Author Topic: An idea for drill sharpening jig  (Read 74799 times)

Offline sorveltaja

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An idea for drill sharpening jig
« on: September 24, 2009, 03:57:53 PM »
When looking properly sharpened drill bit's grinded surface from the side, instead of being flat, it seems to have some kind of thread-like pitch in it.

Maybe an old idea, but for example, piece of trapezoid or similar flat-threaded would act as a 'jig'.

Comparison between metric drill bit, and thread. Pitch is about 4,65 mm.


My lathe's highest(or is it lowest?) metric pitch is only 1,5 mm, so I probably have to hunt some surplus clamp or vice, that has at least 4,5 mm pitch screw in it, to see in practise, if that idea is any good.


Online DICKEYBIRD

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Re: An idea for drill sharpening jig
« Reply #1 on: September 24, 2009, 06:49:55 PM »
That's a pretty brilliant idea!  All we need is a CNC ballscrew with the 4.5 mm pitch and give it a whirl.   :proj:  :ddb:

ps: What CAD program did you use to draw the pic?  Beautiful work!
Milton in Tennesee

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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #2 on: September 25, 2009, 03:22:18 AM »
An evaluation version of Rhino 3D is used. Although it has limited save times, it's possible to make small demonstrations with it ::).


Offline John Hill

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Re: An idea for drill sharpening jig
« Reply #3 on: September 25, 2009, 04:33:07 AM »
Now that is interesting, I suppose one could mount a tool post grinder, set up an appropriate thread pitch and carefully hand turn the spindle half a turn to grind one flute, then, somehow  :scratch: set it up to grind the other flute.
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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #4 on: September 25, 2009, 01:53:52 PM »
Another idea how to make pitch adjustable. Red part is a spring, and blue one adjusts its axial length, and its pitch also:

Next thing would be to add part, that follows spring's pitch. I haven't yet discovered how to achieve that.

Offline Darren

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Re: An idea for drill sharpening jig
« Reply #5 on: September 25, 2009, 02:06:37 PM »
Why not just use the drills own flute to follow as other manufactures do?
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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #6 on: September 25, 2009, 03:13:40 PM »
Doesn't the drill's flute have much longer pitch, than cutting surface has?

Once I had one of those horrible cheap sharpening jigs, and just couldn't get any good results with it. Neither I understood, why it was so clumsy device to use.
Theory that I've read about drill sharpening, talks only about degrees, nothing about that drill's cutting surfaces would have a pitch. They aren't flat at any degree.
Or am I missing something :smart:?






Offline Darren

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Re: An idea for drill sharpening jig
« Reply #7 on: September 25, 2009, 03:17:07 PM »
Sorry I think I've misunderstood what you are trying to do? I thought you meant sharpening the flute itself.... :doh:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline John Hill

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Re: An idea for drill sharpening jig
« Reply #8 on: September 25, 2009, 03:19:19 PM »
Possible procedure.....?

Put drill in lathe chuck.
Set threading gears for required pitch, 4.65mm?
Set up tool post grinder
Turn spindle by hand to take up any backlash while grinder moves towards first flute
Carefully turn spindle to grind first flute.
Disengage threading feed drive at gears or gear box
Carefully turn spindle back half a turn
Reengage threading feed
Turn spindle back to gather up backlash
Turn spindle forward again and (maybe?) it will be in position to grind second flute. :scratch:
From the den of The Artful Bodger

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #9 on: September 25, 2009, 03:27:20 PM »
No problem. Just trying to find simple(?) way to sharpen pile of used drills :dremel:. I guess that sharpening flutes requires highly specificated grinding machinery, so I've skipped it.

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #10 on: September 25, 2009, 04:22:32 PM »
Possible procedure.....?

Put drill in lathe chuck.
Set threading gears for required pitch, 4.65mm?
Set up tool post grinder
Turn spindle by hand to take up any backlash while grinder moves towards first flute
Carefully turn spindle to grind first flute.
Disengage threading feed drive at gears or gear box
Carefully turn spindle back half a turn
Reengage threading feed
Turn spindle back to gather up backlash
Turn spindle forward again and (maybe?) it will be in position to grind second flute. :scratch:
Once first surface is sharpened, turn drill back to starting position. Then turn drill holder(not the jig) 180 degrees, and grind the second half.
Jig doesn't move or rotate during the process.

---
Longest pitch available in my lathe is only 1.5mm, so unfortunately it can't be used for that purpose, unless heavy modding is applied.

Offline John Hill

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Re: An idea for drill sharpening jig
« Reply #11 on: September 25, 2009, 09:10:16 PM »


Once first surface is sharpened, turn drill back to starting position. Then turn drill holder(not the jig) 180 degrees, and grind the second half.
Jig doesn't move or rotate during the process.

