Honing rcbs hardened fls die neck

[paulT]

Hello all
I am looking to open up the Neck of a black coloured .308 RCBS FLS competiton die by 0.005 thousands
I believe its probably hardened and was looking for info with which Lap would work best when lapping by hand,
The die currently re sizes the necks of lapua neck turned brass to 0.3290in and i want to open neck up by 5 thousands to size necks to 0.334in
Would an 5/16 adjustable barrel Lap like the Acro adjustable Barrel Laps cut through the hardened rcbs necks ok and maintain low runout
Ifso which grit compound and cutting oil would work best for this project, Thanks

 

[jepp2]

Ifso which grit compound and cutting oil would work best for this project,

I start with 2xx (would need to check if it is 240 or 280) and finish with 600. TIR less than 0.001", way better than bushing dies. Since I do mine by hand, I use tape to make sure I stay centered (not really an issue).

 

[whatsupdoc]

I have done it a few times with a Acro lap easy to do. Suggest buying a pin gauge to confirm the finished bore size. Centering is not an issue just make steady passes through the die.

I use 30 micron diamond compound from the site below.

DIAMOND COMPOUND medium concentration

DIAMOND COMPOUND medium concentration

www.moldshoptools.com

 

[paulT]

I have done it a few times with a Acro lap easy to do. Suggest buying a pin gauge to confirm the finished bore size. Centering is not an issue just make steady passes through the die.

I use 30 micron diamond compound from the site below.

DIAMOND COMPOUND medium concentration

DIAMOND COMPOUND medium concentration

www.moldshoptools.com

Thanks for info
Would the 1 adjustable Barrel Lap be enough to remove 5 thousands with multiple adjusted passes
With a Hardened die.

 

[paulT]

I start with 2xx (would need to check if it is 240 or 280) and finish with 600. TIR less than 0.001", way better than bushing dies. Since I do mine by hand, I use tape to make sure I stay centered (not really an issue).
View attachment 1312487

Are you using the adjustable barrel lap to open the necks also could you explain tape meathod which helps keep barrel lap centered whielst cutting, thanks.

 

[jepp2]

Are you using the adjustable barrel lap to open the necks

Yes, I have done at least 10.

could you explain tape meathod which helps keep barrel lap centered whielst cutting

The shank of the lap is much smaller than the body portion of your sizing die. By wrapping the shank with tape to "nearly" the ID of the die, it makes sure I don't hold the hone the neck at an angle. Probably isn't necessary now, but it made sure when I started that I didn't lap the neck at an angle.

The die cuts slowly. But I stop often to check my progress. Before I start, I know exactly what I want the finished diameter to be. I check my progress both with pin gauges and by sizing brass with the expander removed.

 

[paulT]

Yes, I have done at least 10.

The shank of the lap is much smaller than the body portion of your sizing die. By wrapping the shank with tape to "nearly" the ID of the die, it makes sure I don't hold the hone the neck at an angle. Probably isn't necessary now, but it made sure when I started that I didn't lap the neck at an angle.

The die cuts slowly. But I stop often to check my progress. Before I start, I know exactly what I want the finished diameter to be. I check my progress both with pin gauges and by sizing brass with the expander removed.

Thanks for reply,
How many full passes with Lap and how long would it take to remove @ 5 thousands of material from the neck of a Hardened FLS Die.

 

[jepp2]

How many full passes with Lap and how long would it take to remove @ 5 thousands of material from the neck of a Hardened FLS Die.

I run my drill on high speed (1500 RPM minus the load) and it takes off maybe 0.001 per 5-10 minutes. Die gets hot, so I wrap it in a paper towel and wear a glove. Very slow process.

 

[whatsupdoc]

Thanks for info
Would the 1 adjustable Barrel Lap be enough to remove 5 thousands with multiple adjusted passes
With a Hardened die.

Yes, but that depends on the abrasive and speed you use. That is why I use diamond abrasive.
You should get one complete lap and one or two spare brass cylinders.
No need for a blind hole lap, get a through hole lap.

 

[paulT]

Yes, but that depends on the abrasive and speed you use. That is why I use diamond abrasive.
You should get one complete lap and one or two spare brass cylinders.
No need for a blind hole lap, get a through hole lap.

Thanks for info.

 

[paulT]

I run my drill on high speed (1500 RPM minus the load) and it takes off maybe 0.001 per 5-10 minutes. Die gets hot, so I wrap it in a paper towel and wear a glove. Very slow process.

Thanks for Reply.