Drill sharpening?

In my experience the life of the resharpened drill is seriously effected by the surface finish on the grind itself. Rough out using the standard grade wheel of 40 or 60 grit, and then finish with a fine wheel of 120 or finer. An alternate is to hone the edge. These will last every bit as long a s a new drill, and if sharpened correctly will drill a hole to be better than 0.05mm of the drill size and have a roundness of the hole better than 0.03mm tir. Hand sharpened or fixture sharpened should be giving the same results. Hand sharpening drills is a skill that some can never manage. Although it looks ok, when used won't be. You know when it is right as the swarf comes off fairly evenly from each drill flute. I have seen many new drills that require a touch up to get them to drill proper holes.

One of the best attachments that I made for my Picador clone was a Harold Hall inspired attachment to ensure exactly 180° rotatation of the drill bit being sharpened.

Details are contained in this excellent book which should be considered as a useful reference for model engineers. Tool and Cutter Sharpening

No affiliation, just a satisfied customer/reader.

* Danny M *

I use one of ***THESE***

The price was far less than I expected, works really well and is very easy to use.

Hi Neil, Guys,

When you have an accurate drill grinder, like the

https://www.gadgetbuilder.com/DrillSharp.html#Facet4 one,

putting a brand new drill into it and marking the facets with a marker. Very lightly touch up the facets and you will be surprised just how often they are way out. Most often one side is longer than the other or the face angles are wrong. Regrinding them makes a world of difference particularly to the larger drills. Also you will find that deeper holes don't wander as much. This I think is because you don't need as much pressure on the drill to keep it cutting, so the drill doesn't flex.

Unfortunately the biggest drill that I can sharpen in the four facet sharpener is 10 mm, so I either do them by hand or use the picador, which once you have set it up properly does a reasonable job.

NOTE: I had to bore out the collet holder to 1/2" to be able to actually get a 10 mm drill in there.

Edited By John Baron on 12/06/2020 08:52:45

Like parting off, this seems to be a bit of a "Black Art"

Perhaps more of a Hit-and-miss exercise.

Newbies to this its worth knowing that to get a drilled hole to size. Drill several holes to .1mm of size needed 6mm then stone the two cutting points of the drill 6mm and it will be on size, as this acts as a reamer. I have several drills ready done in a separate drill box and works well for me.

Bob

We have at work a Darex drill sharpener. It works well, but I still hand grind mine. Yes with deep holes, the more accurate you have the drill sharpened, the straighter the holes turn out. And yes they take less pressure when sharpened correctly. With most drills to 1-1/4 (32mm) I just drill directly. No pilot , just start from a centre drill.

Set up is important as well. Things to check is tailstock alignment when drilling in the lathe.

I've got a drill doctor too and have found it hit and miss, do you position the holder one tooth to the positive side? or?

I have a silver line sharpener for small drills.but would like to learn the art of hand sharpening.i have been told too make a jig to hold the drill at 61 degrees this should make it easy to get a good cutting angle.

Regards

Robin

I have a basic rule of thumb where the larger the angle the easier it is to drill by hand

Here is a totally unscientific drawing

The more pointy it is the easier it is for hand drilling in steel and the more it grabs the work if you push hard with a machine tool so you use it lightly in any machine

The cutting angle is between the part you grind and the inner spiral

If you can hand grind for hand drilling steel then machines are easy peasy

When you hand drill steel always always use a pilot drill of about 3-5mm max to clear the centre area out

Hand drill steel at low speed to save on drill wear, 2-300 rpm, once you get some skill and experience you can up the speed as required

A well ground drill is your pal and cuts into the metal straight away, no metal means a regrind

Grinding for a machine drill is about grinding a less acute angle because even cheap machines can apply such huge pressure at the cutting edge compared to a puny human and the drill should also last longer with more meat at the cutting edge

Edited By Ady1 on 08/07/2021 16:59:02

If you can make / arrange a set up that provides four facets, do so.

They cut like a hot knife through butter, and centre more easily.

Having equal length cutting edges is essential if the drill is not to cut oversize.

Is it my imagination, or do four facet drills wear less rapidly?

Howard

Howard is right ! For really easy and accurate sharpening I use a brierley ZB 32,or the clarkson DPTL grinder. Both these machines are costly but do a good job in seconds. Both use a 60 grit wheel. Noel.

I've got a second hand drill doctor that produced passable results for a while before it started producing zero and negative relief grinds. I've also got a Picador Fig 9 jig that can produce good results when set up precisely, which takes time. Both have the limitation that they only go up to 3/4". I'm not interested in offhand grinding.

What I have been doing it pottering about with the cad program to sort out what's needed for a double size Duplex drilling jig based on the 1951 ME articles. To be honest, it'd be simpler to just make the bits to twice the given dimensions, but it's also an excercise in learning Alibre.

I always ground my drills freehand until a friend who was clearing his workshop came across a Delta drill sharpener.He didn't know how it worked and neither did I until I looked it up on the net and found out that it was missing some bits.I machined up the parts and coppied the instructions,bit of learning curve but when I got the hang of it I got good results.I think it was war surplus as it is American.The instructions I downloaded are very good.

Frank

After you have done your 4 facets put a secondary point angle in and your drills will last even longer!!