There is no jig, the drill is in the lathe chuck and there is a grinder mounted on the toolpost.  The requirement is to rotate the drill 180 degrees in relation to the feed mechanisms.  You can not loosen the drill in the chuck as that would loose longitudinal position so we have to turn the spindle in relation to the feed.  If you have a gear head lathe you could put the spindle in neutral and turn 180 degrees by hand then reengage, if no gear box you could lift out intermediate change gear then rotate the spindle 180 degrees and put change gear back.

---
Longest pitch available in my lathe is only 1.5mm, so unfortunately it can't be used for that purpose, unless heavy modding is applied.
[/quote]
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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #12 on: September 27, 2009, 01:55:04 PM »
It turned out to be too complex to use spring as a guide. So back to the original idea.

Progress so far:


On the left is an old chuck, silver soldered to brass, that has 27 mm(1.06") outer diameter, and 10 mm(~0.4") hole through it.

In the middle are chuck's internal parts. Nothing fancy, but enough to hold the drill bit.

On the right side is the tube that's internal diameter is also 27 mm. Never mind the outer threads, they came as an extra from the scrap yard. Its function is to act as a scaffold.

Essential part is still missing. I'm looking the way to mod my lathe's gears to get 4, or even 4.5 mm thread pitch. Intention is to make two point thread(is that correct term?), one thread/drill side.

Examination is still in process. 





Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #13 on: September 29, 2009, 11:28:37 AM »
No luck with lathe's gears. Might be another future (side)project.

I found one thing, that has two point thread and its pitch is ~4.7 mm :dremel::


Next thing is to duplicate threads to brass part.

Offline NickG

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Re: An idea for drill sharpening jig
« Reply #14 on: September 29, 2009, 11:42:17 AM »
I;ve got one of those cheap grinding jigs too and haven't got it to work properly yet, but i do think it uses the correct method. Having said that, this is very interesting if it can produce more reliable results!

Will be watching!  :thumbup:
Location: County Durham (North East England)

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #15 on: September 30, 2009, 05:40:18 AM »
Here the threads copied. About half turn for both, so                                          When looking drill at the working end, cutting surface   
there is more than enough:                                                                            appears to be ~90 degrees:
                                             



Offline NickG

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Re: An idea for drill sharpening jig
« Reply #16 on: September 30, 2009, 07:39:18 AM »
I'm a bit lost with this now!  :scratch:

What is the rest of your contraption going to look like? Can't quite picture how it's going to work.

With the cheap grinding jigs, you angle the thing up at 59 degrees or whatever, the drill is held against a little thing that contacts the flute, then the jig is swung side to side grinding an arc. I think it depends how far down the flute you set it to hold the drill still that varies what relief you put on the cutting edges! But it'll be interesting if your thread jig removes the need for that, having said that, how are you going to make sure it's in the right position when you start grinding?

Nick
Location: County Durham (North East England)

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #17 on: September 30, 2009, 01:58:48 PM »
I'm a bit lost with this now!  :scratch:

What is the rest of your contraption going to look like? Can't quite picture how it's going to work.

With the cheap grinding jigs, you angle the thing up at 59 degrees or whatever, the drill is held against a little thing that contacts the flute, then the jig is swung side to side grinding an arc. I think it depends how far down the flute you set it to hold the drill still that varies what relief you put on the cutting edges! But it'll be interesting if your thread jig removes the need for that, having said that, how are you going to make sure it's in the right position when you start grinding?

Nick

After reading texts that I wrote earlier, I must admit, that it can be quite confusing

No other adjustments required, except drill tip angle (for example 59 degrees). Jig keeps drill's touching point with grinding wheel diagonal, if it works as I assume.
An animation of the process could maybe clarify the idea :borg:

Here are the basepart, and drill holder. Red circle shows broken M3 tap(yet another SS 316 experience). As it is stuck there, why not use it as a guide for brass part's thread grooves:


Parts together with drill bit:

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #18 on: October 02, 2009, 01:55:21 PM »
Mock-up, that shows the progress so far:


It needs support for the drill, and locking mechanism, that is to be used by the screw, that shows under the plywood piece.

I guess, that it would be simpler to combine the tube and plywood elements to one part.

Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #19 on: October 02, 2009, 04:51:48 PM »
Trying to wrap my head around this. I am thinking you want to have the trailing edge of one flute at a lower rake than the leading edge. (that may not be what you are trying to accomplish) I believe, in production both, edges have the same rake. I think the most important part of sharpening a drill bit is consistency for both flutes, which is difficult to do by hand, thus the machines. Drills for steels, aluminums & plastics have different angles. plastics-25-30, aluminum, copper & brass 45-50 and steel 40-45. It is very important that both flutes have exactly the same cutting angles, cutting edges and lip clearances. Large dia. drills should have a back cut. To test the drill it should give an equal removal of material from both flutes.

