Dangerous Blade Offer!

[Shultzy]

I noticed this on the Aldi web site. http://www.aldi-stores.co.uk/uk/html/of ... 7_6063.htm

"A pair of heat-finished, hard-steel body blades, one for general cuts the other for fine cuts. Can be used in regular table, circular, and of course, mitre saws."

I thought that mitre saw and table saw blades were NOT interchangeable due to the need for negative rake teeth on mitre saw blades.

 

[eggflan]

Ive never been told that you have to have different blades for mitre and table saw :shock: :shock:

I would consider using blades like this for cutting rough stock up as it saves dulling your good blades , at this price you could use for one job/project then throw them away :wink:

 

[Slim]

It is a good idea to use a negative rake blade with a mitre saw, however both saws I have owned came with normal blades. On the other hand, you should never use a negative rake blade on a tablesaw.

 

[wizer]

Spend a little, Curse a lot.

 

[p111dom]

I thought neg rake blades were only for sliding mitre saws and non ferrous metals. Didn't think it made a difference on a fixed mitre saw or a table. Seems like a reasonable deal though but my table saw is 10" and mitre saw 12" so no good for me

 

[Mcluma]

Spend a little, Curse a lot.

:lol: :lol:

 

[George_N]

A negative rake blade will tend to push the workpiece down onto the table of a mitre saw (sliding or otherwise) during the cut and conversely will try to lift the workpiece off the table on a table saw. Having said that, I have heard that negative rake blades are sometimes used in a table saw to get clean cuts with MFC. It would probably be ok on my Triton for example, as it has hold down fingers attached to the overhead guard (which I always use).
I don't know what sort of quality you would get at £4.50/blade, but if there was an Aldi close enough to me I think I give it a go.

 

[skipdiver]

I'm going to Aldi's shopping when 'er indoors gets home from work.I think the problem is always when something is cheap we convince ourselves that it can't be any good.I bought a set of surround speakers in Aldi last week.Five speakers and a subwoofer for 20 quid.They sound good.

Will probably buy them and hang them on the shop wall(when it's built) and never get round to using 'em.I tend to stick to Freud blades.

 

[NeilO]

On the subject of buying cheaply, I was in Aldi`s rival shop, Lidl`s with SWMBO the other day and found some fire extinguishers at £4.99 each, only 1.5 kg bottles but at the price I thought 4 will do on for each corner of the workshop so theres always one in easy reach , and they are suitable for electrical and substance caused fires...

 

[OPJ]

Theoretically, you can use one blade to perform most tasks when ripping or cross-cutting softwood, hardwood or sheet material...

But, wherever possible, it's better to use the right blade for the right job. As mentioned above; positive hook for ripping, negative for cross-cuts. "General purpose" blades will perform as good all-rounders but will still fall behind when compared to blades designed for a certain task.

Even then, you can get further variations on saw blades - some are designed to cut hardwood rather than softwood. It depends on what you want to do and it's always worth spending the best you can afford!

 

[Scrit]

I thought neg rake blades were only for sliding mitre saws and non ferrous metals. Didn't think it made a difference on a fixed mitre saw or a table.

Negative rake blades are generally only suitable for use in overhead saws where, as George N says. There's an earlier thread here which discusses the why's and wherefores in detail, including some rather natty drawings (if I say so myself).

That's not to say that you can't use a negative rake blade in a table saw - it's one way of cutting laminates, e.g. MFC, MF-MDF, etc cleanly, but be aware that the clean cut comes at a much greater risk of kickback so take precautions and use minimum blade projection and appropriate push-sticks

Theoretically, you can use one blade to perform most tasks when ripping or cross-cutting softwood, hardwood or sheet material...

In the words of the comic, "I don't think so...."

As mentioned above; positive hook for ripping, negative for cross-cuts.

Now I really don't agree. Table saws require a positive rake for almost all cuts. Zero rake or negative rake will almost always induce kickback in cutting and so are not to be recommended for such tasks. Overhead saws, on the other hand, require negaitive rake for the reasons given in my earlier detailed explanation (link above)

Even then, you can get further variations on saw blades - some are designed to cut hardwood rather than softwood.

I think that you'd have to look a while to find any TCT blade which says "softwood only" or "hardwood only" (yes I know that Freud specifically market some of their blades as being for hardwood). The main distinctions are between types of cut (rip, combination, cross cut trim/mitre) and type material (solid timber, wet timber, plywood, MDF, laminated man-mades, plastics, etc)

Cheap blades, though, so maybe worth a punt

Scrit

 

[Shultzy]

Thanks for all the comments guys. I wasn't particularly going to buy these blades I just thought the "sales blurb" might be misleading to those buyers not familiar with saw blades.

As Scrit (welcome back) says "Cheap blades, though, so maybe worth a punt", so maybe I'll try some.

 

[ike]

I was in Aldi`s rival shop, Lidl`s with SWMBO the other day and found some fire extinguishers at £4.99 each, only 1.5 kg bottles but at the price I thought 4 will do on for each corner of the workshop so theres always one in easy reach ,

Off-topic, but have to suggest that fire extinguishers are kept either near the door inside, or as I do, outside the workshop in a cupboard. If a fire started when you are out of the building, they are much more likely to be accessible.
:wink:

Ike

 

[Tusses]

My guess would be they are like the blades that come fitted to a cheap new machine (or some not so cheap) - you know , the ones you have to take off and throw away before you can make a half decent cut !



maybe ok for a mitre saw chopping firewood -

yes , I have a cheap mitre saw with a cheap blade just for cutting up firewood

 

[p111dom]

That's not to say that you can't use a negative rake blade in a table saw - it's one way of cutting laminates, e.g. MFC, MF-MDF, etc cleanly, but be aware that the clean cut comes at a much greater risk of kickback so take precautions and use minimum blade projection and appropriate push-sticks

This in one thing I've never understood about minimum blade projection. Surely if the blade is just above the material thickness there would be far greater back to front force increasing the risk of kick back. The higher the blade the more downward the force as the teeth move throught the material more vertically. I'm not saying you're wrong I just wonder why this is always the advice. I presume it's to prevent too much upward force from the back of the blade lifting the material up but with the crown guard on is this really an issue?

