Uneven P&S Facets

[Mewsikman]

Hello,

I'm having an inconsistent error. It's more than likely to be me and how I set up the machine but 8 thought I'd ask if anyone else has had similar issues.

When grinding the P Facet on a 4 Facet drill then moving onto the S Facet I am finding that once I have set a depth of grind, I am then getting an uneven S Facet. To true up the S Facet with the other I might have to increase or back off the grind depth to get even looking P&S Facets otherwise I'll end up losing the P Facet all together.  Is this normal or am I experiencing a warped drill bit or that the drill clamp isn't holding it true?

I've hopefully attached a picture of what I mean. All Facets have been ground to the same depth.

Any pointers would be greatly appreciated

Alex

[RichColvin]

Alex,

If it is only happening occasionally, I doubt it is the DBS-22 jig.  That leaves two other options:

   
• Either your technique is suspect, or
• The drill was not properly made.

Looking at the picture you attached, #2 seems to be a very likely cause.  The shape of the left side doesn't seem to match the right side.

Kind regards,
Rich

[RickKrung]

I am struggling to understand this.  Rich is suggesting the drill geometry is not consistent, I think.  I am not seeing what you are suggesting, Rich.  Some elaboration might help as to what seems to be mismatched between the sides.  The grinds are different for sure and that may be confusing my brain. 

I do see something suspect, to me, however, regarding the outer tips of the primary facets.  The leading edge of the primary facets appear to not be straight.  I see a slight curvature at the tips, sloping rearward.  That seems very odd.  All of my drlls, that tip corner is sharp and the leading edge is straight right out to the tip.  This makes me suspect the drill, which is consistent with what Rich is saying, I think. 

By best example photo is of my first drill sharpened with the 4-facet grind. 


Disregard the weird "third" facet on the lower second facet.  I don't recall how/why that happened, but the point here are the tips/corners of the primary facets.  These corners on your drill do not appear to be sharp, as in my photo. 

My other though it whether it is that the grind of one of the secondary facets is just not complete and wonder if you adjusted the depth on that one facet until it matches/meets the others in the center.  It shouldn't be necessary to do that, but if it works, that might be a way to compare the geometry of the two sides.   

If the geometry of the drill is suspect, what comes to mind is what is the quality level of the drill. 

Puzzling,

Rick

[RichColvin]

In Alex's picture, the left side seems to have either a secondary point angle (see also, https://sharpeninghandbook.info/GT-DrillBits-Twist.html) or a margin (see also the picture below).  The right side does not seem to have that, but it may be the picture.

My thinking is that this may be a drill bit that was not made as well and consistently as it should.

Hope that helps explain my response.

Kind regards,
Rich

[RickKrung]

That was very helpful, Rich.  Thanks.  I agree with you about the OP's drill.  For reference, I've annotated his photo here.
 

A = Margin on the left side,
B = Margin on the right side. 

The A margin seems very much more pronounced than the C margin.  Hard to know if it is real or just the photo, but there certainly appears to be a difference.  Hopefully, Alex can provide one or more additional photos to clarify.

Rick

[micha]

I just want to add that I've seen the very same once in a while. Having sharpened several hundred bits I sorted out a handful. There seem to be some which withstand any attempt to get sensible cutting lips without rounded corners.
I'm still not sure about the reason for this - strange manufacturing with different flutes, bits not being straight or else.
Initially I also tried sharpening such bits over and over, but without success, so meanwhile these go into the metal trash without further regret

[Ken S]

As a retired thirty five year telephone installation/repair technician who used all kinds of drill bits almost every day, not all drill bits needing sharpening have been carefully used. Drill bits are often some of the misused and abused of tools.

Ken

[Mewsikman]

Hi guys,

Apologies for the late reply and thank you for the suggestions. I have experienced this issue across a wide variety of manufacturers of drills, even Dorma. This is what started me to believe that I was doing something wrong.

I have recently been able to purchase a Deckel SOE tool grinder which has massively increased my sharpening productivity. Even with the SOE I am experiencing this issue. I have gone from the Tormek with one of these drills and put it in the Deckel and it replicating the same results which to me means it must be the drill bit.

[ega]

Good to know that the Tormek is  exonerated!
I bet you make some sweet mewsik on the Deckel.

[jvh]

Hello,

I'm having an inconsistent error. It's more than likely to be me and how I set up the machine but 8 thought I'd ask if anyone else has had similar issues.

When grinding the P Facet on a 4 Facet drill then moving onto the S Facet I am finding that once I have set a depth of grind, I am then getting an uneven S Facet. To true up the S Facet with the other I might have to increase or back off the grind depth to get even looking P&S Facets otherwise I'll end up losing the P Facet all together.  Is this normal or am I experiencing a warped drill bit or that the drill clamp isn't holding it true?

I've hopefully attached a picture of what I mean. All Facets have been ground to the same depth.

Any pointers would be greatly appreciated

Alex

Hello,

what was grinded point angle (seems to be 120 °)? Could the original angle be higher than grinded? (Eg. hard steel drill bit with point angle 140-150°.)

jvh