What is the Alure of D bits?

[projectnut]

Lately there have been a number of posts concerning the use, creation, and sharpening of D bits. I must admit in all my years of machining I've never purchased one, and never even used one. The majority of the work I've done has been with standard end mills, and standard profile lathe tooling. Occasionally I'll need to make a form tool or order a special mill, but those times have been minimal.

What can a D bit do that either a standard end mill, reamer, or twist drill can't do?

 

[Jake M]

What can a D bit do that either a standard end mill, reamer, or twist drill can't do?

I don't think the use for them is that they outdo other types of tools (although I'd bet there are some applications where they might be preferred?), rather I think the attraction is that they can be created in house, from scratch, to any size or shape that is needed, on a very (relatively) affordable machine, with far less calculation and design time, and manufacturing time than other tools, and can be ready to go in a very short period of time.

Or maybe they just hit the internet so now everybody needs one. I kinda doubt that though, as commercial D bit grinders have been around for a very long time.

 

[woodchucker]

Exactly as Jake says. simple to create.

 

[jwmay]

I was under the impression they were mostly for pantograph work. Shows what I know.

 

[woodchucker]

I was under the impression they were mostly for pantograph work. Shows what I know.

they work for that too. milling. Anything you can think of where a spinning or drilling bit is needed.
Even a lathe tailstock for drilling or forming a hole.. say you needed a specific shape at the bottom of the hole... like a valve or something, you could create a bit with the profile.

 

[SLK001]

What can a D bit do that either a standard end mill, reamer, or twist drill can't do?

It can be made fairly quickly, when you don't have the correct size drill. It's for "when you absolutely, positively need that bit NOW!"

 

[jwmelvin]

I needed to put in a taper pin a while back, so made an appropriate reamer for the one hole I needed, as a d-bit made from an old end mill:

 

[benmychree]

They really have little use outside of engraving, which is what they are mainly for.

 

[GeneT45]

They really have little use outside of engraving, which is what they are mainly for.

Agreed. The fact that they can cut an obscure dovetail, an o-ring groove, a chamfer, a radius, or some bespoke profile, is unimportant.

GsT

 

[pontiac428]

Versatility. Ease. Low cost. Chatter-free countersinkning/counterboring. Profiles. D-bit drills are a single point tool, too slow for production but drills straighter than a twist drill and produces a reamer-like finish.