Jig-grinding is often overlooked as a significant machine tool that gets the job done accurately and quickly. One reason jig grinding gets unnoticed is because a lot of toolmakers view it as an obsolete machine that can only be used to round holes or create contours a CNC milling machine can ably perform.
Sure, CNC milling machines do much of the work these days, yet a jig grinder is still indispensable for a lot of tool shop operations. In fact, there are shops that run their jig grinder 8-10 hours a day, doing a range of tasks.
A Key Benefit of Using a Jig Grinder
Before we talk about how to use this machine, let us first discuss why people should use a jig grinder. To be honest, it all boils down to one reason: it lets you save money.
To blind hole floors, you need to undergo a tedious process – you either leave stock for post heat treatment or mill them extra deep prior to treatment. Both options can be a bother to get to the right depths within a decent amount of time.
But when you opt for jig grinding, you can leave them shallow prior to heat treatment and you can then just use a carbide cutter or CBN wheel to grind the perfect depth. For bosses, you don’t need to use an EDM machine because jig grinding lets you do it at just a fraction of the time.
Adding relief to cores is also something in which a jig grinder stands out. You don’t have to use a Ded-Tru machine because a jig grinder will do most of the work.
For holes in your ejector and core pins, a jig grinder will also do just fine. In addition, this machine is a great application for cavity blocks and locators in the core, ensuring perfect alignment.
How to Use a Jig Grinder
A jig grinder is one of those tools that have been around for a long time now and it takes skills to be able to use it properly.
If you don’t know anyone who is adept at using this machine, you’ll be hard pressed to find one because this old school skill is quickly disappearing! But hopefully, these tips will give you an idea on how to operate this tool machine.
A sharpening jig is specifically made for woodturning tools and it can be used in 2 ways. First, metal removal is almost basically unnecessary and secondly, your experience will be a lot more enjoyable using consistent tools.
Having sharp tools that can turn properly is vital and having a sharpening jig for your tools for woodturning is one of the most important tools you could purchase. Picking a jig is the first step, but to make the best of it, you need to know how to use it.
First, your grinder should be limited to 1725 rpm. Grinders with 3400 rpm are more affordable, but the speed sometimes triggers balancing issues, leading to excessive vibration.
In addition, a 3400 rpm grinder generates heat that can negatively impact the hardness of carbon steel tools.
The size that is recommended is an 8″ grinder. 6″ grinders are fine but when the wheels show some wear, the hollow grind becomes severe causing the edge to become weak.
Another important consideration is the type of wheel. Gray stones are very hard, so they may end up burning your tools as they are unable to dissipate heat quickly.
White stones, on the other hand, are very soft, so they tend to wear down very quickly. Blue stones, on the other hand, are the ones that come highly recommended. They are long-lasting and durable without burning your tools.
It is important that you fully understand that a jig regulates the angle of the grind however it does not control the shape. Any jig should have detailed instructions on base plates set-up on your grinder base and how to get the desired shape of the grind.
You should keep the stick out of the tool to 2 inches past the jig. You need to drill a hole in the mount or base – to serve as a stop block to make that measurement quickly and accurately.
Then adjust the arm and line this position. In my case, I have two different settings, though others have just 1. You then need to set the extension arm at a consistent distance from the surface of the wheel.
The wheel wears down which means you cannot measure it from the base of the clamp. Use a jig to replicate that measurement. If the gouge is being sharpened, work on the grind’s sides first where much of the material is to be eliminated then work on the fingernail’s curved front.
It’s not hard to remove too much metal when you get to this point. You have more control using this method that if you were trying to sweep from one side to the other in a single pass.
Extension Arm and Flat Tool Rest
Most people use the extension arm for Vari-Grind support and it’s not really worth buying. The flat tool rest, on the other hand, is quite versatile. You should purchase or buy jigs that allow you to set the rest at different angles so you can work with more accuracy and consistency.
You can sharpen skews with straight jig grinding and grind both sides evenly. Scrapers are very easy to grind. All you have to do is set the flat rest at your prefer angle for your scrapers with a jig and then contour the scraper’s shape or you can reshape it as needed.
It’s safe to say that while a jig may be an option, being able to sharpen your tools is crucial to your work. If you can afford it, buy a jig grinder and then learn how to use it correctly. That way you can enjoy your work more and even be more productive.