We’ll finish up our look at Bench Grinders with a few Tips & Techniques.
Every once in a while, we run across something new about Bench Grinders, but most of our knowledge is tried & true, and time-tested.
First off, every ‘store-bought’ grinding wheel that I know of has blotters on its sides. ‘Blotters’ are those pieces of paper, or cardboard, on each side of the wheel. While they might look like just a convenient place for the manufacturer to put warnings and such, they actually do serve a very critical purpose. When a wheel is put on a grinder, there are metal flanges that squeeze against the sides of the wheel. If the wheel had no blotters, those flanges would be tightening up against the actual rock of the wheel and you would stand a very good chance of cracking the wheel. Blotters provide a ‘buffer’ between the flanges and the wheel rock and thereby cushion and distribute the tightening force. Bottom line: Don’t buy a wheel that has no blotters or, if you do, don’t put it on your grinder without making some blotters and using them.
While we’re talking about blotters, they have another use. Most manufacturers put their product warnings on them and one of the major warnings is “Do not grind on side of wheel”. Now, do most of us follow this warning? Probably not, but I am here to tell you that if enough sideways force is applied to as grinding wheel, a wheel explosion is a very real possibility. Years ago, I saw a training film (yes, “film”- not tape or DVD- I’m dating myself) wherein a grinding wheel explosion was created and it is not a pretty sight. Even though I might use the side of the wheel to do some very light & delicate, precise grinding, I’m only able to do so because of my many years of experience with this and I know that I am not applying any sideways force at all. My general advice to everyone is: Don’t grind on the side of the wheel.
Lastly, always keep the tool rest adjusted as close to the wheel as possible, in order to provide the most support for what you are grinding on. Use your safety glasses. Keep the grinder’s eyeshield in place to provide added protection. Make sure the spark arrester is in place and adjusted to within 1/8” of the wheel and always keep an open container of water handy for cooling off your material. If your grinder has a factory water pot, that’s even better. Keep it full.
These hints, and our last two columns, should help you get the most out of your Bench Grinder. Happy Grinding!
Saturday, August 28, 2010
#28 - Dressing your Bench Grinder wheels
Last week we talked about one of the staples in every shop, the Bench Grinder. This week, we’ll continue that theme and talk about the ‘care & feeding’ of your grinder.
Just for a bit of clarification from last week, my point about using a slow speed grinder (which is what a 1725rpm grinder is called in the industry) is that one needs to be careful when grinding metal and not heat the metal up too much. With a slow speed grinder, it is much easier to keep the grinding heat under control.
Ok, let’s talk about one of the natural problems with any grinder. After some grinding time, the face of the wheel will get ridges, or become tapered and one must “re-face” the wheel to get back to a smooth grinding surface. There are a couple of ways to do this.
Some grinders, the more professional models, usually have an accessory that is used to re-face the wheels. It bolts on in place of the tool rest and uses a diamond-tipped tool to re-face the wheel. Having one of these makes the task much easier. Unfortunately, not all grinders offer that. If your grinder isn’t that sophisticated, just buy the diamond-tipped tool and use it free-hand. The technique is not that hard to learn, in fact, if you have had enough grinding experience to get your wheel out of shape, you certainly have enough experience to re-face it.
So, let’s say that you don’t have the re-facing accessory and you must do it free-hand. The diamond-tipped facing tool I am most familiar with has a round shank, so that is what I will speak to. The technique is to place the tool on the tool rest as if you were trying to grind the diamond off of the end. Support it very well with your hands. In fact the tighter you hold it, and control it, the straighter your face finish will be.
Make sure you have your safety glasses on, and turn the grinder on. Put the tool on the tool rest. You would let the diamond tip touch the face of the wheel very lightly- you do not want to ‘deep grind’ this- and move the tool side to side as straight, and smooth, as possible. Keep the tool at 90degrees to the face of the wheel and realize that the high points of the wheel face will require a lot of material removal before you will get close to having a straight wheel face again. With patience and a bit of time, you will again have a smooth wheel face to use.
Just for a bit of clarification from last week, my point about using a slow speed grinder (which is what a 1725rpm grinder is called in the industry) is that one needs to be careful when grinding metal and not heat the metal up too much. With a slow speed grinder, it is much easier to keep the grinding heat under control.
Ok, let’s talk about one of the natural problems with any grinder. After some grinding time, the face of the wheel will get ridges, or become tapered and one must “re-face” the wheel to get back to a smooth grinding surface. There are a couple of ways to do this.
