Gunsmithing Test Indicators

[JimT]

When you are indicating an action or barrel, which level of test indicators are you using? .001, .0005, or .0001?

I have .0005, but have lately been wondering if I should get some .0001's.

 

[tpryder]

Re: Test Indicators

I start out with the .0005, then when I get close I switch to a .0001. With a real heavy barrel and the spindle in neutral I strive to get .0001 total indicator movement. Then run the barrel under power usually gets .0002.

 

[LRI]

Re: Test Indicators

FWIW running a barrel in the machine while the indicator is in the bore will likely ruin the indicator.

The shock loading will fry even the best of them after awhile.

Not sure if that's what you meant, but if it is, just be mindful of it if your instrument starts acting weird down the road.

Good luck

C

 

[JimT]

Re: Test Indicators

No, just want to know if I should pop for the .0001s. I have the indicator and range rods.

 

[LRI]

Re: Test Indicators

FWIW mine is .00005" (no chit)

Brown/Sharp 7033-5

 

[tpryder]

Re: Test Indicators

When I run the lathe under power after dialing in the barrel I'm only running 70 RPM's, I think that's the slowest the machine goes. I hear what you mean though. I only run the machine as a last check, usually by this time, I've spun the spindle in neutral many times.

 

[JimT]

Re: Test Indicators

I popped for a pair of the Brown/Sharpe 7033-5's. MSC had a 35% off sale.

 

[Munimula]

Re: Test Indicators

Very nice.


For my General machining I'm only using down to a .0005 indicator. But I'm seriously considering moving into gunsmithing a bit more and looking at indicators with more precision.


Enco has the 7033-5's for $185


Keep in mind (which you seem to have machining knowledge so you should be fine) that the 0.00005 indicators only have a few thousandths of total travel so you'll have to get pretty darn close on a 0.0005's indicator.

 

[Keith Johns]

Re: Test Indicators

What type of mag base do you use with that indicator?

 

[JimT]

Re: Test Indicators

I have a couple of cheapie small Chinese-made mag bases that came with the first set of cheapie Chinese-made test indicators that I bought when I first got my lathe. I don't trust the indicators, but the mag bases work great.

Mini Mag Base

For the price, put the indicators in a drawer and call it good. I haven't seen a similar mag base (size wise) for the same price. I hope some super shoppers will prove me wrong. I could use a couple more.

 

[Keith Johns]

Re: Test Indicators

I mean what type of mag base to use with a .00005" indicator


A cheapy wont do

 

[Clark]

Re: Test Indicators

I have a:
a) Lufkin V32 .0001"
b) Brown and Sharp 7030-5 .0005"
c) Mitutoyo 513-118 .001"
d) And some other Chinese stuff

I read this in 2000 and started chambering rifles:
Bryant on chambering link
I have been making a gimbal at the breech in the 4 jaw, and dialing in a spud over a length, using the spider to steer. This had been in an effort to get the bore to be both parallel AND concentric with the lathe spindle, local to the throat, assuming some bend in the barrel.

In 2009-10-3, I took (3) 7mmRemMag rifles I just chambered to the range. A 1908 Braz Mauser with a $33 Rem700 take off barrel, that had the reamer accidentally finish .005" off center, shot a .75" 3 shot group at 100yards. That is just about the only group it has shot, but I realized something....

Dialing in barrels when chambering has little to do with accuracy. I should have been able to figure that out before I stumbled onto it.
I had performed yet another accuracy ritual of trivial efficacy [read as benchrest only] for 9 years, like a fool.

 

[lvcatfish]

Re: Test Indicators

I have a B & S 7033-5 (black face) and was looking into getting a second indicator but a 7033-3 (white face). Are there any internal differences to justify the extra $40 or so in cost? If they are the same I can live with two black faces sitting on the carriage. Anyone know the answer or have an opinion?

 

[Keith Johns]

Re: Test Indicators

Can you guys suggest mag bases? I need one in the $200 range. With fine adjustment. Only ones I've seen that I like are Starret, and were like $250

Ill spend extra if its worth it. But buying a $250-$300 mag base... it better be worth it considering my funds right now.

