Metal Spinning How to Part Two -- Tool Rest
Metal Spinning How To, Part Two -- Tool Rest
Our objective is to promote metal spinning as a popular hobby and professional art form. We feel that the best way to secure this objective is to show people how to do metal spinning on wood lathes rather than the typical metal spinning lathe. Because of the success in promoting woodturning in the United States and England after World War II, there are now hundreds of thousands of woodturning lathes in the United States. There are only a few hundred of the old cast iron hand metal spinning lathes. They are hard to find, almost always need restoration, and they don’t have the modern motors and speed controller that are now typical of the large woodturning lathes. I have never spun metal on a “metal spinning lathe”; I have alway spun on large woodturning lathes converted to metal spinning.
The subject of this post is the metal spinning tool rest. The major differentiator between the woodturning lathe and the metal spinning lathe is the tool rest. To convert from a wood turning lathe to a metal spinning lathe you simply need to remove the woodturning tool rest and and replace it with the metal spinning tool rest. I am going to describe the metal spinning tool rests I have used on the big woodturning lathes such as the OneWay 2436, Powermatic 4224, and the Laguna REVO 2436. There are many others and almost all of them could be used as metal spinning lathes very effectively.
The metal spinning tool rest has three parts. The first is the tool rest, a horizontal steel bar with vertical holes along the top surface. Second is a vertical tool post that is attached to the horizontal tool rest.
Third is the fulcrum pin(s).
The tool post is most often tack welded to the tool rest bar. This welded subassembly is also referred to as the “T”-rest, because it is “short” for tool rest and also because it looks like the letter “T”. The tool rest is inserted into the banjo of the wood lathe. When inserted into the banjo, the banjo can allow and/or restrict the rotation and up and down movement of the tool post.
The banjo with the tool rest inserted can then be moved in the X and Y axis and allow rotation about the Z axis. The fulcrum pin can then be inserted to any of the 13 holes in the tool rest and be moved in the X axis as appropriate. Between the tool rest and the banjo, adjustments and movement can made in almost every possible direction to secure the best possible mechanical and strategic advantage during the spinning operations.
The positioning of the tool rest fulcrum pin and banjo are not static but rather very dynamic in that everything is being moved and adjusted as the spinning operation is going on. In general the fulcrum pin is be moved towards the headstock as the spinning proceeds. Each operation and each type of Metal Spinning Tool is likely to require an adjustment of the tool rest and/or banjo.
After teaching for many years I have found that students are very reluctant to make all the appropriate adjustments during the spinning operation. They often try to substitute brute force rather than making the adjustments that would give them the advantage by using the tool rest correctly. However, I do understand and acknowledge that I also get lazy and try to get in a few more strokes before making the appropriate adjustments.
In an effort to encourage students to make these adjustment I have looked at the tool rest to see if it could be designed in such a way to make it easier to make these adjustments. Looking at videos of professional hand metal spinners using the old monster lathes I have noticed that the fulcrum pin(s) tool rests are very worn from many decades of use. My first thought was, why wouldn’t they make themselves a new tool rest and fulcrum pins. What I found out was that these item just get better the more they are used and worn. This allows the fulcrum pin to be moved quickly and easily without even thinking about it. Looking at the Metal Spinning Tool Rests that I sell, the tolerance between the fulcrum pin and holes in the tool rest are much too tight. I have redesigned and reworked the fulcrum pins so they are sloppy in the holes in the tool rest. When the pin is inserted they rattle until your left hand is placed on the pin.
Once the appropriate adjustments have been made the metal spinner places the a metal spinning tool onto the tool rest and the uses their left hand to hold the tool on the tool rest and up against the fulcrum pin. They then place their thumb on top of the fulcrum pin. Think of your hand as being wrapped with a half a roll of duct tape in such a way that the only possible movement is in the fulcrum pin about the “Z” axis.
In this discussion we have described how the addition of the metal spinning tool rest is used to convert a woodturning lathe into a metal spinning lathe. While this is the major differentiator between the wood lathe and metal spinning lathe the next obvious difference is the metal spinning tools. There are three common types of tools used, spinning, trimming and beading tools. I think each of the tools would require and deserve a 1,000 words. In the next post I will describe the spinning tools.
If you missed the first post in this series here is a link http://newproductllc.com/blog/metal-spinning-how-to-part-one-lever-and-fulcrum/