Drilling between mold halves

Boolit Master Join DateDec 2005Posts189

Hello,

I read this post and found it fastinating.

I bought a Lee 6 hole blank from Titan Reloading and drilled it with a .177 drill then reamed it to .185. I read a post somewhere here that said to put a sheet of paper between the blocks and the drill would follow it down, I used a piece of 3X5 index card and it did indeed stay centered.
Measure the length of a finished core to decide how deep to drill, mine is .575 deep now, gives plenty of material to finish a core for a 55gr rf jacket bullet.
All done with a drill press, it works just fine and makes a pile of cores fast!
NickAnyone care to explain this technique? Sounds fascinating. Do you need to do this if you have a mill? Does this eliminate the need for a dial indicator finding the edge or center?

Thanks

A mill is more rigid than a drill press, if you use a center drill or a spotting drill you should be fine, a core does not need to be perfect.
Now I have another project!

Boolit Master Join DateDec 2005Posts189

..., a core does not need to be perfect.but it does need to fall out of the mold.

Boolit Master Join DateNov 2006Posts172

I was really surprised how well the bit followed the card stock, after I de burred the cavities, I did a test pour and the cores did drop OK.
Reaming did smooth the bores some and made a flat bottom. All 6 cavities drop well now, there is some variation in weight, but core swaging fixes that.
A sprue plate with a smaller hole would be better I think, the sprue hole is close to the core diameter.
As far as a setup, I blacked the top of the mold and used a scribe to mark the holes using the sprue plate for a pattern, then lightly centerpunched the location.
A mill would be much better, but I have no mill so I used what I do have!
Nick

Boolit Master Join DateDec 2005Posts189

I was really surprised how well the bit followed the card stock, after I de burred the cavities, I did a test pour and the cores did drop OK.
Reaming did smooth the bores some and made a flat bottom. All 6 cavities drop well now, there is some variation in weight, but core swaging fixes that.
A sprue plate with a smaller hole would be better I think, the sprue hole is close to the core diameter.
As far as a setup, I blacked the top of the mold and used a scribe to mark the holes using the sprue plate for a pattern, then lightly centerpunched the location.
A mill would be much better, but I have no mill so I used what I do have!
NickSo you just took a piece of index card stock the size of the mold and clamped it between the halves?

Did you deburr after you used the reamer?

Did you use a right hand reamer or straight?

Thanks!!
FYI, Harbor Freight has their mini mill on sale for $499 and they also have a 25% off coupon.

My core mold is bigger but I seem to remember I eyeballed it with the straight portion of the bit's tip. Nothing between the halves and tightly clamped, RPMs as fast as the press would allow and lubed with kerosene. Nothing fancy and the cores dropped just fine. You may have to debur at most.

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Boolit Master Join DateNov 2006Posts172

30yr; yes card stock between the halves, moderate clamp pressure.
I used a 4 flute straight reamer, no paper between the halves while reaming in the drill press, Kroil for lube.
Light de burr after reaming, a couple cavities had a burr from not being clamped tight enough, if the core will drop, good enough!
Nick

Boolit Master Join DateDec 2005Posts189

30yr; yes card stock between the halves, moderate clamp pressure.
I used a 4 flute straight reamer, no paper between the halves while reaming in the drill press, Kroil for lube.
Light de burr after reaming, a couple cavities had a burr from not being clamped tight enough, if the core will drop, good enough!
NickVery interesting!! You removed the mold from the vise to remove the card stock then re-drilled with the reamer and still got them centered between the halves. Good work with a drill press.

My brother was a machinist for over 30yrs and he was the one who told me about the sheet of paper so I posted it here. He had another paper trick. If you have an object in the milling vise and it absolutely must not move even a couple tenths, put a thin sheet of paper between the work and the vise jaws and the work will be held more firmly.

Bob

Boolit Master Join DateNov 2006Posts172

Bob thanks for posting the "paper tricks", I had read about paper beside the clamped object, but not about the drill trick. Worked just fine for me!
Nick

There was another trick using either paper or cloth when drilling through sheet metal, especially aluminum. I can't remember how it works but it is to eliminate or minimize burrs. It was useful when he was building a glider. I'm just a new schmuck when it comes to machining but I try to pick the brains of the experienced machinists out there.

Bob

A paper wrapped barrel will not slip in a barrel vice and many times will not mar a blue job if you get it tight. There may be some paper stuck to the barrel but a quick wipe with a chore girl will remove it.

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Boolit Master Join DateDec 2005Posts189

A paper wrapped barrel will not slip in a barrel vice and many times will not mar a blue job if you get it tight. There may be some paper stuck to the barrel but a quick wipe with a chore girl will remove it.Kelblys rifles recommends using an index card wrapped around the barrel when putting a switch barrel in the barrel vise to hold it in. Works well and there's no marks on the expensive Hart barrels.

I found out about using a piece of cloth like a cleaning patch when drilling holes in Aluminum sheet. On Aluminum the bit tends to pull through the sheet very quickly and you get what we call a "triangular hole". With the piece of cloth between the work and the bit you get nice round holes. With bigger holes use more layers of cloth. Don't know why it works but it does.

Bob

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Abbreviations used in Reloading
Pointed Soft Point "Core Lokt"

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