measuring wall thickness

[Ranger007]

Does anyone know if K&M can modify a digital mic or can someone recommend good a digital mic that closely resembles K&M’s concept?
If there is a thread on this by all means please point me in the right direction.

Mitutoyo Wall Thickness Micrometer with 60 Degree Modification

The Mitutoyo Wall Thickness Micrometer measures wall thickness of tubes, cartridges & cylinders. Our 60 degree modification allows you to take better measurements.

kmshooting.com

 

[Patriot007]

It takes years of practice and the correct hold as to not heat up the mic. The speed at which you close the anvil even matters. Best way to learn is to get a good standard like a certified .250/.500 gage block and practice. In the meantime you can get an indicating mic and let it close itself to maybe get a more consistent reading. Another method would be to seat a bullet and measure the outside with your calipers. As long as youre using a good turning tool thatll be just fine, theres no need to measure to the tenths all you need is enough clearance. A weighted mic stand will help if you still want to use a mic. If you hold it by hand this is the most consistent hold pictured hereView attachment 1228433

You holed that Like a real Pro. My FIL/Mentor 86yrs young still spins that mic around in his hands like a young man. Me I'm 56, and I have to cheat. I call this the easy way of holding it. LOL
I bought this From K&M, It has their 60* beveled modification.

 

[Dusty Stevens]

Does anyone know if K&M can modify a digital mic or can someone recommend good a digital mic that closely resembles K&M’s concept?
If there is a thread on this by all means please point me in the right direction.

Mitutoyo Wall Thickness Micrometer with 60 Degree Modification

The Mitutoyo Wall Thickness Micrometer measures wall thickness of tubes, cartridges & cylinders. Our 60 degree modification allows you to take better measurements.

kmshooting.com

Ask hollands gunsmithing. They sell a very nice one- maybe they can get you a digital

 

[Ccrider]

Whether you turn down a spindle or not, you still need a ball anvil for neck measure -because necks taper in thickness. The spindle area only serves to push the neck against the ball.
For those with neck mics, their anvils are adjustable and contact with spindle can be set to sneak right into solid donut measurements, without modifying spindles.
View attachment 1228778
Also, since necks are tapered in thickness, to obtain radial thickness variance you need a case mouth stop to set the contact datum.
View attachment 1228779

Nice. Can you by that stop separately?

 

[mikecr]

Nice. Can you by that stop separately?

No, but you can probably make one with hand tools & garage scrap. That's what I did.
Made them for the K&M, Starrett, and Sinclair.

 

[Patriot007]

No, but you can probably make one with hand tools & garage scrap. That's what I did.
Made them for the K&M, Starrett, and Sinclair.
View attachment 1229305
View attachment 1229306

With the Mic from K&M you are able to measure right into the doughnut area of the case neck.. " Where the case neck meets the shoulder. I am fully invested in the K&M neck turning equipment, for all my rifles that I shoot. By the end of 2021 I hope to have an IDOD neck turner sitting in my reloading room, and I will sell the K&M neck turning tools,,, They ain't cheap, and their all carbide. I have the inside cutters also for removing the doughnuts,,, but If you are not very careful with this tool you can easily screw up a bunch of cases real quick. I prefer not to do that.
Your post on your gauge block for the mics has inspired me to come up with something for my mic. I'm in a habit of taking three readings down the case neck and 4 points around the case neck to check for variations, and Yes,, I'm OCD in my methods,,, LOL So thank you for posting the pics.

 

[Ccrider]

No, but you can probably make one with hand tools & garage scrap. That's what I did.
Made them for the K&M, Starrett, and Sinclair.
View attachment 1229305
View attachment 1229306

You guys that have machining talents put a lot of pressure on the rest of us.

 

[rwj]

I’ve found these to be useful when measuring wall thickness...

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

[Straightshooter1]

You guys that have machining talents put a lot of pressure on the rest of us.

You don't need machining talent . . . just a little talent to do a little MacGyvering.

 

[nilebartram]

one more question, if my chamber is .226, should my neck bushing be .201?

 

[Dusty Stevens]

one more question, if my chamber is .226, should my neck bushing be .201?

If your neck measures .203 or so over a loaded round. Awful thin there you sure that number is right?

 

[muleystalker]

I switched from Corn Huskers to Jerkins

Burts Bee's hand salve.

 

[nilebartram]

neck measures .226, so what size would be the neck bushing?

 

[Brians356]

Make sure you are measuring on same line (distance from shoulder) with all mics.
neck wall can vary from mouth to shoulder.

Unturned necks will vary from mouth to shoulder, as case walls taper continuously, from base to case. If necks are unturned, it's critical to add a stop for the case mouth to a ball mic, to assure measuring the same distance from the case mouth every time. This is a good idea even for turned necks, to maximize consistency.

Here's mine:

which neck wall thickness measuring tool?

I think here is a possible resource. www.semiconsoft.com Measurement instruments with deep detail...

forum.accurateshooter.com

-

 

[Dusty Stevens]

neck measures .226, so what size would be the neck bushing?

If you seat a bullet and the total outside diameter of the neck over the bullet measures .226 id try a .224 and .223 bushing

 

[Uncle Ed]

Keep it simple, one twist of the wrist tells you the thickness variations

 

[mikecr]

No, you need a ball anvil -NOT a pin on the inside of necks.
Put a ball anvil and case stop on that Redding and your readings can be as good as with a neck mic, and faster.

 

[Brians356]

Keep it simple, one twist of the wrist tells you the thickness variations

I'd just twirl between thumb and forefinger.
-

 

[Uncle Ed]

No, you need a ball anvil -NOT a pin on the inside of necks.
Put a ball anvil and case stop on that Redding and your readings can be as good as with a neck mic, and faster.

Do neck turning tools use a ball anvil or a mandril?

The Redding gauge photo I posted tells you the neck thickness and its uniformity. You then turn the neck with a mandril and not a ball.

The OP is getting three different readings with three different ball mics. And if he had the Redding gauge he would be getting one reading.

On top of this Redding tells us below you can't make a silk purse from a sow's ear.

Tech Line & Tips (FAQs)​

https://www.redding-reloading.com/tech-line-a-tips-faqs/146-concentricity-problems

Concentricity Problems​

a.k.a Neck Runout With Bottleneck Cases

We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

 

[Dusty Stevens]

The OP is getting three different readings with three different ball mics. And if he had the Redding gauge he would be getting one reading.

Hey if he only had one mic he would only get one reading too