Six facet grind with DBS-22?

[Elden]

   Is it possible to do a 6 facet grind with the DBS-22? This question started lurking in my mind after reading the article "DRILL POINT GEOMETRY by JOSEPH MAZOFF", the link to which RichColvin posted.

https://forum.tormek.com/index.php?topic=3263.msg19351#msg19351

   After considering the the idea along with some more research, I am thinking that it may be possible.

   This is not the first time this question has arisen on the forum. My memory was telling me that it had been brought up before. That is what the search feature is for, correct? In Oct. 2014, Scott oz posted:

https://forum.tormek.com/index.php?topic=2266.0

Interestingly, the link he posted was by Joseph Mazoff, the same author of the article that RichColvin posted the link to. Much of the the same material is in both articles. I do not remember reading the article Scott posted about at that time.

   The 6 facet grind has 2 Secondary Point Angles (SPA) added to the 4 facet grind. See the below attached photo. The picture also shows an added split point on the drill bit (labeled split). Ignore the split point as I am not referring to it at this time (that may be a future thought to think about).

   As I understand it, the SPA or the 6 facet is simply adding a more acute angle on the outer edge of the primary bevel and part of the secondary bevel.. This makes the sharp outer point of the cutting lip to be less pronounced (a chamfer so to speak) thus increasing the bit's longevity as well as other benefits.

   I found the following sites interesting. The first one is part of the second longer article.

http://www.gadgetbuilder.com/DrillSharp.html#Facet4
http://www.gadgetbuilder.com/DrillSharp.html

   Thoughts anyone?

[Ken S]

Elden,

Bravo! You bring up a most interesting topic. It is humbling to realize how little I know about drills and drilling in spite of soending thirty five years drilling holes as a telephone man. (Everything from star drills, brace and bits, Yankee drills, to cordless hammer drills)

It is late, and even this insomniac must try to sleep. I just wanted to show my interest.

Ken

[Jan]

Thank you Elden for opening this interesting topic. 

The Joe Mazoff definition of 6 faceted drills is a little bit surprising for me. Until now I understood the 6 facet concept as an extension of the 4 facet's concept by adding another secondary relief where all intersection planes meet at the drill axis. The other secondary relief (ternary relief) has an angle of some 40 to 45° (see the first picture).

Nevertheless the full Mazoff term "6 faceted drill with secondary point angles (SPA)" is clarifying the situation (see the second attached picture).

What I have found interesting on my newer drills is that the heel edge of the land is eliminated. They call it CZ002 grind (see the third attached picture).

Jan

P.S.: Following Joe Mazoff the secondary point angles should be half the primary point angles. I am wondering if the DBS-22 would allow to set such a small point angle. 

[RichColvin]

Jan,

I'd always thought as you that a 6-point grind was as in your first picture.  It provides even more space for removal of the swarf.

I don't understand the value of the SPA.  I don't know how that helps with cutting. 

Any thoughts?

Kind regards,
Rich

[Elden]

   In the researching I did, somewhere it was stated that the SPAs helped reduce the breakthrough grabbing that occurs when drilling pipe or tube. Increased drill bit life was brought out. Personally, I have not used one that I am aware of. Below are a couple of quotes.


From http://www.gadgetbuilder.com/DrillSharp.html#Facet4

"Secondary Point Angles (SPAs) can be added to extend drill life, improve hole finish and minimize the exit burr on through-drilled holes.

The 11/32" drill shown at right [below (Elden)] has small SPA's added making it 6 facet. These extra facets cause the drill to have a stronger self centering action plus the shearing action often produces a better finish in the hole. The sharp outer point on the cutting lip, a common failure point (pun), is eliminated so the drill remains sharp longer."


From  "DRILL POINT GEOMETRY" by Joseph Mazoff

"The 6 faceted drill with secondary point angles (SPA) is the most durable of points, but least understood and utilized. The 5th and 6th facets form secondary drill point angles (fig. G & H). The weakest area of the point is the outside cutting lip corners which are also exposed to the greatest amount of stress and travel. Consequently, drill points break down most frequently at those corners. Secondary point angles reduce those acute angles. (fig.H) to reduce corner breakdown, and consequently, reduces regrinding frequency which increases drill life. By actual tests in our shop, we have obtained as high as 700% more holes than a conventional conical ground At the Ford Motors Engine Plant in Ohio, the computer indicated an expected life cycle of 8000 holes. However once the same conventional drills were reground with the fig. H chamfered point, the computer printout showed a productivity of 31,057 holes. In compliance with my recommendation that Ford Motors reduce the cutting clearance, productivity increased to 37,100 holes at which time the drilling project was completed; but the drills were still in excellent condition. The attributing factors for such a sharp increase in productivity were the flat grind combined with the chamfered corners in G and H. Metal being drilled was cast iron. Secondary point angles produce secondary cutting lips that angle toward the heel corners (fig. G). As the drill rotates, the back of the secondary lips cuts metal with a slicing action which further reduces lip corner breakdown and less heat, drill torque, and less binding as the drill exits from the hole. This point is ideal for core holes and to material, producing burr free holes. There is also greater hole accuracy since the secondary point angles offer a self-seating, reaming action that resists lateral pressures. In addition, this point has good chip breaking properties since the primary and secondary cutting edges in fig. G, produces an angular formed ribbon that breaks readily as it curls against the flute surfaces. The amount of degrees that's ground on the secondary point angles is determined by what angles were ground for the primary point angles. The rule to follow is to split the angles evenly. As an example, if one side of the primary point angle is 67?, then the secondary would be half of or 33-1/2 and etc. This splitting of the angles is best seen in fig. H. However, there are some exceptions in splitting the angles such as plastics, in which case, the secondary angles should be decreased (more spearshaped). As to lip clearance angles of secondary cutting lips, they are generally the same as the primary lip clearance angles SPA can be added to all other points for increased accuracy and durability.)"

[Janne]

https://www.dropbox.com/s/c6vpjc3tcxovh4f/6%20facett%201.JPG?dl=0
https://www.dropbox.com/s/zt0zuv1js5yj629/6%20facett%202.JPG?dl=0
Made on the DBS-22 with 7 deg resp 45 deg
Janne

[Janne]

To be more specific and correcting a mistake at typing, 7 degree clearance and 60 degree edge (in stead of 118 degree) for the number 5 and  6 facets. No number 7 or 8 facets ;-)
Regards Janne

[Elden]

Excellent Janne! Did you accomplish that without any modification to the DBS-22? Mine has been packed away in storage due to moving. Just saw the Tormek stuff the other day, hope to get pulled out and in use sometime soon!

[Elden]

   Here is a link to a fairly simple DBS-22 modification by Kurt Johansson allowing the sharpening of brad point and spade bits.

https://forum.tormek.com/index.php?topic=1622.msg7028#msg7028

   I wish this thread was here in the drill bit sharpening sub-topic instead of  the general sub-topic. I believe it was written before the drill bit sub-topic was created.

[Janne]

Hello. I drilled a new hole to the left of the original hole for the locking screw. I happend to use a drill bit sharpened with the DBS-22...
Regards Janne

[Ken S]

Elden,

Good thought to move this topic. (My first move as moderator.   )

Ken

[Elden]

   Thank you for moving it, Ken.

[Ken S]

No problem. Thanks for the good suggestion, Elden.

Ken