Using a cheap mag base like I am now its hard to get it set right. I worry about bumping my indicator arm and damaging it. I also worry about the indicator holder/mag base not holding it steady enough to get a real reading. I mean when you're using that .00005" indicator, dont you worry about your mag base having flex or vibration in it? .00005" is freakin nothin

 

[lvcatfish]

Re: Test Indicators

I have had good luck with Noga brand mag bases. Not too spendy but solid as far as I am concerned. Having the fine adjustment at the base rather than the carried end helps too. Hard to make a fine adjustment right next to a .00005" indicator; if you look at it mean it moves.

 

[300sniper]

Re: Test Indicators

how many of you (other than people with cnc lathes that weigh more than my truck

(and even then i'd be kind of skeptical)) can cut a chamber with only .00005" runout? how tight are your lathe spindles? how accurate are the surfaces you are measuring? what do you honestly think you will accomplish with a .00005" indicator that you won't with a .0001"?

i know i'm just a garage hack but for what i do, i think i'll stick with .0001" test indicators on noga bases.

 

[Clark]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"> what do you honestly think you will accomplish with a .00005" indicator that you won't with a .0001"?
</div></div>

People have lots of things in their heads that are wrong, but could honestly pass a lie detector test.

Gunsmiths dialing in barrels is one of them.

 

[JimT]

Re: Test Indicators

I think either the .00005 or the .0001 will do fine. They are close to the same price, so get whichever floats your boat. I will get it close with the coarser indicator and then get it as zeroed as possible with the super fine indicator.

I know you get what you pay for in an indicator, but I don't see the benefit of spending the kids' inheritance on a mag base. I will let those with more knowledge enlighten me otherwise.

 

[cordovan]

Re: Test Indicators

I have a couple of Interapid indicators which are great. They are swiss and top of the line.

Here is a review of different brands that may be helpful:

http://longislandindicator.com/p14.html

http://longislandindicator.com/p116.html

 

[LRI]

Re: Test Indicators

FWIW:

There are several methods used to support the spindle of a lathe.

One is conventional roller bearings with a thrust collar arrangement to hold position in "Z".

The other (more common on higher end turning centers) is a tapered gamut spindle bearing arrangement.

It's a pair of tapered bearings that are preloaded and always "looking" for the center of rotation.

I can tell you this. I've had my indicator since back when I worked in job shops and used a wire EDM alot. I broke that one while at Nesika and didn't buy another till I got the Doosan up and running.

I can lay that indicator stylus on a warmed up spindle and tap a barrel in (yes, that means beat on the chuck with a soft mallet)to where the needle comes right back to zero on every tick. I can turn a cylinder and lay the stylus on it and have the needle vibrate slightly due to surface finish, but there's no real identifiable HI/LOW that you'd expect to see with runout.

My chambers typically run anywhere from .0002 to essentially nothing.

Is it spot on accurate? I doubt it. I equate it to this: The more I can do to minimize it, the better off I am on the long haul as it hopefully thwarts stacking of tolerances.

The guns shoot well, I'm happy, customers are happy, so I'm stickin with it.

One of the issues I have with conventional gunsmithing is that threading/chambering ignores fundamentals for most. Guys make elaborate 4 jaw chucks using bolts with brass tips to support the barrel. Then wonder why they have thread chatter if they go too fast on the spindle.

Surface contact (work holding) is machining 101. Fix that problem and one will likely discover that suddenly TIR, surface finish, and a number of other things improve significantly.

Just saying. Not trying to start a pissing match with anyone.

Do the best you can with what you have.

C

 

[JimT]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Then wonder why they have thread chatter if they go too fast on the spindle.</div></div> True story.

Chatter is an issue with the spider setups. My experience has been the thinner the barrel, the more likely it is to chatter. I found that if I hand turn the chuck for the last thou or so cleanup, it takes the chatter marks out. My lathe just won't turn slow that slow under power, so it goes to hand power (5 rpm?)

 

[300sniper]

Re: Test Indicators

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

There are several methods used to support the spindle of a lathe.

One is conventional roller bearings with a thrust collar arrangement to hold position in "Z".

