Given that I have a decent old school drill press, not a mill.

I need to drill a 42mm hole into an air cleaner base that is about 1/2 inch thick.

There is already a 38mm hole.
So, I just need to bore it out, centered, by 4mm.

What tool would you suggest?

I have a air grinder and a few carbide end mills that I use in that...but if I used that it would be freehand...
I am good, and might be able to do it...but I could also make a decent mass out of it.

I would rather make/get a tool that would work to mill a nice clean hole.

Rich

Grizzly mini mill. I'm sure you'll use it again,and you can convert it to CNC later.

http://www.grizzly.com/products/Mini-Milling-Machine/G8689

If I felt like writing a check, I would bring it to a machine shop.

Rich

I have a somewhat similar situation,relative to yours....only a milling machine ,or lathe is going to do that job(or Mine) to perfection...what I will do( and you might consider this,..)....is to use my handy dandy cylinder head porting tool(s)....with a medium abrasive round , barrell shaped, grinding(sanding) disc. Iwill be resizing from 40 to 44 mm....in about 1/4 inch aluminum also.......you might try a grinding stone in a high speed drill.(wear eye protection)....If you are careful..(slow)....you might suprise yourself at the quality of the results......afterall ,you have got to be somewhat of a gearhead to even ask your question.You can find reasonable grinding stones in an upguality ,scale hardware store..call around....oh. take a little time to layout the OD?ID hole you want...a sharpie magic marker could work..and go round and round and round,instead of trying to gouge out the bore to the correct size at any one point...good luck.

Hole saw, lots of cutting oil. Only way to make good large holes in metal on a drill press. 42mm = 1.653 inches. if you can find a bi metal 1 5/8 hole saw that is 1.625. If there is any run out in your drill press, that will probably account for the last .028 inches.
Zach

just answered YOUR question, chief.

end mill in a drill press, free hand...a hand file (Old school) and a round sanding unit on my hand drill....

Perfect..the sander at the end was perfect for a thousanth at a time....
I just took is slow...

Rich

How about this;

Tack weld a piece filling the hole.

In that drill a centering hole and then just use a normal hole saw.


That comment about it being 1/2" thick makes me wonder if you are talking aluminum!! In that case, make a plug that you can hammer in and then go at it with the guide hole and hole saw.

Wes

nd sweet and sour sauce... but mostly sour.

all done...

Rich

Does this mean that my idea worked for you?

Wes