chamber. The Gretan is adjustable so this isn’t an issue with that particular holder but, you loose the "Feel" when you use a floating reamer holder and that isn’t a good thing 100% of the time.

The floating pusher requires my hand to be in constant contact with the reamer shank and tap handle. I can easily feel when it gets in a bind or I'm feeding too fast.

I know a smith that pushes the reamer with a dead center while holding the reamer with an open end wrench. He just set a record during a sanctioned HBR match. He is regularly in the top 3 if he's not winning.

There’s more than one way to skin a cat but, in the end, it really boils down to solid machine shop practices.
 
#20
Re: Question about why to use a reamer holder

Does Gre-tan only make that one model? We'll look into Gre-tan too.

What about one from GTR? GTR seemed to be the favorite among a group of guys talking about the subject with me. That was going to be where I looked first.





And you guys holding the reamer holder with the tool post, how is that done? How are you indicating it in to "Z"(bore line)? Ive never seen a fixture for that.
 
#21
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Does Gre-tan only make that one model? We'll look into Gre-tan too.

What about one from GTR? GTR seemed to be the favorite among a group of guys talking about the subject with me. That was going to be where I looked first.
</div></div>

Keith, I'm pretty sure you're talking the same one. GTR Tooling: <span style="font-weight: bold">G</span>re'-<span style="font-weight: bold">T</span>an <span style="font-weight: bold">R</span>ifles Tooling, no?
 
#22
Re: Question about why to use a reamer holder

I have used the tail stock or if you have a quick change tool post with a boring bar holder you can indicate that in and use the carriage. Place a piece of reamer blank in the holder and indicate it in for center and perpendicular / straight. Using the carriage is nice especially if your machine has a DRO or trav-a-dial for depth.

Floating holder for reamers is similar to floating tapping holders. It corrects small mis-alignment between workpiece and tool. Roughing out the hole saves wear on your reamer. Use lots of oil and reasonable RPM and you should not have a problem.
 
#23
Re: Question about why to use a reamer holder

I have a 3 MT tool holder for my tool post so I square it to the barrel face then put the GTR holder in the tool holder with the collar and reamer removed. I then center it up on the barrel bore by eye which gets it real close, then I fine tune it with an indicator quickly with a few sweeps. Next the reamer is installed into the collar and then that all goes onto the reamer holder, I tighten the three screws till all the springs have a few turns of compression on them. I then bring the reamer up to the bore and adjust the screws till the reamer is centered in the bore and I don't have to help it get in.

I'm using a big ol tank of a lathe so rocking the carriage up would take some serious cranking, I can just hold pressure on the hand wheel and let the reamer choose the feed rate. It seems that the tail stock feed has more of a mechanical advantage when advancing which makes it harder to feel the feed. My free hand is on the reamer and holder and I have good feel there as well. When I hit my depth I just reverse out, clean up and lube then right back in, don't even shut the lathe of since there is nothing that has the possibility to flop around.
 
#24
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WhiteDingo</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Does Gre-tan only make that one model? We'll look into Gre-tan too.

What about one from GTR? GTR seemed to be the favorite among a group of guys talking about the subject with me. That was going to be where I looked first.
</div></div>

Keith, I'm pretty sure you're talking the same one. GTR Tooling: <span style="font-weight: bold">G</span>re'-<span style="font-weight: bold">T</span>an <span style="font-weight: bold">R</span>ifles Tooling, no? </div></div>


Ah. Thanks
 
#25
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bigngreen</div><div class="ubbcode-body">I have a 3 MT tool holder for my tool post so I square it to the barrel face then put the GTR holder in the tool holder with the collar and reamer removed. I then center it up on the barrel bore by eye which gets it real close, then I fine tune it with an indicator quickly with a few sweeps. Next the reamer is installed into the collar and then that all goes onto the reamer holder, I tighten the three screws till all the springs have a few turns of compression on them. I then bring the reamer up to the bore and adjust the screws till the reamer is centered in the bore and I don't have to help it get in.
</div></div>

I see.

