Drill sharpening on a D bit grinder AKA Deckel clone.

[Flynth]

I've been researching this subject for ages as this D bit grinder comes with a "drill sharpening" attachment and (of course) no instructions...

I've been using Luc Wybo method that works great for drills of 5mm and bigger, but I can't get 4mm and smaller to work despite adding an extra 3 degrees clearance as described in the pdf doc. If anyone knows how to get those smaller drills to work please let me know.

First let me clarify for those that don't know what I'm talking about.

This is the tool cutter grinder I'm talking about:

This is the attachment:

Now, there are various videos online showing drill sharpening on it, but most of them are quite useless. They omit a lot of info, they obscure what they're doing etc. But, there is one youtube creator that took the time to write a pdf document alongside his video. His english is ok-ish. I can understand what he says and writes, but his written descriptions could be better. Still, he is the only person in the know that took the time to share this knowledge so he has my thanks for it. His youtube channel (and I assume his name) is Luc Wybo. I strongly recommend anyone interested to start by reading the pdf here: https://drive.google.com/file/d/11gtweV-mVcSftFvA3ZSR8xOS-gqZyFhX/view
Also attached.

Then the youtube video here

will make a lot more sense.

The method can be briefly described as:
- 3 small 1.5mm (60 thou) sheet metal plates have to be made, drawings are in the pdf document as stops to replace the useless stock plate. Those plates are used to position the drill flutes in the attachment. There are 3, one for small drills, one for medium, one for large
- a set of tables with precise dimensions was created (also in the pdf) that specify stick out (flute edge to plate) based on helix rate, and attachment stick out (based on drill diameter)
- the main angle is set to 14 degrees for 118 degree drills and 22 degrees for 135 degree cobalt drills
- secondary angle is set square to the wheel with a help of a test rod that is accurately faced. Allegedly extra 3 degrees are added there for drills under 5mm
- a method to grind additional faces on cobalt drills (6 face method) is described. I haven't tried it. I'm sticking to 4 face method as it is much easier.

The 4 face grinding process requires no repositioning for each face. The settings are set. Then one feeds the wheel in and makes a swinging motion with the attachment. Both faces on one side of the drill are ground as well as the web is defined. Then one turns the drill around, repeats those moves and it's done. It's a very quick method if one has a printout of those tables on hand. It is even faster if multiple drills of the same diameter are sharpened.

There are drawings in the pdf that describe all the angles, the relations etc.

As mentioned I've had very good results with this method with drills over 5mm. Initially I had my drills cut oversize, but then I got the hang of it and they're right on point. However I can't get 4mm drill to work. It looks the part, but it gets destroyed when entering the material (mild steel plate).

So I wonder, how many of you know and use this method? How many of you have this attachment and not use it due to a lack of proper instructions. Hopefully this information will spread further and it will be refined to make small drills to work too.

I'm also interested if there are any hss end mill sharpening manuals for this grinder

 

[GeneT45]

Count me among those that have the attachment, but have never used it. I do use the 4-facet grind as described by Stephan Gotteswinter on YouTube:

.

If you dig around on Stephan's channel, there's a video of sharpening the ends of endmills, but not the flutes.

GsT

 

[Flynth]

Count me among those that have the attachment, but have never used it. I do use the 4-facet grind as described by Stephan Gotteswinter on YouTube:

.

If you dig around on Stephan's channel, there's a video of sharpening the ends of endmills, but not the flutes.

GsT

Indeed, however he is not using the drill attachment. In one of his videos he said he couldn't get it to work (or it was annoying to use - I forgot which) and he sold it.

Likewise, I believe the end mill flute grinding he showed was on a big boy tool cutter grinder. He did use the little Deckel clone for the tip of a two flute end mill, but that is quite easy It is the flutes of an end mill I had some issues with(I tried so many times my 10mm end mill ended up as 8mm), but coming back to drills as end mill grinding is well described in few places while drill grinding with this attachment seems to be some mystic knowledge few people possess and they guard the secret very well

I'm pretty happy with it now that I found a good method for 5mm and bigger drills. I wish I had an equivalent fast and easy method for small ones as I mainly go through small drills quickly. Larger sizes last quite long in my workshop.

