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Gunsmithing Different ways to indicate and thread/chamber a barrel

McLarenross

McLarenross

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Minuteman
Nov 20, 2009
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Jacksonville NC
www.diamondxcustom.com
OK. So Im getting ready to start doing my own barrels and Im deciding how I want to indicate the bore in. My lathe has a 1.4" bore and front and rear spiders and I have a steady with 37" between centers so all options are open to me. From what i can find there are typically 4-5 ways of doing indicating the bore in.

1. Range Rod - PTG made precision rod that is inserted into the bore and indicated to less that 0.0001" runout with dial test indicators. Designed to be used for fresh blanks. People knock this method for inaccuracy as the rod may or may not give a true reading off the bore. Rods cost about $37 per caliber plus the cost of bushing sets.

2. Indicator Rod - PTG made precision rod that is inserted into the bore and indicated to less that 0.0001" runout with dial test indicators. Designed to be used for already chambered blanks. People knock this method as well for inaccuracy as the rod may or may not give a true reading off the bore. Rods cost about $37 for a caliber specific rod plus the cost of bushing sets.

3. Grizzly Range Rod - PTG made precision rod that is longer than the others and is supported between the bore and the tailstock and indicated to less that 0.0001" runout with dial test indicators. Can be used for fresh blanks or already chambered ones. Im not exactly sure what the purpose of holding the other end of this rod in the tail stock is. That doesnt seem like it would be conducive to precision. These rods are $37 for a rod that covers a small range of bores but you still need a set of bushings for the specific bore you are doing. Again may or may not be accurate.

4. DTI directly in the bore - Using a long stem 0.0001" dial test indicator directly inside the bore to indicate off of the lands or grooves to 0.0001" runout. Im not sure how well I am gonna do at this cause of the interrupted measurements caused by the lands/grooves.

5. Between centers with steady rest - Simplest method for truing the OD versus the ID and cutting concentric threads(given good tail stock alignment and a precise live center) but when you go to chamber you must support the right end with the steady and this causes problems for some people, not a big deal for me though as I have a good deal of experiance indicating in a steady. Still must use one of the aforementioned methods to indicate precisely though.

Now all thee methods require a good DTI but the range rods, indicator rods, or Grizzly rods can add up but the bushings are the really expensive part. So my question is for the gunsmiths on here, professional or not, what is your preferred method for indication and whats are your thoughts on the different methods.
 
I'm certainly not a professional and probably less experienced than you, but I just bought a Brown and Sharpe 0.0001 DTI with a 2.75 inch stylus and plan to use that for now. I'm not sure why you would want to stack tolerances with rods if you can measure directly with a DTI. Of course, with the longer stylus, your reading loses some accuracy, but my gut tells me that it'll still be more accurate than having a rod flopping around in the bore and/or tailstock. I know a B&S isn't as good as say an Interapid, but so far with my test take-off barrels (I'm a long way from trying this on a real barrel) it is not hard to get it dialed-in despite the land/grove transitions.

I hope some real pros will chime in on this as I'm very interested too.
 
Like Dave Tooley told me. With a Brown & Sharpe 312b-15(long stem) you can indicate all barrels. With a little practice you will be surprised how easy it is.

I believe mine is a .0005. There is plenty of room between the hash marks to extrapolate to .0001-.0002. Now machining to those numbers is a different problem.

R
 
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Rthur said:
Like Dave Tooley told me. With a Brown & Sharpe 312b-15(long stem) you can indicate all barrels. With a little practice you will be surprised how easy it is.

I believe mine is a .0005. There is plenty of room between the hash marks to extrapolate to .0001-.0002. Now machining to those numbers is a different problem.

R
Click to expand...

A 312b-15 is an Interapid indicator (w/2.75" stylus and .0005" divisions). I'm pretty sure you meant Interapid and not Brown and Sharp.
 
#4, cheapest, easiest, best

I started out on indicator rods until I soon noticed how every time you took it out and replaced it the reading was different, meaning you have no idea when it is actually accurate.

You will still need a lot of bushings though for chambering work, and I still use the rods to measure bore runout at the muzzle when the chamber is dialed in to clock the the 12:00 position.
 
I have always used a hardened gage pin in the bore ID and indicate off of it. I had a nice set of gage pins so getting a nice fit to the bore was easy.
 
I'd been at it long enough to use several different methods of dialing in a blank for chambering, cutting the tenon, and threading before buying the DVD of Gordy Gritters doing a barrel. What he was doing made perfect sense to me, and offered several improvements over the most recent method I'd been using. Called up the gals at PTG and ordered a set of three Gordy rods (they use the same pilot bushings that your live-pilot reamers use), and was set to go. Have been chambering my own barrels as well as all customers barrels using this method since I visited with Gordy & Shiraz at SHOT 2009.

