Author Topic: How are four facet drills shapened on a tool and cutter grinder?  (Read 1827 times)

Offline sparky961

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There's not much more to say than the title/question itself.  I'm asking in relation to what I believe is a "Deckel" style grinder, of which there are now many clones available.  I suppose the question extends to other machines as well, if the method differs.

The main concept I'm not getting is how you get the point centered in a reliable, repeatable way.  I've seen some videos of four facet grinding where they just sneak up on it for the secondary facet, but I'm looking for something faster and more accurate than this.

Offline Metalman

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #1 on: March 12, 2017, 05:10:41 PM »
sparky
You may find some useful information within the video for which I have just added a thread.
Also from my website page here http://www.homews.co.uk/page360.html
Harold

Offline sparky961

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #2 on: March 12, 2017, 06:17:18 PM »
Thanks, Harold. I watched your video in the hope of just that, but I found that you've only added to the confirmation thar current DIY methods could be improved upon.

Your results look very good but I'm still not comfortable with the idea of sneaking up on the point to make it meet in the centre. For a small HSS drill, the time spent getting it right is just too great.  Being honest with me, and yourself, how long does your method take to resharpen a 3/8 drill that isn't completely trashed?

Offline b4dyc

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #3 on: March 12, 2017, 07:40:17 PM »
Hi
Not sure if you have seen Johns web page  http://www.gadgetbuilder.com/DrillSharp.html
That drill grinder will grind around a central pivot point and achieve fairly quick results
I didn`t do it...

Offline sparky961

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #4 on: March 12, 2017, 08:50:06 PM »
Hi
Not sure if you have seen Johns web page  http://www.gadgetbuilder.com/DrillSharp.html
That drill grinder will grind around a central pivot point and achieve fairly quick results

Yes, I've seen it.  I was a bit confused as to how the pictures and descriptions matched up.  There's a lot of information on that page and not very well organized.

If you can narrow it down for me which one you're referring to and how it works I'd be grateful.

Offline b4dyc

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #5 on: March 13, 2017, 02:08:19 PM »

This is the style of sharpener.

The drill and grinding wheel are all on the same axis (when built correctly) so when you have ground secondary angle the table is dropped so that the primary angle is ground with no further trial.



If you read the page, John suggests that you contact him for plans if you do not have them already. He has in fact posted the files to me.
I didn`t do it...

Offline Metalman

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #6 on: March 14, 2017, 07:17:17 AM »
sparky961
In answer to your question about the time to sharpen a 3/8" drill by the four facet method, I would say 10 minutes if you did it enough to come to terms with the method.  Less of course, if you had equipment permanently set up for the task. For me, sharpening drills by any method is a rare task, particularly in recent years as other pastimes have taken priority.

You mention creeping up to a point being difficult, but leaving a short length of the original chisel is quite acceptable.  However, percentage wise, the acceptable error becomes smaller as the drill size becomes smaller making it very much more critical, and therefore more difficult at smaller sizes.

Therefore, I consider there is a minimum size at which it ceases to be practical, unless time taken is of no importance. For me that would be 1/4”, but above that size it becomes progressively more worthwhile as the cost of a new drill escalates.  Certainly, 3/8” and above it becomes, financially, the approach to take, not necessarily using the four facet method but equally by any other method, cheap DIY methods excluded.

I mention cheap DIY methods, as for me using a drill set in increments of 0.1mm, there is no purpose in sharpening a 11.2mm drill if it then drills a hole 11. 4mm diameter.

I must try to find time to visit the gadgitbuilder web site

Harold

Offline Fergus OMore

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #7 on: March 14, 2017, 08:19:10 AM »




I must try to find time to visit the GadgetBuilder web site

Harold


John Moran is quite practical and not just for his thoughts on tool grinding.

Kind Regards

Norman

Offline sparky961

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #8 on: March 14, 2017, 10:56:56 PM »
It's a very clever idea to use a dished wheel and stick one of the fixture's hinges inside the wheel.  I have to admit that I never thought of that when trying to get the pivot point of the horizontal plane to match with the drill's point.  Though, for the sake of accuracy, he's not using a T&C grinder like I had asked about.  But I did include "other" machines in my question too... so it's all good. ;)

Now, if you've been following any of my other recent posts you'll be aware that I'm actually focusing my efforts on a fixture for a surface grinder.  This is for no other reason than I have one readily available and it seemed the better way to go. 

