centering bits

[skeenum]

I have read where several of you use a centering bit to start holes in your blanks. What is the advantage to using a centering bit versus just using the brad point/other regular bits to center and bore the hole all the way through the blank?
How deep do you bore when boring with a centering bit? Do you under-size the hole made with the centering bit and then ream the hole with a regular bit to complete the through hole?
How much more accurate is this method?
Thank you center bit users for any information you might provide to me.

Thanks,

 

[PaulDoug]

Stan thanks for asking the questions I've had. Anxious to read the responses.

 

[its_virgil]

I suppose since I'm no center bit user that answering this question by saying, for me at least, using a center bit seems to offer no advantage when drilling pen blanks. Nor would my comment that I use a drill doctor and sharpen bits with the split point attachment and that they drill straight and true and don't seem to wonder or follow the grain. So, I'll just keep my comments bottled up inside and keep the info to myself. ;-) Also, I can't seem to make the emoticons and smiley faces work for me anymore. :-(
Do a good turn daily!
Don

Thank you center bit users for any information you might provide to me.

Thanks,

 

[Sylvanite]

For starting holes in bullets and brass, I find a center bit to be a necessity. In these situations, however, I'm drilling on the lathe and I need as good concentricity as I can get. When I'm drilling wood blanks with a drill press, I don't bother.

Pretty much, I start the hole with a center bit whenever:
1) I need to drill in the exact center of the blank, or
2) I am drilling with a bit that tends to flex or doesn't bite well.

Even on the lathe, there's a bit of play in the tailstock when drilling. Center bits tend to pull themselves into the center, rather than wander out of it. That makes them very useful when drilling a big hole in a little blank.

Othertimes, when I'm drilling a small diameter hole, or using a long bit, the center bit comes in handy. If a bit doesn't want to bite, a short pilot hole drilled with a center bit will keep it from skating. As Don points out, a sharp split-point bit usually bites and centers well, so I don't often need a pilot hole. The advantage of a center bit here, is that it is quite stiff (very little flex). It won't wander, even when drilling into an uneven surface.

I don't drill very deep - just enough to provide a good start for the regular drill bit.

I hope that helps,
Eric

 

[VisExp]

While drilling on the lathe without a center bit I was struggling to get the entry hole perfect. The bit would wander a bit before finding the center. The majority of the hole and the exit hole would be tight and concentric, but not so with the first section of the hole. In effect I was drilling a funnel.

After reading a post by Rherrel I ordered a set of center bits and starting using them. I found a big improvement and am now drilling cylinders as opposed to funnels.

Eric, has expressed better than I could the reasons/advantages that I've observed using a center bit.

 

[jkeithrussell]

When using the drill press, I mark the center and use a center punch to tap a very shallow starter hole, then drill it out. This works well 95+% of the time. When I forget to tap the starter hole with a center punch, I have mixed success in getting holes straight and true with the drill press.

 

[skeenum]

thanks

Guys,

Thanks for the replies and for the great information conveyed. I certainly have a new perspective now thanks to each of you and your contribution.
Thanks again!

 

[Texatdurango]

Without revealing where I stand on this issue and for some friendly conversation and brainstorming, would it sway anyones opinion after looking at this image?

Which bit do you think has a better chance of starting out dead center?

FYI, it takes me an extra 18 seconds to center drill a blank before using the full size drill, Oops, I gave away my stance didn't I!

 

[BRobbins629]

Lets put it this way - its the cheapest insurance policy I own.

 

[hughbie]

the center bit is used to make a starter hole in a material. these are mostly used in metal working, drilling and lathe work and milling.
take a close look at a center bit. notice how 'meaty' the bit is. compare that to a drill bit. the drill bit seem to drift and wander (on hard materials). the short and stocky design on the center bit and the chuck which holds the bit is very close to the work. the center bit doesn't drift/wander. using this to start a hole ensures the hole is centered.
did i wander too much? is it clear as the muddy mississippi?

 

[BruceA]

Brad Point bits are awesome-

I just tried a couple brad point bits this weekend (3/8", 27/64ths") and they are an excellent way to go! I simply put a dimple in the blank with a spring-loaded punch, centered the blank in my pen vise so the brad point of the bit was in the center of the dimple, and drilled away with the drill press.

The bits were from Woodcraft, and are very sharp, and produce a clean hole, and no problems during exit in the amboyna I was drilling.

The brad point solves a recurring problem I was having of knowing if the drill was centered on the blank, because a standard bit is difficult to see exactly where the tip is landing. With the brad point, it's very easy to see precisely where it's landing on the blank.

If you haven't tried one of these bits before, check one out.

Looks like Lee Valley has a complete selection of the same type of brad point bits, too.

Bruce in TN.

 

[alexkuzn]

I don't know why nobody mentioned it so far.
To minimize "wandering" you can use short length drill bits.
(after punching and center drilling of course)
Regular length normally referred as "jobber" length.

This is common technique for drilling metals. Should work for wood too.