Thanks
 
#26
Re: Question about why to use a reamer holder

http://www.bryantcustom.com/articles/rebarrel.htm

I read this by Mike Bryant 10 years ago, and since then I have been pushing a free floating reamer. The torque reaction goes through a tube over the tap wrench handle to the lathe bed. I push the reamer with a MT3 chuck arbor in the tailstock.

I dial the barrel in in a gimbal to .000" to start.
When I finish the chamber I check the the chamber run out, and .001" is typical.

I chamber a barrel ~ 4 times a years, all for my own consumption, and I am satisfied with the results.

 
#27
Re: Question about why to use a reamer holder

I aligned the tailstock and use a torque wrnch to set it each time to get the same height. I use Greg Tannels GTR floating reamer holder. I start with a piloted rougher and finish with a piloted finish reamer. It works pretty well. I keep a finger on the holder to get some tactile feedback while working.
 
#28
Re: Question about why to use a reamer holder

When your finish reamer starts cutting, after having hogged most of it out with you rougher, drill, boring bar, whatever.... Does the finish reamer start cutting before the pilot touches the bore? Seems like it would cut almost all of the chamber without the pilot touching.


Do you all think its more "accurate" to do the whole thing in one go with a finisher? Seems like it would be, although harder on it.
 
#29
Re: Question about why to use a reamer holder



In machining as a general practice rigidity is a direct function of mass, surface area contact, and clamping power.

Lots of ways to skin cats as previously mentioned, however its been my experience (after 12+ years of doing this) that resorting to fundamentals always wins.

Below is my attempt to address the challenges on all fronts:

DSC_0015.jpg


1. Collets to hold the barrel= almost 360* of surface contact

2. Hydraulic collet closer= over 800lbs of clamping force.

3. Massive turret ensures rigid tool holding which minimizes tool chatter.

4. Massive reamer holder ensures rigid tool holding which again mitigates tool chatter.

5. Chip evacuation: One can only pack so many chips in the tool's gullets before really bad things start to happen. Be it pressurized cutting fluid delivery through the barrel or removing, clearing, and reinserting, the tool has to be clean at the cutting surface in order to make an accurate cut with a good finish.

6. Speeds and feeds. Take the major diameter of a given reamer and look up the speeds/feeds for barrel steel. Now compare to the S/F commonly used by gun plumbers. 99% of well below published recommendations. Why is that? Its because you have to rob Pete to pay off Paul. Holding the tool by hand sacrifices a cardinal rule. The only way to get it back is to slow stuff down.

Why break the rules when you <span style="font-style: italic">can</span> have it all?

Just something to consider.
 
#30
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">When your finish reamer starts cutting, after having hogged most of it out with you rougher, drill, boring bar, whatever.... Does the finish reamer start cutting before the pilot touches the bore? Seems like it would cut almost all of the chamber without the pilot touching.


Do you all think its more "accurate" to do the whole thing in one go with a finisher? Seems like it would be, although harder on it. </div></div>

7mmRemMagdrillboreandreamplantocutchamber.jpg


Here is how I kept between .188" and .650" of the reamer pilot engaged in the bore, while cutting a 7mmRemMag chamber, while removing the bulk of the metal with the drill.

This is my plan for staying concentric when repeating:
1) Drill
2) Boring bar
3) Reamer with minimum of pilot engaged in bore

What does it all mean?
4 Phases?
It should have been called 4 baby steps to avoid needing a reamer holder!
 
#32
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">When your finish reamer starts cutting, after having hogged most of it out with you rougher, drill, boring bar, whatever.... <span style="font-weight: bold">Does the finish reamer start cutting before the pilot touches the bore?</span> Seems like it would cut almost all of the chamber without the pilot touching.


Do you all think its more "accurate" to do the whole thing in one go with a finisher? Seems like it would be, although harder on it. </div></div>

Keith,

Since there have been no direct replies.

