Javascript Menu by Deluxe-Menu.com

CATEGORIES

HomeWorkshop

Sharpening methods
One of the biggest difficulties faced by inexperienced turners is keeping the tools sharp. Woodturning needs sharp tools. Blunt tools tear the wood, leaving a poor finish; they fight back when you try to control them, hindering accuracy; they need pressure to make them cut. Blunt tools make turning an ordeal.

A good edge makes all the difference. The tool is controllable - for example it can pick up a fine shaving half way round a bead to refine the shape. The wood is cut smoothly and quietly, leaving a polished surface. Sharp tools let you make those easy cuts and long shavings that are simple pleasures in a turner's life. But because sharpening needs skill, even using jigs, inexperienced turners don't always keep their turning tools properly sharp. They may not even know when they are blunt. Sharpening is part of turning, and the techniques have to be learned as diligently as the turning itself.

Testing an edge
Every time you start a turning session you should check that the tools are sharp. A quick way to test sharpness is to try the edge on your thumbnail. You can feel the sharpness as the edge catches. If it slides over your nail without catching, it is blunt. As the work progresses, bluntness gradually creeps over the tool edges. It is easy to forget this as you keep going without thinking of the tools. So get into the habit of checking the edges again after a few minutes of cutting, and if not satisfied, sharpen again. Some wood species are more abrasive than others.

Sharpening methods
There are a number of options, some considerably more costly than others. They include dry grinding, wet grinding, buffing, honing and stropping, all either with or without jigs to present the tool at the correct angle. I have tried most of the methods available. Currently I use a high speed dry grinder with a homemade jig for bowl gouges, the grinder's own tool rest for scrapers, and a second homemade platform jig for my roughing gouge, and when necessary my skew chisels; a Tormek grinder for spindle gouges; and a diamond stone for skew chisels and tungsten carbide tipped tools. I also strop chisels.

Dry grinder
I use a grinder with two 200 x 25 mm fine wheels. You might prefer a slow speed machine with wide wheels, but high speed grinders work perfectly well, with a light touch, even on carbon steel. I have not found wider wheels necessary if care is taken not to let the gouge 'fall off' the edge. Some turners prefer a flat bevel as given by a belt sander instead of a hollow ground one that a grinder wheel gives. I haven't found an advantage, but the hollow made by the 200 mm wheels is shallower than that from the more usual 150 mm size. I would not recommend wheels smaller than 150 mm. If you hone the bevel, it becomes flat next to the cutting edge.

One wheel has the rest permanently set at the angle I like for scrapers. Below the rest is the extendable arm for my homemade gouge jig that lets me sharpen gouges over the top of the grinder rest without moving it. The arm and jig are similar to those used by many turners. They can be made easily, or purchased even more easily. This one, and the angled tool holder I use with it, are based on those shown by Eddie Castelin at 



Homemade extending arm for grinding gouges. Used together with an angled holder for the gouge.


The other wheel is also set up with a jig. This one is easily made of plywood. Similar platform jigs can be bought. I use this jig for my roughing gouge and for skew chisels when honing is not enough. To set the plywood jig I use a pair of very useful gauges. They let me quickly set the platform to the exact grinding angle. These setting jigs are easily made from plywood. First set the platform to the correct angle, then hold a piece of ply for the gauge with its straight edge on the platform and mark the curve of the wheel on it with a pencil. Cut out the curve and make the middle of the curve more hollow so the ply will contact the wheel rim only at the ends of the curve. This ensures a positive location as the wheel gets smaller. To use, just put the gauge on the wheel rim and set the grinder platform to the gauge. You need a gauge for each different bevel angle.These jigs work very well. but when I began turning such jigs were not well known and I learned to grind spindle and bowl gouges freehand. Having made the jigs I find I have lost some of that skill.



Grinding jig 



Setting gauge for grinding jig. With the contact points touching the wheel, the grinding jig platform is adjusted to touch the flat section of the gauge.

Tormek wet grinder
The gouge jig and fine grinding wheel on this machine produce a great edge on my spindle gouges. But it is expensive and I would probably not buy another. I found it a bit too slow for bowl gouges, which tend to need more metal removed to refresh the edge, so now use the high speed grinder for them. Scrapers need more sharpening than any other tools so I use a dedicated tool rest on my high speed grinder for those too. Water cooling is not necessary for high speed steel, nor for carbon steel if you take care. I rarely use the Tormek honing wheel as I find the gouges cut well straight from grinding. Nor do I use the other Tormek jigs.So although the Tormek works well, I would not recommend it over a good quality high speed dry grinder.

Buffing
A stitched cloth or hard felt high speed buffing wheel dressed with appropriate abrasive can keep long bevel spindle gouges extremely sharp. The tool is presented to the wheel freehand with the edge trailing. The wheel tends to round over the bevel quite quickly, so grinding is also needed to keep them in good condition. Buffing is not so good on chisels as the sharp points are too easily rounded off. It is not so effective on scrapers either as it is hard to present a short bevel to the wheel at the proper angle.

Honing
Many turners do not hone their tools. I find that gouges are not worth the trouble of honing, but perhaps that is just because I am not skilled at it. I am mindful that the old time turners did hone more and grind less. I do hone my skew chisels, perhaps because they are easy to hone if they have long bevels. I have used oil stones, water stones and diamond stones and all work well. I found that ceramic stones were too slow.

Stropping
A strip of leather glued to a strip of wood makes an excellent strop. Dressed with a little fine abrasive such as paint cutting compound, it can put a really good edge on a chisel with just a couple of pull strokes on each side with the bevel lying flat. It removes the honing burr and leaves the tool ready to go. Care must be taken not to dub over the edge or take off the points of a skew chisel. I do not use any kind of jig with the strop.

 
Terms and conditions | Privacy policy
| Powered by: Bigcart.com