In considering John's (Gadget Builder) fixture, I would be hesitant to use it on a surface grinder due to a safety concern.  As clever as the idea is to tuck that hinge into the wheel, this is just asking for trouble when you have a lot of table travel and it's easy to travel right into the wheel.  Perhaps this problem is negated through the judicious use of table stops/dogs, but I'm not sure I'd ever be quite comfortable with it.  It also limits the wheel selection to a dished/cup type of wheel, where otherwise you could use a standard wheel that has the face relieved for side grinding.

I'm a little surprised (disappointed even?) that no one has commented on the other fixture I presented for feedback.  I just checked and there have been 80 views but no replies.  What does this mean?  Got lost?  No interest?  Nothing to add?  It's a piece of Rube Goldberg crap but I don't want to hurt your feelings?

Let's see if I can't drum up some replies though a link here...

http://madmodder.net/index.php/topic,12011.msg142291.html#msg142291

Offline sparky961

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #9 on: March 14, 2017, 11:05:12 PM »
sparky961
You mention creeping up to a point being difficult, but leaving a short length of the original chisel is quite acceptable.  However, percentage wise, the acceptable error becomes smaller as the drill size becomes smaller making it very much more critical, and therefore more difficult at smaller sizes.

Perhaps it will still drill an acceptable hole, but if the point isn't near perfect doesn't this negate the benefit of the drill being self-centering?  You end up with a chisel point that isn't any better than the "standard" conical grind.  Maybe you re-gain the advantage after splitting the point (on the four facet grind)?  But of course, the centering of the split is very critical as well.

Offline Joules

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #10 on: March 15, 2017, 02:38:46 AM »
This caught my attention recently.

https://www.tormek.com/uk/en/grinding-jigs/dbs-22-drill-bit-sharpening-attachment/

3D printed/machined hybrid forming as an idea here.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline mexican jon

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #11 on: March 16, 2017, 07:12:16 AM »
This caught my attention recently.

https://www.tormek.com/uk/en/grinding-jigs/dbs-22-drill-bit-sharpening-attachment/

3D printed/machined hybrid forming as an idea here.

I have 1 and can confirm they are very good  :drool: :drool:
People say you only live once ! I say thank F@*K can't afford to do it twice.

Offline John Stevenson

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #12 on: March 16, 2017, 07:28:26 AM »



John Moran is quite practical and not just for his thoughts on tool grinding.

Kind Regards

Norman

Thank Christ on a push bike that someone is.
10 minutes to grind a 3/8" drill ?

Anyone taking that long in my shop will be looking for another job.
John Stevenson

Offline Metalman

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #13 on: March 16, 2017, 09:23:01 AM »
I am sorry sparky but I should have quantified the amount when I said leaving a little of the initial chisel was acceptable. To add some values to the task, lets assume the length of the chisel established on your 3/8” drill after the first stage is 0.100”. Ideally then, the next stage is to grind the drill equally on both sides and by an amount that just removes the chisel fully.

However, that needs very precise final setting, and as you say, creeping up to that point once you get close to it. This will need doing  a few thou at a time and can be time consuming.  Because of this, and I understand it is preferable, it is better to leave a very small amount of the initial chisel than to go too far when a forked end is produced. How much then am I saying can be left, well the amount is not critical but I would say in the order of 0.010”,  that would avoid the time taken to finally make such fine adjustments, but will still have all the benefits of a four facet drill.

Those amounts are though based on your 3/8” drill and will get progressively smaller as the drill size gets smaller making it more difficult. For the home workshop therefore, I consider there is a downward limit to what can be sharpened by the method being in the order of 1/4” as I suggested earlier in the thread

John
I think you have overlooked that I said “Less of course, if you had equipment permanently set up for the task” For most home workshop owners they have one grinder with my grinding rest and the four facet jig stored away somewhere. Now I admit that my grinding rest is not quick to set up, few sharpening machines are, especially for four facet drill sharpening,  added to which it will only be a very occasionally undertaken task.

Out of interest, I would though like to know what equipment you use to sharpen by the four facet method and what it the minimum size practical with it, cost of drills excluded.
Harold
     

Offline John Stevenson

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #14 on: March 16, 2017, 06:55:07 PM »
Harold,
 I have two machines that can do 4 facet, well one is close but more later.

One is a German Meteor drill grinder that goes from 0.1mm up to 6mm in two stages. ).1mm to 3.2mm and 3mm up to 6mm on a second collet.