Then along comes Nathan at Straight Shot Gunsmithing with his Tru Bore Alignment System, which I see as a further improvement in workholding. I bought one of his systems & the indicator rods, and am slowly becoming more proficient at dialing barrels & actions in using this new system.

Bottom line - there's way more than one way to skin a cat - find a method that works for you on your specific machine, and go with it. I liked Gordy's train of thought because it allows you to get that portion of the barrel's bore where the chamber's going to be cut running dead-nuts true with the spindle's axis. Nate's chucking system just takes Gordy's alignment method to the next level.
 
Flatland1, Ive watched the Gordy Gritters method videos and I just cant wrap my head around the right end of the rod being held in the tailstock and people hanging a plumb bob off the rod to get consistent measurements. Can you give me your input on this as you use this method?

To me the cheapest method requiring the least amount of additional tooling is measuring with a DTI 2.75 up in the bore but Im worried about how had it will be to indicate with the lands/grooves going around. Yall say its easy, so I may just be mind f***ing myself. It is probably like indicating a 4-jaw for the first time, intimidating before you do it, but pretty easy once you try it.
 
Indicating directly from the bore is surprisingly easy. When first attempting this, I thought that it'd be tough to do with the indicator jumping over the lands and into the grooves, but it's not a problem at all.
 
I'd been using range rods, but have since switched to #4. Couldn't be happier. As far as the interrupted feedback on the dial, I have trouble with that when its way out. My solution to that was to put a tight fitting bushing where I wanted to be indicating. Indicate off the ID of the bushing . Once indicated, remove bushing, check with the stylus directly on the bore, and make any adjustments if needed.
 
McLarenross said:
Flatland1, Ive watched the Gordy Gritters method videos and I just cant wrap my head around the right end of the rod being held in the tailstock and people hanging a plumb bob off the rod to get consistent measurements. Can you give me your input on this as you use this method?

To me the cheapest method requiring the least amount of additional tooling is measuring with a DTI 2.75 up in the bore but Im worried about how had it will be to indicate with the lands/grooves going around. Yall say its easy, so I may just be mind f***ing myself. It is probably like indicating a 4-jaw for the first time, intimidating before you do it, but pretty easy once you try it.
Click to expand...


It's very consistent if you know what your doing.


Precision gravity costs nothing.
 
I put an in between size pin gauge in the breech end as a spud and test close and far from the breech to get the bore parallel with the spindle. I use a gimbal made of thick Copper wire in the 4 jaw, and a 4 jaw spider on the left side of the lathe.
I dial in with a .0001" Intrepid test indicator.

But all this does almost nothing for accuracy.
Sorry, concentricity in chambers is not as important as concentricity of ammo. [ammo eccentricity enters the bores with random rotational orientation, but the chamber's eccentricity stays the same.]
Don't tell old gunsmiths, that have been dialing in barrels for a lifetime.
 
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7mmRM said:
I'd been using range rods, but have since switched to #4. Couldn't be happier. As far as the interrupted feedback on the dial, I have trouble with that when its way out. My solution to that was to put a tight fitting bushing where I wanted to be indicating. Indicate off the ID of the bushing . Once indicated, remove bushing, check with the stylus directly on the bore, and make any adjustments if needed.
Click to expand...

To keep it from being way out, stick your live center in the bore when you are clamping the 4 jaw on, this will guarantee you start out at least close.

Galaxy S3 on tapatalk
 
I have been dialing in with range rods for years.
Recently, I made up a set of rods that are like the grizzly range rods, but my rods retain the pilot from rotating so that i don't introduce any pilot wall thickness runout into the equation.
I hang a plumb bob and use an interapid tenths indicator.
I like that i can slide the pilot right into where the jack screws on my front spider are.
Then I dial that in as close as I can get it and move to the end of the barrel.
Then I use the outboard spider to dial that in.
I go back and re-check the inboard spider runout and then touch-up the outboard again if I had to fine-tweak the inboard.

I am really likeing this method the last couple months I have been using it.
It is certainly faster than fighting the range rod where your outboard jack screws completely change your inboard dial-in as you go back and forth trying to get the range rod running true at the barrel face and at the end of the range rod.
 
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2156, question for you.

Have you tried dialing a barrel in as perfect as you can, pull the rod out, rotate the spindle, re insert the rod, and check it?

This was what got me away from the rods, every time I would do that the reading would never be what it was before taking it out. This is a nightmare if you want to check your setup after threading and before chambering.