 

[craniac]

Indeed, however he is not using the drill attachment. In one of his videos he said he couldn't get it to work (or it was annoying to use - I forgot which) and he sold it.

That's one thing about Stefan, he's ready to go the extra mile and invest the time to rid his shop of annoyances. There's a lesson in that for me anyway.

Tim

 

[Flynth]

That's one thing about Stefan, he's ready to go the extra mile and invest the time to rid his shop of annoyances. There's a lesson in that for me anywa

Personally I think the attachment became a lot less annoying after Luc Wybo published his method

Previously, I agree it was. Watching some youtube videos, trying to replicate it and getting results much worse than putting a drill in the collet chuck (as shown SG 4 face grind video).

Then Stefan is running a professional shop these days so I can understand it makes less sense for him to sharpen his own drills unless he just happens to need one particular size for a job now.

The main advantage of the attachment to me as it is now is that:
- it has a back stop letting you achieve far better repeatability between drill sides than by putting a drill in the collet chuck. For example one 10mm drill I sharpened recently is measured at 9.98, it cuts a 9.99 hole.
- it grinds both the flat cutting edge and the relief in one motion, also the web is formed at the same time. So there is no need to add relief manually later.
- if you have multiple drills of the same size you can set the attachment once and just swap drills. It is very quick. I had a bunch of tap drills I sharpened this way.

One extra bit of info to mention for anyone wanting to try it. Use a diamond grinding wheel. The aluminium oxide wheel requires more skill not to wear it between drill sides resulting in different cutting edge size and drill cutting oversize. If aluminium oxide is all you have it is doable by using half of the wheel for roughing and half for a final pass. This way you can keep the final side almost unused between sides.

And my additional comment is that the description of the method looks very complex with geometric drawings etc, but once you get the hang of it, it is very simple and quick.

For a hobbyist like me it makes sense to be putting all dull drills in a container and once it is full (20 drills or so) I sit down and sharpen them all at one time. If I just needed to sharpen one drill I was missing this very time. Perhaps having to setup this special attachment would still be annoying?

 

[pontiac428]

Luc Wybo has a couple of good videos on drills and drill geometry. It's funny how I can watch that mumbling old man with complete engagement, but can't sit through 30 seconds of "influencer" machine shop videos. Luc has some key information in his head, that's worth watching!

 

[Illinoyance]

Instead of using the drill sharpening attachment, I hold the drills in a collet. It is a quick job to grind a 4 facet point.

 

[Flynth]

Instead of using the drill sharpening attachment, I hold the drills in a collet. It is a quick job to grind a 4 facet point.

There are a couple of issues that matter to me with the collet method.

The most important is that by using the collet method I would loose the web on the drill unless all I do is very light retouching of the drill(then one just makes the web smaller with each grinding). The web is there to stabilise the drill, it prevents the drill wandering when it enters the cut. It matters less if one predrills each hole with a smaller drill. If the purpose is to get the drills to better than factory condition (including the web) the attachment is better. If one just wants drills to work and one don't mind spot predrilling each hole collet method is fine too.

The attachment forms the correct web every time. Stefan Gotteswinter in his video on 4 facet grind talks quite a bit about it, but he erroneously says the web is impossible to do on a D cutter grinder in machine fed way(Luc Wybo method wasn't known to him I think). So he uses a big cutter grinder to "fix the web" after doing a 4 facet grind on the d bit grinder. This(using two separate cutter grinders) is in my opinion quite impractical. If one uses a collet method one has to be OK with loosing the web.

Then there is aligning the drill in the collet so the cutting edge is horizontal.
For me, aligning the drill in the collet is quite fiddly (especially for anything smaller than 12mm). In the attachment, you just lean it with the flute against the plate.

