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Sharpening Machine Drills / Clarkson T&C Grinder

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James Jenkins 106/10/2019 09:35:17
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123 forum posts

Hi all,

I have purchased a Clarkson Tool & Cutter Grinder, for sharpening various tools in the workshop. It's in really nice condition and came with a Jones & Shipman universal vice, but sadly not an actual Clarkson universal Head.

I need to make some sort of indexable way of holding drill bits (and mill cutters), much like a spin indexer. However, I tend to buy taper or machine bits, as I prefer them. How would these be sharpened? My understanding is that holding the drill on the spiral is not good practice. I guess a block with a 1MT taper in it would work - but wouldn't the end of the drill, near to the grinding wheel, need supporting?

Along the lines of this I guess?


All and any thoughts very welcome.

Many thanks,

James

Clive Foster06/10/2019 10:30:31
1835 forum posts
59 photos

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

peak406/10/2019 11:42:34
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846 forum posts
71 photos

For drill sharpening on my Clarkson, I use a cup wheel and a Reliance Drill Sharpening jig.
I'm sure its not as good as the proper Clarkson attachment, but these can be had for about £15-20, rather than £400-600, and I'm a skinflint. wink

Mine didn't come with a universal head either, though I've since found some old J&S bits and cobbled one together.
In the short term to sharpen the cutters to make something more exotic, essentially all you need is a tubular hole which you can orient and lock in two planes.
For several years, I used a rear brake slave cylinder, bolted to a piece of substantial angle iron. The face that would go on the brake backplate already had a round register, so all it needed was a hole in the angle iron to suit and a couple of curved slots for the fixing bolts. A separate holder was made for each size of cutter to drop in the brake slave, indexing being carried out in the normal manner with a pointed finger on each flute.

Yes it was crude, but worked fine and allowed me to get the machine up and running quickly.

Have a look at TheBedroomWorkshop for information on more official methods.
It's the second time I've mentioned a slave cylinder recently, I'll see if I've still got it and add a couple of photos further down this thread.

Bill

paul rayner06/10/2019 11:53:23
122 forum posts
39 photos

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

peak406/10/2019 14:05:25
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846 forum posts
71 photos

Here you go, I found the bits lurking behind the grinder.
Crude but it works; if I needed to buy the parts to make another, rather than raiding the scrap box, I'd use a single leading shoe slave cylinder, which has two opposed pistons. That way, one would have a through hole to accommodate longer items for sharpening.
I was house/workshop bound at the time, with one leg in a pot.

end mill jig 01.jpg

end mill jig 02.jpg

end mill jig 03.jpg

The individual end mill holder were cut from a length of hex bar I had in stock and then turned and bored to suit, with a pair of grub screws to hold the cutter in place.

Bill

Howard Lewis06/10/2019 16:38:15
2327 forum posts
2 photos

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

Bazyle06/10/2019 20:20:38
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4719 forum posts
186 photos

Nope, The drill tip doesn't need to be in line with the taper as it will align with the pilot hole. Also for smaller MT drills it would not be rigid enough to be held by the taper and not wobble/vibrate when sharpening.

James Jenkins 109/10/2019 11:10:58
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123 forum posts

Hi all, thanks so much for your help with this - looks like (as usual) I have been over thinking it! I will do something along the lines of your suggestions and come back and post pics when done.

Kind regards,

James

Martin Kyte09/10/2019 15:02:46
1484 forum posts
24 photos

How about a hollow ER collet holder, that way you may grip the drill close to the cutting edges and the rest of the drill can hang out the back.

regards Martin

Clive Foster09/10/2019 16:32:19
1835 forum posts
59 photos

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

John Reese09/10/2019 22:17:21
782 forum posts

I grip my drills on the OD of the flutes using either 5C or ER32 collets depending on the size. I grind a 4 facet point. The greatest need in any drill grinding setup id that it can index exactly 180 deg. to get the flutes equal. I am thinking of getting a 4" 6-jaw chuck so I can expand the range of drills I can sharpen.

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