With a long reach indicator it's repeatable no matter how many times I take the indicator off and re test.

Not doubting that indicator rod indicated barrels shoot the same as non, just my .02

Galaxy S3 on tapatalk
 
jonaddis84 said:
2156, question for you.

Have you tried dialing a barrel in as perfect as you can, pull the rod out, rotate the spindle, re insert the rod, and check it?
Click to expand...

Yes, many times.
They are uually within 2-3 tenths.
Realistically, there is probably nothing gained beyond a 5 tenths dial-in so it would not matter if you removed and re-installed the rod.
Most of the guys with long reach indicators are only able to dial in to 5 tenths.
 
2156SMK said:
Yes, many times.
They are uually within 2-3 tenths.
Realistically, there is probably nothing gained beyond a 5 tenths dial-in so it would not matter if you removed and re-installed the rod.
Most of the guys with long reach indicators are only able to dial in to 5 tenths.
Click to expand...
I think that most that use a long reach indicator would disagree with your statement. I have no problem indicating to 1 or 2 tenths.
 
I think he was alluding to the fact that the geometry of the longer stylus necessarily reduces the accuracy at the gauge.
 
I am a previous rod and bushing user. When faced with a backorder on another rod and bushing set for a new caliber chamber I purchased a long stem indicator and am now a #4 method convert.

To me there is no issue reading between lands and grooves, I simply re-zero my dial and can get the indicator pretty close within a few minutes. Works just as well on crowns.

Using a tool holder for the long stem indicator in my Aloris to get inline with the bore saved a lot of headache versus a magnetic mount. Works just as nice on doing the crown work.
 
No one touched method #5 but I have a friend who builds rifles by truing the outside of the barrel and indicating off of that. All his rifles including my competition rifle shoot sub 1/4" groups. I didn't know until after my rifle was built it was indicated that way. I would not have believed it would work that well but I guess you can't argue with success.
 
I've had enough .284 reamers made/modified that I've got an assortment of ground .284x pilots. I use the tightest fitting pilot and a DIY range rod setup and plumb bob. A tight slip-fit on a piece of drill rod cut on a precise Hardinge in a single setup using ground pilots works pretty well. I also use a ±.0001 interapid test indicator with long stylus for verification. I'm just a hobbyist though.

http://i42.tinypic.com/14mfjeo.jpg
 
Turbobo said:
Using a tool holder for the long stem indicator in my Aloris to get inline with the bore saved a lot of headache versus a magnetic mount. Works just as nice on doing the crown work.
Click to expand...

This is key. I have mine setup the same way, the only thing you need to adjust is the stem height for differing calibers. Makes its super easy to set up and be able to re check throughout easily.
 
2156SMK said:
Realistically, there is probably nothing gained beyond a 5 tenths dial-in so it would not matter if you removed and re-installed the rod.
Most of the guys with long reach indicators are only able to dial in to 5 tenths.
Click to expand...

You can do a lot with a .0005 resolution large face indicator. If it isn't moving you are close man. I almost always used a half to get close and the tenth to verify in the precision grinding days. The half indicator rarely lied. Interapid are good pieces.....as are Bestest

ll of my mic's read tenths, but I can tell you the measurement withing a tenth accuracy without rolling it over to line up the marks.
 
I have poor vision. So reading in between Graduations is pretty difficult for me. Does anyone make a long reach DTI that reads in 0.0001's. i'v been looking but not having any luck. Any input would be helpful.
Thanks
Donald
 
Twisted300Win MAG said:
I have poor vision. So reading in between Graduations is pretty difficult for me. Does anyone make a long reach DTI that reads in 0.0001's. i'v been looking but not having any luck. Any input would be helpful.
Thanks
Donald
Click to expand...

As far as I've been able to ascertain, only the Interapid M1.7x0.35 threaded stems run longer than 1.5 inches. The longest I've been able to find is 2.75 inches, but remember, as you increase length, you lose accuracy. The side-splitter theorem of similar triangles (with the fulcrum of the DTI as one point and the line swept by the tip of the stylus forming the other two points of a triangle) says that as the length of the stylus increases, the distance measured by the tip decreases by a proportional amount. So, if your DTI is designed to read in 0.0001 inch increments with a 0.5 inch stylus, it will only read in 0.00055 increments with a 2.75 inch stylus (0.0001 * 2.75/0.5 = 0.00055 ).
 
