Newbie question on modifying a sizing die?

Vettepilot · May 9, 2020

Well, first post here, so don't beat me up too badly. No formal machining training, but I manage to get things done. Have the use of an old, but decent and tight manual lathe and a milling machine.

I want to convert a Lee full length brass cartridge sizing die into a "body die" that sizes the body of the brass only and leaves the neck basically untouched. So I would like to machine the neck portion of the die out to the size of a fired brass case, which in this case would be .347". That way when the fired brass enters the die, it will be centered by the neck, but only the brass body itself will be re-sized,

How to do it?? Reamer? HSS? (doubtful) Cobalt? Carbide?

Or attempt to lap it out??

Thanks in advance for any help!

Vettepilot

john.k · May 9, 2020

Ive heard reports that a Lee die can be cut with a cobalt drillbit.However ,I suggest you get a carbide reamer of the size you want off Ebay (used)......you will need to drive it with a drillpress or lathe ,but that shouldnt be difficult.............I see you have a lathe....bore it out with a small solid carbide boring bar....you will likely need high revs for a hole that small.

GGaskill · May 10, 2020

I doubt that a Lee sizing die is hard enough to need a carbide reamer. Since you are looking for a clearance hole, I would simply chuck it in your lathe backwards and run an appropriately sized HSS twist drill through from the top. However, after doing this, the neck will provide zero guidance since it will not be contacting anything.

Vettepilot · May 10, 2020

Well, I am wanting to make the neck portion of the die the diameter of a fired case neck, which is about .347" in this case. That will center the case when it is inserted into the die. Then the case body will be re-sized, but not the neck, which is exactly what I want to accomplish.

Thanks,
Vettepilot

NRDock · May 10, 2020

Good luck finding the size reamer you want. Maybe you can bore it close and lap it in. Make a lap on your lathe.

An alternative solution is to buy a full body sizing/neck bushing die from Redding.

I like neck sized cases and T/C Contenders, but Contenders are more reliable with full length sized cases. This Redding die has helped the most accurate Contender barrel I've ever owned.

BruceS · May 10, 2020

You can always chop saw the die off and trim it back to the shoulder diameter on the lathe.

Only if you cannot drill it out with Cobalt or HSS

GenePoole · May 10, 2020

I did this once upon a time. The steel in Lee rifle sizing dies is not terribly hard. You can work it with HSS pretty easily. After a couple of tries with OK results, I ended up just buying a Redding body die. Works great!

Redding Small Base Body Die 308 Winchester

Vettepilot · May 10, 2020

"After a couple of tries with ok results"...

Does that mean you accomplished your goal and ended up with useful body dies, or gave up and bought the Redding body dies?

I'm trying to avoid buying the quite expensive and sometimes hard to find Redding body dies, and recently scored a Lee full length sizing die for "a song" so I have an extra one to play with. An 8.8mm reamer would work, and they're available if they would cut it...

Vettepilot

john.k · May 10, 2020

OK,if Lee die is not very hard, a simple boring job and maybe a light hone to break the sharp edges left.......I must say ,the Lee dies Ive fiddled with were incredibly soft for any kind of steel....but they were the mallet Lee-loaders ,which I adapted to a neck sizer .....But I do know of a Lee 577/450 sizer enlarged to .5" at the neck ,which is the correct size,with a cobalt drillbit and a brake hone...I suspect the dies may be lightly nitrided.

kenton · May 16, 2020

McMaster-Carr

You can buy pretty much any size reamer to within .0005". Mcmaster is just one option,

Tozguy · May 17, 2020

I would attempt to bore it out with a carbide tool. Chances are there is not a lot to remove to get to your final size but it might be more than can be removed with one reamer. Surface finish is important if the brass rubs in the neck of the die so some lapping will be required.
Another approach to case alignment might be to make your own stem that fits the inside of the fired neck. That way the size and finish of the neck in the die is not as critical.

Butch Lambert · May 17, 2020

I have done several in the past. Just drill out your shoulder and neck. Cut .030 off the base of the die. Charles Huckaba, Benchrest Hall of Fame member, showed me this.

MIBill · May 17, 2020

Vettepilot said:
Well, first post here, so don't beat me up too badly. No formal machining training, but I manage to get things done. Have the use of an old, but decent and tight manual lathe and a milling machine.

I want to convert a Lee full length brass cartridge sizing die into a "body die" that sizes the body of the brass only and leaves the neck basically untouched. So I would like to machine the neck portion of the die out to the size of a fired brass case, which in this case would be .347". That way when the fired brass enters the die, it will be centered by the neck, but only the brass body itself will be re-sized,

How to do it?? Reamer? HSS? (doubtful) Cobalt? Carbide?

Or attempt to lap it out??

Thanks in advance for any help!

Vettepilot

PTSolutions | Holemaking > Reaming > Solid/Brazed Reamers > Chucking Reamers | .3470 Dia-HSS-Bright Straight Shank/Straight Flute Chucking Reamer | MT5029539

or

PTSolutions | Holemaking > Reaming > Solid/Brazed Reamers > Chucking Reamers | .3470 Dia-HSS-Carbide Tipped Chucking Reamer | BF533470

no point making it harder than it needs to be...

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Newbie question on modifying a sizing die?

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