Clarksons own drill sharpening attachment uses a 6 jaw chuck to hold the drill via the flutes which is clearly satisfactory. The instructions specify the distance by which the drill should stick out from the chuck. Its quite short.

The issue when holding a drill on the flutes is primarily one of getting sufficient contact points to hold the drill securely and in line with the spindle. In principle long jaws on a normal 3 jaw chuck would work fine but thats a cumbersome solution which will almost certainly have accessibility issues.

The Clarkson universal head simply holds the cutter by the shank is a simple parallel sleeve. Its probably over versatile for normal mortals. If I din't have the official tooling I'd probably make a simple bored block to hold each size of cutter arranges to bolt to a right angle bracket with a few indexing steps to get the necessary angles. Three might well be enough. A similarly small number of indexing steps to set the right angle bracket should do. I see no vital need for the graduated scales. To the book angles have more to do with getting maximum life under industrial conditions. Folk like us rarely work cutters hard so sharp at a good enuf angle is all that matters so you want a set up that makes it easy to sharpen cutters. If sharpening is a faff you will run them blunt.

Folk do use collets to hold cutters but that seems a potentially expensive way of doing things given all the grinding dust. Sidelock (weldon) holders in a block having the same taper as your mill would work for milling cutters too and be less vulnerable to grinding dust than collets.

Getting back to drills its a pity no one has published the geometry of the Clarkson attachment. Its fairly straight forward and well within home shop fabrication capabilities. I'd probably start by cutting down a spindexer. But I have the real thing.

Clive

peak4 beat me to it, the bedroom work shop is an excellent site, there is drawings for the universal head on there as well as the fingers. You could use the er collet system to hold the drills as I'm planning on doing.

regards

Paul

If your "machine bits" have Morse Taper shanks, to ensure that the centre of the finished article is concentric with the taper which holds it, surely the way is to hold the bit in a Morse Taper socket for grinding?

If the flutes are not concentric, or the drill is slightly bent, locating on the flutes will not produce a cutter with the point accurately on centre, so cutting oversize.

The only concern is whether there will be room for the length the larger drills.

Howard

Re the suggestion from Martin about using ER collets.

Before spending serious money on a set (or deciding that you won't be grinding enough drills for the dust to wreck your good ones) it would be as well to verify that the actual parallel holding portion is long enough to properly grip the two flutes of a drill. I imagine two points each side is the minimum for acceptable results.

One of the inexpensive drill attachment breed used Nylon collets witha long taper and correspondingly long collapse range. They were said to be satisfactory.

Clive

Sorry for the revive, but I need to weigh in after using mine a bit today, that drill grinding attachment that Clarkson sold is way more than adequate and blows my little Craftsman style one out of the water. It further blows my mind how close this one is to the newer ones that you can buy. The only thing Clarkson didn't do, which they should have, was include a cam for grinding drill bits.