I was looking thru screwfix site, for a thin s/steel blade for my cutoff saw, and I noticed they do a diamond blade, 14'' for £60. What do ppl think?
It's a lot, but then if the standard blades are going to keep wearing down at such a rate, would a £60 blade last forever?
Cheers, ben

Actually, are diamond blades just for tiles?

As good as diamond blades sound - they are not quite as good as they sound. The product is CBN (Cubic Boron Nitride) the hardest manmade substance - almost. Trouble is - it's in a powder state. The stuff they use to cement the CBN is obviously softer. The problem occurs when cutting materials which are not inert to the cement (known as a binder) which is common. The binder leeches out exposing more and more of the CBN... this causes the CBN to be less secure and falls out... wear can actually be increased not decreased as was the intention.

As the material being cut is softer than the cutting medium, the cutting speeds of the cutting medium need to be higher - much higher! If you dont increase speed the cut material fuses to the cutting medium causing built up edge condition. A little like aluminium on drills, this is caused when not cutting fast enough. Using lubricant helps but only for so long.

The best thing to cut with CBN is ceramic, very, very hard material like High Speed Steel or hardened tool steel etc as this needs the hardness CBN provides... depending on what you are cutting buy tooling to cut the material in hand. Buying expensive tooling with little knowledge works out to be just that, expensive! Using the correct cutting medium on the related material saves a fortune, if in doubt ask.

When drilling always use the calculation:

RPM = V/D * 318

where V is recommended cutting velocity
where D is diameter of drill or cutting diameter.

Example:
Mild Steel V = 100

therefore when drilling a 5mm hole:

RPM = (100/5) * 318
RPM = 6360

No drill will go this fast normally so fastest will do

for Aluminium V = 600 - go figure!

What are you doing with them? Mine last ages and I use them for cutting all kinds of stuff. I did a load of steam pipe with a 5mm wall for the bro in law and didn't wear a blade out completely. Let it get up to speed before you start cutting and don't force it through, let it proceed at more of its own pace and they will last longer.
http://www.johndavies.co.uk/nabdisc.htm
These do a stainless disk so someone else will have them if you look around.

Peteff, the problem is that although there is still a reasonable diameter to use on the disc, it isn't wearing down uniformly, so after about a week I start getting wedge-shaped cuts, which on a chassis isn't really accurate enough. I was looking for a thin blade, but the thinninst i can find for 25.4mm bore is a 2.6. Anyway, i'll check out that LIverpool list, cheers for that, ben

Sounds to me like you are feeding too hard... or the wheel is not spinning fast enough.

Looking at your two posts - in your first post you state you're looking for a s/steel blade, in the second post you mention chassis. Are you making your chassis from stainless? If not you need a standard good quality wheel for metal, if you are using St.St then the wheel you need will be different. St.St has got Chrome in it which will knacker a standard blade quickly...

We only ever use diamond coated blades for cutting granite/slate.

If blade starts being inefficient, it's dumped into some sandstone to clean.

Wouldn't dream of using it for cutting steel!

BTW, why aren't you just using a hacksaw. Much cheaper, larger particulates, less (airborne) dust, quieter, tidier workshop - the list goes on!!

ATB

Simon

[Edited on 23/2/05 by Simon]

I've used 3" diamond blades on my Rotozip (tm) when dissasembly my donor. slow, smooth, and loud cutting. but, blade shows no wear after cutting through 2 1.5" hardened steel tie rods.