For Long Nose (Celtic) Bowl Gouges
Written by Gordon Warr reproduced by kind permission of The Woodturner Magazine.
I once heard a well known turner say that in his opinion bowl gouges with extended wings were one of the best advancements in tool development over recent years. The problem he said is that it is virtually impossible to maintain the continuity of the ground surface from one side of the gouge to the other by normal hand-held grinding techniques. "I have found the answer" he said "and that is this jig which gives exactly the shape required and the shape can be easily maintained every time the gouge needs further sharpening." He then gave a demonstration of the jig he was using say that it was available from Hamlet. I've managed to gain a sample of this jig which can be fitted to any dry grinder without impinging on its normal use. It consists of two main parts plus a bolt for securing down and this is included when you buy the jig.
The support bar is around 200mm in length and is slotted for most of its length and it is through this slot that it bolted to the bench on which the grinder is mounted. It is secured exactly in line with the centre line of the wheel with the slot allowing for adjustment forwards and backwards. Close to the front of this base component is a dimple and it's in this that the leg of the clamp rests and is free to move.
The clamp supports the gouge in a vee block with a strap scross the top being tightened to hold the gouge securely. The amount of projection of the blade from the front edge of the block can be varied in its setting but is typically 35mm to 55mml The jig caters for gouges up to 25mm in diameter but I dont think too many of this size occupy the average workshop!
It is imperative for the gouge to be mounted correctly in the clamp. This is achieved by first clamping it as described then visually checking by looking from the side to see if the existing grinding bevel is in full contact with the wheel of the grinder. Adjusting the protection will make any correction needed while adjusting the position of the support bar will alter the extent of the wings of the ground surface. Actual grinding is now very straightforward. The gouge is manually rolled from side to side its movement being fully controlled so that only one ground surface can be produced and this with total uniformity. If a gouge is being ground for the first time when using this gig then a little extra attention might be required in order to gain a new continuous surface. Provided the appropriate settings are made then the jig is failproof.
The jig could not be simpler to use yet the results are totally consistent accuracy. We all know the necessity of not just using the correct tools but in having them sharpened so as to give maximum performance. This jig is the answer to bowl gouges with extended wings.
|Same as the normal grinding jig but with an extended bar to sharpen a variety of tools with handles on - up to 16 inches in length.|
|The tool handle is cradled in the fully adjustable cup for ease of use.|
Bore 10mm hole in bench below grinding wheel and 1" in front. Fix bottom slide.
Position stem of square jig in pivot hole. Adjust slideway to suit angle required. Advise 60°. Jig should be placed on gouge 2" from end - measurements will vary according to individual settings.
To sharpen Celtic/Long Grind touch nose on stone to determine correct angle and swing blade from side to side maintaining contact with nose on grinding wheel.