Plunge Saws

This is what I found out about plunge saws. Note that all the below is from research – I am not an expert.

In particular note that I have also included some comments about safety features, again, gleaned from t’internet. If you value your fingers do your own research to be sure. With that said, onwards!

terminology

here are three terms I was vaguely familiar with but did not completely understand until doing my research:

  • kerf – this is the width of the cut made by a cutting edge
  • kick-back – this is what happens when a workpiece catches on a spinning blade, rides up the blade and is thrown away from it. This can be very dangerous – particularly on a table saw (the workpiece can be thrown at great speed to towards the operator) and hand held saws (where the machine can jump from the workpiece).
  • riving knife – a safety device to reduce the chance of kick-back. This is a narrow piece of metal, slightly wider than the blade, and shaped with the same contour. It is organized to rise and fall with the blade and – being a bit wider – helps to keep the two parts of the cut workpiece separated after they pass over it. The riving knife thus stops the cut parts from closing up and ‘pinching’ the blade – one of the causes of kick-back. Riving knives are de rigueur on European made equipment, but for some reason seem less popular in the US.

 

riving knife

 

table saw vs plunge saw

..or to be fairer portable table saw vs plunge saw. Surprisingly, you can get a decent portable table saw for not much more than a high-end plunge saw:

http://www.dm-tools.co.uk/product.php/section/10076/sn/METTS254#.UxAynPR_uQw

Table-saws are the go-to machine of choice for the experts (although they prefer very heavy fixed position versions), but plunge saws have their place, particularly for amateurs and occasional users:

They are easier to use without incident, take up less room, and can do many of the things a table saw can do. In one area they have a significant advantage too, namely when cutting large (e.g 2.4×1.2m) sheets since they can be taken to the workpiece, rather than the other way round.

Having said all this, in the long-run the more accomplished amateurs – even when enthusiastic fans of plunge saws – typically end up with a table-saw too. So it seems the plunge saw has its limits…

circular saw vs plunge saw

The main advantages are of the plunge saw are:

  • safety – circular saw blades are permanently exposed, whereas the plunge saw blade retracts when the machine is removed from the work-piece
  • (easy) accuracy – you can use a plunge saw on a specially designed rail to get a perfectly straight cut. Note that you can do straight cuts with a circular saw too, but it is an almighty faff involving marking out the offset between the edge of the blade and the edge of the base on the other side, and fixing a securing a straight edge as a guide. With the plunge saw you just mark where you want to cut, pop down the guide (which has grippy rubber strips to stop it moving) and go.
  • clean cutting – plunge saws press down on the workpiece on all sides as they cut: The rail holds the left side of the cut, there is a special foot type device on the that presses down at the point of the cut on the right, and you can adjust the cutting depth exactly, enabling you to support the underside on a workbench without cutting into it. This prevents the fibres in the wood lifting up and creating a ragged edge.

in the interest of balance I should point out there are various adaptor kits that can be used to augment a standard circular saw to give it some of the advantages of a plunge saw (c.f Eurekazone track saw). These kits have the obvious advantage of not requiring you to buy an additional saw – assuming like me you already have a circular saw – but are not readily available in the UK.  And of course it is possible to use a circular saw with a piece of straight timber as a guide, although this is less convenient than using a purpose designed rail.

a plunge saw (aka rail or guide saw)

so which is the best plunge saw? .. tune in for the next installment.

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