It seems drilling aluminum gives the most problems. A lubricant called Boelube (you can google it and find many suppliers) is used by aircraft manufacturers and airline maintanence. It has a low melting point and lubricates as the heat builds up. I have drilled thousands upon thousands of holes in aluminum with no difficulty using the correct lube and techniques. Using the proper dia. pilot drill, then stepping up to final size with core drills or reamers also. Manufactures and airlines use the sharpening machines with good results and save a ton of cash doing so.
Tink

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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #20 on: October 02, 2009, 06:17:44 PM »
Intention of this jig is to make it easier to grind drill's both cutting surfaces identical, regardless of the tip angle.

In this project, I have abandoned technical terms, that usually relate to drill's sharpening. Instead I have in mind, that drill is like a screw, whose tip angle(and the pitch) dictates, how fast it can dig into certain materials. Something like automatic feed. It also has a pitch. Lower the pitch, higher the feed, and vice versa.

I have clear image in my head about this thing, dirt simple, but in practise... we'll see.


Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #21 on: October 02, 2009, 10:42:35 PM »
Cool. I am still confused about the pitch part unless you are talking about the angle of attack. Kind of like a prop on an airplane engine. Same angles involved on both blade, but appears to screw itself through the air. I'll be watching with interest on how this works.
Tink

The desire accomplished is sweet to the soul.
Prov 13:19

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Re: An idea for drill sharpening jig
« Reply #22 on: October 03, 2009, 02:21:38 AM »
Sorveltaja,

I love what you are doing here.

You are taking a glimpse of an idea thru to trying out a prototype.

To me, it means nothing if you are successful or not.

The fact that you are trying to solve an age old problem by looking at it from another angle is the remarkable part.

I wish you success in your challenge, but don't be disappointed if it doesn't work as you have planned. Think of all the experience you have gained getting this far.

Bogs

Offline NickG

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Re: An idea for drill sharpening jig
« Reply #23 on: October 03, 2009, 05:43:47 AM »
Hear hear  :bow:
Location: County Durham (North East England)

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #24 on: October 05, 2009, 01:02:42 PM »
I skipped that plywood/tube -combination, and made it altogether a little more solid component:


Original plan was to make this jig for small (3mm(~0.11") and below) drills, but the chuck is bigger, and so will be the whole device.
 :offtopic: To add even more confusion, I intend to use a small(dia. 13mm(~0.51")), slowly rotating(~100-200 rpm), diamond coated grinding drum for sharpening:


Ordinary grinding wheel would wear on such a low speed. Instead, the thing above seems to last. I have used (and abused) that thing with glass, plastic, wood, HSS, carbide, and various other metals.

Anyway, the jig itself needs still some work to get it ready for testing :dremel:.



 


Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #25 on: October 07, 2009, 01:12:38 PM »
The jig looks something like this, when finished. Only two fastening parts needs to be done:


... But there is (at least) one mechanical puzzle, that I haven't been able to solve. It relates to the pitch, that I mentioned earlier.

Took some photos of actual drills, but they were too blurry to demonstrate. Maybe this picture explains, what I mean:


Smaller one is half the size of the left one. Both have the same pitch, but smaller has also half of the axial length(red lines) on its cutting surface :scratch:.
Anyway, drill bit doesn't seem to be so simple as it looks :smart:.

...On the other hand, that can't stop me to finish, and test the thing. Many drill bits are just waiting to be the test pieces :thumbup:.

Offline sbwhart

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Re: An idea for drill sharpening jig
« Reply #26 on: October 07, 2009, 03:49:56 PM »
Hi Sorveltaja

Real nice job your making of that jig, I've been watching your progress with interest,  :clap: :clap: :clap: could your puzzle  :scratch: with axil length be due to the difference in diameter in the two drills.

Have fun

Stew

A little bit of clearance never got in the road
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Location:- Crewe Cheshire

Offline Bernd

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Re: An idea for drill sharpening jig
« Reply #27 on: October 07, 2009, 03:53:46 PM »
That picture reminded me of what the Drill Doctor drill sharping machine looks like.

Bernd
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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #28 on: October 07, 2009, 05:48:21 PM »
sbwhart: Yes, I'm on the same track, that the drill diameter is (one of) the key factor(s).

Possible (although laborious)solution: To make different size guides (the cylindrical brass part, see my previous posts), that have diameter, that matches certain drill sizes, all having 4.65 mm pitch.

