Before answering it is good to understand what is happening when you cut with the different types of blade so 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 because you can use both tips of the blade).

White core or general acid free boards are mid-range on the hard-to-cut scale so carry out some cutting trials using both types of blade and see what gives you the best result.

When cutting any 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!   More blade stress = more blade bending.

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.

3000 micron = 3mm = just under 1/8″

Firstly, 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.  This is the most common reason for ‘hooks’ at the start of the cut.

Then check the cutting head and the blade holder has 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.  The cutting head on the Futura, however, has been designed to give absolutely zero side-play, this is because the sliding bearing system and the bearings the blade holder rotates about are all ‘pre-stressed’ so there is no possibility of unwanted movement between the blade tip and the cutter bar of the machine.

Lastly, make sure the board is being clamped properly and check the surface you have the cutter on is flat and not bent or twisted.