Harold Hall
Workshop Processes
Photograph 24 shows the device being used for its main purpose, sharpening the spiral edges of an end mill. In this case it is secured to the rest's table using the method in photograph 23 and the end mill fed by sliding the barrel within the attachment. Rotation of the cutter is controlled by a finger that sits in the cutters flute, this seen just to the left of the grinding wheel. Grinding starts at the shank end and the barrel pulled backward finishing at the outer end, the rotation of the grinding wheel keeping the cutter in contact with the finger. This being the reason for the wheel being on the right hand side of the end mill. If a conventional off hand grinder is being used with the fine grit wheel on the right the cutter will have to pass between the wheel and the grinder's motor.
The clearance is set by tilting the table down on the right but just setting this to the required angle is no guarantee that the clearance angle on the cutter will be correct. For this the cutter must also be set as shown in Sk. 8. If, having sharpened the spiral cutting edges, the cutter fails to cut as you would like, almost certainly the clearance angle is insufficient. For smaller cutters you may need to provide secondary clearance.
Using the shops every day off hand grinder.
Whilst I have illustrated all the methods using the complex rest and my adapted off hand grinder, many will wish to use the shops' off hand grinder. All the processes described will work in this situation needing only very slight changes to the set up and so comparable results should be achieved. I am confident regarding this as for some time I used the rests in this way.
One variation that the reader may consider is to plunge the end mill into the curved face of the wheel. As the width of the resulting face is very narrow its curved finish will be of no consequence. This is perfectly adequate and I have done it many times. To set this make a card having the required angle and mark it at the height the cutter will be ground above the tables face, then use this to set the table's position as shown in Sk. 9.
If using my simpler rest then all the above methods will work equally well with this but with minor changes in a few cases.
Final Comment
We are all tempted to continue working with a blunt cutter even though it needs to be sharpened, every effort should though be made to avoid the temptation. One method is to obtain more than one of each cutter frequently used and when one is blunt it can be placed in the “to be sharpened box” and a sharp cutter replaced. With that approach one can then have the occasional sharpening hour. Do hope you have found these pages useful!
Drawings
For much more information on sharpening workshop tools see my book “Tool and Cutter Sharpening”
Do also look at the pages on shaping and sharpening boring tools
24