Other solution might be to use an eccentric jig, whose eccentricity depends on the drill size. Smaller the drill, the more eccentric the jig.
Let's take a 10mm drill as a reference, that's eccentricity is 0. It takes ~90 degrees turn to sharpen using the jig.

With 1mm drill, it has to be eccentric, if same size jig is used, as on 10mm drill. If 10mm drill takes ~90 degrees, 1mm takes only ~9 degrees.
During that ~9 degrees, it has to rotate ~90 degrees, just like the 10mm drill does.

---------------------------------
Bernd: It's not intentional. I admit, that I have examined the Drill Doctor -devices patents, among many others, but haven't got the grasp of any of them.
That's the main reason, why I'm going to make and test this thing in a hard way. Be it failure or success. If success, I'll be glad to share it. If total failure, it means food for my future projects. 

Offline Joachim Steinke

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Re: An idea for drill sharpening jig
« Reply #29 on: October 07, 2009, 06:29:43 PM »
Hi Sorveltaja,

as I’m concerned with the drill subject too I will take the chance and try to explain a little bit about the mysteries of the helical tool called drill, hoping not to jam your interesting and already started article here?

Your idea of using the pitch of a special thread as a guide for grinding the relieved surface of drill tips sounds interesting, some commercial drill grinder use a similar technique in form of axial control curves embedded in the drill fixture bearing. But I think it is a little bit too complicated, there are much more simple techniques to achieve a really good performance at home.

But first of all, the pitch of the flute (helix) has nothing to do with the relief angles, it only generates the rake angle (if this angle is not corrected or changed by extra grinding the cutting face for non standard boring tasks). This will come obvious if you compare a drill with the front cutting edges of an end mill, end mills are only the special case of the hole system “helix tools”, the case with the point angle 180deg.

The relief or clearance angle is more or less independent of the drills geometry, naturally this angle must nevertheless follow the rules of making chips….a first clearance angle in the range of perhaps 8 to 15 deg makes sense for our several metal drilling jobs.

In principle there are two major techniques for grinding drills, the four or more facetted relief flanks method and the conically shaped flanks method, normally you will find the conically type on most of all standard drills at your tool store.

But the conically drills don’t make a better job, I think it’s easier for industrial manufacturing having only one process on each cutting edge than several passes like you will need on the more facet types. So to my opinion, it’s up to your free choice what grinding technique you will prefer at home.

If you like it conically a simple swinging fixture will work fine. In fact the cheap fixtures from your tool warehouse use the correct technique, but most of them are not build precise and tough enough for holding the drill exact in the axis of rotation. And they have problems with indexing the both cutting edges precisely from 0 to 180 deg when changing to the other cutting face…..therefore a lot of frustration for there users is preprogrammed….ha ha ha….

So you can buy a reliable and expensive fixture from a serious tool grinding machine builder like Cincinnati or Deckel or you  have to build your own device.

To achieve the needed clearance face by swinging the drill in front of a grinding disk the rotating base of the tool fixture has to be arranged with a defined offset distance to the axis of the drill, the shifting vector of this off set is pointing in the direction away from the cutting edge. The principle of the conically method is easier to present by changing the moving systems, here, contrary to reality,  the drill stands still and the grinding disk is performing a conically rotation:





The drawing shows two of many possibilities for arranging the rotating base in relation to the disk surface (90 and 70 deg), they both works fine and only need some different calculation of the setting parameters.

This is a drawing from the last year when I was starting to design my second grinding fixture:





And here an intermediate result of this in the mean time further enhanced fixture:





Some details like the graduation of the rotating base and the fine indexing of the tools axis  are not really necessary for only drill operations, but I designed this for additionally grinding all forms of d-bit routers.

But very important is the precise and rigid mounting of the tool, my choice was an ER20 system. And we have two linear adjustments, in tool direction for setting the cone radius in relation to the disk surface and perpendicular to this axis the off set value, together both parameters define the relieving characteristics of the desired clearance.

A good method for evaluating the clearance angle is having a frontal look at the drills chisel. As evident the chisel line rotates clockwise in direction towards the cutting edge, more rotation means a higher value of clearance. Number 1 and 2 are related to the numbers in the first picture above, as you can see, the different setting angels of the rotating system make no great difference to the result of the clearance value.





Okay, further details and the description of the other method (four or more facetted) could develop in to a really large article and my concentration needed for writing and translating at the same time is going to fade away for this night…..ha ha ha…..

I will try to continue as soon as possible in the next days, and I hope the stuff is not too dry presented, don’t wont to bore you with too much theoretic.


