Modeling twist drill tips

[McLeod]

[Cross-posted from the "Sharp Tool Engineering" forum]

I'm modeling a custom twist drill in Solid Edge and having trouble creating the tip features which are defined by the following standard parameters:

- lip relief angle
- chisel edge angle
- point angle

Machinery's Handbook (26th ed, p. 828) and other references define how those parameters are measured, but some of them cannot be used to create the features directly because the software uses different input parameters (e.g. pitch vs. helix angle of the flutes). I've checked some similar in-house drawings and models, but apparently I'm not the only one who's confused, because the more complex details look like they were fudged into the model, and the drawings rely heavily on note verbiage. I've also been all over the web searching for custom mfg. vendor design guides or actual models and drawings - so far I haven't found much beyond what's already available in Machinery's.

Can anyone provide insight regarding good modeling and specification practices for this type of part? What kind of cutout features (helical, extruded, conical, etc.) or combinations of features best mimic the mfg. process for the geometry behind the three listed parameters?

 

[meintsi]

Create your helix as you have suggested but end it flat. (ie. a dill bit cut in half)

Now a cut-loft will get you half of your tip and mirror the featur for the second flute.



Remember...
"If you don't use your head,
your going to have to use your feet."

 

[McLeod]

meintsi -

By "cut in half", I assume that you mean transversely to the long axis, which is what I've got so far: a plain cylindrical extrusion with two helical flutes. The ends are flat and perpendicular to the axis.

If I cut away material by any method (revolved, helical, lofted, extruded, etc.) to create the tip, then the cutting lips are no longer straight edges, because the edge is following the helical path of the flutes as it moves away from the end of the axis. The standard drills, both actual parts and the handbook diagrams, indicate that the leading edges are straight.

Could a lofted protrusion achieve the correct profile? If so, how should the directing curves be constructed?

 

[EdDanzer]

Your model should reflect what is done in manufacturing. The method of sharpening should provide a clearance angle that your company decides is best.
A solid model is just an electronic representation of what the manufactured product looks like. Communication with manufacturing as to what they actually ship, not what you think is being shipped, will relieve many problems.
If you are trying to make a new design, then you must work with manufacturing to be sure they can make what you design, by finding out how they will produce it.