Toolpost Grinder for a Sherline Lathe

After seeing them in action in various YouTube videos I decided to make a toolpost grinder for my Sherline lathe. Sherline sells a Micro Grinder Toolpost that is designed for a particular high-speed grinder. But the Sherline post has the same problem that led me to develop my own boring bar holder. The fact that the post only has one tiedown bolt means that it will rotate if force is applied to the end of the grinder. Any rotation, even a small one, will cause the face of the grind stone to not be parallel with the work which will affect the quality of the finish on the work.

The holder I made for the grinder was based on the one I made for the boring bar holder which has two tie down bolts which prevent it from turning.

I already had a dental drill setup that I used for close work on my models so I wanted to use that. See figure 1.

Figure 1: Dental drill system

Figure 1 was taken from one of the many sites on eBay that sell the Marathon III controller with a footswitch and mini-motor head. The motor is capable of 35K RPM according to the adds. It does not have much power at that kind of speed, nor is it very controllable, so I use speed reducing heads with it. For example, I use a 64:1 reducing head (which I found on eBay) for drilling on a model and I use a 4:1 reducing head (also from eBay) with the tooolpost grinder. See figure 2

Figure 2: 4:1 reducing head

This reducing head is perfect for the toolpost grinder application because it separates the clamping control for the tool (the left hand set of ribbed rings) and the fixed rings that can be used for clamping (the right hand set of ribbed rings).

I detailed the construction of the toolpost in my article about making a boring bar holder. Please go to that article to see how to make it. The only difference is the size of the hole. The hole in the grinder holder was based on the particular grinding head I got. Figure 3 shows the toolpost.

Figure 3: toolpost for grinder

Figure 4 shows the grinder mounted on the lathe.

Figure 4: Toolpost grinder on lathe

Make sure that the grinder is turning in the opposite direction of the lathe for maximum grinding contact speed.

2024-09-05