Easy tool grinder questions

There's a lot of info about this online already, but off the top of my head:

If you're holding the HSS in your hands, you will never get it hot enough to affect the heat treatment. You can pretty much get it glowing red hot, and it will burn its way through your hand, and still be fine. I personally keep a 5 gal bucket of water next to my grinder that I dump outside every few months. I use it to cool off anything I need.

This wasn't specifically part of your question, but practice freehand grinding. You can do so much more a lot faster than setting tables to specific angles. One of the best things you can do for yourself is get a grinding gage like this one (Clicky). I have the same one and love it. In fact, I suggest you buy that one in the link lol. Before I do......

You can pretty much get by with whatever wheels come with whatever cheap grinder you get. There are of course better ones, I've been happy with this one (Clicky). It won't grind carbide though. Make sure to get a diamond hand held wheel dresser too, to flatten the wheel as grooves are worn in. Balancing isn't usually a thing with cheap grinders, but you can do pretty well with a simple skateboard bearing jig and adding/removing weight on one of the flanges, like by drilling holes on one side or adding screws to the other.

Of course this is all assuming single point lathe bits or flycutters. If you want to grind fluted endmills, you'll really need a proper grinding jig.
 
I went with a good but used bench grinder. I'm new to grinding HSS tools, and it works fine. Had I done a little more research, I'd have opted for 2X42" belt grinder. Read the link Stafants suggested.
 
Masterjuggler said:
If you're holding the HSS in your hands, you will never get it hot enough to affect the heat treatment.
Click to expand...

Was going to mention this but you beat me to it.

I do not keep water by the grinder; instead I have a hunk of aluminum (3/4" thick, I think 3x6", from everyone's pal Stoner) that I set a tool on if it gets too hot. I read somewhere that the worry with water and oil is microfractures, though I'm not going to pretend that's the reason for this: I had the block of aluminum, the shop has no plumbing, and things were getting hot to the touch.

I use an 8" variable-speed grinder. The lower speeds (~1300 RPM) are kinder, especially to carbon steels. I bolted some thick angle iron connecting the two toolrests, and use that as a rail for sharpening jigs. The jigs are just 2x3" sleds of 1/8" aluminum flat, with two dowel pins to register on the vertical side of the angle iron, and from there it's per tool (fence at an angle, thumbscrew-tightened hold-down, etc).

Loads cheaper than the baldor-style shown above, and less fiddly. Currently making jigs for the plane/spokeshave irons and drawknives that have been occupying my time for the past six weeks.
 
Oh yeah, pretty much regardless of what you end up getting or if you join us in the master race of freehand grinders (LOL), some 1/4" square mild steel stock is good to practice on.
 
You can use a belt sander or a bench grinder to grind your lathe tools; both work. The choice really depends on a lot of factors, including personal choice about what you feel most comfortable with.

Another consideration if you go with a bench grinder is what kind of wheel to choose and a lot of guys who grind HSS are going to CBN wheels - safer, cooler, faster and no risk of fracturing - but they are more expensive. Still, the fact that a CBN wheel will far outlast a standard friable wheel makes them a viable choice in the long run. I use Norton wheels on my bench grinder because I rarely use it nowadays other than to grind my gravers but they work fine for grinding HSS. What is good about having standard kinds of wheels is that you can grind other steels, too. You should not use a CBN wheel for fabricating or sharpening your mower or garden blades. I'm rambling but what I'm trying to say is that if you need to use the bench grinder for tasks other than grinding lathe tools then go with standard abrasive wheels. If you only want to grind lathe tools then consider CBN.

