How does a CNC machine find the center of a barrel or action ?

[butchlambert]

But the threads will look “trued”

Yup!

 

[Cloudrepair]

I perused Chad doing a receiver in his mill. He indicated a mandrel and I asked him how he shimmed his chuck to dial in the other axis. He didn't answer that question. Maybe he has learned how to take 2 different measurements to properly set up the receiver before machining.

That chuck is probably set in a fixture plate that uses 4 screws like a set true chuck only the screws are pointed toward table instead of the chuck.
To set true perpendicularity to z axis on the mill. Then G54 or 55-56-57.... for your origin/location.

 

[shortgrass]

I've been looking back in the "Gunsmithing" section for a thread where Tucker has built himself an adjustable set-up to hold a round receiver for truing on a CNC mill. It'd work, but like I said, you can't just stand anyone in front it and expect good results. It'd take a skill machinist to "make it happen" properly and in a timely manner. No way am I suggesting that all gun smith machining needs to be done on CNC machine tools, just that some use them successfully.

 

[butchlambert]

That chuck is probably set in a fixture plate that uses 4 screws like a set true chuck only the screws are pointed toward table instead of the chuck.
To set true perpendicularity to z axis on the mill. Then G54 or 55-56-57.... for your origin/location.

Probably doesn't get it. The photo that he had on the Practical Machinest was an indexing head mounted to the table.

 

[Shrek]

The original video is from TS Customs, Travis Stevens. A friend had him chamber a rifle and sent a link to the video I posted. I’m not sure how the rifle shoots. I still don’t see that being aligned with the bore at the throat.

 

[butchlambert]

The original video is from TS Customs, Travis Stevens. A friend had him chamber a rifle and sent a link to the video I posted. I’m not sure how the rifle shoots. I still don’t see that being aligned with the bore at the throat.

I ain't referencing your video. I'm speaking of thread milling on a mill.

 

[Shrek]

Looking at the thread milling plate with the screws I understand completely how that would work fine. The video I posted was posted because I really don’t like what I saw and thought I didn’t understand what was going on. It still looks like a hack barrel thread, chamber , and installation if it’s actually just chucked up in a collet. I now understand how it can be done well in a CNC machine but I’m not really sure that’s what is going on in the video.

 

[Cloudrepair]

Probably doesn't get it. The photo that he had on the Practical Machinest was an indexing head mounted to the table.

Do you have a link to the pic I haven't seen it. I was just thinking of a way I would set it up in the cnc mill I program and operate at work.

 

[Shrek]

Do you have a link to the pic I haven't seen it. I was just thinking of a way I would set it up in the cnc mill I program and operate at work.

It’s the original post that I’m referring to. There’s a video I posted.

 

[Shrek]

I’m not sure which thread had the picture of the thread mill plate. It was a plate with four set screws with a chuck on top. It was concurrent to this thread here or over an Practical Machinist.

 

[Tucker65]

On the set-up I used it has four jacking screws to true up a mandrel that fits in the receiver and sticks out about 6" It took a little while to get the first one indicated in but I did another one for a friend and the second one when a lot quicker. Are they perfect after cutting them? That's a good question. I do know that after I indicated the mandrel in and checked the factory receiver face and lugs that they were definitely not true to the mandrel. I have yet to put a barrel on the trued up action but I'm confidant that it will be just fine.

 

[butchlambert]

On the set-up I used it has four jacking screws to true up a mandrel that fits in the receiver and sticks out about 6" It took a little while to get the first one indicated in but I did another one for a friend and the second one when a lot quicker. Are they perfect after cutting them? That's a good question. I do know that after I indicated the mandrel in and checked the factory receiver face and lugs that they were definitely not true to the mandrel. I have yet to put a barrel on the trued up action but I'm confidant that it will be just fine.

That setup should work.

 

[Roeder]

The original video is from TS Customs, Travis Stevens. A friend had him chamber a rifle and sent a link to the video I posted. I’m not sure how the rifle shoots. I still don’t see that being aligned with the bore at the throat.

All I see in the video is threading cuts. Without knowing what the guy did to set up the barrel it is impossible to tell how good it is. The collet chuck setup may raise suspicions but a skilled machinist can have a lot of tricks up his sleeve. I would not assume that there is anything wrong with the set up without knowing how he prepped, set up, and indicated.

 

[IdahoCTD]

You could run a collet chuck with a knuckle type joint like the True bore Alignment (I'm trying to remember who makes it) and dial it in. A long stem on a Blake CO-AX indicator and you could check it at several depths off of a alignment rod. I think that is how Chad does it. He got a bit butt hurt, if I remember right, when the guy did the True Bore Alignment thing.

The only down side I can see to the set up pictured above is the jacking screws wearing into the surface of the mill table unless you had a sacrificial piece of thin steel for a pad below the screws.

 

[Dusty Stevens]

He got a bit butt hurt, if I remember right, when the guy did the True Bore Alignment thing.

Whys that did he invent it first?

 

[IdahoCTD]

I think he did something similar but didn't market it.