Neck Threading

T

Twud

Guest
Just took delivery on a new 6 BR with a tight neck. No matter what I do I can't get rid of the thread pattern. I'ts not super noticable but I would prefer it not be there at all. I've gone as slow as possible to no avail. I've taken the
.006" in 2 passes, no help. My Sinclair turning tool is new. I'm thinking of investing in a case lathe, but I don't want to drop $250 on something I'll use once. I'm using Lapua brass.
Help!!

Mark
 
Sounds like the cutter has too sharp of a point on it. The edge that cuts needs to be sharp, but the profile being cut does not. Most lathe tools that are used to cut a smooth surface have just a bit of a radius when looked at from above the work, even though the edge parallel to the work that does the cut is very sharp.
 
Adjust the tool...

Vibe said:
Sounds like the cutter has too sharp of a point on it. The edge that cuts needs to be sharp, but the profile being cut does not. Most lathe tools that are used to cut a smooth surface have just a bit of a radius when looked at from above the work, even though the edge parallel to the work that does the cut is very sharp.
Click to expand...


+1... Make a slight radius on the point of the tool and adjust it so that it's turned correctly.
 
Twud said:
Just took delivery on a new 6 BR with a tight neck. No matter what I do I can't get rid of the thread pattern. I'ts not super noticable but I would prefer it not be there at all. I've gone as slow as possible to no avail. I've taken the
.006" in 2 passes, no help. My Sinclair turning tool is new. I'm thinking of investing in a case lathe, but I don't want to drop $250 on something I'll use once. I'm using Lapua brass.
Help!!

Mark
Click to expand...

It seems to me, if you can keep the heat down, the faster you spin the cases, the less thread appearance will be there. Ron Tilley
 
You may be doing the 'threading' when removing the turner from the case. Go real slow and make sure you don't cock the tool when you reverse direction.
 
threading of case necks

Because of the brass being elastic, which causes "spring back", the cutter cuts both ways. So, if you aren't careful about your feed speed, it will give you a thread. You need to be uniform with your feed and return rate of feed. However as Wilbur said, Shoot 'em and it disappears.
Good luck.
jeremiah
 
Make sure your mandrel to neck fit is snug with no slap.
Because if loose it will slop about on the way back.
It will also cut a bit on the way back so go slow.
A neck expander is a handy tool to get the right ID size to fit the mandrel snug. You can polish down the expander mandrel until it produces just the right ID size.
 
Are you turning by hand or by machine? You do not need a case lathe. You can use a drill press or a power screw driver.
Butch
 
Sinclair caseholder

Butch Lambert said:
Are you turning by hand or by machine? You do not need a case lathe. You can use a drill press or a power screw driver.
Butch
Click to expand...

+1

You probably have a 800+RPM Cordless drill (corded works as well:D)...
The drill and a wonderful little Sinclair case holder will take ALOT of the work off your hands and precision cuts with NO cork screw patterns on the necks...
You'll see.

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RECPNT&item=05-230&type=store

cale
 
Gee, I'm sitting here turning 30 BR cases and they are as smooth as
if you polished them with fine steel wool. My mandrill it to tight for electric
and yup there all with in a tenth. I do take a break and let it cool.
Aluminum bodied turners are fast to heat
 
a threaded finish is caused by a rough grind on the cutter.A loose mandrill
will allow a fast feed rate and can contribute to the problem.
 
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