My First Attempt at a "D-Bit" Bullet Mold

[DoctorBill]

My first mold was made with a Ball End Mill in a block of Aluminum.

I want to warn everyone that I am a rank amateur with almost no machining experience.
I have a bench grinder, Air Compressor, and a Bench Drill Press - That is it.

My machinist friend (Gary K), bored the holes followed by the Ball End Mill (Grizzly.com)
in his Lathe.

See: http://castboolits.gunloads.com/show...70&postcount=1

That Thread became rather lengthy and wordy with lots of side issues.

Anyway - I was convinced by some contributors that I should make a "D-Bit" and bore a mold with that method.

This Thread is concerned with my first D-Bit attempt....

My machinist friend told me about ENCO - http://www.use-enco.com/CGI/INSRHM

So I ordered some Oil Hardened Drill Rod in one yard sections(7/16ths and 0.452").

Using an Air Cut-Off Saw, I ground off a four inch section of 0.438 (7/16") rod and shaped a
bullet head 'free hand' on my Bench Grinder.

Finished it off by polishing it on the end of my Bench Drill Press with emery paper and
then "FLITZ" metal polish. Took no more than 30 minutes to do !



Now I have to grind half of it off lengthwise for a D-Bit.
That part worries me....I could 'booger up' the whole thing !

Oh well....I can get nine 4 inch chunks of Drill Rod out of each $9 Drill Rod piece.
Repeat until I get it right...

Am I off to a decent start, fellows ?

DoctorBill

PS - Now to repeat this employing the 0.452 Drill Rod for a larger diameter bullet.

[FrankG]

Looking good ! Paint it up with a felt tipped marker for cheap lay out blue . Lay the un touched shank on flat surface and clamp down then adjust micrometer to half of boolit width , lock in place and use it to scribe the length of boolit marking the half way point.

Thats my hayseed method when Ive made the 'D' type

[DoctorBill]

My friend (Gary the Machinist) advised me to grind the center rounded
inward so that the edge has a positive "rake" to it to attack the Aluminum.
That would be at the final grinding stage.

I ground down both sides as far as I want to w/o my friend Gary having
a look at my work.

Here are two different views of the 0.438 rod ground down.
I kept the metal cool in cold water - never let it get too hot.





There are a lot of reflections in the metal - looks boogered up - it isn't.

Should I grind off 'most' of the straight part so just the rounded tip and
just a bit of the straight touches the cavity ? It would bore out a
straight hole and the round tip w/o dragging chips along the wall.

DoctorBill

[montana_charlie]

I ground down both sides as far as I want to w/o my friend Gary having a look at my work.

Hmmm ... !
I thought that one side stayed round and the other side disappeared on the grinder, so you have (like) half of a bullet with a rod attached to the base.

Didn't expect to see material ground off of both sides of a remaining center piece.

But, I'm even more rank than the amature running this thread. I haven't even watched a machinist work ...

CM

[FrankG]

Uhmm..............Should have been ground from one side only . Thats why I scribe a center line to keep me on track. The back side also applies the pressure for the cutting edge to cut .

[DoctorBill]

I was thinking of this cutter...from another thread.

http://castboolits.gunloads.com/show...2&postcount=17

It would cut on the leading edge of both sides, no ?

What I wonder about is how the very tip of the bullet shape (of the tool) can cut ?

I suppose that if you pre-drill to just under the diameter of the tool, it
should work (in Aluminum).

This is hardened steel against Aluminum.

That is why I want Gary (the machinist) to see it.

I suspect that he will tell me to grind the tip portion down to the half-way point.

I can always grind another one.....

DoctorBill

[montana_charlie]

It would cut on the leading edge of both sides, no ?

What you have there is a form of 'spade bit' rather than a 'D bit'. It would need something on the front end (like a spike or a pilot) to keep it centered.

You want a shape like the letter D.
The round rod you started with was the O and you need to grind away half of it so only the D remains.

CM

[FrankG]

Never tried one like that . Have always went with the 'D' type . But , hey if it works , all the better !

[HollowPoint]

On my first attempt at making and using a "D" type reamer/bit I used a Grade-8 bolt.

In a state of laziness I didn't bother trying to harden it when it was done. Hardening didn't
turn out to be necessary because I was using it in an aluminum mold. I did have to make sure it was sharp though.

I'm sure the hardened drill rod would have worked even better but, I just happened to have a
grade-8 bolt in my junk-drawer to experiment with.

From the look of your finished tool it appears that you may encounter some metal shavings getting
trapped between the walls of your cavities and the rounded parts of your bit but, I've been wrong before more times than I can count.

HollowPoint

[uscra112]

What you've got there has a cutting edge with what lathe hands call "negative rake". The top surface of the edge is tilted toward the metal it's cutting. This IS sometimes used in very heavy roughing cuts in steel, but it's done more to strengthen the edge for longer life. Negative rake doesn't work in aluminum at all. You need positive rake, which is what you will have if you start from one side of the tool and grind right to the center. (Actually grinding to the diameter gets you zero rake, which will work. Looking at the end of the tool, it looks like the letter D, hence the name. If you are skillful enough, holding to tool so that the flat side of the D is actually hollowed out a bit is best. Doing this free-hand is hard, but it can be done. I did one on a little surface grinder I picked up years ago.

The tool in that other thread has been doctored quite a lot to create the positive rake, and also to relieve the part below the edge so it doesn't drag. Even harder to do free-hand. And he's ground reliefs on the nose so it will drill in.