Very similar to a Christian but not as many bells and whistles and because they are not so well know they can be picked up cheap. I paid £40 for this off Ebay. It can only do 4 facet, it has no means of doing what I call a swept grind which we are all used to. It has preset stops so you do the two primary angles first, then drop down to the lower stop and it does the secondary with the cross over exactly at the centre of the drill. It has a microscope fitted so you can see what the drill is like before removing it from the collet.

Quite quick, I recon on  a 2.5mm drill it's between 1 and 2 minutes to do a drill.

I do a lot of CNC drilling in 2.5, 3.0 and 3.12 [ 1/8" ] sizes hence buying this machine. I grind brand new drills up from straight out of the box.

The reason for this is these parts have from 250 to 750 holes in per part and even buying good drills like Guring I can get 2 parts and 'may' break the drill in the third part because the web has degraded. It's not the cost of the drill or part for that matter but they can be on the machine for just over 1 hour so I loose this time.

If I turn a new drill into a 4 facet I can guarantee 4 parts before I swap the drill over so it does pay.

The second machine is one I'm working on with the Chinese. It goes from 3mm up to 20mm in two sets of ER collet ranges, ER20 up to 13mm and ER32's from 13 to 20mm.



Small collets are carried inside the machine, larger collets are carried in an external box. as you can see from the picture. It can handle HSS, cobalt and carbide in the 3mm to 20mm range.

To use you select the right collet and holder from the two supplied and insert the drill. The left hand side is for setting and the right hand side is for grinding. On the left you wind the top knob in to whatever size drill it is on the scale then push the drill thru the collet and rotate it clockwise until it comes up against the scale stop and tighten the collet. A bit like a drill doctor but in this case there is no plastic it's all hardened steel and very, very robust.

That's it for setting. All the skill needed is built into the machine, not the operator, my grand daughters at 11 and 12 can use this.

You then move the holder to the front hole right hand side and push in and rotate the cam a few time, not endlessly like a drill doctor, even on a 20mm drill it only takes about 4 or 5 wipes per flute.

Now this is where it gets clever although it's not a 4 facet in that its a swept grind and done in one pass with no extra settings the cam is very subtle in that the first part is same as a 4 facet and flat and then it sweeps away.

When I say subtle you can feel it, only see it in the correct light.



This is the best I can do with a camera phone on a 16.5mm drill.

The top hole is for split points but we are still working on this. We are on the 4th cam but still not right over the whole range.
I timed that 16.5mm drill at 1 minute 20 seconds and I dare say there are a few people on here who have seen this work at Harrogate and Doncaster and can back up the speed and lack of skill need to use it.
John Stevenson

Offline sparky961

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #15 on: March 16, 2017, 07:51:46 PM »
That Meteor grinder sounds like just what I need.  Still see any around?  Meh... shipping would kill me.  But on second thought, could be worth it when you consider the time and uncertainty with my other idea.

What is the mechanism and/or technique to get the point dead on with the Meteor?

Offline sparky961

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Offline Biggles

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #17 on: March 17, 2017, 02:02:32 PM »
There are a few cheaper items around ranging from Record to Tormek which have a Jig for 4 facet drill grinding https://www.youtube.com/watch?v=fSUa1iFUzkM
 :)

Offline Metalman

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #18 on: March 17, 2017, 03:54:40 PM »
Thanks John for having spent so much time to give me such a detailed explanation, very interesting.

If I were a younger man I may have looked out on ebay, etc. to see if I could locate one like the first machine going at a reasonable price. Nowadays it would be just a novelty as I have done nothing of any size in the workshop for a few years and that is not likely to change.

Thanks again.
Harold

Offline Houtenkrullen

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Re: How are four facet drills shapened on a tool and cutter grinder?
« Reply #19 on: March 19, 2017, 06:48:03 AM »


Harold,
 I have two machines that can do 4 facet, well one is close but more later.

One is a German Meteor drill grinder that goes from 0.1mm up to 6mm in two stages. ).1mm to 3.2mm and 3mm up to 6mm on a second collet.........and because they are not so well know they can be picked up cheap. I paid £40 for this off Ebay.

John, I have been looking for one like this for some time. Apparently they are better known in the Netherlands, because I haven't seen one anywhere near that price. More like €600-750.
Do you have the user manual of the machine? I am very curious about how it achieves such a high accuracy.
Peter