I do have to measure the stick out, but that is much easier that eyeballing the cutting edge is exactly horizontal.

Even Stefan in his 4 facet grind video mentions the collet method it is not really very reliable (due to precise alignment required?), but he uses it "because good drills are expensive". So if there was a better method known to him I guess he would use it too.

Nothing wrong with using the collet method if it works for you well.

 

[Lucas E]

Is the point of the finding the helix angle and using the table solely to position the cutting edge in line with axis of the fixture that goes into the collet?

I watched his video and looked at the PDF and still don't understand all the calculations. Im also slightly hesitant because after modifying the tool, and all those calculations, the split point tool he sharpened only cut on one side.

 

[Flynth]

Is the point of the finding the helix angle and using the table solely to position the cutting edge in line with axis of the fixture that goes into the collet?

Not exactly, but close. It is to set the angle of rotation of the spiral (defined as the cutting edge being 10 or 20 degrees past vertical-or more if you remove lots of material) so when you grind a new cutting edge by removing material. It still matches the rotation of the spiral. Also by positioning the existing cutting edge slightly past vertical you can just touch off on drills that don't require much grinding.

In theory you could eyeball it, especially on bigger drills, but consistency is important with this method so the table is given.

I watched his video and looked at the PDF and still don't understand all the calculations.

I didn't even try understanding the calculations. I didn't care about them. For me it was important if the method works well for me (drills cutting exactly the same amount on both cutting edges resulting on a hole that's exactly the size expected).

To use the method one doesn't need to understand the calculations. One can just use tables of already calculated values in the pdf.

If you(or anyone else) needs further explanation how to apply the method let me know and I'll do my best to explain.

Im also slightly hesitant because after modifying the tool,

Perhaps there is some misunderstanding. There is no requirement to modify the tool. You have to make 3 additional steel plates you then use with the tool instead of the useless plate included with the device. If you want to sell the attachment later and have it "in stock condition " you can put the old plate back on. It is held on the tip of the tool with a tiny m3 hex screw.

and all those calculations, the split point tool he sharpened only cut on one side.

I haven't seen that part. (perhaps I missed it). For me 99% of the value of the method is in the pdf document. Videos are popular these days, because they are "entertaining", but when it comes to transferring knowledge written text is what I prefer. So I admit to not have watched the videos in their entirety...

As for the results. All my tools sharpened with his method cut perfectly on both sides unless I made an error by for example grinding one edge further than the other.

Grinding involves a measure of skill that comes from experience. It is not enough to position the dial on the same graduation to ensure two cuts are the same. There is wheel wear(even diamond), there is flexing of the tool post, and inherent lack of precision in positioning by eye. Being able to do that, to know for example to cut the bulk of the material with one portion of the wheel, then just "kiss the surface" with previously untouched part, to hear and recognise if the wheel has finished cutting and any spring tension is relaxed, or if after a cut material remains and that "debt" grows with each successive cut making it cut harder and harder eventually wearing the wheel or overheating the part a lot more than necessary...

All this comes from experience. One can't learn it without his/her hands on the wheels (or his/her ear next to the machine in case od cnc). Perhaps the author is a good theoretician, but his application of his method is lacking in the practical side? Still, the value of the method is in that it gives us a (relatively) simple set of steps to follow. If you do tgat right your drills(from 5mm up in diameter) will cut as expected.

This brings me to my problem. Drills under 5 mm. I wonder, perhaps I was just trying this with an annealed drill. I have to try another one at some point. Unfortunately author's English is a limitation in how stuff is explained. Therefore I don't know if I'm misunderstanding "add extra relief angle of 3 degrees for small drills" or if I'm making another error.

Being able to sharpen reliably those tiny drills from 4mm down to 2mm would be of great value to me. They are cheap. True, but it would be great not have to replace them when dull.