The other (more common on higher end turning centers) is a tapered gamut spindle bearing arrangement.

It's a pair of tapered bearings that are preloaded and always "looking" for the center of rotation.

I can tell you this. I've had my indicator since back when I worked in job shops and used a wire EDM alot. I broke that one while at Nesika and didn't buy another till I got the Doosan up and running.

I can lay that indicator stylus on a warmed up spindle and tap a barrel in (yes, that means beat on the chuck with a soft mallet)to where the needle comes right back to zero on every tick. I can turn a cylinder and lay the stylus on it and have the needle vibrate slightly due to surface finish, but there's no real identifiable HI/LOW that you'd expect to see with runout.

My chambers typically run anywhere from .0002 to essentially nothing.

Is it spot on accurate? I doubt it. I equate it to this: The more I can do to minimize it, the better off I am on the long haul as it hopefully thwarts stacking of tolerances.

The guns shoot well, I'm happy, customers are happy, so I'm stickin with it.

One of the issues I have with conventional gunsmithing is that threading/chambering ignores fundamentals for most. Guys make elaborate 4 jaw chucks using bolts with brass tips to support the barrel. Then wonder why they have thread chatter if they go too fast on the spindle.

Surface contact (work holding) is machining 101. Fix that problem and one will likely discover that suddenly TIR, surface finish, and a number of other things improve significantly.

Just saying. Not trying to start a pissing match with anyone.

Do the best you can with what you have.

C </div></div>

maybe you are missing what i was getting at. most of the guys here using a 1000-1500 lb (usually chinese) lathe are not going to benefit from going from a .0001" indicator to a .00005" indicator. i include myself in this category.

 

[lvcatfish]

Re: Test Indicators

I already have the indicator I spoke of previously and would like to purchase another one. The cost difference between that and a quality .001 or .0001 indicator is nominal. I may order up a $1000 test indicator and post pictures of it on my G4003G lathe to see just how badly it pisses some people off...

Whatever happened to the friendly and helpful nature of this site from 6+ years ago? I profoundly acknowledge that everyone else reading this is a better machinist than I am. There perhaps now we can remove egos from the equation.

My G4003 has upgraded ABEC 5 spindle bearings and has been somewhat "massaged"; it is not as sloppy as some might think. I am capable of indicating a bore to a few tenths (but I am slow). I am not in this for profit. I am in this for personal satisfaction. I have used both 00005 and.0001 test indicators and for me the former is simply easier to read although not as simple to use due to sensitivity and decreased net travel capability.

I do not recall ever suggesting that I could indicate a bore to .00005; the range rod does not run "true" to that tolerance nor am I capable of maintaining the temperature control necessary to achieve this. The bore certainly is not manufactured to this tolerance. Perhaps in time I will become enlightened as well, I simply come here to learn where I can. In the meantime I am only two beers into a freshly tapped keg of Sierra Nevada; I have all night to learn. There is always a better way, its called ingenuity. Now who has something worth learning???

 

[300sniper]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body">
Whatever happened to the friendly and helpful nature of this site from 6+ years ago? I profoundly acknowledge that everyone else reading this is a better machinist than I am. There perhaps now we can remove egos from the equation.</div></div>

what was not friendly and helpful in this thread?

 

[border_reiver]

Re: Test Indicators

It also depends on the limit of the indicator. If I chuck a barrel in a 6 jaw buck chuck, and it's normally out 3 thou and my indicator only spans 2 thou, well it's not going to be good for me or the indicator. How close you have to indicate is how close to zero you want to get, but I've used 2" travel plunger gages to get to the point I could use delicate indicator gages to dial in to where I need to be. Mileage may vary.

 

[Mark Housel]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">If I chuck a barrel in a 6 jaw buck chuck, and it's normally out 3 thou and my indicator only spans 2 thou, well it's not going to be good for me or the indicator.</div></div>

This is somewhat of an aside.

I recently purchased a Set-Tru type of Buck Chuck but have not received the adapter yet so it's not installed.

Once adjusted to run true at a particular diameter, what sort of repeatability can I expect?

Any idea what the range of diameter is that it will still be true?

