DBS-22, sharpening drill bits for metalwork. with little to no success

[Lokepus]

Howdy folks. I have recently aquired myself a DBS-22 that im going to use for metalwork. i have sharpened about 60 drill bits so far. and everything was looking perfect. most of the drill bits are made of HSS steel and around 5-12mm in diameter. after sharpening them all i tried drilling with them in both aluminum and mild steel. but they wont cut at all. not even the smmaller ones. i am using the correct angles and everything. but it seems to me that the "center of the drill" wont cut comparet to a "new" one the primary facets dont cut the center. is there anything i can do to fix this issue? or is it just one "flaw" of the 4 faced sharpening method? if i predrill with say a 3mm for a 6mm hole everything works like a charm. but i dont think that should be needed for a 6mm drill. Thoughts?

[tgbto]

Hello,

Do you think you could post a picture of the bit point after sharpening ? What grinding wheel did you use ? I have sharpened HSS bits up to 12 mm on a diamond wheel or SB wheel without any issue afterwards.

If anything, a four-facet grind should cut better at (around) the center instead of walking as a standard two-facet grind.

[Lokepus]

Yeah, ill try and get some photos for you

herre they are
https://imgur.com/4vvaT92

https://imgur.com/dCcdAtO
the drill bit in the images i have not yet tested, but the rest of the bits ive sharpened look exatly like it. ive been using 118 - 9 - 9 for most of the bits


im using a 250mm blackstone wheel on my tormek t8

i can get some more photos later today of the ones that didnt cut

[tgbto]

That looks as clean as it gets...

I'm no drill bit specialist so I might be dead wrong, but I believe the primary facets kind of never cut right in the center. Still, in soft metals that shouldn't be an issue with a 12mm bit, let alone a 6mm one.

Your clearance angle might be a tad shallow for soft metal but again that should just decrease the amount of metal removed per turn, not prevent them from cutting. I wonder what the point looks like on a bit that couldn't cut. Is it flattened ?

[Lokepus]

Ill go fetch some of the "not cutting ones" later this evening and take some pictures of them.

[aquataur]

My brother in law, when he bought the jig, sharpened some drills for me. It was the first drills he did and they refused to cut as well, although they looked alright.

Later he gave me the jig and everything worked for me.
He must have done something wrong, I don´t recall what he made differently.

The only explanation is that there is little or no relief angle on the primary cutting edge.
Note that due to the geometry of the pins on the pin vise there may be some intermediate sizes (around 10mm) that won´t grip symmetrically. It has been explained here and a simple solution has been presented.

[Ken S]

Welcome to the forum, Lokepus.

Looking at your photos, it appears that your primary bevels may extend too far across the cutting face. Compare your bits with the one in the photo at the start of this video. Notice the primary bevel is very small. If your primary bevel is too,large, that would put extra drag on the drill bit.

Ken

[aquataur]

it appears that your primary bevels may extend too far across the cutting face. (...) Notice the primary bevel is very small.

I don´t see anything wrong with that grind. It is perfectly symmetrical.

If your primary bevel is too,large, that would put extra drag on the drill bit.

Mazoff says that a single (primary) bevel works but produces congestion on the heel. Therefore the necessity of a secondary bevel. Indeed small drills are ground that way exclusively.
Such a bevel has more "meat" behind the cutting edge and is thus stronger.

On the contrary, too small of a cutting edge (i.e. to much relief) would weaken the edge.

On second thought, the problem @Lokepus encounters may be no real one at all:

If he is used to drilling (with larger drills) that have a split point, than you will feel the 4F grind does not cut at the center. The truth is, it does not (well). It has a point only slightly less blunt than the conventional conical grind. The fact that the drills work with a pilot hole is indicative for that.

[Lokepus]

thanks alot for all the info guys. i think ill try some of the ideas here. ill post some more photos of the drills that didnt cut properly later today when i get back.

this might all be my fault all together. i think ive been a bit quick when getting to drill bit nr 50 for the day. below 3 drills with explanation.
question: Is there any reason for the secondary bevel to be there on drill bits from 3 - 6 mm? what good does it do? i know its suppost to keep it from wobling about, and to make you drill without that much preassure. but besides that should it not cut about the same?

the way i see it. the more you grind in the secondary facet the more you remove from the cutting edge near the center of the drill. witch i think again makes the center cut alot worse than it needs to.

Drillbit one: 
https://imgur.com/8p7f5zM
https://imgur.com/iELdfK9
For some reason 5 of the 80 bits i sharpened seem to be sharpened the "wrong" way around. the cutting bevels wont even touch the material one is trying to drill. i have no idea what so ever why this happened or how its even possible. kinda hard to explain but see pictures. this one obv didnt cut at all.

Drillbit two:
https://imgur.com/kC0PzCb
Here is one that didnt cut. i did not bother to cut the seccodary bevel on this one just as an experiment

Drillbit Three:
https://imgur.com/osopbP6
Here i can tell the secondary bevel was not ground far enough. that is my bad, but is there any reason for this one not to cut properly. The primary cutting bevel is the only one that is touching whatever you are drilling anways. should kinda think it would work just as well as a perfectly 4 faceded one.

sorry for all the stupid questions. but i apreciate all the help

[RichColvin]

Daniel,

It looks to me like you are not aligning the bit rotationally correct in the DBS-22 jig.  The leading edge of the bit needs to be aligned with the line on the DBS-22.  This is outlined in the manual for the DBS-22 on pg. 7 (pictures on the 2d row).

DBS-22 Manual ==> https://tormek.com/download/18.681cbd68182e94c066a21e2d/1688042189465/InstructionDBS-22%20Drill%20Bit%20Sharpening%20Attachment.pdf

Kind regards,
Rich

[aquataur]

Is there any reason for the secondary bevel to be there on drill bits from 3 - 6 mm? what good does it do? i know its suppost to keep it from wobling about, and to make you drill without that much preassure. but besides that should it not cut about the same?

I am not sure what exactly your question is.

the more you grind in the secondary facet the more you remove from the cutting edge near the center of the drill. witch i think again makes the center cut alot worse than it needs to.

I think with "the cutting edge near the center" you mix up the chisel, which is a result of the web with something that cuts. It does not. It pushes metal away. The technical term is extrusion.

the cutting bevels wont even touch the material one is trying to drill.

On a drill with conventional conical grind (most of the factory grinds for jobber drill bits) the center never grinds. You have to push it into the parent metal a fair bit until the facets are catching. Close to the center their effect is limited for several reasons. The 4-facet grind is slighly better, but does not eliminate that flaw.

Drillbit two:
Here is one that didnt cut. i did not bother to cut the seccodary bevel on this one just as an experiment

This obviously had some web thinning measures employed on the previous grind. It should cut despite the absence of a secondary relief, but run hot eventually.


Bit #3 suffers from what RichColvin explains.
Bit #1 (second picture-high spot):

Excessive lip clearance is extensively practiced througout the U.S. (...) Such excessive clearance is due to the tendency to incorrectly view the drill(...). In viewing that drill, most readers would insist that the
drill has little or no lip clearance.

This is a quote from Mazoff´s brilliant article "drill point geometry".

looking at a drill this way you mix up two different angles.
For my taste, Mazoff did not make it entirely clear as how to look at the drill correctly. I think what he is driving at is to look along the cutting edge as if you would aim over notch and bead sight on a gun (English speaking guys please correct me if this is not the right term).

However, this way you see immediately, if the heel is lower or not.