Circular saw blades

[dean]

I have a DeWalt DC390 18v cordless circular saw. This takes 165mm diameter blades on a 20mm arbour. I can't find any blade finer than

30 tooth to fit this saw. I have seen a Trend 48 tooth blade that has the same size arbour (20mm) but is 160mm diameter (5mm less).

I have 2 questions. The first of course is if I fit the smaller Trend blade, will it be dangerous? Secondly, will it give me the fine cut that the blade is designed for?

Whilst on this subject, am I right in thinking that the smaller the blade diameter, the fewer teeth are needed for finer cuts? For example, the trend described above has 48 teeth around its circumference. This gives 0.095 teeth per centimetre of circumference. On a 300 mm diameter blade, to get 0.095 teeth per cm you would need 90 teeth around the circumference. Which is a "fine" or even "extra fine" cut if you read the adverts. Is this sort of conversion the right thing to do?

[Grunff]

No.

Yes.

No, it doesn't.

Definitely not.

[dean]

Thanks for your reply Grunff. For interest though my maths for the above is as follows.

Circumference = PI * diameter

so for the 160 diameter trend, we get

3.142 * 160mm = 502.72 mm for the circumference.

Now there are 48 teeth around the circumference so

48/502.72 = 0.09548 teeth per centimetre.

To get this number of teeth per centimetre on a 300 mm diameter blade, we would need a blade of

300mm * PI * 0.095 = 90

So a 90 tooth 300mm blade would have the same number of teeth every centimetre as a 48 tooth 160mm blade.

Now my maths may be flawed, but could you expand a little on where I am going wrong.

Thanks again.

[PC Paul]

cm != mm

You make the error twice and it cancels out, leaving sensible results, but the main teeth/cm figure is actually teeth/mm.

[David Lang]

Hi Dean

There is a whole lot more to saw blades that just the number of teeth, pitch, angle, rake etc. I recently replaced the blade on my DeWalt radial arm saw. Same size, same bore, same number of teeth.

Performance was entirely different. Splintering underneath, blade grabbing the stock etc. Had the old blade sharpened and it's now a different saw entirely.

I'm not up on the whys & wherefores but do check it out first with someone who knows.

Dave

[Rick]

I have had a similar issue, and have a slighlty smaller than designed blade in my circulr saw, to get more teath, and a finer cut. I did acheive a finer cut.

I decided that as long as the blade if fimly held in, and the hole is the right size, that I would not increase the danger level. However I have no specalist knowledge to back up this decision, it just felt right.

Of cource the speed at the top of the blade decreses as the diamater decreases.

Rick

[Matt]

Not all blades that are similar diameter are suitable. The blade thickness, especially on very fine blades may be such that although you can locate the blade, you cannot properly clamp it.

[bigcat]

Codless circs are significantly different to mains circs. Theyre much lower power, tend to run at slower speed, and use a coarser cut blade, and possibly a thinner blade too, to make up for some of the lost ground. Whether theyre ground the same I've no idea, but would not assume so.

I would not want to replace a codless blade with a mains one except as an experiment to see what happens. I would expect to get significantly lses cut per charge - theres good reason they use coarse blades.

If you want something decent, use mains when poss.

NT

[PC Paul]

Seconded. Cordless screwdrivers/drills are brilliant, best thing since sliced bread.

Cordless circular saws are for quick cuts on a roof or somewhere else where getting an extension to it is next to impossible. Mains is still the way to go.

[Owain]

Can you upgrade with an optional codpiece?

Owain

[Andy Luckman (AJL Electronics)]

Something very fishy about that sentence. :-)

[bigcat]

hmmm... What I always wondered is if the codless ones swell for such a premium, why dont they get mains ones and just take the cod out?

NT