Bye from Achim

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #30 on: October 07, 2009, 07:46:46 PM »
Joachim Steinke: No worry, you have excellent presentations of the subject. So much information, that it might take some time for me to digest.

Feel free to post more.



Offline sbwhart

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Re: An idea for drill sharpening jig
« Reply #31 on: October 08, 2009, 02:24:27 AM »
Hi Achim

Very interesting post your quite right about the problems with shop bought drill grinders, not including the drill doctor in this because I have never seen or tried one.

My father taught me many years ago to grind drills by hand, which I'm quite good at, but hand grinding can never be as good as a jig grinding, the action you described is exactly the action, It's easy to demonstrate but difficult to describe.

Sorveltaja

Drill grinding and geometry when you get into it is a complicated subject this is a great thread you've started.

I'll watch progress with interest.

Cheers
 :beer:
Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline Joachim Steinke

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Re: An idea for drill sharpening jig
« Reply #32 on: October 08, 2009, 08:12:14 AM »
Hallo, only a short message in between,

this may be a little off topic, but as the “Drill Doctor” has already been mentioned above…….

I, similar to Stew have never operated with the relative famous Drill Doctor myself, but I have a friend who works with this Vertex Drill Grinder:

http://www.vertex-tw.com.tw/products/products_list.php?language=_eng&cid=591#pro

I took the chance to test it by myself and the little machine is astonishing well and rigid build (okay, it’s Vertex from Taiwan and not as bad as the most Chinese machinery), very smooth and quiet running and does a really good job on standard drills.

They use special made and inverted mounted ER collets (a clever idea) and axial control curves build in the circumference of a particular collets chuck. This curve is in contact with a corresponding curve in the mounting opening of the machine housing and generates the desired axial movement while rotating the drill in front of the grinding wheel.

Accommodation to the drills diameter is made by using a preset fixture (left side of the machine) where the drill is pre mounted in the collets. As the back rotation angle of the existing cutting edge (relative to the fixtures coordinate systems abscissae) has an effect on the relief characteristic in direct dependency to the tools diameter this single collet chuck can be used to a wide range of drill diameters with one and the same control curve.

This all is very similar to the technique of the Drill Doctor, but Vertex made the wear parts out of hardened steel and hard steel castings, so the well known wear out problems of the Drill Doctor (drill chuck partial made from plastic) should not appear.

As Vertex delivers the machine with a CBN grinding wheel you have a relative constant plane surface on the wheel over a long operation period, dressing the wheel is not necessary.

But this neat little machine is really expensive (just under 900,- Euro here) and you can grind only one type of relief form. It would devinitely do a good job in the commercial shop for daily use, but for unfrequent home grinding it might be a little bit too overshooting….ha ha ha….

Bye from Achim

Offline Bernd

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Re: An idea for drill sharpening jig
« Reply #33 on: October 08, 2009, 08:19:30 AM »
Joachim,

A bit  :offtopic: here. I've been to your web site and find it very interesting. One question. Is the material you use to make all those nice looking tools brass?  Thanks.

Bernd
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Offline Darren

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Re: An idea for drill sharpening jig
« Reply #34 on: October 08, 2009, 10:51:58 AM »
Hi Achim, I have a drill doctor and I believe Bernd has one as well. I must say I am very impressed with it. I have sharpened about 200 drills so far with mine and it was second hand when I bought it. The result is without a doubt a better finished point than when purchased new. Nice smooth drill with little or no chatter. If the relief option is used (split point) the effort in drilling is remarkable esp with larger diameters.

Just my take on the tool. A big improvement on my freehand grinding  :doh:
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Offline Bernd

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Re: An idea for drill sharpening jig
« Reply #35 on: October 08, 2009, 04:15:23 PM »
I have to second what Darren has said. Although mine was new.

The intersting thing about yours is the way you plan on rotating the drill.

I'm hoping this experiment will work out for you. I will keep watching your progress. I figure when my Drill Doctor doesn't work any more I'll build one like yours.

Bernd
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Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #36 on: October 09, 2009, 02:40:53 PM »
I tested the jig with 4 mm drill. Result: that ~4.7mm pitch is way too long. Meaning, that the axial feed is also too high.
Seems that if this method is in use, there should be matching thread for every size drills. Without doubt, it wouldn't be simple, or even practical.

I guess that it needs some kind of compromise to simplify whole thing. Assuming, that requirement isn't industry-level cutting speeds for the drills.

Anyway, next I'm going to try with milder, 1mm pitch, which should be closer to what I'm looking for :borg:.

Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #37 on: October 09, 2009, 03:09:34 PM »
I believe 0 pitch is what will be required.
Tink

The desire accomplished is sweet to the soul.
Prov 13:19

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #38 on: October 09, 2009, 04:00:38 PM »
0 pitch.. hmm. If burnout of the drill is desired, that would be fine. With cutting oil you would get even nice smoke cloud.

Since I'm not going to make any smoke signals(at least not from drilling) in the near future, I'll rather prevent myself from using 0 pitch.

Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #39 on: October 09, 2009, 04:31:11 PM »
I am speaking of pitch as in a screw. You must be talking about rake, or I just have no understanding of which aspect of the drill you are changing from 4.7mm to 1mm. My not understanding may be attributed to everything on a drill bit except diameter is usually presented in degrees. It appears to me that as you turn the bit 180 deg, you are also moving it in a screw like action. If I am wrong please accept my apologies and I will continue to follow your process.
« Last Edit: October 09, 2009, 05:13:50 PM by tinkerer »
Tink

The desire accomplished is sweet to the soul.
Prov 13:19

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #40 on: October 09, 2009, 05:14:23 PM »
Yes I meant the screw pitch, that is to be used on the jig. My use of the term "pitch" might not be the most correct way, when describing things on a metric system.

   
 

Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #41 on: October 09, 2009, 05:24:33 PM »
I am sorry, I was editing the previous post as you were answering. A drill bit does not have pitch from one side to the other. Each flute forms an equal angle from the point that is measured from the center of the bit. Any deviations in angle from one side to the other will result in only one flute cutting and the other just following along. Swarf (I love that word) should be removed equally down each flute when cutting.

I may still not understand the process and will follow with interest. I do believe you have a great design in the tooling if you take the pitch out and just provide rotation. It may take two grinding heads, one for the angle and another for the rake and that could be difficult to incorporate.
Tink

The desire accomplished is sweet to the soul.
Prov 13:19

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #42 on: October 11, 2009, 11:23:05 AM »
The brass piece, before I turned the 4.7mm pitch threaded part off:

Next I made 2 point thread with 1 mm pitch to it. It's barely noticeable in the photo, so demopicture instead about it:


With that, test-sharpening a 3mm drill gave a lot better result. The angle (in the picture) was quite small, allowing only slow feed, when I test-drilled aluminum, brass and mild steel.


Next thing to test would be to increase the jig's guiding thread's pitch to 1.5-2mm, to get closer to average cutting speed, when drilling.   

Offline Joachim Steinke

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Re: An idea for drill sharpening jig
« Reply #43 on: October 12, 2009, 05:31:59 PM »
Hi Sorveltaja,

I spent some time over the weekend thinking about your helical grinding method, but I don’t know if something wise had come out of my brain….ha ha ha….okay, let’s try it….

First of all your pitch problem, you wrote that your last testing version made too little relief angle, as you already mentioned the helix pitch is too low.  

The calculation of the helix angel is still quite simple, you only need to unwind the surface of the cylinder and so the angel for a given diameter (D) and a give pitch (s) follows the equation    

                                         tan alpha = s / (pi * D).

So one and only helix curve of a multi purpose grinding fixture should become a problem, variations of the drill diameters will require a wide range of pitch value. Here for example the pitch table for a relief angle of 10deg at the circumference of the tool:





And here, for a constant pitch of 2mm the table of the variations of relief angles you would get for the various diameters from 1 to 10mm, you see, the range is really wide:





As evident, alpha is inverse depended to the helix diameter, large diameter means a small helix angle. This in fact also will create an increasing relief angle from the circumference to the center of a drill. Within limits this effect is helpful and even desired, but if the value of variation on one and the same drill is too heavy it might become a problem.

So I consulted some articles from the web and then tried too visualize the theory for Helical Drill Point Grinding by my self a little bit further. What came out is a schematic model for a Universal Helical Grinder System, which, depending on the highly manipulable axis system can create all imaginable relief surfaces on a helical drilling tool.





This model can create all sorts of grindings, quadratic surfaces as well as planar like the multi facet method, so planar is only a special case of the whole process.

To simplify the system, some parameters like the distance S and B can be fixed during the operation. But the problem of rotate the tool along the pitch of a helicoid (H) under the implemented angel PHI and with the distance S relative to the tool axis (index of rotation) can not be solved with a collet fixture collinear to a single helix curve like this:





If the axis of rotation and indexing (toolholding) coincide you will have no influence on the relief characteristics distribution on the flank surface from center to circumference. But I might be mistaken, that is only a first glimpse on this geometrical problem. For a real calculation it is really not quite a simple task, for it is complex vector analysis of a multi determined 3D system, I don’t do that normally every day…..ha ha ha……

I just tried to simulate the simplified process in AutoCAD and the results were not satisfying, had some problems with boolean operations on complex sweeped bodies. So I should try it with Inventor in the next days.