 

[Sgian Dubh]

That's not to say that you can't use a negative rake blade in a table saw - it's one way of cutting laminates, e.g. MFC, MF-MDF, etc cleanly, but be aware that the clean cut comes at a much greater risk of kickback so take precautions and use minimum blade projection and appropriate push-sticks

This in one thing I've never understood about minimum blade projection.

There are several factors in play but a strong one with regard to that recommendation concerns itself with reducing the chance of your fingers coming into contact with the blade. With the blade set so that the teeth only project above the wood by 10 mm the crown guard is similarly set close to the wood. With this setting it's difficult to get your fingers under the guard thus keeping them away from the spinning blade.

Other factors that I don't have time to go into at the moment concern themselves with blade height and cutting ability and relate to the quality of the cut, burning, spelch and so on. There is, for instance, the ability or inability of the gullets between the teeth to carry chips or shavings out of the kerf to factor in and this depends on the blade type and tooth pattern.

Certainly you're right that there are interesting forces going on whether the blade is set low or high. A low set blade requires more force to feed the wood than a high set blade, and induces more of a horizontal kickback should this occur, and a high set blade causes more of a vertical lifting force. Neither is desirable of course.

And I'll be honest in that I don't always follow the HSE recommendations to the letter. I sometimes do set the blade higher than recommended, particularly for ripping solid wood to rough size. I always set the blade pretty low for cutting man-made board, especially if it's got expensive veneers on the face that I don't want all ragged and spelched on the cut edge: but I 'cheat' here because I use a sliding table saw and a scoring blade in front of the main blade for these cuts anyway, ha, ha. Slainte.

 

[OPJ]

In the words of the comic, "I don't think so...."

What about "general purpose" blades? I know they're certainly not ideal for ripping but it can be done... We've got a large panel saw at college that's mainly used for sheets, of course, but in our workshop, we also have to rip some timber when the smaller dimension and circular saws in the mill are being used by the carpentry students.

My tutor admits that it's not ideal, but with two workshops using the same saw, it's inconvenient to have to keep changing blades (I'm sure there are plenty of "lazy" joiners/makers out there as well - I should know as I've worked with them! )

On a similar note, whenever someone has to cut a laminated or veneered product, instead of fitting a scoring blade and the smaller one to go with it (which takes time) we slide a sheet of MDF through the saw first to give that zero-clearance clean cut. It just saves time.

 

[Scrit]

I'm not saying you're wrong I just wonder why this is always the advice. I presume it's to prevent too much upward force from the back of the blade lifting the material up but with the crown guard on is this really an issue?

Really? Kickbacks often have little to do with the height of the blade above the workpiece - in the main they are caused by the rising teeth catching the workpiece and ejecting it forcibly at the operator. A positive rake blade in a table saw will tend to push the work downwards onto the table surface, a negaiive rake blade will tend to push the work back at the operator, which if you had much experience of sawing you'd be aware of. It is the converse of the requirement for negative rake blades on overhead saws - where, incidentally, positive rake saw blades can be hazardous. Re-read my original post on overhead saws and the dynamics are explained. The same dynamics apply (in reverse, so to speak) to table saw blades.

In the words of the comic, "I don't think so...."

What about "general purpose" blades? I know they're certainly not ideal for ripping but it can be done...

Yes, but they are at best a second rate compromise. In a conventyional joiners shop a separate saw is set up for the two tasks, ripping and cross cutting and the appropriate blade will always generate a better quality cut.

My tutor admits that it's not ideal, but with two workshops using the same saw, it's inconvenient to have to keep changing blades

Which is why the "classic" joinery shop has a rip saw and a crosscut (and that can be a simple £50 chop saw)

On a similar note, whenever someone has to cut a laminated or veneered product, instead of fitting a scoring blade and the smaller one to go with it (which takes time) we slide a sheet of MDF through the saw first to give that zero-clearance clean cut. It just saves time.

Aha. But that only works well with certain types of blade. Try it with a rip balde and the quality of cut would be terrible - with an ATB (alternate top bevel) it works well.

Not all blades can perform all cuts

Scrit

 

[chipchaser]

Hi all,

just bought a pair of these blades for £6.99 in Aldi. Fitted 36 tooth which has positive rake into my old cheap mitre saw which had 24t tct blade also positive rake as supplied when new. No perceptible change in vibration or noise levels but now cuts B&Q pine cladding very cleanly (only the very best materials used here :wink: ) I am very happy for that price!

The other Aldi blade with 80 teeth has, as far as I can tell, no rake at all, the tooth front face being on a radial line. Will try that one later, maybe in the scms.

Whilst mentioning the scms that was also bought from Aldi, last year so not the same as their current offering. It works ok but the scale for tilt of the blade is so tiny, and I suspect perhaps innacurate, that I don't use it. I have a Wixey digital angle gauge which is good for setting many blade or tool angles

Scrit: thanks for educational comments/advice in this thread. Very useful for such as myself who are late dabblers in woodwork