Thanks,
Mark

 

[LRI]

Re: Test Indicators

Mark the chuck will likely repeat very well.

However you have to factor that not all barrel holes are in the center of the barrel.

I had one today that was close to .01 out on the OD compared to a zero TIR in the bore.

This is where the adjustable chuck really helps.

The Buck stuff is really nice. If I may offer a suggestion:
Ditch the factory jaws and get some blanks from MSC. Bore the centers to the common nominal sizes of cylinders you work with and use them to captivate your barrels like a collet does instead of 3 lines of contact.

You may be surprised how much difference it can make.

Good luck and great thread.

C

 

[lvcatfish]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body">
Whatever happened to the friendly and helpful nature of this site from 6+ years ago? I profoundly acknowledge that everyone else reading this is a better machinist than I am. There perhaps now we can remove egos from the equation.</div></div>

what was not friendly and helpful in this thread? </div></div>


Sorry, I usually do not post until after my third beer and the second was actually a little foamy. I perceive condescension in two of your posts and absolute condescension in Clark's post. I can not accept that there is only one way to accomplish something; I've been around the block too many times to accept this way of thinking. There is no wrong way to build a rifle as long as it is safe and shoots well.

If that was not the intention ( or even if it was) then I will learn to get over it.

 

[lvcatfish]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">
The Buck stuff is really nice. If I may offer a suggestion:
Ditch the factory jaws and get some blanks from MSC. Bore the centers to the common nominal sizes of cylinders you work with and use them to captivate your barrels like a collet does instead of 3 lines of contact.

You may be surprised how much difference it can make.

Good luck and great thread.

C</div></div>

I have a buck chuck and have had someone else previously try and describe something similar. I am not certain I understand how this works. I can appreciate the benefits of having more contact between the work being held and the chuck/spindle. If the jaws are modified to create a "collet like" contact then how is the gimbal action between the chuck and outboard spider maintained? If the chuck side contact can not pivot then any adjustment to the outboard spider is probably bending the barrel rather than moving the bore closer into coaxial alignment with the spindle???

I am trying to understand what has been suggested and am not certain that I follow correctly.

 

[300sniper]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body">
Whatever happened to the friendly and helpful nature of this site from 6+ years ago? I profoundly acknowledge that everyone else reading this is a better machinist than I am. There perhaps now we can remove egos from the equation.</div></div>

what was not friendly and helpful in this thread? </div></div>


Sorry, I usually do not post until after my third beer and the second was actually a little foamy. I perceive condescension in two of your posts and absolute condescension in Clark's post. I can not accept that there is only one way to accomplish something; I've been around the block too many times to accept this way of thinking. There is no wrong way to build a rifle as long as it is safe and shoots well.

If that was not the intention ( or even if it was) then I will learn to get over it.
</div></div>

that was not my intention at all. i asked a few questions that i felt if answered by someone looking for a dti would help them decide what they really need and to make their own decision. i don't think i ever said anything was right or wrong or one model was better or worse than another. i feel people need to realistically look at their needs and not pick something simply because some anonymous person on the internet said they have that one.

 

[Mark Housel]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">Mark the chuck will likely repeat very well.

However you have to factor that not all barrel holes are in the center of the barrel.

I had one today that was close to .01 out on the OD compared to a zero TIR in the bore.

<span style="font-weight: bold">I've not had a barrel that far out at the chamber, but always they seem to be out somewhat at the muzzle.
</span>

This is where the adjustable chuck really helps.

<span style="font-weight: bold">I understand. This was one of the reasons that I decided to cough up this rather large (for me) chunk o' change for a lathe chuck. </span>

The Buck stuff is really nice. If I may offer a suggestion:
Ditch the factory jaws and get some blanks from MSC. Bore the centers to the common nominal sizes of cylinders you work with and use them to captivate your barrels like a collet does instead of 3 lines of contact.

You may be surprised how much difference it can make.
<span style="font-weight: bold">
Thanks, I hadn't thought of that. Sounds like it would make the barrel much more solidly held in the chuck and make repeatability that much better.</span>

Good luck and great thread.

