Hinge Cup Bits

[Curt Putnam]

I'm asking this from complete ignorance. The stuff I need to install requires a hinge cup (I assume Forstner bit for the drill press). According to my calipers, the cup portion is precisely 35 mm. What size bit do I need?
A 35 mm bit leaves no clearance.

Thanks for your help.

[Paul F Franklin]

I've always used a 35mm bit. You don't want any slop because the strength comes from the cup part fitting snugly in the door, not the screws.

[Jamie Buxton]

All the cup hinges I've used go into a 35mm hole. Try a test. Bore a hole with a 35mm bit, and see if your hinge fits.

[Jacques Gagnon]

Curt,

In line with the information provided by Paul and Jamie, this is similar (different brand; same tool) to what I use:

https://www.leevalley.com/en-us/shop/tools/power-tool-accessories/drill-bits/100167-kreg-35mm-hinge-bit-for-kreg-european-hinge-jig?item=25K6073

You will also want to validate the correct spacing from the edge of your door; different models call for different spacings.

[Rod Sheridan]

You need a 35mm hinge boring bit, I use a carbide one from Lee Valley.

The spacing from the edge depends upon the hinge, the mounting plate model and the gable thickness,

You have to determine the hardware based upon the overlay if any...Rod

[Bruce Wrenn]

I have a couple of "no name" hinge cup bits. 35MM and carbide tipped. They all work well, doing what they are supposed to do.

[Matt Day]

Kreg hinge jig

[Curt Putnam]

Thank you all! I did not want to spend money on a bit that would not work.

I'm actually going to build sliding doors. The hardware requires a 35 mm bit and the result may have to be bored again or else squared up along the sides with a chisel. I'll get the bit and then some experimentation is in order.

[Lee Schierer]

A 1-3/8 inch bit is 1.375 inches. A 35 mm bit is 1.37795 inches. So a 35 mm bit actually makes a slightly larger hole than a 1-3/8" bit. I haven't done a lot of cup hinges, but the cups have all been drilled with my 1-3/8" Forstner bit and the cups fit just fine into the holes. My 1-3/8" bit is actually 1.3755 inches in diameter so it cuts a slightly larger hole.

[Tom M King]

I use either the 35 mm one, or an 1-3/8's, depending on which is closer at hand.

[Jim Becker]

35mm is the correct size for the tooling. The hinge cups are supposed to be snug as they provide the strongest support that way.

[Bruce Wrenn]

I use either the 35 mm one, or an 1-3/8's, depending on which is closer at hand.


The 35Mm has a shorter point, meaning it won't project through 1/2" materials. Amazon sells the Rok brand bit for less than ten bucks.

[Jon Grider]

A 1-3/8 inch bit is 1.375 inches. A 35 mm bit is 1.37795 inches. So a 35 mm bit actually makes a slightly larger hole than a 1-3/8" bit. I haven't done a lot of cup hinges, but the cups have all been drilled with my 1-3/8" Forstner bit and the cups fit just fine into the holes. My 1-3/8" bit is actually 1.3755 inches in diameter so it cuts a slightly larger hole.


What Lee said. 35mm X .03937(conversion factor)=1.3779". I use a 1 3/8 (1.375) always and have not had a fitting issue in dozens of doors. My 1 3/8" came in a set and I never had the need to by a metric set too.