Purpose of basal grinding?

[Tonawanda]

I don't understand why the base only is ground on some points.
Projectile points and many knives are attached to shafts or handles, but on some point types what does that have to do with basal grinding?  Wouldn't a sharper base better grip into the mounting material?
I can see why the SIDES of a point or stem might be smoothed: to avoid cutting into the hafting material used to secure the point to the shaft.  But why grind a base?

[GA_Dave]

maybe better balance

[CliffJ]

To keep from splitting the shaft of the haft.

[11KBP]

Tonawanda wrote:

I don't understand why the base only is ground on some points.
Projectile points and many knives are attached to shafts or handles, but on some point types what does that have to do with basal grinding?  Wouldn't a sharper base better grip into the mounting material?
I can see why the SIDES of a point or stem might be smoothed: to avoid cutting into the hafting material used to secure the point to the shaft.  But why grind a base?

  Part of the hafting material oftentimes extended above the base edge. Studies have also demonstrated that the edge grinding on the basal area can help reduce breakage in that area upon impact.
11KBP

[Bill]

That's a great question Tonawanda. There is no definitive answer to your question so anybody's guess is as good as anybody else’s.
I believe Cliff has it right because basal grinding would have had a functional purpose and a conventional one too because lateral basal grinding was a technique that was held over from the PaleoAmerican Period.
During the PaleoAmerican Period tying the basal ends of the long lanceolates of the Period securely to a stick would have made made them less likely to move sideways off the haft. If the bases were ground along both lower side edges and arcoss the basal edge, if the projectile attempted to move sideways then it couldn't cut throgh the binding.   
Since it probably would have made hafting a lanceolate type of projectile point to a stick better, everyone did it and this technique continued until the end of the Early Archaic period in the southeastern US.
Beginning in the Late Early Archaic Period in the South East even though projectile point grinding continued on the basal top edges the practice of dulling the basal side edges and across basal end had stopped.
This was probably because long lanceolate type points were no longer needed and the shorter ones that were used then could be more easily tied securely.

[Tonawanda]

Thank you for the explanations.  They're a reminder that form does derive from function whether we completely understand the reasons or not.  If there were courses offered (college, community college, etc.) on the specific subject of Native American artifacts, I'd sign up!  Nothing like that here that I know of in Western New York.