Drill bit question

Re: Drill bit question

Ken Vaughan

Machinist use center drill bits to start holes. Available in different quality from Harbor Freight cheap up. Often available in sets or 5 or so

Under $10 for cheap set

Re: Drill bit question

Keith Newton

I usually grind a little flat where I start the hole.

Use caution on the exit size too, since it will break through on the sides before the middle, which will cause it to climb the bit on a fast spiral. If you have a DP vice this helps hold it down

I sometimes grind a flatter cutting edge on the face to change to more of a scraping cut to prevent breaking a bit,

Re: Drill bit question

John in NM

I agree with Ken, what you want is what machinists use.

Should be available at Amazon, but if you prefer look to Harbor Freight, MSC, or McMaster Carr.

Highly recommended *LINK*

Henry Higginbotham

One of the best gizmos I've ever bought. Hasn't let me down yet. All you need is a clamp or two.


Big Gator Drill Guide

Re: Drill bit question

TomD

In the old days before the ubiquity of live centers, and it still works great today, if you drilled into the end of a rod with one of those, just short of the major diameter, what you end up with is a 60 degree angled hole, and a minor diameter hole in front of it. You fill the hole/reservoir with oil and the piece is ready for bearing on a fixed center in a metal working lathe. But good for spotting holes also.

A reasonable way of ensuring your bit will drill to the center of the rod is to place a piece of feeler stock, or any other flattish thing across the rod, carefully bring the drill bit (not powered) down onto the stock and if the drill is centered, the stock will remain flat, if it is off center, then you will cause the feeler stock to tip off like a see saw plank. Keep re-clamping until you get it pretty flat.

Nothing special needed.

Virgil Johnson

Use a combination square to scribe a line the desired distance from the end of the rod where you want the hole. Put a good heavy center punch mark on the rod next using the line you scribed. Put the rod in a regular drill press vice (punch mark up) and rotate the rod in the vice until the center punch mark is vertical.V block will work also. Use a scale to assure the mark is centered measuring from the vice jaw. Use a regular small diameter jobbers drill to "spot drill" the hole 1/16 or so deep. The small drill will flex and follow the punch mark. Next step up to the desired diameter. No need to clamp the vise in place as you want the bit to center on the punch mark. Center drills are just that. Drills to drill centers in the ends of shafts for live or dead centers. Probably the most misused/misunderstood bit in the world. ( I misused one today while drilling a 1/8 dia. hole through an 8 mm dia shaft)..:-)

center drills vs spotting drill bits

John K Jordan

I use the center drills when drilling in wood on the lathe. I also have "spotting drill bits" https://www.amazon.com/gp/product/B009NNFK96 commonly used on CNC machines for precise spotting. I like the center drills better for wood.

JKJ

Re: center drills vs spotting drill bits

Barry Irby

What's the difference? Shank diameter? Point geometry?

I was thinking all I really need is a drill with a short shank to make the bit stiffer.

Re: center drills vs spotting drill bits

John in NM

The point is smaller on center drills.

plus

Bruce, a MN Galoot

The center drills are usually used for starting holes. I use mine a lot, especially in coarse wood like oak.

for 1/4" or bigger you could use a Forstner