C </div></div>
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">
I have a buck chuck and have had someone else previously try and describe something similar. I am not certain I understand how this works. I can appreciate the benefits of having more contact between the work being held and the chuck/spindle. If the jaws are modified to create a "collet like" contact then how is the gimbal action between the chuck and outboard spider maintained?

<span style="font-weight: bold">At school we've had this discussion a number of times. It doesn't allow the barrel to "gimbal", but of course neither does any support that has greater than 0 length.

Put even a 1/4" flat end of a bolt on a flat surface and hold it solidly against the surface and try to rock it. It won't easily.
Now imagine four of them holding a cylinder and trying to gimbal the barrel at that point.
This seems to show that a support collar with bolts, lathe chuck of any sort, etc. won't gimbal either without something giving.

We came to the conclusion that what could be used is something circular (or spherical) to provide a near zero length support that would allow the remainder of the barrel sticking through the head stock to be moved to align the bore.

The question really seems to be, how far down the bore from the chamber towards the muzzle needs to be directly in line with the spindle bore?
And, are you trying to hold the entire barrel rigidly with the muzzle end also in line or letting that part of the barrel do whatever it needs to and merely holding it there to keep it from flopping about.</span>

If the chuck side contact can not pivot then any adjustment to the outboard spider is probably bending the barrel rather than moving the bore closer into coaxial alignment with the spindle???
<span style="font-weight: bold">
This is exactly the case that was made. That any attempt to hold the barrel at the chuck and 'straighten' the muzzle to be in line with the chamber (unless the bore were already perfectly straight) would at least put bending forces on the barrel, if not permanently bend the barrel.

This was where we came up with the thought of making the holding contact at the chamber spherical or circular to reduce the contact length close to a point.

My thoughts were that so long as the bore is in line and centered to where the chamber and throat are, the remainder we can't do anything about anyway?
</span>

I am trying to understand what has been suggested and am not certain that I follow correctly.</div></div>

 

[LRI]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">
The Buck stuff is really nice. If I may offer a suggestion:
Ditch the factory jaws and get some blanks from MSC. Bore the centers to the common nominal sizes of cylinders you work with and use them to captivate your barrels like a collet does instead of 3 lines of contact.

You may be surprised how much difference it can make.

Good luck and great thread.

C</div></div>

I have a buck chuck and have had someone else previously try and describe something similar. I am not certain I understand how this works. I can appreciate the benefits of having more contact between the work being held and the chuck/spindle. If the jaws are modified to create a "collet like" contact then how is the gimbal action between the chuck and outboard spider maintained? <span style="font-style: italic">[<span style="font-size: 14pt">b]If the chuck side contact can not pivot then any adjustment to the outboard spider is probably bending the barrel rather than moving the bore closer into coaxial alignment with the spindle???
[/b]</span></span>
I am trying to understand what has been suggested and am not certain that I follow correctly. </div></div>



Ahhhh, the million dollar question.

Here's the 2 cent answer.

Why gimble, why allow a barrel (ecourage it actually) to flop around like a jump rope?

Lets perform a simple test.

Get a sheet of paper and draw a line in the shape of a large radius arc going from the right edge of the paper to the left with the center about 1/4" above the imaginary straight line.

This represents your barrel.

Now draw a straight line intersecting both end points about 1/8" above the arc's endpoints.

This represents your spindle bore.

Imagine this rotating around the spindle center. It's a jump rope. All the indicating in the world can't center a jump rope because the center point is constantly changing as you move up/down the length of the cylinder.

This is what I suspect inspired the idea of indicating where the bullet bites the lands initially.

BUT what about the ass end of the case? It's still very likely going to be non tangent to the bore. Meaning the case/bore are pointing in two different directions.

Literally what I'm getting at is if the cylinder of the barrel is turned reasonably parallel to the bore for the first few inches (about 2) then really who gives a darn where the muzzle is pointed? It's not like it'll magically stay that way after the barrel is chambered anyway. You can crank, tweak, indicate all you want. The moment you pop the thing out of the machine it does whatever the hell it wants to.