Some grinders, the more professional models, usually have an accessory that is used to re-face the wheels. It bolts on in place of the tool rest and uses a diamond-tipped tool to re-face the wheel. Having one of these makes the task much easier. Unfortunately, not all grinders offer that. If your grinder isn’t that sophisticated, just buy the diamond-tipped tool and use it free-hand. The technique is not that hard to learn, in fact, if you have had enough grinding experience to get your wheel out of shape, you certainly have enough experience to re-face it.
So, let’s say that you don’t have the re-facing accessory and you must do it free-hand. The diamond-tipped facing tool I am most familiar with has a round shank, so that is what I will speak to. The technique is to place the tool on the tool rest as if you were trying to grind the diamond off of the end. Support it very well with your hands. In fact the tighter you hold it, and control it, the straighter your face finish will be.
Make sure you have your safety glasses on, and turn the grinder on. Put the tool on the tool rest. You would let the diamond tip touch the face of the wheel very lightly- you do not want to ‘deep grind’ this- and move the tool side to side as straight, and smooth, as possible. Keep the tool at 90degrees to the face of the wheel and realize that the high points of the wheel face will require a lot of material removal before you will get close to having a straight wheel face again. With patience and a bit of time, you will again have a smooth wheel face to use.
#27 - A shop ‘must have’: The Bench Grinder
I would wager that most anyone who has a shop, or works in one, would be among the first to tell you that one of the most necessary tools in their shop would be their bench grinder. This may not apply for some specific woodshops, but since Toolsmartz is about ALL shops, we can cover it.
Bench grinders come in many different sizes and the major defining factor about them is the wheel diameter. Most people would not say, ‘yea, I have a ½ horsepower bench grinder’. No, they will be saying, ‘yea, I have an 8” bench grinder’. Even the bench grinder manufacturers set up their advertising literature in this fashion. The grinder’s horsepower and speed are somewhat of a secondary matter, after the wheel diameter, but don’t mis-understand, the horsepower and speed are critical factors when selecting the correct bench grinder, but what is usually seen is that as the wheel diameter gets larger, so does the horsepower. This allows the bench grinder to tackle harder jobs.
The deal is, when you have a large item to grind on, you really need a decent sized bench grinder. My personal philosophy is that if you have a large (meaning 10” wheels) bench grinder and need to do a small job, it can handle it. On the other hand if you have a small (meaning 4” or 6” wheels) bench grinder and need to do a big job, you can’t…or if you try to, you may burn up your small grinder. So yes, when considering what bench grinder to choose, size does matter.
Another factor to consider is the bench grinder’s speed. This is also known as the RPM of the grinder. For most grinding operations, I prefer a speed of 1725RPM. Many grinders only come in a speed of 3450RPM, which is fine for many operations, but again, if you have a 1725RPM speed, you can pretty much always do whatever it is that you need to do. If you only have a 3450RPM grinder, I can promise you that you will overheat some items real fast.
As I suppose you have gathered, my personal favorite bench grinder is my 10”, 1725RPM unit. It has no problem grinding small parts and it can handle all of my lawnmower blades without overheating them and burning them up.
Next week, we’ll continue this Bench Grinder discussion and get into some of the typical problems that you might encounter and recommendations for solving them.
Bench grinders come in many different sizes and the major defining factor about them is the wheel diameter. Most people would not say, ‘yea, I have a ½ horsepower bench grinder’. No, they will be saying, ‘yea, I have an 8” bench grinder’. Even the bench grinder manufacturers set up their advertising literature in this fashion. The grinder’s horsepower and speed are somewhat of a secondary matter, after the wheel diameter, but don’t mis-understand, the horsepower and speed are critical factors when selecting the correct bench grinder, but what is usually seen is that as the wheel diameter gets larger, so does the horsepower. This allows the bench grinder to tackle harder jobs.
The deal is, when you have a large item to grind on, you really need a decent sized bench grinder. My personal philosophy is that if you have a large (meaning 10” wheels) bench grinder and need to do a small job, it can handle it. On the other hand if you have a small (meaning 4” or 6” wheels) bench grinder and need to do a big job, you can’t…or if you try to, you may burn up your small grinder. So yes, when considering what bench grinder to choose, size does matter.
Another factor to consider is the bench grinder’s speed. This is also known as the RPM of the grinder. For most grinding operations, I prefer a speed of 1725RPM. Many grinders only come in a speed of 3450RPM, which is fine for many operations, but again, if you have a 1725RPM speed, you can pretty much always do whatever it is that you need to do. If you only have a 3450RPM grinder, I can promise you that you will overheat some items real fast.
As I suppose you have gathered, my personal favorite bench grinder is my 10”, 1725RPM unit. It has no problem grinding small parts and it can handle all of my lawnmower blades without overheating them and burning them up.
Next week, we’ll continue this Bench Grinder discussion and get into some of the typical problems that you might encounter and recommendations for solving them.
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