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I have 2 endmills as well as several Forstner bits. The endmills I have do not have a pilot bit. One is a 4 flute 13/16"and the other is a 5/8" with only 2 flutes. What is the purpose of the center, pilot bit in a counterbore that is built to hold one? I'm assuming that the pilot bits purpose is to make first contact with the shank face and or rod surface you are facing?
Second question is does it matter if you use a larger endmill and or Forstner bit or counterbore than the size of the stem you wish to use? For example, if you intend to use a 5/8" stem can you use a larger Forstner like say a 3/4" or 13/16"?
Thank you

The pilot rides the mortise which you should have already drilled. The front cutters on the counterbore cut the shank face perpendicular with the mortise. Depending on how rigid your drill press is, it may be more accurate than an end mill or the Forster bit.
Those who can chuck the briar in their lathes can cut the shank face directly or use a pin gauge and cut it from the other side.
The cutter size should be large enough to cut the entire face of the shank where the stem/rod meets the shank but there is no problem for using a larger one.(unless you you want a recessed shank face, in which case you need one close to, but slightly larger than, the stem/rod)
DocAitch

Perhaps there is a terminology thing going here. The pilot on an aircraft type counter bore is not a "bit". It has no cutting function at all. It is solely there to guide the cutter since the cutting surface of the tool is virtually flat it can wander unless the setup is super rigid as Doc says. The fit of the pilot to the hole that is being c-bored must be right on or, again, things can wander off.
That being said I had some cutters made for me by Fuller (the usual go-to for tapered bits) that do have a cutting pilot, thus I can cut the airway and mortise in one shot. You see this a lot in the European factories where time is money. One set up instead of two.

Thanks guys. I think the light finally went on about the pilot's purpose after I re-read docs comment, and Reds. I meant to say 5/16" not 5/32" delrin.
Sorry.

I have used those Fuller devices and I have 2 minor problems with them. They have ears which have to be ground off to get a larger flat surface, and the mortise drill has to be exactly the right size if you are using Delrin tenons.
I use a reamer after drilling my mortise 1/64" under sized cause I like to have the option of using Delrin.
DocAitch

DocAitch wrote:I have used those Fuller devices and I have 2 minor problems with them. They have ears which have to be ground off to get a larger flat surface, and the mortise drill has to be exactly the right size if you are using Delrin tenons.
I use a reamer after drilling my mortise 1/64" under sized cause I like to have the option of using Delrin.
DocAitch

Doc,
If you dig deeper into Fuller's catalog (page 33) you will find a section dealing with specials. My bits do not have the spurs. They take a standard twist drill and modify it to your specs (within their limitations). Mine are Style 3 with 180 degrees called for under "G". In my case the short pilot drill reached the chamber. If one has a situation where is does not reach, it is quick and easy to follow up with a 5/32 to get to the chamber. This one started as a screw-machine length bit with a .406 diameter. I also had them grind a slight taper on the body. Works great.

End mills and Forstner bits just complicate things, imo. Unless using a high quality machine lathe AND high precision tools at EVERY link in the chain, each step adds slop.

Here's a simple method that does away with all that:

-- Drill mortise & ream w/chucking reamer

-- Chuck whatever pin gauge is "squeak tight" into that mortise into the lathe jaws.

-- Center pin gauge w/dial indicator

-- Push the stummel onto the pin gauge, fire up the lathe, and gently cut straight into the end of the shank from the side with a glinty-sharp cutting tool of the appropriate shape.

No tailstock slop, no chuck (in the tail stock) slop, no cutter (in the chuck in the tail stock) slop... And you are working from the ACTUAL mortise hole, not the "theoretical" one you TRIED to drill (they are never the same).

End result? Dead-on, light-tight fit every time.

LatakiaLover wrote:End mills and Forstner bits just complicate things, imo. Unless using a high quality machine lathe AND high precision tools at EVERY link in the chain, each step adds slop.

Here's a simple method that does away with all that:

-- Drill mortise & ream w/chucking reamer

-- Chuck whatever pin gauge is "squeak tight" into that mortise into the lathe jaws.

-- Center pin gauge w/dial indicator

-- Push the stummel onto the pin gauge, fire up the lathe, and gently cut straight into the end of the shank from the side with a glinty-sharp cutting tool of the appropriate shape.

No tailstock slop, no chuck (in the tail stock) slop, no cutter (in the chuck in the tail stock) slop... And you are working from the ACTUAL mortise hole, not the "theoretical" one you TRIED to drill (they are never the same).

End result? Dead-on, light-tight fit every time.

You're absolutely right George and that is the technique I normally use. The bit I show above was for a special case and the combo approach simplified things greatly.

LatakiaLover wrote:End mills and Forstner bits just complicate things, imo. Unless using a high quality machine lathe AND high precision tools at EVERY link in the chain, each step adds slop.

Here's a simple method that does away with all that:

-- Drill mortise & ream w/chucking reamer

-- Chuck whatever pin gauge is "squeak tight" into that mortise into the lathe jaws.

-- Center pin gauge w/dial indicator

-- Push the stummel onto the pin gauge, fire up the lathe, and gently cut straight into the end of the shank from the side with a glinty-sharp cutting tool of the appropriate shape.

No tailstock slop, no chuck (in the tail stock) slop, no cutter (in the chuck in the tail stock) slop... And you are working from the ACTUAL mortise hole, not the "theoretical" one you TRIED to drill (they are never the same).

End result? Dead-on, light-tight fit every time.

This is so helpful, thank you. I need to get some pin gauges and a dial indicator.

Then there are those of us using a $500 Harbor Freight lathe and a $200 Harbor Freight drill press.( and who have never heard of a pin gauge prior to 2 years ago).

These ain't Swiss watches.
DocAitch

DocAitch wrote: These ain't Swiss watches.

But you can always tell which pipe makers approach their cutting, shaping, and finishing as if they were.

Always.

And then there are the rest of us.
DocAitch

DocAitch wrote:And then there are the rest of us.

As in, those who choose not to, or those who claim they can't for some reason?

#1 is valid, #2 is BS.

And 3) those of us who do the best we can with the time, equipment and funds that we choose to commit but realize that there is a point of diminishing returns when chasing "Swiss watch" standards. We individually choose that point.
DocAitch

What I was referring to is an attitude, not a boundary.

Thank you, thank you, thank you! For your awesome comments.
I'm embarrassed to admit it but I'm still trying to wrap my head around what pin gauges are used for. George, I'm having difficulty picturing your comments in my mind. Any chance you could please possibly post a few pics?

Jam the mortise onto a cylinder of steel (must be a tight fit) after the cylinder is chucked into your lathe and centered, then cut the face closest to the chuck jaws.
Sounds tricky to me, but a couple guys do it that way.
I'm still using the counterbore.
DocAitch

I use a counterbore with interchangeable pilot, I got it from Enco, now MSC. Dead on everytime.