Bye, Achim
« Last Edit: October 12, 2009, 05:39:48 PM by Joachim Steinke »

Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #44 on: October 12, 2009, 05:48:37 PM »
Achim,
Kind of what I was saying, only with science to back it up. Try with two grinding heads, one for the angle and one for the rake. May be too close proximetry to accomplish. Take the pitch on rotation out. Another solution could be two seperate tools, one for grinding the angle and one for grinding the rake. The back cut can be done by hand, as it is only needed on larger diameter bits.
Tink

The desire accomplished is sweet to the soul.
Prov 13:19

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #45 on: October 12, 2009, 06:13:16 PM »
Achim, that's an excellent interpretation of the idea :clap: :clap:. It describes clearly those different factors, that I have in mind, but didn't know how to explain or visualize them. 

Offline Joachim Steinke

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Re: An idea for drill sharpening jig
« Reply #46 on: October 12, 2009, 08:51:35 PM »
Tinker,

yes and no, the rake angle is actually not concerned in the whole process. Normally it is not necessary to grind this part of the cutting lip, unless you want to adapt the drill for special purpose. And with Sorveltajas fixture and operational base there is no way to realize this, I think he don’t want to do this either.

And the pronounced chisel between the two cutting edges is an accessory symptom of the helical grinding method. As you mentioned, eventually picking out material to minimize the chisel will help, but it’s only needed on larger drills. An alternative way to ease the chisel phenomenon a bit is to leave the helical method and generally switch over to the four and six facet grinding, the reduced chisel generates less pressure and the drill is nearly self centering.





And I think two grinding wheels are really not necessary and would make the things highly complex to adjust and operate too.

If  Sorveltaja wants to build a universal fixture based on the real helical curve motion he should design a collet based chuck housing with a not collinear, angel adjustable swivel axis and an adjustable off set feature. The helical curve then has to be placed in the axis of the swivel motion, like shown above, and should have a variable pitch, which is naturally no easy job to design and build. Nowadays the machine designer are used to solve such problems with NC moved axis, with the pure conservative method it will become really complicated.

But by the way, the advantages of such complex possibilities for modelling a perfect and highly task optimized relief surface are not necessary for just average home use. This are methods of industrial production for use on high effective machine tools and for people who have to earn money with them.

So an alternative could be coming back to a relative simple swivelling fixture, like the design for my Mini Bonelle. It does the job really good and  build with adequate precision you can grind drills even down to 1mm diameter (with additional Schaublin miniature collets) with very good performance.





Since I have added a second, differential dividing system which operates independent from the main indexer I am able to position the cutting lips in precisely repeatable orientations to the main axis system which produce very reliable results.





Bye, Achim

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #47 on: October 13, 2009, 04:48:16 PM »
I have decided to test 2mm pitch next, and already started making an extra gear for my lathe, that is required for the task.

While making that gear, another crazy idea popped to my mind, relating to this very subject of drill sharpening . :med:

It appears to be an alternative method, since it would use gear(s) instead of thread(s). I'm not sure at all, would it be any simpler mechanism in practise, than the current one. But enough for that. Maybe I'll start an another thread about that thing.

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #48 on: October 17, 2009, 03:15:37 AM »
Finally got the 2mm pitch made. Did some test sharpening, resulting quite asymmetrical cutting surfaces. The problem appears to be the chuck, that just isn't precise enough to keep the drill concentric.


Using mandrel(s) instead would be an ideal solution, but rather expensive one.

Anyway, back to stomping bugs :dremel:.


Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #49 on: October 19, 2009, 05:17:43 PM »
This may be an :offtopic:, but it loosely relates to this project.

To make that chuck little more precise, I fastened it just enough that its 3 jaws touched the abrasive element, that was fastened on tailstock.
   
It's one of those cheap diamond-coated things, having 4mm diameter ballhead.

Next the chuck was fastened to lathe's chuck. While lathe is on, ballhead is fed back and forth, to grind chuck's jaws. Resulting this:

All jaws have nice and even grooves in them. It improved the chuck a little, but not enough. Maybe most certainly due to lack of dial indicator.
If the centering is done properly, results would be even better.

« Last Edit: October 19, 2009, 05:21:25 PM by sorveltaja »

Offline MrSleepy

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Re: An idea for drill sharpening jig
« Reply #50 on: October 20, 2009, 02:29:10 PM »
Achim

Your "relatively simple" mini bonelle fixture looks beautiful... It doesnt deserve to be covered in grinding dust etc.