I think maybe that your answer is the process that was described in the book we received at school?.

Or at least it implies the answer to your question?

His process was to run the rougher in a short distance follow to that point with the finisher and repeat the process (ad nauseum?) finalizing the chamber for headspace with the finisher.

This implies that perhaps the finisher pilot DOES NOT reach all the way to the bore if the rougher is run in past a certain distance?

Mark
 
#34
Re: Question about why to use a reamer holder

Form tools tend to follow what's already there. Meaning if the hole is concentric and tangent to the bore a pilot becomes nothing more than something that rubs the bore ahead of the throat. Freaky huh? Take a barrel you don't care about once and try it. Bore a taper just smaller than the shoulder. Finish the taper slightly larger than the throat over the span of an inch. Pull the pilot and chamber it. Making the assumption tools are aligned and machines are straight there's no good reason to think the chamber won't be perfect. I own every reamer pilot PTG makes from 17 to 338 caliber. I find myself using them less and less. Todays 6.5x47L is a good example. -.00005" was the runout according to my B/S indicator. Is it reeeeeaaaalllly that good? Prolly not but its the highest resolution indicator I own from back when I programmed/setup wire EDM's. I know those machines will go that small and I made a lot of good parts back then so I gotta think its dern close.

Find a piloted chucking reamer in an MSC catalog. You won't. Now why is that?

Look for a reamer with a pilot setup to ream tapers. Won't find one there either.

I see a trend. . .

Give it a try sometime and see what you come up with. Better leave the tap wrench in the drawer though.

Good luck

C.
 
#35
Re: Question about why to use a reamer holder

I like to feel the reamer as it cuts. That is why I use a floating reamer holder. If I feel any bind caused by chips, I can back the reamer out immediately and get a better finish that takes less polishing at the end. If you get any chatter, I have found that if you wrap the reamer with some paper, one wrap only, and recut, it will take the chatter out and the next cut can be done without the paper and it cuts smoothly again. I have done about 150 chambers with a floating reamer holder and they are all concentric and are very accurate.
 
#36
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RCRGuns</div><div class="ubbcode-body">I like to feel the reamer as it cuts. That is why I use a floating reamer holder. If I feel any bind caused by chips, I can back the reamer out immediately and get a better finish that takes less polishing at the end. If you get any chatter, I have found that if you wrap the reamer with some paper, one wrap only, and recut, it will take the chatter out and the next cut can be done without the paper and it cuts smoothly again. I have done about 150 chambers with a floating reamer holder and they are all concentric and are very accurate. </div></div>


Has it ever occurred to anyone that maybe the reason your feeling it grab, ring up, chatter, etc is because your holding onto it?

It's kind of like coaching a shooter and just staring at the target. The target is the effect, a good coach is watchful of the shooter to determine the cause. The target is nothing more than feedback to tell the coach if he's right.

Does any machinist anywhere hold onto an endmill or a turning tool with his hand to be able to immediately retract the tool the instant chatter or chip weld is detected?

Just something to ponder.

I think peeps insist on using this practice because it's been done that way for a long time. It's what "skoolz" teach and so it's "solid doctrine."

My response:

Reaching for the banana

FWIW I'm in the process of barreling a 300 Winchester Magnum as we speak. No pilot on the tool during the entire chambering operation.

Just finished (half hour later) .0001" at the breech and .00013" at the shoulder junction. I think it works.
smile.gif


Back to work!

C.
 
#37
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">

In machining as a general practice rigidity is a direct function of mass, surface area contact, and clamping power.

Lots of ways to skin cats as previously mentioned, however its been my experience (after 12+ years of doing this) that resorting to fundamentals always wins.

Below is my attempt to address the challenges on all fronts:

DSC_0015.jpg


1. Collets to hold the barrel= almost 360* of surface contact

2. Hydraulic collet closer= over 800lbs of clamping force.

3. Massive turret ensures rigid tool holding which minimizes tool chatter.

4. Massive reamer holder ensures rigid tool holding which again mitigates tool chatter.

5. Chip evacuation: One can only pack so many chips in the tool's gullets before really bad things start to happen. Be it pressurized cutting fluid delivery through the barrel or removing, clearing, and reinserting, the tool has to be clean at the cutting surface in order to make an accurate cut with a good finish.

