Simple jig for drill bit sharpening

[Jan]

Tormek Drill Bit Sharpening Attachment DBS-22 remains on my wish list while the dull bits fill my drawer. So I have decided to make a simple jig for drill bit sharpening. As you surely know they are dozens videos on web concerning twist drill bit sharpening.

In the attached picture you can see that my drill bit jig consists of a pertinax plate which slides on the scissors jig base. An aluminium L profile is used as a guidance for drill bit orientation. The guidance profile shown in the picture is for the most common drill bit point angle of 118°. The lip clearance angle is set by tilting the base. I have used a lip clearance angle of 10°.

Originally I have planned to sharpen the drill bits with the basic cone geometry, where the two cutting lips meet and form a chisel edge. When I have learned this basic approach, I began to think about whether this simple drill bit jig would enable to ground 4-facet point also. 

It turned out that with careful work it is well possible. First I have ground the primary facets using a clearance angle of 10°. Than I have tilted the base by another 10° and ground the secondary facets. So the clearance angle of the secondary facets is 20°.

I have tested the re-shaped drill bit in iron and can confirm that the 4-facet geometry works well. At first glance it is obvious that it performs better than a drill bit with the basic cone geometry and chisel edge. 

Jan

[Dutchman]

Great idea. Thanks!
The tilting makes the difference.

[Jan]

Yes, Ton, you are correct, the clearance of the cutting lips is crucial! 

The attached picture shows how simple is the setting of the clearance angle for the secondary facet to 20°. The 10° and 20° marks on the side of the stone are for a specific distance between the USB and the shaft. The alignment bar has a height equal to the drill bit radius. 

Jan

[RobinW]

Jan

When sharpening say several drills, do you start creating grooves in the surface of the stone?

Behind my question is a previous subject I posted some months ago. I found that when sharpening gouges the surface of my stone ended up with grooves and ridges, which is a pain as most of my sharpening is flat blades (planes and chisels).

Also my immediate thought was to adapt your method and sharpen drills on the side of the stone. (I must admit it is years since I sharpened any drills and I just buy new as required. More effective use of my time.)
Robin

[Jan]

Good question, Robin.

My experience is limited to SG stone. Yes, I have observed a tendency for creating grooves and because of this I move the drill bit sideways and use the whole width of the stone. I often re-activate the grindstone.

The major factor influencing creation of grooves is steel hardness and grindability. I have found that drill bits with HRC up to 40 do not generate grooves. The tendency for creating grooves starts circa with HRC 50, which is the hardness of the majority of my drill bits.

The worst situation is with high quality tools made of cobalt high speed steel (HSS-E) because their HRC is more than 65. This cobalt steel is often used for countersinks.

Sharpening and re-shaping of drill bits is a quite good fun, plus you can remodel your broken or burned drill bits into unique tools designed for aluminum, plexiglass or composite with special point angles and cutting lip clearance. I see it as my small contribution to sustainability.   

Jan

[Dutchman]

... The attached picture shows how simple is the setting of the clearance angle for the secondary facet to 20°. The 10° and 20° marks on the side of the stone are for a specific distance between the USB and the shaft. The alignment bar has a height equal to the drill bit radius. 
Jan

Very clever !
I was already thinking how to solve that adjustment   
I made a PDF-file with the description and attached it.

[RichColvin]

Jan,

I have the DBS Jig & find it a worthwhile investment.   But what intrigues me about your idea is for bits too large to fit in the DBS Jig (>22 mm).   Have you tried any that large ?

Kind regards,
Rich

[Ken S]

Jan,

You are the jigmaker.

Very clever.

Ken

[Jan]

Tony and Ken, thanks for your appreciation! 

Rich, my larges drill bits are about 15 mm, but I did sharpen them yet.

From geometrical point of view there are no limits to the drill bit diameter. If you use my method to set clearance angles please keep in mind that the height of the aligning bar has to be equal to the drill bit radius. 

Otherwise I would recommend the attached Tormek advice for thicker drill bits.

Jan

[Ken S]

Jan,

By reversing the direction of your angle bracket, your jig could be used with left handed drill bits. A left hand jig would also be useful for professional sharpeners already using the DBS-22 for day to day right handed bits.

Ken

[Jan]

Yes, you are correct, Ken, by reversing the direction of the drill guidance the jig can be used for left handed drill bits also. I cannot test it because I probably have no left handed drill bits in my collection.

Jan

[Dutchman]

Thanks  Jan
I made an update of the attached PDF-file

[Jan]

Thank you also Tony, it is practical to have it stored together in one pdf file for future use. 

Jan

[Jan]

Recently I bought the fine diamond wheel DF-250 and started to use it for drill bit sharpening. My simple jig for drill sharpening remained unchanged, the only difference is that the scissors base I use as a platform is mounted to the side of the diamond wheel using multi base MB-100.

Setting the lip clearance angle is very simple. I prepared two angle setting blocks 11-14⁰ and 7-9⁰ for different drill bit diameters.

The diamond wheel allows to sharpen masonry drill bits also.

Jan

[Ken S]

Fascinating idea, Jan!

Ken