How can I make Go/ No Go gauges?

[ironhat]

tding got me thinking about headspace gauges - sorry tding, I don't have an answer for you. I have a machine lathe that I seldom use and that thread got me thinking about gauges. Why wouldn't that be a good 'learner' project for the lathe, given that the lengths are critical? When I see gauges for sale, though, I don't see sizes but only "go" and "no go". Is there a standard ' greater than' and a 'less than' from the base measurement length - heck, I don't even know what the base measurement would be. I'm thinking that since a non-rimmed cartridge headspaces on the shoulder the base measurement would be from the bottom of the shoulder to the heel. Can anyone clarify, please?

TIA

 

[MMCSRET]

I have used a factory cartridge to get me where I wanted to be, give it a try.

 

[ironhat]

This is more about the project of using the lathe. But, thanks for the post.

 

[BADUNAME27]

gauging.

Here's what your up against bud.

1. You'll need an accurate print of the cartridge. A great source for this is Pacific Tool and Gauge. David Kiff publishes a book that has prints for just about every cartridge in our galaxy.

2. You'll need to manufacture it. Since you have a lathe, your well on your way.

3. Metrology/inspection. You have to know the gauge is to print. The best way to do this is with a no contact inspection method. That requires an optical comparator and these aren't cheap. (check ebay once. . .) This is because of how the datum is figured at the shoulder.

Using a fired case or a new one has been done before and it's worked but you assume some risk. 99% of the time you'll be fine (especially if you are reloading) but there is a risk of inviting case head separations due to a gun being too deep in H/S. It's a zero to .006" tolerance so it's not super big.

Just be careful, measure twice, and cut once.

Better yet, spend the 29 bucks on a gauge that's made perfect. (That'd Be PTG again)

 

[ironhat]

Yes, Chad, it's not worth losing an eye and/or hand over. I was wondering how to establish the meaurement when the datum line is so ambiguous. It's not a very sharp demarcation on the cartridge, is it?! Thanks much for the input. BTW, your work is beautiful!

Later,
Chiz

 

[Jim Watson]

The modern datum line is a .375" diameter circle on the shoulder (for .30-06, etc.), there is no visible demarcation. The shoulder-body corner is typically cut clear away so as to not bear.

The old datum line for the .30-06 was the hypothetical intersection of shoulder and body, but the gauge was made to contact on the shoulder with an appropriate offset in the dimensions. Hatcher's Notebook has a drawing of the mil-spec headspace gauge and the gauge ring used to set the key dimension.

 

[ironhat]

What then establishes the datum line?

 

[BADUNAME27]

It's different on each case and its determined by the original design for that particular cartridge.

To my knowledge there isn't a "God said do it this way" kind of answer for this.

I may be wrong but I think its as simple as where I/you/we decide. If, for example, I were to dream up a new cartridge called the "338 pimple popper" and I establish the datum point .100" below the neck/shoulder junction I don't think SAAMI is going to send the Gestapo to my shop. All the same, there's nothing that prevents you from inventing the 338PP improved and using the middle of the shoulder as the datum line.

In practice all this stuff means almost nothing. If I have a reamer, a barrel, and a Go Gauge its all I need to fit a barrel. That's all I care about. I don't need to know any math beyond basic addition and subtraction to finish the job. People love to make this stuff waaaayyyyy toooooo complicated.

In ten years of doing this the only time I resort to comparing prints and/or doing fancy math is when I'm "bench racing" cartridges with a customer or making up a set of actual case forming dies used to manufacture brass.

Thanks for the kind remarks.


Chad

 

[fguffey]

ambiguous, nothing ambiguous about the DATUM LINE, if it is perceived as having another view, look at it one way it is a line, rotate it and it is a circle.


Hard hat, 'can not make head space gages' there are many that can not do it, they purchase, I make gages and tools to test the gages, comes in handy when I check (purchased at the range) once fired cases for case length (head of case to shoulder).

I have two + lathes, a mill, 2 in-line/butt/angle grinders, etc., and make gages in .000 thousands, in my opinion the go-gage is useless but it can be turned into a below/go-to infinity gage with little effort, I make gages that are .017 under a go-gage to .11 over in increments of .002 thousands. When reaming a chamber the short gages are ANOTHER WAY to keep up with 'where you are' articles I have read about 'how to ream a chamber' always include the line, 'check often because no one knows where they are when reaming a chamber'. I know where I am and how far I have to go in .000 thousands from .017 below a go-gage to 'spot-on' and it is possible to do the same with a go-gage, not easy to convince someone it is possible, not my job.

I do not use the tools mentioned above to make gages, I use a reloading press, shell holder, die and machinist feeler gage, the feeler gage allows me to make accurate adjustment in thousands (.000) instead of guesstimates like 1/4 turn 1/16 turn, 1/2 turn etc.. Long cases. from head of case to shoulder, are not available COMMERCIALLY, I purchase from a firing range produce them with an Eddystone M1917, it produces cases that are .011 over a go-gage, .016 over a standard length cartridge. In my opinion the difficult part is the concept, you have to have drawings? You have to read Hatcher?, etc., I shoot ammo, not gages.

F. Guffey

F. Guffey

 

[fguffey]

Hard Hat, I moved the above response from a draft file, I failed to add the last part.

I checked to see what area of the country you are in, too far to help. There are two terms that are not in the reloaders vocabulary, one is 'machinest feeler gage' the other is 'transfer' and they tend to repeat what they heard or read, all my life those that can not do it refer to the DATUM as a line without a dimention as in 'What does it look like if it is rotated'?

