The precision grinders used in a tool and die shop or injection mold making shop are some of the most important machine tools of all. These silent workhorses include the manual surface grinder, CNC surface grinder, and jig grinder.
With the extensive use of wire EDM the need for precision grinding has diminished in volume, but not in importance. There just is not as much work in the grinding department, but the grinding operation is absolutely essential to the overall process of toolmaking.
Some of the typical work done on precision grinders include the basic squaring up of core and cavity blocks, die blocks, finishing core pins and punches, finishing parting lines and shut offs and fitting slide lock angles.
Just imagine not having the capacity to do these few tasks and the entire process comes to a halt. You may be able to hard mill a lot of the details, and the sinker EDM can do a great deal, but surface grinding is still an essential part of toolmaking.
One of the old school precision grinders is the jig grinder. It is a very precise grinder, capable of many different operations, yet it is often overlooked as a viable machine tool. Besides the round holes, such as ejector pin holes or die openings, there are many unusual things this tool can do.
One good use is the adding of radii on components. This is often done by hand, with sometimes questionable results that tend to take a long time to achieve. Think of ejector blades, for example. The top area needs to have a radius in order to fit in the opening it will work in. If you only have a few to do, it is not hard to do them by hand. However, if you have 50 blades and all of them require 4 corners to be fitted, the jig grinder can do this accurately and quickly.
Both the jig grinder and surface grinder need good accessories in order to perform as they should. The sine plates, precision vises, angle plates and wheel dressers need to be of the highest quality. These need to be so trustworthy ใบเจียร that they repeat 100% of the time and do not wear out.
A typical grinding area should include a granite surface plate, surface gage and test indicator, drop indicator and stand, height gage for scribing lines, squaring block and indicator, angle plates, magnetic squaring blocks, magnetic and non-magnetic sine plates, and spin fixtures.
You also need gage pins, gage blocks, and much, much more. It is wise to get the best you can afford, so that the toolmaker can work quickly and confidently.
Getting a good edge on a wood lathe tool is one of the great difficulties for a beginning woodturner and an ongoing concern for intermediates and experts. While the grinder is the tool of choice for woodworkers sharpening tools for wood lathes, getting it set up with the correct wheels can be a confusing challenge. It need not be with a couple of simple steps.
First it is necessary to move in thinking of the grinder as a sharpener. Many people come to woodturning from general woodworking where the grinder is used to remove lots of metal in a hurry so as to grind away nicks and breaks in chisels, plane irons and the like. Water stones and honing implements are used for final edges. Woodturners move from the grinder to the wood. Most shop grinders are not set up for this and the problem is largely the wheels.
Thus the second consideration is to replace the grinder wheels. While it is agreed that since woodturners generally use high speed steel tools they should have aluminum oxide wheels, there is a lot of confusion in the catalogues as to what color wheel to get and what bond to have. The color reflects individual manufacturers attempts to make choosing between grades of their particular wheels and has little to do with other wheels on the market. Consideration then should be given to grit and bond.
The bond of a wheel refers to how friable the material is that holds the aluminum oxide together. More friable bonds allow the material to break away quickly thus leaving a sharp cutting and cooler grinding surface. Unfortunately, the most friable bonds manufacturers recommend for woodturners groove, pit and wear quickly requiring a lot of wheel dressing and expensive replacement. Thankfully, almost any aluminum oxide wheel generally available to the home market is sufficiently friable for good sharpening with good wear so making sense of the friable numbers of bonds is not necessary. Just get a good wheel.
Third is consideration of the grit. While it may encourage argument, a good setup is a fast cutting wheel of about 46 grit on one side of the grinder and a sharpening wheel of eighty to one hundred on the other. With a good jig especially, this will meet all the shaping and sharpening needs of the woodturning shop.
Simply put, a couple of inexpensive aluminum oxide wheels of appropriate grit will give a lot of sharpening satisfaction and help to make a lot of shavings for a long time to come. Keep it simple and keep it fun.
Darrell Feltmate is a juried wood turner whose web site, Around the Woods, contains detailed information about wood turning for the novice or experienced turner as well as a collection of turnings for your viewing pleasure. You too can learn to turn wood, here is the place to start. Wondering what it looks like? There are many free videos on the site dealing with everything from sharpening to making a bowl.