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Multi faceted drill bits - really necessary?

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JasonB27/06/2019 11:18:24
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On the subject of drills I would say a beginner would be best off buying a reasonably priced set and then as they need replacing top up with better quality ones particularly in the commonly used sizes eg whole and half millimeter plus tapping sizes. The others that you may not use so much replace as budget allows.

When I started off individual drill bits were bought as and when needed from the local tool shop with pocket money or a twist of Dad's arm. That was back in the day when ME show was over the Christmas - New Year period so a set or two of unbranded drills followed as Xmas presents, probably still got 50% of the original bits some 35yrs on. Over the last few years as I have been spending a bit more time on this hobby the worn or rarely broken ones have mostly been replaced with the above mentioned Dormer (not Brittish made).

Even then I tend to wait until they are on offer from one of the suppliers or keep an eye out for boxes of the sizes I am likely to use most at the shows where they can be picked up at good prices and should have enough now to last me quite a while. I still don't always get Dormer as although I could quite easily go out and spend a few hundread on new boxed sets of all the sizes or even individuals I do think twice about the cost of there drills as the sizes go up so may got to another brand like Guhring.

Similar applies to Stub drills which I like as they save me cranking the head up on the mill all the time as well as being less flexible so they cut straighter and combined with the split point can in most cases be started without spotting/punching though I still do that for critical holes. As mentioned above I only have them in common sizes and the larger few in more economic brands.

I'm happy with my workshop which is mostly far eastern equipped and feel selective purchase of tooling makes a more cost effecting improvement than spending out lots on fancy machines and then scrimping on the item that actually does the cutting. Hardest thing for those entering the hobby is finding reasonable tooling at reasonable prices of which there is plenty from the far east but there is also a good amount of poor stuff that you may or may not get when buying at the very cheap end of the scale

Howard Lewis29/06/2019 10:34:10
2382 forum posts
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With regard to the comments about the clearance of four facet drills; a thought.

An End Mill with spiral flutes is effectively a four facet drill with a flat end, rather than the usual 118 degrees of a twist drill. And they work OK.

Twist drills ground with four facets cut extremely well, and with less effort than "round ended" ones, for the reason that Jason gave. The central chisel point has minimal are so the pressure generated by the axial force applied, is enormous, and the point cuts despite the minimal cutting speed.

D A G Brown made jigs, to allow drills to be four facet ground on a flat abrasive.

It ought to be possible to make up two jigs, in which the drill could be clamped at the appropriate clearance angle to be moved across the face of the wheel on a bench grinder to give a four facet effect.

Of course, using a cutter grinder is the ideal way.

Not having one, would the Eccentric Engineering sharpening device provide such a fcailty? Iwners/Users comments?

Howard

David Caunt02/07/2019 22:26:19
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Andrew,

I spent ages with the Draper and eventually filed it in a drawer. The instructions were so poor. I ended up with chisels not drills

It was only after reading Harold Hall's excellent article on using the drill sharpener that the penny dropped.

Only 2 things mattered.

  1. Getting the drill projecting the correct distance from the axis of swing.
  2. Orientating the cutting surfaces so they meet the grinding wheel vertical. (This I believe means getting them parallel cone in effect)

With respect to the distance from the grinding surface I decided that it was a pain trying to measure. So instead I mounted the attachment on a surface with a scale attached and a line when the front of the trough touched the wheel see photo.

Harold had said the correct position for the drill was the one that gave the correct chisel angle (130deg). A larger angle was caused by the distance being too small and a smaller angle when the distance was too large. So I started with a 10mm drill and found 10mm was too close and gradually moved the attachment further out until the chisel angle was correct (against a pre-cut credit card ). Then carried out the same procedure with larger and smaller drills and plotted drill diameter against the distance to which the attachment should be set to give the required chisel angle. I now wouldn't be without it.

 

Edited By David Caunt on 02/07/2019 22:26:58

Edited By David Caunt on 02/07/2019 22:29:09

John Haine03/07/2019 07:29:07
2637 forum posts
134 photos

Posted by Howard Lewis on 29/06/2019 10:34:10:

........

Of course, using a cutter grinder is the ideal way.

Not having one, would the Eccentric Engineering sharpening device provide such a fcailty? Iwners/Users comments?

Howard

It certainly would with an appropriate jig.img_0121.jpg

this is the end mill holder I made using an er16 collet chuck. Not obvious is that the top and bottom faces of the block are not parallel to give the two clearances. Might need to make an alternative block for the drill angles but it's straightforward. Max drill size would be 10mm. I might give it a go.

Norman Billingham03/07/2019 09:22:27
22 forum posts

Not sure if it counts as advertising - in which case i'm sure mods will remove, but there is a recent book by Jorg Hugel called Drill Sharpening. It covers all the details of setting angles for cone and four facet drills in great detail and has a CD of spreadheets which let you see the effects of changing setting parameters for yourself. It's only available from SMEE and all profits go to the Society. Not for the mathematically faint heated. A message to the SMEE secretary via the web site will put you in contact.

Gary Wooding03/07/2019 12:51:19
584 forum posts
139 photos

When I posted this ***LINK*** to a demo of the Sealey SMS2008 I was surprised that there was no response at all.

Here's a couple of before-and-after pictures of a drill sharpened on my device. It's really easy to use - just as shown in the video.The sharpened drill cuts very well - like it should.

drill blunt.jpgdrill sharpened.jpg

Howard Lewis03/07/2019 20:09:53
2382 forum posts
2 photos

being one of the fortunate ones with a cutter grinder, (a mWorden so not the most complicated ) when my inertia can be overcome, ,sharpen my drills by the four facet method They cut , subjectively anyway, better than conical ended drills. The accuracy.of the resulting hole depends entirely upon my dexterity, not the machine or the process.

For those without a cutter grinder, there is still hope. D A G Brown produced pland for one or more jigs to produce four fcaet drills without a bench grinder, just a flat oil stone, or sheet of emery.

Howard

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