M
mcm308
Guest
I want to turn my case necks on a lathe and am trying to come up with a way to spin the cases true. I think I have a way but would like to hear from someone that does this and how? Thanks!
JerrySharrett
Senile Member
Here's one way. Turn a mandrel so that the first fit (looking from the right end) is about 1/4" long and about 0.230".
The center fit is exactly 0.2433" (the diameter of most benchrest bullets. This allows you to measure the actual case neck size, just like a bullet is seated.
The left hand fit is about 0.260". Just a place to park the turning tool.
(disregard the grungy looking threads on the left. That is just the remains of a class 8 bolt shank I used to make the mandrel)
This picture shows actual turning. Hand feed left end to shoulder then slowly hand feed back to the left end.
This picture is a slide-hammer I made to install and remove cases. I press the case on using the tool and the tailstock.
Then I hammer it off with the slide-hammer feature.
The blue thing on the left is simply a K&M case holder.
Since the cross feed dial is graduated in 0.001" graduations, I install a 0.0001" indicator directly to the tool post. That way I can hold diameters to 0.0001" by reading the indicator. I do not feed the tool in and out for each case, just to make corrections.
One more thing, I make a new mandrel for each batch of cases. That way the mandrel runs perfectly true.
The center fit is exactly 0.2433" (the diameter of most benchrest bullets. This allows you to measure the actual case neck size, just like a bullet is seated.
The left hand fit is about 0.260". Just a place to park the turning tool.
(disregard the grungy looking threads on the left. That is just the remains of a class 8 bolt shank I used to make the mandrel)
This picture shows actual turning. Hand feed left end to shoulder then slowly hand feed back to the left end.
This picture is a slide-hammer I made to install and remove cases. I press the case on using the tool and the tailstock.
Then I hammer it off with the slide-hammer feature.
The blue thing on the left is simply a K&M case holder.
Since the cross feed dial is graduated in 0.001" graduations, I install a 0.0001" indicator directly to the tool post. That way I can hold diameters to 0.0001" by reading the indicator. I do not feed the tool in and out for each case, just to make corrections.
One more thing, I make a new mandrel for each batch of cases. That way the mandrel runs perfectly true.
Last edited:
jackie schmidt
New member
Mcm
I wrote an article on this very thing and had it published in NBRSA News a few years back.
Go over to WWW.6mmbr.com, go to the Article Archives,then type in the search window, "neck turning cases in a lathe". You will see an article that is just about identicle to mine, written by Mike Bryant. It is very consise and east to follow........jackie
I wrote an article on this very thing and had it published in NBRSA News a few years back.
Go over to WWW.6mmbr.com, go to the Article Archives,then type in the search window, "neck turning cases in a lathe". You will see an article that is just about identicle to mine, written by Mike Bryant. It is very consise and east to follow........jackie
Bill Leeper
New member
I turn mine on the lathe and use a new mandrel for each batch. I have shellholders which mount in the tailstock chuck to press on and remove the cases. Case neck turning is still a pain in the tush but it's better than getting blisters for a manual turner! Regards, Bill.
Bill,
Do you bite the tit on your shell holder right in the jacobs chuck, and slack off, allowing it to rotate?
Ben
Bill Leeper
New member
I hold the shell holder tight but just back off a bit after pressing the case on. There is a enough clearance in the lip of the shellholder to allow the case to spin OK. Every once in a while, there will be acase which is crooked enough that it hits on the shellholder. Invariably, this is a case which is quite eccentric in the neck and elsewhere. I cull these out. In Lapua brass this amounts to about 2 or 3 out of 100. With Remington brass it's more like 10 or 12. Regards, Bill.
Bill Leeper
New member
I machine the mandrel at 800rpm but turn the brass at 240. Regards, Bill
Jerry W
Jerry Wick
Jackie's Article
Here's a link to Jackie's article right here on Benchrest Central:
http://www.benchrest.com/jackie/
Here's the one on the 6mmbr site:
http://www.6mmbr.com/powerneckturn.html
Jerry
Here's a link to Jackie's article right here on Benchrest Central:
http://www.benchrest.com/jackie/
Here's the one on the 6mmbr site:
http://www.6mmbr.com/powerneckturn.html
Jerry
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Bob Smeltzer
Member
When I turn cases I use a 3/8 in. piece of stainless, I made A jig out of an old clevis,turn a bolt to fit in the tailstock, put a nut on it.After pushing the case on just back up a bit,turn the case, then back up put the shell holder on and pull the case off. Then push another on
Bob Smeltzer
Member
I would post a picture of the clevis however I don,t know how to resize the pic.
