Running Saw Blades Backwards
This was in response to a customer’s question about running a saw blades backwards.
Comment:
I have been having an argument with several people regarding cutting aluminum on a table saw with the saw blade reversed so that the back of the teeth do the cutting. My argument was that it was possible, but not good practice. The others argued that it was a perfectly acceptable method. My argument was that the right saw blade should be used if it was done on a regular basis, but you could get away with the blade reversed, if done infrequently such as a DIY project where the cost of a different blade wasn’t warranted.
Dear Sir:
Executive Summary:
1. This is a case where the tool is being used in the direction it is weakest.
2. This practice may work with some saw blades but some saw blades are much weaker than others.
3. Saw blades, even from the same manufacturer, can vary greatly in quality.
4. Cutting situations that appear to be identical can vary greatly.
5. A circular saw is quite possibly the most dangerous tool the most people ever use. It is a very thin piece of somewhat brittle metal traveling at up to 200 mph.
6. Cutting accidents occur all the time and always by surprise. Anyone who has ever used a circular saw has had experiences with saw blades jamming or binding.
7. You never really know what you are cutting. The most obvious example is knots in wood or staples and nails in other materials. Metal is often regarded as an entirely homogenous material. If you have enough experience with metal than you realize how hard it is to get a sheet, bar, billet or similar to be 100% consistent.
To put it plainly, it is just best to use a tool as it is intended to be used and to find the right saw blade for your application. This keeps you safe and ensures the longest life out of your tools.
You may not get hurt but you are greatly increasing the odds that you will.
In 1993 I was 47 years old and decided to take afternoons off and go home and paint my own house. I did it when I was in my teens and 20’s and figured I could still do it. I could save some money and spend afternoons out in the sunshine doing physical work instead of in the office shuffling paper. Everything worked really well until the ladder slipped and I broke both legs. I spent about six months in a wheelchair and four years more on crutches or a walker as I had repeated surgeries to try and save my legs. The good news is that I still have both legs although neither one works very well.
Since then I have become much more careful about assuming that I was invulnerable and about taking chances to save a couple dollars.
Legal
As a manufacturer, with a great deal of concern for the safety and health of my customers, I cannot advocate using any tool improperly.
In this case I have a horrible vision of the carbide tips getting shelled off the saw blade like corn off a cob.
Okay. The legal is out of the way. Let’s get down to the practical and real life.
Saw Tips Do Come Off And Saw Blades Do Come Apart.
Over the decades I have had way too many calls, letters and emails from people who have lost the vision in one eye because a carbide tip came off the saw blade and blinded them.
There are a great number of sawmills where the roof over the saws is full of holes because the saws hit something that was thrown up at the roof, the saw tips came off or the saw hit something much too hard, such as a railroad spike buried in a log, and the saw blade shattered and came apart as shrapnel.
Explanation Of The Dangers
It is very difficult to make saw blades that are consistently safe to use when used as designed.
I am aware that people deliberately use saw blades to cut aluminum extrusion, roofing panels and other materials by putting the saw blade on backwards. I am also aware that there are a fair number of people out there who do this successfully and have done so for a long while.
Every time a dangerous practice is discussed on the Internet invariably there are a couple of people who post and say something to the effect that they have been doing it for decades and they are just fine. Assume that this is entirely true.
No Two Things Are Identical
The first problem with this is that no people are absolutely identical. If you have ever known identical twins then you know that there are differences, no matter how slight. So someone who misuses chemicals without harm may have a particular body chemistry that allows them to do that. This does not mean that anyone else can do it.
At a certain level no two manufactured parts are identical. If you have ever done anything that involves a large number of parts you have undoubtedly had the experience where you found a defective part or a bad batch.
If you have ever dealt with parts that are made in a batch then you have had the experience of having some parts in the batch being different than others. I bought a box of saltine crackers last week. Three tubes of crackers were just fine. The fourth tube of crackers was a little overcooked on one edge which affected the color and the taste to a minor extent.
There is a huge amount more I could provide but that should give you a pretty good idea of my position on the matter.
Tom Walz
Tags: saw blades
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