Rob

Offline Joachim Steinke

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Re: An idea for drill sharpening jig
« Reply #51 on: October 20, 2009, 10:32:09 PM »
Rob,

okay, at first sight some parts of the Mini Bonelle grinder (and some of my other tooling) may appear mainly build for showcase use only, but normally all my projects are intend to have a real practical and frequent use in my home shop.

Naturally building some of the components from 7075 Aluminium and Bronze is not as robust for daily use as having made the complete apparatus from cast iron and carbon tool steel. In fact there are really no problems with rigidity, 7075 Aluminium has a mechanical strength comparable to mild steel, so with a suitably design and the right dimensions all will work well.

I have to be a bit careful with grinding dust on the sliding surfaces, but keeping the moving parts well greased and cleaning things after every session helps a lot. I am operating with this little grinder for several months now and had no problems with the sliding parts up to now. And as my normally used CBN and DIA wheels don’t produce that lot of swirling around abrasive dust as normal corundum wheels the whole dust problem is not so dramatic. But sometimes I although have to dress a corundum wheel with the diamond dresser and that is always a real big mess. For this part a vacuum cleaner can help a little, but this sort of dust is real evil and hardly to tame. That’s the reason I always try to sneak out of this procedure as long as possible when I need to do it…..ha ha ha ha…...

Perhaps I should explain a bit of the circumstances witch determines my work and my design. My little machine shop is not located in a building extension or in a garage, it’s located in my second floor apartment.

So I operate with only small “toy” equipment, all things are done with a Proxxon PD360 and a Schaublin70 lathe and a Proxxon FF400 mill, larger machine tools would create some real problems depending on noisemaking, machine dimensions and machine weights. That limits the possibilities of work piece dimensions and also limits the exclusive usage of high strength steel for my machined parts. Okay, I use steel if it’s real necessary, and with a lot of endurance and the proper tooling you can mill carbon steel even on a Proxxon FF400. But to generate the larger components from 7075 Aluminium makes really more fun and saves a lot of time with a small mill like mine.

Being specially interested building tools and fixtures for my own machining purpose I desired a universal tool grinder for a long time. I although have several bench grinders with convenient swivelling tool rests, but for most of all grinding tasks a universal grinder with a linear moving table is simply the first choice.

Unfortunately, a full grown grinder like the Cincinatti No.1 or the Norton Universal etc. does not fit in my shop, believe me, I wish it would. Anyway, so I started to build the Mini Bonelle, which is a neat and handy grinder for table top use but with most of all opportunities the bigger and professional types offer. If you can live with the limited dimensions (13mm collets capacity) nearly all operations on tool sharpening and new tool grinding are realisable. The range goes from all sorts of drills, end mills, reamers, d-bit engravers and turning tools to special things like gear cutters and other experimental form tools. But relief faces on the circumference of helical tools can not be treated, for such tasks I would have to build a new linear sliding spindle for the main work head.

Anyway, for me the MB offers a good experimenting and testing base for a lot of tooling ideas, or otherwise said, it’s always a nice toy to play with……ha ha ha……

Bye, Achim

Offline tinkerer

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Re: An idea for drill sharpening jig
« Reply #52 on: October 20, 2009, 11:16:30 PM »
Achim,
I just spent over an hour on your website. I can't read German, but the pictures kept me involved. You do great work and documentation. I would recommend everyone check it out.
Tink

The desire accomplished is sweet to the soul.
Prov 13:19

Offline sorveltaja

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Re: An idea for drill sharpening jig
« Reply #53 on: October 21, 2009, 03:02:32 PM »
Achim,
I just spent over an hour on your website. I can't read German, but the pictures kept me involved. You do great work and documentation. I would recommend everyone check it out.

I'll second to that. I wish it was in english too... as there seems to be a whole lot of information :coffee:.

In the meantime, I'll take a break of the drill sharpening-thing, and maybe get my main project finished(among others).

Anyway, this thread is always open to any kind of ideas, that relates to subject. Feel free to post :thumbup:.

Offline Tinker

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Re: An idea for drill sharpening jig
« Reply #54 on: October 22, 2009, 06:22:20 PM »
 :offtopic:

I just spent over an hour on your website. I can't read German, but the pictures kept me involved. You do great work and documentation. I would recommend everyone check it out.

Wow...

Um...

 :lol:
Quote
Pimp the China twisting

 :lol:
Quote
Universal spindle second, or it goes also whisper-quietly and compactly

 :lol:
Quote
Comfortably sharpen is worthwhile oneself

I think Babelfish just broke my brain.

Somebody fluent in both languages needs to volunteer to translate Achims site for him.  There seems to be a hell of a lot of useful information there.