Angle grinders are a versatile tool and a necessity for the home and commercial fabricator, they are also useful for many other trades, so what should people look for when buying one.
There are two main types of angle grinder and these are the cheap DIY units and the industrially rated units, so how do they differ? basically its in their construction and duty cycle, a cheap grinder will have an open type motor and a very low duty cycle meaning you cannot use it for long periods. Industrially rated units will often have shielded or enclosed motors and very specialised or specific airflows using anything from ducted air to vortex airflow and a lot if cooling fins to keep the motor temperature cool during heavy and prolonged use, it will have generally better and more substantial components.
1/ Always buy an industrially rated grinder and check its duty cycle.
Angle grinders come in many sizes and size really matters, there is the 4", 4 1/2", 5", 7", and 9"; so which one do we choose and why?
Thread size is the major difference, the smaller 4" and cheaper 4 1/2" grinders come with an M10 thread and a 16mm bore in their attachments such as grinding discs while the majority of 4 1/2" and above grinders come with an M14 thread and a 22.2mm bore in their attachments. Most attachments come with the M14 thread while many attachments for the M10 thread are limited and often are more expensive and often are a lighter duty attachment aimed at the home user as opposed to the commercial user.
4 1/2" grinders are the most versatile as they have the most attachments for them, therefore they are the best option as they are the most popular model in industry, they are followed by the 9" grinders which have superseded the earlier 7" grinders, but why?
Cost is the answer as buying the 9" version of attachments such as grinding or cutting discs costs pennies more but they have an additional 2" of medium on them and it is this which makes them cost effective over the 7" grinders, and cost is very important to industry.
2/ Always buy a 4 1/2" grinder first, then a 9" grinder second for heavier work.
Motor wattage isn't as important as some people think, with an industrially rated grinder you may get a proven 500-600 watt motor, a domestic rated grinder may substitute this for an 800-900 watt motor to give an impression of power, but power equals heat and a domestic grinder may struggle to remove this heat. Remember the cooling systems of industrially rated grinders.
Therefore a higher powered domestic unit will generate more heat quicker, but this alone is enough to significantly reduce its duty cycle and actual working time without it burning out, but in reality people don't reduce their working times and they do burn out, kerching kerching, its money in the manufacturers pocket. Many people are correct in their assumption that manufacturers do this for profit and want people to burn out their cheap grinders so they sell more of them.
Its all about TORQUE and not power, a cheap high powered domestic grinder may produce the same torque as a smaller 500 watt industrially rated unit but its also using more power to do so and is generating more heat, so in use economics becomes a major factor for a heavy user. Its more about how the grinder generates its torque as industrially rated units have a better torque curve when under heavy load and generate more torque when under load, and use less power to do so, and generate less heat while doing so and the cooling system keeps its temperature more consistent.
3/ Forget the motor power and focus on the torque and cooling systems as they are more important.
Variable speed grinders are a fairly new addition to the angle grinder market and have a few extra components fitted which cost the manufacturers pennies to buy and incorporate into their grinders, yet in reality it is these speed control features which are their nemesis as they are unreliable. At the time of writing they are not a viable option due to their unreliability and propensity to be the main cause of failure, and while the customer is paying anything up to double the price of the manufacturers fixed speed models. In simple terms; would you pay twice the price for a grinder and know you are paying this extra money for unreliability? this may change in the future as their electronics become more reliable. At this time they are best avoided.
4/ Avoid variable speed grinders and don't pay the manufacturer to build unreliability into your grinder.
Other things to look for; some may sound silly but are equally annoying when you use your angle grinder.
Does the locating or backing ring lock onto your spindle? all the decent grinders locating rings do lock onto the spindle for accurate location of any grinding/cutting discs and this is an important feature. Is the locking nut flat or recessed on the front? again this is important as those not flat or recessed fronted will not lock anything thinner than about 2mm so you cannot fit a plasma or very thin cutting disc to your machine.
Does your chosen machine come with a side handle and is it multi positional? most angle grinders come with two positions to screw the side handle into, one either side, better machines come with a third position on the back which is beneficial for using cutting discs as you get more control and accuracy.
Does your guard lock and unlock easily and does it fully rotate 360 degrees? many guards have stops on which limits their rotation and this limited rotation limits the ability of the grinder, although this was Health and Safety gone mad, many manufacturers guards now offer a full rotation for flexibility.
Does your guard come off quickly and easily? once again its often required to be removed for fitting accessories such as backing pads for resin bonded discs, Velcro backing pads for Scotchbrite pads or similar, and for wire brushes or wire wheels.
What problems do angle grinders give and can they be overcome?
Most problems are with overheating, with a shielded or enclosed motor the solution is to blow them out with an airline in the reverse direction of the airflow; it is prudent for hard working grinders to have their covers off annually and scrape away any hardened debris and blow them out.
Bearing wear can be an issue, they will begin to get noisy and the solution is to simple remove the bearings and replace them; they are always standard bearings and cheaply and readily available from bearing stockists. Usually it is only the bearing at the opposite end to the gearbox which wears, replace them with a fully sealed bearing.
Brush wear is an issue on all grinders, for what they cost it is always better to use the original manufacturer supplied brushes or find a very reputable supplier of brushes, forget the cheap replacements.
Gearbox grease becomes contaminated over time and this causes excessive wear in the gears, remove the cover and clean out any old grease and replace with new grease, most have the gearbox cover mounted behind the grinding disc so can be removed and the spindle bearing can be checked at the same time.
