Carter Hollow Roller
Friday 17 February 2012
On opening the box, I was impressed with the build quality of the system. The front toolrest was very smooth, polished and chrome plated, as were the roller bars in the torque arrestor assembly. All the aluminium parts - including the tool handle - were blue anodised. It was also nice to see all the Allen keys needed to set up and mount the system were included in the kit. The instruction manual was very clear and contained plenty of diagrams and colour photos. I also found some helpful video clips on the Carter Products website regarding the setting up and use of the system.
I assembled the front toolpost with the longer stud supplied with the mounting stud - various studs are available to fit most lathes - and fitted it to the bed on my lathe. I then fitted the stud to the torque arrestor and mounted that on the banjo - following the advice to rotate the banjo so the assembly was in a better position for hollowing.
I shaped a piece of boxwood (Buxus sempervirens) which was going to have a few holes in it as my test piece. This isn't the easiest of wood to use but I thought it would make for a good test. I drilled the opening to 25mm (1in) diameter. Given the width of the hollowing bar, I don't think I could have gone any smaller. I mounted the Hunter carbide bit on the hollowing bar. These are small circular cutters which mount on a short round bar that is fitted to the hollowing tool shaft. The cutters are not intended to be resharpened; you just rotate the edge when needed and replace the cutter when you have used all the edge. The manufacturer claims that these carbide cutters will hold their edge for 20-30 times longer than high-speed
steel equivalents. When cutting the side of the hole, wood was removed very easily and very quickly. There was no need to grip the tool to my side or to take care with presentation and rotation of the bit because all that was done for me by the system. Once the cutting height is set and the position of the cutter in the holder is fixed, the torque arrestor prevents the tool from rotating and from being pulled downwards inside the hole. The whole hollowing process was now a very relaxed affair, all I had to do was to make sure I didn't go through the side.
When I got to cutting across the bottom of the hole, I found I couldn't get a good cut with the Hunter tool. On closer inspection, it looked like the mounting shank was protruding slightly too far, preventing the cutter from engaging with the wood so I removed the cutter, ground the end of the mounting shank back so it wasn't getting in the way and went back to hollowing. With this small modification, the cutter performed without any further problems and cut across the bottom of the hole without difficulty.
It was useful to be able to set the position of the banjo to use the torque arrestor as a depth stop to prevent me from hollowing too deep. This was simple to do and pretty much foolproof.
My only difficulty with the system was the tendency for forward and backward movements into and out of the hole to require less effort than sideways movements because the roller bars are mounted on bearings. This made it slightly more difficult when trying to follow the undercut curve under the opening. That was probably compounded by me having to angle the tool across the roller bars instead of having it parallel to the bed. This was necessary to achieve the degree of undercut needed for the chosen shape.
I switched to the high-speed steel scraper cutter to try that too and it also cut very well. One problem I found with both cutters was that due to their small size, it was difficult to achieve a smooth surface without ridges from the tool - which was partly made more difficult by the problem with forward/sideways movement described earlier. I found a larger scraper bit from another tool and used that for finishing.
I found the system to be very simple to use. I can see the captive system might be of benefit to anyone with back trouble or with limited grip, arthritis, etc. Hollowing over the bed can be done with this tool without the need to lean over at awkward angles. You can stand upright alongside the lathe bed. There are a few additions I would like to see to make a good tool even better. These include a larger finishing cutter, a swan-neck hollowing bar to make the system even more versatile and the Hunter shank could be shaped to avoid the need for modifications. Also, the screw used for the Hunter cutter is tiny; it would be reassuring if a spare was included, and lastly, a narrower hollowing bar for smaller openings might be useful
to makers of smaller hollow forms.