[Flinchrock]

My friend (Gary the Machinist) advised me to grind the center rounded
inward so that the edge has a positive "rake" to it to attack the Aluminum.
That would be at the final grinding stage.

I ground down both sides as far as I want to w/o my friend Gary having
a look at my work.

Here are two different views of the 0.438 rod ground down.
I kept the metal cool in cold water - never let it get too hot.





There are a lot of reflections in the metal - looks boogered up - it isn't.

Should I grind off 'most' of the straight part so just the rounded tip and
just a bit of the straight touches the cavity ? It would bore out a
straight hole and the round tip w/o dragging chips along the wall.

DoctorBill

I don't think it's gonna cut well,,if at all...

Needs to be a "D"

If ya want to make another one and send it to me, I'll do it for you on my surface grinder,,free...

[DoctorBill]

OK then...I will make another round nosed rod and grind off only half of it.

From what uscra112 says, it looks like I had best grind off about 90% of
one side and then take it to my machinist friend to finish off on his
tool grinder.

I do have positive rake on one side of the tool - I pushed it into the grinding
stone and let it take the shape of the stone.



As to not centering - I plan to have a 1/8 inch pilot hole plus several different
sized drill holes to remove most of the Aluminum before using this tool.

I had thought that that is what you do first - get most of the Aluminum out
with drill bits.

So if I grind each side "Hollow Ground" - would this work to ream out a pre-drilled
cavity ?

Here I ground it a bit more and put an LED Flashlight on each side to illustrate
the curve of the edges. They are sharp. I can try it on some pre-drilled, scrap Aluminum.



Which direction does a Milling Machine rotate the tool (if viewing my picture above) ?
CW or CCW ? I could "relieve" the following edges since they don't do any cutting.

DoctorBill

BTW - I grind the rod end close to what I want, by hand, then put the 7/16ths
rod in my 1/2 inch Black & Decker Drill and then grind the end while the rod spins.

Much easier to get the shape I want quickly.
.

[Flinchrock]

Make a roughing tool and a finishing tool.
as long as you leave some material for the finish tool, they dont have to match exactly, then pilot, rough, and finish. you oughta come out alright.

[DoctorBill]

First off gentlemen, let me say that I am not challenging anyone's comments
or opinions here !

This is how I do things - if it is new to me, I try to understand why things work
as they do.

It just seems to me this ought to work with a pre-drilled cavity.

If it does not, I will be right back telling you it doesn't work !

Here is a close up of the bit's end.

Photo taken with a jeweler's loupe held over a Digital C613 Kodak EasyShare's lens.
Press button half-way down, move camera in and out to get best focus, finish clicking.
PhotoShop the result. Any photo handling software will do the job.

The edges have positive rake and are sharp.
Gary (the machinist) thinks I need to heat harden it also.

I'll watch him do it and learn by observation....my main method.

I WILL make a Kosher D-Bit also !

Having come this far, I want to see what THIS ONE does....on a piece of
scrap Aluminum....
just for my brain cells to see.

DoctorBill

PS - I guess I just have to accept the fact that I cannot make a bullet mold
without using some special tools....
.

[Longwood]

Bill
Start over and grind it to the half way point to get enough rake.
All that tool will do is sqeek.
You could use an endmill to repair your attempt but I kanow you don't have that luxury.
It does not necessarily need to be heat treated but it does need to be sharp.
The photos clearly shows it is EXTREMELY dull.
It can and should be sharpened to a RAZOR edge.

It is possible to machine one with two or three cutting edges but a small lathe or mill is necessary.

[longbow]

+1 on what Longwood says about sharpness. I use a diamond hone on the flat until the edge is sharp enough to shave fingernail with a light stroke.

You can make a spade bit (sort of what you have done) but a D bit being 1/2 the diameter will cut like a drill bit and ream at the same time. It is best to remove most of the metal with drill bits or by boring before using the D bit but they will actually cut a lot of metal if taken slowly. A spade bit may cut faster but will require side clearances ground on it or it will bind.

Longbow

[Longwood]

I do have positive rake on one side of the tool - I pushed it into the grinding
stone and let it take the shape of the stone.




.

Draw an imaginary line between the cutting edge and the center of the tool and you will see that you do not.
If you use a smaller diameter wheel and grind your flats exacty the same depth on each side, then your tool may work if you get it sharp enough.
A dull tool will make marks you have to polish out so either get it very very sharp or make sure the tool will drill a smaller hole than you need.
You can tell when it is sharp. It will give you little razor cuts if you handle it.

[DoctorBill]

Alright gentlemen - it is in the garbage can going out tomorrow night to the dump.

I will cut off a 7/16th inch by four inch rod tomorrow morning and grind
the bullet nose shape I want into it. Maybe ask Gary to finish it off in his Lathe.

Then I'll do the D-Bit thing to it - or ask Gary to show me how he would handle it.

DoctorBill

[montana_charlie]

Can your 'oil hardened drill rod' be cut with a saw or file?
CM

[Rojelio]

Dr. Bill, don't throw your first attempt away you may be able to salvage it. If not, you may want to make something else out of it.

The way you made yours, I don't think it will ever cut, but if you grind away the back edge of each side and sharpen it real good, it might work. I don't think it will plunge cut. You'll have to predrill the hole.

I made mine as a flat nose centercutting design because I like a wide meplat because I mainly use my bullets for hunting not target shooting.

Here's a picture of the cutter that you tried to copy from a different angle so you can see what I'm talking about.

Good luck and keep after it. You'll master the demons.

PS:Before this thread, I never heard of a D reamer. My next one may be that design