[Chip645]

'Turns out a ping-pong ball is 40 mm in diameter.

I'm trying to build a check valve.

I need to drill a fairly precise 40-mm hole in a 3/4 x 1 1/4 PVC adaptor.

Do "they" make drill bits that large?

Any other suggestions on constructing check valves?

Can one get fairly precise Teflon spheres for building check valves of various sizes?

[Trandy]

As a machinist, I envision you creating your check valve, and driilling a 40 mm hole with a drill to fit a 40 mm ball I do not think will work. You need to get a hole saw, perhaps, that is say... 38 mm, that way your ball won't come out of the hole. You want to create a precise hole, a drill bit or hole saw would waller around, making the hole larger than you intended. Start with a smaller size, that way your hole won't be too big. You would probably also need some sort of rubber seal to seat against the ball, and I wouldn't think that a ping pong ball would be very efficient as a seal anyway. How much pressure are you attempting to hold? Perhaps one of those rubber balls you buy in a quarter machine would float? You'd only be out a quarter, and if it floated, you could use a smaller diameter, maybe a standard and readily available drill would work.

[KISS]

Balls to 1" are available at Industrial Supplies.

As Trandy states, drill bits won't work, they drill triangular holes. There is a kind of hole saw that will cut a precise size hole. It mounts a cutter in an adjustible mandril with a centering hole. It must be used with a drill press. Not too precise.

An adjustible wood boring bit MIGHT work if it was in a piece of flat stock.

If I understand what your trying to do. I think your trying to enlarge a hole. In that case drill a hole. The problem big bits do exist, but they are not the right way. If this was a hole one might use a big bit and then an adjustible reamer to get a nice round hole.

Big bits in an end of a PVC fitting will just grab.

Boring heads for milling machines can guarantee a nice round hole that size so would a lathe.

It's probably difficult getting a countersink that big too.

Soapy water makes a nice lubercant.

Yep, have machine shop skills too.

[speedball1]

Hey Chip, What are you attempting to accomplish? Why not just purchase a 1 1/2" check valve? Regards, Tom

[massplumber2008]

I am wondering about the ball.. Seems a FLAPPER would work better here..?