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Rule of Thumb for Chamfer Dimention in Drilled Holes

Rule of Thumb for Chamfer Dimention in Drilled Holes

Rule of Thumb for Chamfer Dimention in Drilled Holes

(OP)
Hey folks,

We are dealing with a cylinder (rod) with a few full-depth holes drilled cross-wise.

I am wondering if anyone has a rule of thumb for chamfer / fillet sizes for the edges of drilled holes.

Basically, I am trying to figure out if there is a easy way to rough guess at the optimal chamfer / fillet sizes as either a function of the diameter of the hole versus the diameter of the bar or as a function of the diameter of the hole.

I am not looking for any sort of perfect number, but more a conceptual model as to what 'reasonable' looks like...

Cheers!

RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

Optimal for what?

RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

(OP)

The primary purpose of the chamfer / fillet is to reduce stress risers that result from non-axial loads.

I recognize that this will vary depending on the angle of the load, but I am not looking for a ideal number. I am more looking for a rule of reasonableness. If you any any such rule you tend to go by even if not perfectly applicable I would be quite interested.

 

RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

With cross-drilled holes, take into account the curvature of the rod, then a chamfer that is visible all around the hole would be good. Hard numbers would be hard to calculate.
 

"Wildfires are dangerous, hard to control, and economically catastrophic."

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RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

For tight tolerances in space-limited applications, I sometimes use a .047±.005 chamfer with a .032±.010 radius so that the features never bump. I wouldn't consider holding either tolerance any tighter than that.

RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

(OP)
In the interests of full disclosure I should say that an old machinist told me told me that his experience was that on curved materials that are thicker than the hole diameter (like rods) a good approximation is chamfer so that the narrowest part of the chamfer is about 10% the diameter of the hole. I was just trying to get a feel if that was a reasonable starting point.  

RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

If the chamfer is to fit a screw head so the head is flush with the surface, then you have to start with the available screw sizes (Nbr 6, nbr 8, nbr 10, nbr 12, 14, 1/4 inch, 5/16, etc.), decide what size suits the forces you need, plot the screw against the diameter of your work so the head is recessed, then get the chanfer from what's left over.

 

RE: Rule of Thumb for Chamfer Dimention in Drilled Holes

(OP)
I am sorry I should have been more clear. This is just chamfering to avoid undo stress risers. Obviously, it will vary with material etc. Thanks for all the feedback!

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