Birch Plywood Blade

[Scrit]

What's the advantage with going to the negative rake blade, as I have one of these in my RAS.

In a RAS the negative rake has the effect of pushing the work downwards and backwards, thus pinning it against the table and back fence, so the reason has little to do with finish, per se, however the negative rake makes a less aggressive entry/exit from the workpiece and therefore produces less chip-out, a major bugbear with melamine/laminate coated workpieces.

Transferring a negative rake blade onto a table saw will confer the advantages of minimised chip-out enjoyed by the RAS, however it will be a the cost of a much increased tendency of the workpiece to climb the blade and to kickback, so if using a negative rake blade on a table saw extra caution is advised and there is a need to keep the workpiece firmly pressed down to the saw table at all times. It is therefore a technique which needs to be used with care.

If longevity is more important than finish then go standard triple chip. I'd expect the hollow ground triple chip to come between the two - I've not tried one of these, probably Scrit will have the full SP.

Agreed, standard triple chip has a longer life between sharpenings, more sharpenings in lifetime but really requires a pre-scorer to work to maximum effectiveness, i.e. speed of cutting and quality/longevity of good cut - one reason almost all commercial panel saws use the system (cost/performance benefits). I tried hollow grind triple chip a few years back and it really wasn't that much better than a standard triple chip to warrant paying the premium. The negative rake trick was one I picked up from Keith Smith (Woodsmith) and is a lower cost way of clean-sawing on even relatively small table saws, providing you're careful. I've used it a number of times on installations where my "table saw" is a DW flip-over saw and all I can say is that the results are pretty good

As to blades, I'm not that impressed with CMT and much prefer either Omas or Freud given a choice - but then I mainly use Bennett (made in Sheffield), Leitz, Freud and Omas at the moment, so maybe it's just bias on my part :roll: .

Scrit

 

[johnnyb]

i have been using a freud lu04m and this blade is just for ply. it has 48 teeth on a 10 inch blade. i cant fault it really, it leaves a great finish that needs nothing else. it is also quite free cutting not needing excess pressure to saw. the diagram on the blade suggests 40mm max cut and 10mm saw showing through. as to its vital angles i dont know. my own feeling is 18mm birch ply is a very tough material to saw well combining ripping and crosscutting in the same piece and fe ply is even worse for breakout being very stringy. even with the correct blade height and feed some will chip a little and some will be perfect. ps this blade is a year or two old and may not be available now

 

[Scrit]

The diagram on the blade suggests 40mm max cut and 10mm saw showing through. As to its vital angles i dont know.

I think that's part of the point. To cut plywood well you'll end up raising and lowering the blade until you find the "sweet spot" where it seems to cut cleanly on both sides but even there if you switch from ripping to crosscutting it can all go very wrong and you may need to resort to packing the blade (i.e. making a zero clearance insert) to achieve an acceptible result, more so with stuff like Gaboon ply which is as stringy as anything and makes birch ply look really mild in comparison. Having a recently sharpened blade does help in any case.

Scrit

 

[PJ]

Thanks to all the people who posted on this topic. There is certainly good information/advice given and I think I will give the negative rake blade a try before looking at other blades.
Is there anywhere where I can good information/specs on all the freud blades.

 

[Scrit]

Rather than depending on American web sites (where in any case some of the available products are not the same) why not contact Freud (UK)? They do have a printed general catalogue available

Scrit

 

[PJ]

Scrit, thanks for the link. Will have a look at there online catalogue and then contact them to find a local supplier.

Thanks

Philip.