|James Jenkins 1||06/10/2019 09:35:17|
125 forum posts
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.
|Clive Foster||06/10/2019 10:30:31|
|2029 forum posts|
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.
1043 forum posts
For drill sharpening on my Clarkson, I use a cup wheel and a Reliance Drill Sharpening jig.
Mine didn't come with a universal head either, though I've since found some old J&S bits and cobbled one together.
Have a look at TheBedroomWorkshop for information on more official methods.
|paul rayner||06/10/2019 11:53:23|
|136 forum posts|
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.
1043 forum posts
Here you go, I found the bits lurking behind the grinder.
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.
|Howard Lewis||06/10/2019 16:38:15|
|2886 forum posts|
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.
4986 forum posts
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 1||09/10/2019 11:10:58|
125 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.
|Martin Kyte||09/10/2019 15:02:46|
1651 forum posts
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.
|Clive Foster||09/10/2019 16:32:19|
|2029 forum posts|
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.
|John Reese||09/10/2019 22:17:21|
|824 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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