6. Speeds and feeds. Take the major diameter of a given reamer and look up the speeds/feeds for barrel steel. Now compare to the S/F commonly used by gun plumbers. 99% of well below published recommendations. Why is that? Its because you have to rob Pete to pay off Paul. Holding the tool by hand sacrifices a cardinal rule. The only way to get it back is to slow stuff down.

Why break the rules when you <span style="font-style: italic">can</span> have it all?

Just something to consider. </div></div>

I don't have a collet closer on my lathe, but I'm curious how do you get the ID centered up with a collet closer?
 
#39
Re: Question about why to use a reamer holder

OD turned concentric to bore?

If you put it between centers and turned a concentricity pass bringing it to like 1.200", then put it in a 1.200" collet, bore at that end would be centered. Doesnt deal with runout but in the 3" a reamer runs in there isnt much runout.

Would that work?


Support muzzle end with a universal tapered bushing set that you could make to fit different barrels, or maybe just use a spider?
 
#40
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">OD turned concentric to bore?

If you put it between centers and turned a concentricity pass bringing it to like 1.200", then put it in a 1.200" collet, bore at that end would be centered. Doesnt deal with runout but in the 3" a reamer runs in there isnt much runout.

Would that work?</div></div>

Depends on who's barrel manufacturer your getting. Acceptable tolerances on some is .010 from ID to OD. Would you want your case to be .010 off the center line of your threads and bolt face?

IMO centering up the ID prior to cutting threads and chamber would be optimum instead of cutting off the OD. How do you know that the center of the bore is concentric to OD?

Now if you use a collet closer or set-tru and can still center off the ID....I'm all ears! Because that's a faster way then using independent 4 jaws and a spyder on both ends of the spindle bore.
 
#41
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Animal</div><div class="ubbcode-body">Depends on who's barrel manufacturer your getting. Acceptable tolerances on some is .010 from ID to OD. Would you want your case to be .010 off the center line of your threads and bolt face? </div></div>

I said you'd cut a concentricity pass on the barrel between centers. Then the bore would be centered, not accounting for runout. Runout in the 3" of chamber length wouldnt be much, but if its in a collet I dont see any way to indicate runout out. Only get the end of the bore on "Z"
 
#42
Re: Question about why to use a reamer holder

i really hope none of the barrels we are using have bores anywhere near .010" eccentric between the breech end and the throat area. 18" or so down the bore, maybe.

i don't want to speak for chad but i believe he is dialing in the throat area dead nuts while holding the od of the barrel, then single point boring and feeding the reamer with a rigid holder in a nc lathe that weighs more than my 4x4 2500 dodge.
 
#43
Re: Question about why to use a reamer holder

Question.
The idea of a floating reamer holder is that the reamer can move around to line up with bore, but it stays parallel to the Z axis(bore) correct? To make up for slight misalignment of the tailstock?

The GTR picture on midway does not look like it stays parallel to Z when it pivots. It looks like it pivots the same way it would being pushed by a center.
 
#44
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Animal</div><div class="ubbcode-body">Depends on who's barrel manufacturer your getting. Acceptable tolerances on some is .010 from ID to OD. Would you want your case to be .010 off the center line of your threads and bolt face? </div></div>

I said you'd cut a concentricity pass on the barrel between centers. Then the bore would be centered, not accounting for runout. Runout in the 3" of chamber length wouldnt be much, but if its in a collet I dont see any way to indicate runout out. Only get the end of the bore on "Z" </div></div>

id agree with you and bet money that the barrel od is finished between centers from most manufactures but you can dial out runout in at least one spot with a collet and a set-tru style collet chuck. i'd want that one dead nuts spot to be the throat.
 
