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Hoffmann Dovetail Joining System

KEENCUT Advice

Mike Labbe

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This was passed on to us, from the UK framer's forum and a tech from KEENCUT:

Bendy bevel cuts When cutting modern tough boards, particularly conservation boards on a manual cutter there are a few important factors:

* The cutting head should have minimal (ideally zero) side play or the board will use that loose movement to pull the blade slightly off track and once the blade starts to veer offline it will bend the blade tip so it can continue on its path. Then sometimes, on a large mount, you may find the blade comes back in as the cut progresses, this could be due to your arm/elbow position influencing the attitude of the cutting head as you pull the head towards you.

* Make sure the board is being clamped properly, as has been said before check the surface you have the cutter on is flat and not bent or twisted.

* As mentioned above blade depth is all important, it should just be cutting into the surface of the slipmat. The longer the blade tip the more flexible it becomes and will obviously bend easier. On a side point here, it is often a mistake to think a thicker blade will prevent the blade bending in this situation, a thicker blade should always be the last resort.

* Lastly, but in most cases in most cases has most influence, is blade type. Quality is all important and your Keencut bladesare at the top of the scale, so no problem there, but I feel the type is wrong unless you are cutting a comparatively soft board. For most white-core/acid-free boards and especially conservation board they will need a chisel or single edge blade like the Keencut TECH S 012, making sure they are positioned the right way round in the blade holder (you can only use one tip).

Why single edge? imagine cutting a slice of bread with a double edged knife, for the slice to be parallel different things happen either side of the blade. The slice effectively moves away half a blade thickness as the blade cuts and on the loaf side the bread is pushed over or compressed by half a blade thickness so the blade can take a straight path and the slice cut parallel. Now, if the bread was stale and hard it would be more difficult to cut a parallel slice as on the loaf side it would resist being compressed and therefore try to push the blade over half a blade thickness and start it on its way to produce a tapered slice. So to prevent this using a single (chisel) edged blade with the flat side on the loaf side (rather than the slice side) it does not require the loaf to compress at all but it will push the slice away by the full thickness of the blade, which is no problem, and therefore cut parallel. So, tough/hard boards need a single edge blade - but a double edge blade can be used on soft boards (works out cheaper).

What about a thicker blade? When cutting a tough board always use the thinnest blade you can, a thicker blade will try to part the board more as it cuts, put it under more stress and create rub marks on the bevel, particularly at the end of the cut as the blade is retracted. Putting a board under more stress means the blade is under more stress and so is the framer! Using a thin blade (providing it is set up properly) will glide through the board making it easier on your hand/arm/fingers and produce a clean straight cut. The only time I have had to go for a 015 blade is if the board is over 3000 micron but even then this, as in all cases, should be supported by a little experimentation.
 

wvframer

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That is useful for any manual matcutter. Thanks.
 
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