Headspace in Lathe - Depth Mic, Dial Indicator, Or??

[INTJ]

I have a job where I am chambering several barrels for a barrel nut application. I have a spec to hit with go gauge protrusion from the barrel, and the tenon is flat. I used a depth mic on the first one but it's a clunky way to measure headspace. And yes, I put two wraps of Scotch Tape on the headspace gauge to take out the wiggle when it's in the chamber.

I was thinking a dial indicator on the carriage might be a better solution. Just zero the indicator on the flat of the breech and then move the carriage over and check go gauge protrusion.

How do you guys do it?

 

[WSnyder]

If you need a quick and dirty just make yourself a ring from a barrel drop. Make it 1" exactly so the math is easy. I made one for a completely different job and it works perfect for this. Mine is 1.125" OD .625 ID and 1" L finished on the surface grinder to exactly 1". Gives you a stable flat surface to put your mic on. If you plan on doing many of these I'd make a tool like stated above with a fixed indicator or mic head.

 

[DaveTooley]

I have a gage I made for a different job. It's for measuring the distance from a threaded muzzle to a tapered section. I drop it over HS on barrels that don't have a shoulder. Look around you probably have something that will work. Hell a 3/4" socket will do it.

 

[Will Henry]

I've been using a depth mike on the gauge to the face of the barrel for about fifty years. I'm satisfied with it. WH

 

[urbanrifleman]

Dro.

 

[LVLAaron]

reamer stop?

 

[Machinist John]

I use this setup to check bolt float with receiver hand tight on barrel. One of the measurements I put on the data sheet as we discussed earlier. Then to the barrel vise, torque down, and check again to see if my .002 crush calculation comes out right. No gauge in the chamber, here I am checking the bolt nose/lug clearance against the end of the barrel.

I do a similar operation with the gauge in place. I also check with a new unfired case. In most instances the go gauge is too long, so it actually is a no go gauge.

A similar setup would work with your headspace gauge as you described.

Things change with big bore cartridges. That 458 Lott or 500 Jeffery needs a lot of room, if the hunter runs out of ammo he may wind up using cartridges found under the seat of the Land Rover. Who knows what make of cartridge and how big the case is.


I have a dial indicator holder that is machined to fit the end of the barrel, zero the indicator, push the holder against the end of the barrel, and the indicator shows how much the gauge is protruding. I will take a photo today and post.

I have several depth mikes, the easiest to use is one with a flat blade instead of round. One of the depth mikes has a short foot, it also works great. Again, I will take a few photos.

With over 50 years of using all types of micrometers, especially the depth mikes, I have my fingers trained to hold the darn things for proper measurements. Two fingers of the left hand pulling the foot back, the right hand turning the thimble. "Egg Shell" touch on the thimble!!! Lightly turn in the thimble and you will feel a solid stop at contact. Forget the little ratchet stem, after a time your finger sensitivity will increase.

 

[INTJ]

Dro.

I like it--use the built in digital micrometer.....

 

[INTJ]

reamer stop?

I like to direct measure when I don't have an action to test for.

 

[INTJ]

Two fingers of the left hand pulling the foot back, the right hand turning the thimble. "Egg Shell" touch on the thimble!!! Lightly turn in the thimble and you will feel a solid stop at contact. Forget the little ratchet stem, after a time your finger sensitivity will increase.

@Machinist John. Well that's how I did it on the first barrel. Flat tipped depth mic held and ray he's ignored.

The sad thing is none of this matter with a barrel nut setup, but the spec gives me a .001" tolerance to hit.

 

[LVLAaron]

I like to direct measure when I don't have an action to test for.

Make a ring

 

[WSnyder]

reamer stop?

View attachment 1378208
Make a ring

There you go! Another tool that’s already in the drawer. Lambeth 1” reamer stop body.

 

[INTJ]

View attachment 1378208
Make a ring

Guess I could make a long ring. Not excited about making internal M27x1.5 threads though.......

Here is what they look like after threading. Class 6G fit, which is a bit of a pain, especially since I can't disengage the half nut.

 

[LVLAaron]

The ring only needs to sit on the breech end and have a hole big enough for your gauge to fit through. Think "thick washer"

 

[WSnyder]

The ring only needs to sit on the breech end and have a hole big enough for your gauge to fit through. Think "thick washer"

Exactly. Something like the reamer stop body or as Tooley suggested, a socket is what you’re after. You could make a body that slip fits over the threads and stops against the face of the barrel to help hold it in place but all you really need is a ring as previously described by several.

 

[AccelR8]

Simple holder machined from bar stock. Drilled through same size as dial indicator which is held by a set screw. Bottom portion drilled larger to allow clearance for headspace gauge protrusion. Stand it up on a surface and zero the indicator. Hold it against the face of the barrel and it'll indicate + or - from flush.

 

[Machinist John]

Same as above This one is for the Remington's, I have another with an indicator that has more travel for the Mausers etc. where the case head extends out of the barrel.

https://imgur.com/tmVuFrQ

 

[Machinist John]

And the depth micrometers. Note the one with the thin blade, works great for the headspace gauge. Snuggle the blade against the gauge, take your reading.

The center one has a thick foot about 2 inches long, I find this style easy to use also on the gauge.

DRO's? I find myself often checking them with a manual instrument, don't fully trust them. Although I have DRO on the vertical mill and use it extensively.

When chambering, I use a variety of measuring tools and cross check each against the others. Prevents goof ups

 

[Machinist John]

The problem with stop collars on reamers is a bit of dirt or a chip may throw your distance off. Keith Francis made them, I have his brochure and may take a photo.

But the old master H M Pope used them on his reamers.

Just got to pay attention to detail.

 

[LVLAaron]

The problem with stop collars on reamers is a bit of dirt or a chip may throw your distance off. Keith Francis made them, I have his brochure and may take a photo.

But the old master H M Pope used them on his reamers.

Just got to pay attention to detail.

For sure. You can feel it in the tailstock if something is funny. I keep a hand lightly on the reamer holder. Easy to know if things are correct. Especially with a flush system. (I’m loving my flush system!)