In my mind the potential sine error of the muzzle being "off" over a typical barrel length is so small its not worth the effort to chase after. I'm much more concerned with knowing that the breech end of the barrel is tangent AND concentric to the spindle bore center than anything else. The additional holding power of a collet/profiled chuck is icing on the cake as it delivers significantly more surface contact compared to the point/gimbled contact so often encouraged/stressed over in barrel fitting OZ.

<span style="font-style: italic"><span style="font-weight: bold">I've done it this way for 8+ years and it's not effed me yet.</span></span>


My shiny new set of Lyndex collets are for holding the OD of the muzzle inside the bore of the machine while I thread/chamber. I don't indicate anything on the muzzle side when chambering. If I could get the barrel to sit still well enough during these operations I wouldn't even use that, but they whip around at the RPM I run when turning/threading. This induces vibration and causes poor surface finish. So I use these to support the muzzle end to facilitate the speeds/feeds I use.

Yes, I know this defies a great many doctrines when it comes to the "sacred acts of barrel fitting". This wasn't just a shot in the dark and it's not something I started doing yesterday. I've discussed it extensively with formally educated ME's and I've done it enough now to know that it's just another way to skin the cat. The rifles shoot exceptionally and the thread fits/chamber accuracy are good enough that I'll lock horns with anyone that'll suggest it's a half ass way to do something. I use canned cycles for threading the barrel. I run a "roughing pass" to get the bulk of the material out of the way. Then it's a series of "squeaker" passes until the action runs up/down the cylinder like the thimble on a micrometer. I've had Nesika's to where once threaded, the ass end of the rear receiver bridge indicates to within .0005" from the bore center. That's on a Model M which is the longest receiver they make. Who says you cant center on a threaded joint? I don't buy it.

FWIW Glen Harris at Defiance witnessed this himself as he was my boss at the time.

Lots of ways to do stuff and so much of "gun land" is kept in this "fog of hysteria" by some who spend more time in front of a keyboard rather than making chips. One also has to understand that by and large the gunmaking process hasn't changed a bit in the last 60 years. When something becomes that entrenched it's difficult to initiate/inspire change.

Great thread and hope this helped explain a few things.

Bag of P corn in the oven as I'm sure red star clusters will be flying here before too long.

C.

 

[CS223]

Re: Test Indicators

I've been watching this thread and have a few thoughts to ponder. The obsession of dialing in the bore to Zero TIR at least for chambering purposes seems to be a bit over kill simply because of the use of a floating reamer holder along with a removable pilot reamer.

There has to be clearance between the pilot & the bore and the reamer & the bushing. 0.0002" is the typical clearance that I'm told PTG uses for bushing to bore clearance. I suspect something close to the same between the reamer & the bushing so lets say .0004" "slop" for the reamer. The floating holder certainly has the potential to push the reamer at an angle to the bore because of the running clearances. In addition, if you are using a range rod, it can "conceivably" be canted in the bore due to the bushing clearances. An exaggerated example would be to put a tapered drift punch in a bore.

Now, dialing in the bore to Zero TIR certainly is advantageous for machining & threading the tenon to keep the chamber & bore axis concentric with the receiver. There still has to be clearance for the threads. For further consideration, the tenon is normally about 1" long, at what point, angular error wise with respect to the muzzle, does the misalignment exceed the metal stretch? I suspect it has to be pretty significant, (more than a mil?), before contact with the receiver face is affected.

For final consideration is those smiths that dial in the neck position for zero TIR and ignore the rest. In my mind I see the rotating bore axis resembling an hourglass. I know for a fact that a long range champion uses this method for the rifles he builds & shoots himself.

In addition, I'm certain because I've seen it myself, that the machine flex/rigidity and vibration has an effect on the end result. It's one thing to turn the chuck by hand and dial in to Zero TIR using a .0001 or .00005 DTI but what happens when you turn on your motor? Does the belt vibration cause your DTI to jump? What about when you engage the chuck? If your DTI is jumping .005 due to flex & vibration and lack of machine rigidity, was it worth the extra hours effort to split the division on the .00005 DTI?