If you think about it, what determines how well your lathe tools work is the tip geometry of the tool. There are those who grind tools totally free hand, with no tool rest; how well this works I cannot say. Then there are those guys, like me, who prefer a controlled geometry because this impacts on how well a tool works in different materials. Here, a good tool rest is indispensable and that tool rest should be made from steel to prevent the tool from sticking or dragging during the grinding process. It should also be quickly, easily and precisely adjustable to the angles you require. When you set your grinder up, keep this in mind because it really does make a difference. Just a few degrees more or less relief or rake can make a huge difference in how the tool performs and to get it right you really need a good rest. Once you have that then understanding what you're grinding will allow you to make that tool do pretty much whatever you want.

Insofar as cooling the tool while grinding, water is fine. You will find that a wheel will take longer to grind a tool with and that tool will get hot. Before it gets too hot to hold, dip it. I use a belt sander with ceramic belts that grinds so fast that the tool doesn't even change color, even when grinding the side face. I dip the tool but most of the time it isn't anywhere near hot.

Now, with all this said, if I were looking for a machine to grind lathe tools with but also had to do fabrication or just use it for general shop use, I would look at buying or building a 2X72 belt sander. My personal belt sander is a little 2X42 and it grinds 3/8" lathe tools complete in under 4 minutes; a 2X72 will do it twice as fast. Try that with a bench grinder.
 
I vote for the belt sander for a newbie tool bit grinder. I picked up an old delta 1x42 for $40 after having nothing but problems trying to use a bench grinder. To grind a HSS tool bit you have to be able to grind a compound angle. Very easy to do on a belt sander. You set the table at one angle and then use a combo square for the other angle. Here is my setup

IMG_3705.JPG IMG_3706.JPG IMG_3707.JPG

On a bench grinder you will have to fabricate a titling bed. The rests that come with your typical bench grinder are worthless. Another problem with a bench grinder is that you get a concave grind whereas on a belt sander the grind is flat and easy to hone to perfection.

You really need to read Mikey's thread on grinding tool bits. The good stuff starts on page 4 or 5. The fine details are covered over the next 40 pages.
 
Glad I could start a thread that's of interest. I have a typical bench grinder with the usual blue/gray rock-like wheels, and that'll stay. I do have a belt sander but it's a small 4x24(?) size. While I can understand a longer belt being an advantage for life and staying cool, what's the advantage of 2" wide, belt life again? I'd probably go with a narrow belt sander over a wheel grinder simply because I don't have one yet. Remains to be seen if I can afford the height though.
 
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My belt sander is 18.5" tall, 20" deep and 9" wide. The switch adds to the width as I have it laid out. I could move the switch to keep within the 9" width if I needed to. My 1" wide belt is a little narrow at times. The 2" wide belt gives you a little more grinding room.

If your 4x24 has a table that can be angled I would give it a try before buying another belt sander. The 4x24 will give you some experience to go by in making a decision on another belt sander.
 
The 2" belts are more readily available, are wide enough to grind tools and most anything else and in the longer lengths, run cooler. It is truly amazing to see how fast a 2X72 grinder eats steel. Even more impressive is a Burr King or Wilton grinder that runs at high speed - cuts steel like butter.

I would highly recommend you look into the 2X72" grinders on the forum and the market right now. The cost for one of these has come down and if you buy or make the key components yourself you can really cut your costs down.
 
It's quite easy to make a simple belt grinder out of any old scrap, steel or even wood. I made mine out of tubing from an old bench press, skateboard wheels for the idlers, turned MDF for the drive wheel, and a 2hp 3 phase motor. There are a ton of over-engineered plans available online. With a 36 grit ceramic belt I can feed stock in with my body weight and it disappears.

Personally I use it to rough in HSS then go to my bench grinder for fine adjusting and getting the concave bevels. I think the concave bevels are a HUGE time saver and make the tools more consistent because when you go to a hone, you only need a few strokes and you know you've gotten the entire edge. With a flat bevel, you need to hone the whole face to get to the edge without rolling it over. If there's even a slight gouge from a stray piece of grit on the belt, it takes forever to hone out of a flat face. The same is true for my wood chisels, hand plane blades, and anything else.
 
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