M
mcm308
Guest
After reading those articles..If I machine a mandrel that runs true.. It should run true when I reuse it, yes or no? I am also thinking I should machine the mandrel to the same size as my neck sizing die? yes or no? I'll take pictures of what I am doing and post later... Thanks for all the help.
Bob Smeltzer
Member
When you make a mandrel, make it the same size as your bullet, 243-284- 308 etc. Make a new one each time,It is not worth setting up to zero runout again
jackie schmidt
New member
Mandrel
As Bob said, do not try to re-use the mandrel. Remember, we are dealing in tenths when turning necks, it would be virtually impossible to true the madrel back up as close at it needs to be........JACKIE
As Bob said, do not try to re-use the mandrel. Remember, we are dealing in tenths when turning necks, it would be virtually impossible to true the madrel back up as close at it needs to be........JACKIE
M
mcm308
Guest
If I machine the mandrel to the bullet size...won't that expand the neck and then there is like no bullet tension?
Here is my Lathe...Southbend Model A. and here is what I made today.. The end is machined to .310...When I trim my cases...I will true it up to the proper size after I have the bullets I am using.
Am I on the right track here? And any info I can get about that Lathe would be nice. Thanks!!
Here is my Lathe...Southbend Model A. and here is what I made today.. The end is machined to .310...When I trim my cases...I will true it up to the proper size after I have the bullets I am using.
Am I on the right track here? And any info I can get about that Lathe would be nice. Thanks!!
JerrySharrett
Senile Member
You want to make the part of the mandrel that fits the case neck EXACTLY the same diameter of the bullets you use. That way when you mike a finished neck that is still on the arbor you will get the exact size that neck will be with a bullet seated. No struggling with devices to measure wall thickness and the math it involves.
Yes, you will have to resize the finish turned necks before reloading just as you will after each firing.
If your case necks are concentric around the diameter with a bullet seated, and if they are all the same diameter within about 0.0003" then you did well.
Your South Bend Model A is a great little bench lathe. It just has a spindle bore too small in diameter (3/4") for most barrel work. If you choose to fit barrels using the steadyrest method as have many great gunsmiths, it is useful for barrel fitting also.
Your South Bend lathe also did not;
1) add to the balance of trade deficit of the US.
2) did not add to the armament of the best armed nation in the world, Communist China.
3) did not take any US jobs off shore to make.
M
mcm308
Guest
ahhh, the resizing of the neck after turning is what was getting me..Thanks
Rob Carnell
Member
Dont worry about bullet tension
You can fix that later by sizing.
Turn the mandrel to exactly the same diameter as your bullet (use a .0001" micrometer to do this).
Then you can use the micrometer to measure the turned case while it is still on the mandrel to adjust for the correct outside neck diameter (make this .001" to .002" smaller than your reamer neck diameter).
This makes this method much quicker and easier than setting up a hand neck turner. But at least you can leave the hand turner setup and not touch it again!
There is a video of this on my website. Let me know what you think.
www.benchrestbulletin.com.au
Its under the personal projects tab.
Rob Carnell
Sydney, Australia
You can fix that later by sizing.
Turn the mandrel to exactly the same diameter as your bullet (use a .0001" micrometer to do this).
Then you can use the micrometer to measure the turned case while it is still on the mandrel to adjust for the correct outside neck diameter (make this .001" to .002" smaller than your reamer neck diameter).
This makes this method much quicker and easier than setting up a hand neck turner. But at least you can leave the hand turner setup and not touch it again!
There is a video of this on my website. Let me know what you think.
www.benchrestbulletin.com.au
Its under the personal projects tab.
Rob Carnell
Sydney, Australia
M
mcm308
Guest
That video was perfect. What kind of cutter is best to us??