I'm not negating a smiths quest to be perfect for the personal pride of being perfect but at what point does is become an issue with ego & argument instead of practical reality? Like using a tenth reading micrometer for carpentry.

In the essence of full disclosure, I own three Interapid & B&S .0001 DTI's and two Tesa .00005 indicators and a host of other lower resolution DTI's & indicators. Not trying to start a pissing match, just informative conversation.

 

[LRI]

Re: Test Indicators

<span style="font-weight: bold">. . .seems to be a bit over kill simply because of the use of a floating reamer holder along with a removable pilot reamer. . .</span>


The next excellent point.

The only thing "floating" in my machine is the way oil in the coolant sump.

Properly fixtured, there's no reason to float any tool as it conflicts with machining 101 rule of tool/work rigidity.

Anyone use a floating drill chuck or endmill collet with any success?

 

[JimT]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Bag of P corn in the oven as I'm sure red star clusters will be flying here before too long.</div></div>

Ain't that the truth. I asked the machining instructor at the local college about some of this. It was interesting getting his perspective, as he has more years of experience than most of us on here have been alive. Regarding indicators and mag bases, he said mag bases haven't been around for a long time, and other methods were used to hold the indicators. He said as long as the holding device was rigid (Chad's rule 101) it didn't matter if it cost $5 or $500.

When it comes to most machining problems, he likes to say "You ain't making a watch." I like to add "for the space shuttle."

One thing I have noticed when it comes to gunsmithing, is that a lot of folks seem to think that their way is the ONLY way to do it, and if you don't do it that way, then you are a (pick your epithet). Methinks that if the gun shoots to a certain standard, then you must be doing something right.

 

[CS223]

Re: Test Indicators

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

One thing I have noticed when it comes to gunsmithing, is that a lot of folks seem to think that their way is the ONLY way to do it, and if you don't do it that way, then you are a (pick your epithet). Methinks that if the gun shoots to a certain standard, then you must be doing something right. </div></div>

Likewise (this is a generalization directed at no one) many people do things because "that's the way it's done" or "that's how so & so does it" with no concept of why it is done that way or if there is a better way or more efficient way. If you can't explain or don't know why it's done that way, then I find calling oneself a machinist or gunsmith, or a doctor etc. a bit narcissistic.

The epitome of a gunsmith or machinist or any skilled person is one who can teach his craft or at the very least explain it to an ordinary person such that they comprehend the reasoning behind a certain subject. If you understand the root of the concept, like mathematical relationships, you can build an amazingly precise building using string & barley corns, yet there are carpenters & framers with electronic levels & laser transits that can't hang a door plumb, or frame a wall square.

An old mentor of mine always said "Accuracy comes from the machine, precision comes from the machinist".

 

[LRI]

Re: Test Indicators

<span style="font-style: italic">Likewise (this is a generalization directed at no one) many people do things because "that's the way it's done" or "that's how so & so does it" with no concept of why it is done that way or if there is a better way or more efficient way. If you can't explain or don't know why it's done that way, then I find calling oneself a machinist or gunsmith, or a doctor etc. a bit narcissistic. </span>

Reaching for the banana

 

[border_reiver]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body"><span style="font-weight: bold">. . .seems to be a bit over kill simply because of the use of a floating reamer holder along with a removable pilot reamer. . .</span>


The next excellent point.

The only thing "floating" in my machine is the way oil in the coolant sump.

Properly fixtured, there's no reason to float any tool as it conflicts with machining 101 rule of tool/work rigidity.

Anyone use a floating drill chuck or endmill collet with any success?

</div></div>

Yes. Not by choice, and was hoping to prove that out, but I've got Rohm floaters running chamber reamers thru bores chucked in bored soft jaws. Had to play with the programming so the float wouldn't introduce chatter, and I may have OD runout of .003 but with the float even at the base of the case the chamber runs out max .0005" from bore axis. So far. Again, I was really hoping for worse results.

 

[Mark Housel]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body"><span style="font-style: italic">Likewise (this is a generalization directed at no one) many people do things because "that's the way it's done" or "that's how so & so does it" with no concept of why it is done that way or if there is a better way or more efficient way. If you can't explain or don't know why it's done that way, then I find calling oneself a machinist or gunsmith, or a doctor etc. a bit narcissistic. </span>

Reaching for the banana </div></div>
aaaaaaahahahahahahaHAHAHAHAAH!