Sorry about that.

 

[ironhat]

Thanks, Guffy and you too, Chad. I appreciate the input!

Chiz
aka ironhat (the German meaning of my last name) although the wife says it's ironhead.

 

[dagger dog]

ironhat,

There is another gauge that is called a feild gauge it is used with the bolt assembled, the go and no go gauges have to be used with a stripped bolt so the extractor doesn't interfere with the "feel". If the rifle bolt closes on a feild gauge, it is absolutley out of headspace spec. Just on a thought you could take a cerrosafe casting of a good chamber and work from that.

Brownells has a full line in their catalog listings.

 

[fguffey]

the Eddystone M1917 I referred to in previous post has .016 head space, again that is .011 over a go-gage, .005 over a no-go gage and .002 over a field gage, the rifle is not unique but when someone puts all of their confidence in a go-gage they miss all of the 'must know' information, If it is important I want to know what will not-go. The go-gage will go in everything unless it is short chambered-or the wrong chamber.



Stripping the bolt, I have no clue how that got started, there is too much said about specifications of the chamber test gage, I did not say I did not have one, I said I do not find it necessary to use one, I do not want to know if IT will-go, I want to know by how much in .000 thousands because my press-es are adjustable (incline plane). I have one go-gage that requires the extractor to be removed, the gage does not have an extractor groove, it was designed to be used before the extractor was installed and served another purpose.



Again, in the perfect world there is one chamber and one cartridge, I do not live in that one, my Eddystone could be chambered to 308 Norma Mag, I have a Winchester P14 in 308 Norma Mag, I do not need another, I could chamber it to 30 Gibbs by moving the shoulder forward .187 thousands (.202 - head space of .015=.187) would give me .001 head space or I could continue to eliminate head space with a long cartridge, difference; the rifle has .115 case protrusion (unsupported) instead of .090, .115 case protrusion is .005 + or - one when compared to a Mauser, military cases web thickness is .200 + a few, commercial case web thickness is .260+, I suppose it could be said the commercial case is the safest because of the thick web, but again, the case body is thinner.



F. Guffey

 

[BADUNAME27]

Guff,

While that certainly works bud (and if it works for you then that is certainly all that matters) there is another way.

I only buy GO gauges and I buy them from one source, David Kiff, owner of PTG in Oregon.

I use a go gauge, a spool of .001" shim stock, and a pair of scissors.

I set up through the spindle bore, indicate both ends, get my numbers, fit the tennon, and then start cramming the reamer up the but of the barrel.

About 3/4 of the way I stop and screw the receiver onto the barrel with the bolt inserted and in battery. (all the guts of the bolt are removed so there is no kind of spring anything contacting the gauge) The Go gauge is in the chamber with its back end hanging out in space. The bolt face picks up the gauge and I can't screw it on anymore due to the gauge preventing the action going any further. Light, careful pressure is used so I don't accidentally put inclusions on the gauge's qualified surfaces.

I take a pair of calipers and get a measurement between the barrel shoulder and the receiver ring. I then factor in the thickness of the recoil lug (where applicable)

That is my new zero point and from there I clear out the Z axis on the DRO and go back to my deep hole drill cycle on the CNC. I realize calipers aren't the most accurate way to do this, I could stack up gauge blocks and get it to the tolerance of a nats pubic hair but I don't really need to cause that wouldn't be accurate eitehr due to barrel crush when pulling things up tight on final assy.

I'll always end up short because the barrel is going to suck up another .002-.004 when I put it on for good and I actually want this. it's a built in safety buffer to keep me from going too deep. (A REAL pain in the arse if you take the time to clock flutes on a fluted barrels)

Once I'm there I take a piece of .001 shim stock trimmed down to fit inside the bolt face. The bolt closes on a GO and sticks open on a GO + .001". This is my HS dimension. I call it GO plus one.

That gauge then stays with the rifle for life. If the customer has an oops and double charges a case at the reloading bench, they can quickly/easily determine if the lugs were damaged without having to ship the thing. Since all my guns are built on Nesika actions I have little fear of them breaking a bolt handle to get the buggered case out. The bolts are 100% billet free of welds and solder.

In 10 years of doing it this way it's never failed, never produced an inaccurate rifle, and never given me cause to go searching for another way to do it. Over a 1000 guns have been chambered this way ranging from $3500 dollar varmint rigs to presentation rifles valued over $20,000.

Obviously we all have our pet ways and it comes down to what makes the belly warm and fuzzy. Not trying to change minds, just passing info someone might find helpful.

Cheers and all the best.

Chad

 

[fguffey]

Above all things I want to thank you for taking the time, there is a small circle of us (three) that understand the 'philosophy of philosophy', that is nothing more than understanding a persons philosophy is 'what one thinks', this gives us the luxury of disagreeing, and we are allowed to ask 'why'?

One (of the other 2),my resources person does not use gages, I do not disagree with him, I understand what he is doing and why. He chooses to go on the (-) minus side of a go-gage .003, .002 over a standard cartridge, meaning a go-gage will not chamber in one of his rifles. I have an in-line/butt and angle grinder that would allow me to grind a gage to any length, this would not be an advantage to him or me, the gages would be nice to have but neither of us would use the gage.

Shim stock, good stuff, I purchase machinist feeler gages, that is like purchasing an assortment of shim stock in a bundle with no duplications.

F. Guffey