Gene Poole said:
As far as I've been able to ascertain, only the Interapid M1.7x0.35 threaded stems run longer than 1.5 inches. The longest I've been able to find is 2.75 inches, but remember, as you increase length, you lose accuracy. The side-splitter theorem of similar triangles (with the fulcrum of the DTI as one point and the line swept by the tip of the stylus forming the other two points of a triangle) says that as the length of the stylus increases, the distance measured by the tip decreases by a proportional amount. So, if your DTI is designed to read in 0.0001 inch increments with a 0.5 inch stylus, it will only read in 0.00055 increments with a 2.75 inch stylus (0.0001 * 2.75/0.5 = 0.00055 ).
Click to expand...

I figured that out when i started looking at dial test indicators. Still though, on the ID of a bore your looking for as little movement of the needle as possible, not necessarily an actual measurement so that 0.00055" accuracy should be a non-issue if the needle isnt moving right?
 
Yes I realize the added length may affect the actual measurement. I'm looking more to compare method, range rod vs Dti method. I'm waiting on an order from PTG so I can chamber my first barrel. I want to try the range rods and check with the indicator. I
 
Yes I realize the added length may affect the actual measurement. I'm looking more to compare method, range rod vs Dti method. I'm waiting on an order from PTG so I can chamber my first barrel. I want to try the range rods and check with the indicator. I have a few scrap barrels to play around with.
Thanks
Donald
 
Here is the indicator I use for dialing in barrels, since we are only judging "wiggle" and not actually measuring, metric indicators work great (2µm = 0.00007"). I have extended the point on this indicator to measure directory off the grooves in the barrel.

DSC_0663_zps37bf4c2d.jpg


Tac drivers can be built with any of the 4 methods above, and there is actually a 5th method you can add as well that Chad originally posted a few years ago. It is similar to shoving an indicator in the barrel to jump the lands and grooves. This method uses a length of drill rod with balls on the end (I ground flats and soldered mine) held in the tail stock with a plumb bob to keep it stationary. This allows you to use a regular DTI without extending the point. Of course, this picture was just the setup to show an "exploded view", the closer in you get everything, the better precision you will end up with.

IndicatorSetup.jpg
 
wtopace

I like your lathe. It looks like mine - chips all over the place. I guess you and I actually do some work.
 
Im doing 308 M40A1 schnider barrel tomorrow and I will indicate from the bore like #4 for threading and chambering and on the outside for runout and index the barrel with max runout at 12 or 6 o'clock so it lays straght in the barrel channel ill try and get some pics this is my first new barrel I've just been playing around with used takeoff barrels until now and making my own reamers
 
boltstop101 said:
Im doing 308 M40A1 schnider barrel tomorrow and I will indicate from the bore like #4 for threading and chambering and on the outside for runout and index the barrel with max runout at 12 or 6 o'clock so it lays straght in the barrel channel ill try and get some pics this is my first new barrel I've just been playing around with used takeoff barrels until now and making my own reamers
Click to expand...

Interesting. Excuse my ignorance, but I've never heard of making reamers, but I guess it makes sense. How is this done?
 
Both Brown & Sharpe and Interapid are made by Tesa as well as a few others and I've seen them with either name...cant speak to th part number though.
 
I have indicated and chambered barrels in before using an outboard spider and the tapered rod with bushing. I understand that process. When using just a long stylus indicator and indication at the throat what do you use to support the muzzle end of the barrel? Outboard spider with the OD of the barrel centered?

Thanks
 
skog said:
I have indicated and chambered barrels in before using an outboard spider and the tapered rod with bushing. I understand that process. When using just a long stylus indicator and indication at the throat what do you use to support the muzzle end of the barrel? Outboard spider with the OD of the barrel centered?

Thanks
Click to expand...

You do everything exactly the same as when using a rod, just without the rod. You are basically moving the two contact points you get from the rod to the inside of the bore, thus removing any tolerance stacking from the bore to the rod and the rod to the indicator.
 
2156SMK said:
Most of the guys with long reach indicators are only able to dial in to 5 tenths.
Click to expand...

There is a lot if space between the graduations on the large face long reach interapid. If the needle isn't wiggling, you are better than half a thousandth.



And to stay on topic, I start out with a grizzly rod then double check the throat with the long reach interapid.
 
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Jonaddis I have seen the mitutoyo used like that and with a short bore made to accommodate the body to reach into the throat area. While list price on the interapid 312b15 may be 275 you can buy them from ebay for 175ish new.

R
 
Yeah when I chamber I dial it in, then drill a .400 or so by 1.2" (except on shorter cartridges) so I can reach into the throat with it, then dial in perfect, then single point bore a few thou off to make the prebore concentric, then rock and roll.

The pic above was just for a chop and crown job.
 
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