Boy aint' that the truth!

 

[Clark]

Re: Test Indicators

One reason guys have been floating reamers is that any error between the ridged reamer center and the bore center results in double that error in chamber size at the rear.

And those Chinese tail stocks and ways did not fall out of heaven.

 

[lvcatfish]

Re: Test Indicators

OK, thanks for the replies. Had to work late today and am only into my first beer. At least this one isn't foamy. I am thinking about this and can appreciate that zero runout (or at least as close as possible) does not directly correlate to improved accuracy. There are setup tricks that I understand are important when dialing in on a gimbal. Radiused contact points help (but at the detriment of workholding rigidity). It also helps to adjust slowly and only methodically increase tension as you get to your finish point. Too much tension too early and I agree that you are probably not aligning things anymore so much as bending them.

I have also used the buck chuck for other chores. It is nice to crank down on something and then align it as a separate step. I still do not understand how to indicate the barrel onto center with this method. At this point I am not referring to .0000000anything. I am not certain where the reference for center is obtained. Two points on the range rod are not likely to agree. How would I adjust the buck chuck to center the barrel?

The guy I bought the lathe from used the buck chuck and then rough centered with an indicator in the grooves at the breach end. He would then use an endmill to pre-bore a hole that would be chased with a boring bar. He made this large enough to insert a long stem indicator to re-center off of the grooves near the throat. Then he would lightly clean up with the boring bar and proceed to ream. Aside from being a drawn out process I am not partial to the idea of starting the reamer in a pre-bored hole.

I am interested in exploring this method of using the buck chuck. I still do not comprehend how one centers the work when setting up this way. I think I need to chuck up a barrel tomorrow after work and play with this some. One of two things will happen, It will either come to me or I will gather my thoughts to ask better questions.

 

[CS223]

Re: Test Indicators

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body">How would I adjust the buck chuck to center the barrel?

<span style="font-weight: bold">Basically as you surmised here:</span>

The guy I bought the lathe from used the buck chuck and then rough centered with an indicator in the grooves at the breach end. He would then use an endmill to pre-bore a hole that would be chased with a boring bar. He made this large enough to insert a long stem indicator to re-center off of the grooves near the throat. Then he would lightly clean up with the boring bar and proceed to ream.
</div></div>

If the bore was perfectly parallel with barrel OD, it would simply be a matter of using the Set-Tru feature of the chuck to get the bore centered up. Assuming the jaws were concentric & chuck scroll was accurate. You can use a tool post grinder and a boring ring to grind the jaws for the barrel OD to improve your accuracy.

Another method would be to a split ring of sorts, copper, around the barrel, like what Bryant Customs describes. This would give enough, (perhaps too much), and allow the barrel to move instead of bend when adjusting the muzzle end.

What would work well, which I haven't experimented with yet, would be a pair of large self aligning flange bearings (ID close to the spindle ID) one mounted on a faceplate and the other at/on the spider. The bearings would be best if the seals had been popped out and the grease replaced with Acraglass. You'd have what is refereed to in the Ag world as "pig eyes" typically found on a 3 pt. tractor hitch. You would make bushings that allowed you to fit the barrel dia. in each end of the flange bearing bore. This would allow you move the barrel in any direction in the lathe spindle without imposing bending stress on the barrel. Once aligned, you would have to use something like a lathe dog to lock & prevent the bearings from moving in the flanges. Your Set-Tru chuck and spider/cat-head would work as normal when aligning the bore.


ETA: After a little more thought, a pair of spherical bearings would be ideal for this jig.

 

[lvcatfish]

Re: Test Indicators

I was just reaching for that brass ring and all I got my hands on was this damn banana!

I missed the banana reference last night. Now THAT is funny. Maybe I could get it bronzed and replace the operating handle on my QCTP???

Time now to experiment with alternate workholding techniques...

 

[dmg308]

Re: Test Indicators

Just had a Mitutoyo .0001 shit the bed today.