Boring, cutting and drilling question ?

[EVILDR235]

So my question is, I am building a custom intake manifold for a mini bike I am building. I bought some 3/8 thick brass plate I will be using for the flanges for mounting to the engine block and for the carb to mount to. I need to bore some holes thru it appox 7/8 in diameter. I don't have a mill to machine the hole. The brass is expensive, so I don't to waste any trying to bore a nice clean hole in it. I have a drill press and some Silver and Deming reduced shank drill bits. I also have hole saws, but I believe both these methods are not go to produce a proper size hole. What should I use to bore the hole with ?

EvilDr235

[amecks]

What are S/D bits?  I don't suppose you have a small lathe?  You could use a 3/4" hole saw and turn the hole to open it to 7/8.  I think a hole saw mounted in a drill press will do a fairly clean cut with the bit and the work clamped securely.  I don't remember ever cutting brass with a hole saw but it should cut smoothly.
Al

[Bill Houghton]

You may need to bore it undersized and file to fit.

[EVILDR235]

S&D bits are Silver and Deming drill bits with a reduced shank so a larger bit can be used in a smaller chuck. I will edit my original post.

EvilDr235

[Plyerman]

Clamp the part down securely so it can't move. Then pre-drill the hole with a 13/16" drill bit. Then follow with the 7/8" bit it should cut pretty clean and on-size.

Of course, try a test hole first in a piece of scrap aluminum if possible.

[p_toad]

you might want to try one of those step drill bits.   I have used them in wood and in metal (steel) and they have worked nicely.   the cutting edge(s) depending on who makes it sweep the edges clean as they cut and gave me nice holes; even in glueboard.

[lptools]

Hello, p_toad. Do you mean a UNIBIT style? They do cut really well, and are also great for drilling stainless steel. They are limited in depth of cut, though, anything thicker than 1/8"( + or -),  will advance to the next step/hole size. Our electricians use them for making/enlarging holes in panel & junction boxes. Regards, Lou

[EVILDR235]

Thank you all for your replies. I had a small piece of scrap brass that I drilled with a 7/8 bit and got a nice clean hole. I also tried a hole saw with good results.

EvilDr235

[lptools]

Hello, EVILDR235. Way to go!!

[Bill Houghton]

Well, this certainly wasn't a boring question.  You cut to the chase and drilled right down to the problem - and solved it.

[p_toad]

Yup, Unibit style.   They come in many different configurations (width,  steps, depth, etc).   Been using them since my one neighbor gave me one of the original Unibits some years ago.

[Plyerman]

Well, this certainly wasn't a boring question.  You cut to the chase and drilled right down to the problem - and solved it.

<groan>

[lptools]

I have found the Unibits extremely handy for opening up peened over socket chisels. You know, the ones where the guy lost or broke the handle, and then beat the socket end to death!! Regards, Lou

[p_toad]

Yeah, good idea.   I've got a couple of those socket chisels that have been "beat up" like that.   Irks me no end.   Since a have a couple of the "stepless" tapered drills i may have to give
that a try.   had considered originally using a tapered stone.

[lptools]

Hello, p_toad. I believe the taper is different with each diameter Unibit, and with other manufacturers. In the 1st photo, left to right are 3 Irwin Unibits,  the 4th one is a Klein.       
2nd photo is a set from HF ( I hate to admit it), these also work well to enough to rough out the mashed chisel socket. When I get close to the inside wall, I switch to hand filing. Regards, Lou