Sharpening Drill Bits - Anyone for an AM Handbook Article?

[KC4VWU]

To check that 114 degree angle, take two hex nuts and hold them together between your thumb and index finger on one of their flat edges. Use the resulting angle on the top or bottom to "gauge" the sharpening progress on your bit.

[W7TFO]

I already said that several posts back....

73DG

[kg8lb]

VK7ZL had good comments as were the comments regarding the spur bit for thin metals earlier.
Good (Twist )drill sharpening is best done on specialized machinery . Different point angles, relief angles etc apply very strongly for different uses. While this may not be as apparent for most of the stuff put together by ham radio people proper machine sharpening does indeed make a huge difference in output , tool life and quality over the long haul.The right tool for the job ! The brad point, or tip and spur bit,already mentiond used with a pilot hole provides a fairly good hole in thin metals and wood. These are available store bought but are often shop made from plain twist drills. When drilling grabby metals like brass , the cutting edge of the drill is blunted a bit to avoid the drill hogging and self feeding.( It doesn't take much, A hand whetstone works well on most small drills )
 Most twist drills have flute webs that become thicker as you move away from the tip. This makes effective sharpening of shortened drills increasingly difficult.
  Still, hand grinding and making up of special purpose drills takes place. However for good , productive work within the normal range of sizes we use, machine sharpened drills are hard to beat.
  The right cutting fluids are often overlooked in importance. Most drilling and tapping operations are greatly improved by the application of the correct fluids or compounds.

 BTW: Hole punches are a good alternative to drilling when possible.

[K1JJ]

How about sharpening hole punches?

I have an old Greenlee 2.75" punch that I've used for 30 years to pop out those common, old buzzard  3" round meter holes.  It's gotten to the point where I needed an extension pipe to make it turn and cut through. Dull, after going thru countless steel and aluminum panels..

I brought it to a metal shop and they waved it off, saying it was difficult to sharpen without ruining it. A friend tried to sharpen it and it appears to be ruined - doesn't cut thru anymore... sigh. I guess once a little metal is removed from one of two halves, the tight fit is gone and it doesn't work well.


This is the one - goes for about $220 now. I paid $40 back in 1972... :-)
http://www.all-spec.com/products/730BB234.html


Anyone have ideas on this?  

T

[W7TFO]

Tom, you need a good-sized flat wheel to start with.  Take the open end cup part and run it flat against the side of the wheel for enough time to bring up a new surface only.

Then take the punch part and run each shearing edge to the same extent.  Keep the minimal grinding such that the point formed by the two edges is centered.

You will notice that edge is perfectly straight on each side.  If the punch has been ground in any other area, it is probably ruined.

I have many of them and all are still going strong after years of use with this technique.   It also really helps to keep the pull screw lubed with a bit of light oil while using.

73DG

[Jim KF2SY]

How about sharpening hole punches?

I have an old Greenlee 2.75" punch that I've used for 30 years to pop out those common, old buzzard  3" round meter holes.  It's gotten to the point where I needed an extension pipe to make it turn and cut through. Dull, after going thru countless steel and aluminum panels..

I brought it to a metal shop and they waved it off, saying it was difficult to sharpen without ruining it. A friend tried to sharpen it and it appears to be ruined - doesn't cut thru anymore... sigh. I guess once a little metal is removed from one of two halves, the tight fit is gone and it doesn't work well.


This is the one - goes for about $220 now. I paid $40 back in 1972... :-)
http://www.all-spec.com/products/730BB234.html



Anyone have ideas on this?  

T

Why pay more ?
This nifty set comes with an ironclad 30 day guarantee:

http://www.harborfreight.com/knockout-punch-kit-91201.html

    

[kg8lb]

How about sharpening hole punches?

I have an old Greenlee 2.75" punch that I've used for 30 years to pop out those common, old buzzard  3" round meter holes.  It's gotten to the point where I needed an extension pipe to make it turn and cut through. Dull, after going thru countless steel and aluminum panels..

I brought it to a metal shop and they waved it off, saying it was difficult to sharpen without ruining it. A friend tried to sharpen it and it appears to be ruined - doesn't cut thru anymore... sigh. I guess once a little metal is removed from one of two halves, the tight fit is gone and it doesn't work well.


This is the one - goes for about $220 now. I paid $40 back in 1972... :-)
http://www.all-spec.com/products/730BB234.html


Anyone have ideas on this?  

T

  The male side (punch) and the female side (die) have very little life for sharpening. There is usuall a relief or slight taper to the ID of the die . Some punches have a relief on the OD as well. The set is designed with a clearance between the two, depending upon the material type and thickness. Sharpening should be done only sparingly. If you would like to send the set to me I could probably reweld and grind them to near new spec.

[Steve - K4HX]

http://amfone.net/Amforum/index.php?topic=26458.0