There are two main types of angle grinder and these are the cheap DIY units and the industrially rated units, so how do they differ? basically its in their construction and duty cycle, a cheap grinder will have an open type motor and a very low duty cycle meaning you cannot use it for long periods. Industrially rated units will often have shielded or enclosed motors and very specialised or specific airflows using anything from ducted air to vortex airflow and a lot if cooling fins to keep the motor temperature cool during heavy and prolonged use, it will have generally better and more substantial components.
1/ Always buy an industrially rated grinder and check its duty cycle.
Angle grinders come in many sizes and size really matters, there is the 4", 4 1/2", 5", 7", and 9"; so which one do we choose and why?
Thread size is the major difference, the smaller 4" and cheaper 4 1/2" grinders come with an M10 thread and a 16mm bore in their attachments such as grinding discs while the majority of 4 1/2" and above grinders come with an M14 thread and a 22.2mm bore in their attachments. Most attachments come with the M14 thread while many attachments for the M10 thread are limited and often are more expensive and often are a lighter duty attachment aimed at the home user as opposed to the commercial user.
4 1/2" grinders are the most versatile as they have the most attachments for them, therefore they are the best option as they are the most popular model in industry, they are followed by the 9" grinders which have superseded the earlier 7" grinders, but why?
Cost is the answer as buying the 9" version of attachments such as grinding or cutting discs costs pennies more but they have an additional 2" of medium on them and it is this which makes them cost effective over the 7" grinders, and cost is very important to industry.
2/ Always buy a 4 1/2" grinder first, then a 9" grinder second for heavier work.
Motor wattage isn't as important as some people think, with an industrially rated grinder you may get a proven 500-600 watt motor, a domestic rated grinder may substitute this for an 800-900 watt motor to give an impression of power, but power equals heat and a domestic grinder may struggle to remove this heat. Remember the cooling systems of industrially rated grinders.
Therefore a higher powered domestic unit will generate more heat quicker, but this alone is enough to significantly reduce its duty cycle and actual working time without it burning out, but in reality people don't reduce their working times and they do burn out, kerching kerching, its money in the manufacturers pocket. Many people are correct in their assumption that manufacturers do this for profit and want people to burn out their cheap grinders so they sell more of them.
Its all about TORQUE and not power, a cheap high powered domestic grinder may produce the same torque as a smaller 500 watt industrially rated unit but its also using more power to do so and is generating more heat, so in use economics becomes a major factor for a heavy user. Its more about how the grinder generates its torque as industrially rated units have a better torque curve when under heavy load and generate more torque when under load, and use less power to do so, and generate less heat while doing so and the cooling system keeps its temperature more consistent.
3/ Forget the motor power and focus on the torque and cooling systems as they are more important.
Variable speed grinders are a fairly new addition to the angle grinder market and have a few extra components fitted which cost the manufacturers pennies to buy and incorporate into their grinders, yet in reality it is these speed control features which are their nemesis as they are unreliable. At the time of writing they are not a viable option due to their unreliability and propensity to be the main cause of failure, and while the customer is paying anything up to double the price of the manufacturers fixed speed models. In simple terms; would you pay twice the price for a grinder and know you are paying this extra money for unreliability? this may change in the future as their electronics become more reliable. At this time they are best avoided.
4/ Avoid variable speed grinders and don't pay the manufacturer to build unreliability into your grinder.
Other things to look for; some may sound silly but are equally annoying when you use your angle grinder.
Does the locating or backing ring lock onto your spindle? all the decent grinders locating rings do lock onto the spindle for accurate location of any grinding/cutting discs and this is an important feature. Is the locking nut flat or recessed on the front? again this is important as those not flat or recessed fronted will not lock anything thinner than about 2mm so you cannot fit a plasma or very thin cutting disc to your machine.
Does your chosen machine come with a side handle and is it multi positional? most angle grinders come with two positions to screw the side handle into, one either side, better machines come with a third position on the back which is beneficial for using cutting discs as you get more control and accuracy.
Does your guard lock and unlock easily and does it fully rotate 360 degrees? many guards have stops on which limits their rotation and this limited rotation limits the ability of the grinder, although this was Health and Safety gone mad, many manufacturers guards now offer a full rotation for flexibility.
Does your guard come off quickly and easily? once again its often required to be removed for fitting accessories such as backing pads for resin bonded discs, Velcro backing pads for Scotchbrite pads or similar, and for wire brushes or wire wheels.
What problems do angle grinders give and can they be overcome?
Most problems are with overheating, with a shielded or enclosed motor the solution is to blow them out with an airline in the reverse direction of the airflow; it is prudent for hard working grinders to have their covers off annually and scrape away any hardened debris and blow them out.
Bearing wear can be an issue, they will begin to get noisy and the solution is to simple remove the bearings and replace them; they are always standard bearings and cheaply and readily available from bearing stockists. Usually it is only the bearing at the opposite end to the gearbox which wears, replace them with a fully sealed bearing.
Brush wear is an issue on all grinders, for what they cost it is always better to use the original manufacturer supplied brushes or find a very reputable supplier of brushes, forget the cheap replacements.
Gearbox grease becomes contaminated over time and this causes excessive wear in the gears, remove the cover and clean out any old grease and replace with new grease, most have the gearbox cover mounted behind the grinding disc so can be removed and the spindle bearing can be checked at the same time.