INEVITABLY every home workshop machinist needs to maintain and keep tools sharp in order to cut metal cleanly and produce good work.  That statement may seem obvious yet I have seen lathe and milling cutting tools that are a long way short of sharp and the resultant work often leaves a lot to be desired.

There are, of course, many books written about the theory and technical aspects of sharpening tools and relief angles etc. However, the typical home workshop enthusiast simply wants to make things and sometimes neglects these finer details and actually ends up making the job a lot more difficult than it should be.

I am of the opinion that the home workshop is completely different from professional production environments and as such we need to understand and respect the limitations of the equipment we use and the type of cutting tools.  Once you accept it is a completely different environment (for the majority of home workshops) then it becomes obvious that all cutting tools need to be sharp, preferably low cost and simple to sharpen. 

Let’s start by considering the major difference of the machines in the home workshop and those in professional workshops.  The most obvious difference is the size and cost of machines.  A small Myford lathe is an incredible design which can be used to machine metal objects which are comparatively too big but because this is what we have then the home lathe is pressed into coping with a vast range of different tasks. 

In the specific case of the Myford lathe because of its small size it lacks mass and in many cases mass is what enables cutting forces to be absorbed and large depths of feed to be made.  The same analogy is equally true for the home milling machine.

Because of this the home machinist has to ensure tools are sharp, depths of cut, feed rates and speeds are reduced from that of the larger machines.  The only disadvantage is one of production time because several passes may have to be made.  The common factor is that cutting tools must be sharp!  Most modern production machines have now moved on to carbide inserts and in so doing increased cutting speeds and feeds while maintaining accuracy.  So, for the home machinist having

the capability to sharpen cutting tools is essential and as a minimum a good bench grinder is needed but to simplify matters the introduction of a Tool and Cutter Grinder (T&CG) makes the sharpening task dead easy. A  T&CG can be very basic, as in the case of a bench grinder with homemade add-on guides and rests, or similar to the Stent, Quorn, Worden or many other designs available.

In my case I made the Stent as the basic set-up and operation is very easy though it does have limitations when sharpening more sophisticated tools.  In the case of this article I am only interested in the common cutting tools like those used in the small lathe or milling machine. 

Many newcomers think that building a machine that is very versatile is the best decision but quite often these machines require a lot of set-up time.  Consider the type of tools that you will want to sharpen and then decide on the type of T&CG design that is best suited.  There are a great many tools in the workshop that can be sharpened but sometimes the set-up complexity and skills required mean that it may be a more sensible decision to replace these tools.

Drills

There are many different techniques and jigs available to enable drills to be sharpened.  I always admire those expert shop-floor engineers who sharpen drills by hand.  It looks easy but it isn’t and there are many reasons why it is better to invest in a special jig designed specifically to sharpen drills.  The crucial requirement for a drill is that it cuts metal easily and produces a consistently accurately dimensioned hole. 

I made the jig designed by G H Potts and this has proved to be excellent but not so for small diameter drills!  Small drills are difficult simply because they are small and setting the drill in any jig is challenging! 

While I use a very crude and effective jig (Fig. 1 - similar in concept to the Potts)  for small drills this is a case where it may just be cheaper to buy replacement drills, especially in the case of  ‘micro’ drills. Note the micrometer head used to ensure very fine feed.

PART 2 - SHARPENING MILLING CUTTERS AND LATHE TOOLS.

Figure 1