#45
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Question.
The idea of a floating reamer holder is that the reamer can move around to line up with bore, but it stays parallel to the Z axis(bore) correct? To make up for slight misalignment of the tailstock?

The GTR picture on midway does not look like it stays parallel to Z when it pivots. It looks like it pivots the same way it would being pushed by a center. </div></div>

and this is the primary reason i use a floating reamer holder. i know my tailstock is about .0015" high (changes with temperature) and the ram travel isn't dead nuts parallel (go figure with a sub 1500 lb chinese lathe). if your tailstock isn't dead nuts throughout the ram travel, using anything that centers off it will most likely create an oversized chamber. i say most likely because there is probably quite a bit of flex on that same lathe. the reamer will want to follow an existing hole. will the tendency of the reamer wanting to follow the existing hole overcome a misaligned tailstock? i'd rather not have to worry about it.
 
#46
Re: Question about why to use a reamer holder

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">
i don't want to speak for chad but i believe he is dialing in the throat area dead nuts while holding the od of the barrel, then single point boring and feeding the reamer with a rigid holder in a nc lathe that weighs more than my 4x4 2500 dodge. </div></div>

I understand being able to dial in the the bore to Z if it has the adjustments like those chucks do, but still, how do you then adjust out runout in the first 3" of barrel out like you might between two spiders?

You cant in a collet right?


BTW, Im not saying getting runout out of the first 3" of barrel is important to the procedure Im describing. If you get the very end of the bore perfectly indicated in(or the throat area), held in a 1.200" collet by a surface cut between centers and perfectly 1.200" parallel, then just barely support the muzzle end from wiggling around, that 3" or 4" you are chambering will be straight on Z.


It would kinda be like magically being able to chamber between centers.

correct?



And contoured barrels will always be barrel spun from the maker right? Blanks... I contour, then barrel spin before starting machining. So either way they're barrel spun when my process starts. Because of this I cut a light concentricity pass on the cylinder to do my work, then barrel spin it out later before mounting.
 
#47
Re: Question about why to use a reamer holder

those of us using entry level import lathes/chucks or well used american iron probably have to do a bit more compensating than those using heavy, more modern iron.

but yes, i think if you held the od with a collet and dialed in the throat to a tenth of a red cunt hair, there would still be measurable runout at the breech. do i think it's the best way? not really. do i think those using that method are getting the results they and their customers are after? you bet.
 
#48
Re: Question about why to use a reamer holder

Im thinking a 6 jaw precision scrolling chuck with the 4 adjustments behind like you mentioned.
Cut Cylinder OD concentric to to bore ends between centers, put cylinder in 6 jaw, center muzzle end one of a few different ways, then double check the throat area with an indicator. Make slight adjustment if necessary.

Use a reamer holder that allows the reamer to move around while staying parallel to Z, not just pivoting off the back of the reamer like it would being pushed by a center. This way if the tailstock is not aligned perfectly you're ok.

Is that how some people are doing it? Or same thing minus the 4 way adjustment that the 6 jaw scroller has.


And I have to ask again. Which type of reamer holder will allow the reamer to move side to side,up/down, 360 degrees... while keeping it parallel to the bore?
Does the GTR do that, keep it parallel to bore?

Like I said, the GTR really looks like it pivots at the rear like a tailstock center would allow it to do, but with springs to apply pressure in whatever direction you want.
This pivoting motion wouldn't make up for the tailstock being a little off though.
Thats how it looks in the picture on midway anyways.
 
#49
Re: Question about why to use a reamer holder

I have to ask again. Which type of reamer holder will allow the reamer to move side to side,up/down, 360 degrees... while keeping it parallel to the bore?
Does the GTR do that, keep it parallel to bore?

It(the GTR) really looks like it pivots at the rear like a tailstock center would allow it to do, but with springs to apply pressure in whatever direction you want.
This pivoting motion wouldn't make up for the tailstock being a little off though.
Thats how it looks in the picture on midway anyways.
 
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