Precise Sanding

Hexagon Sanding Jig 29 November 2020

Segmented patterns that have 3 or 4 sided elements are not difficult to make, but I want to make geometric shapes with more facets and they are difficult because the eye is very good at noticing when they are not accurately made. I decided to make a jig capable of producing extremely accurate regular polygons, which are difficult to make accurately, and in my opinion they look terrible if they are not. I wanted to be able to make a hexagon jig but there is no reason why any number of sides could not made by modifying the jig. The specification required was repeatability across flats and end to end of a few thousands of an inch; ideally significantly less than 10.

I came up with this design which comfortably meets the specification, with which I was able to make the hexagons below.

The workpiece, turned round, is mounted between two spiked support blocks.

One, the right hand, has a spike, locking collar, and an allen head screw to apply a securing load to the workpiece. The left-hand block (below) has a centre spike and an anti-rotation feature rather like that on a steb centre.

It also has a split shaft; the outer half is locked by a grub screw and the inner half is free to rotate when not constrained by the knurled brass screw which bears on the hexagon milled about halfway down the shaft. The two halves of the shaft touch at a ball glued to the end of each, this allows the inner half of the shaft to be rotated to the next facet can be sanded, whilst continuing to react the clamping load, and locked on the hexagon face for sanding.

In the picture below the clamp has been turned over to show the guide pins that move freely in the ‘T’ slots so that the workpiece can be carefully sanded to size. The base plate is screwed to a laterally sliding table on the sander.

Jet JDS 12 Sander

I wasn’t looking for a new disc sander but the opportunity to acquire a very good second hand one presented itself, and so I took it. I added the optional legs from Axminster and made a very precise slide with almost zero side play. And so I now have this rather beautiful 300mm Jet Sander, which has its own very effective built in dust collector.

Sanding Boards June 2015

Segment rings have to be very flat before they are assembled and so flat sanding boards are essential. I made mine from MDF because this material has two very big things going for it if not a lot else, it is extremely flat and very stable, as long as you don't get it wet. The bench clamped version is one inch thick and to minimize weight the hand held one for use at the lathe is one inch thick for about a third of its area and half an inch for the rest. I use 80 grit and double sided carpet tape. The rough abrasive gives a good key for the adhesive; you do not want a fine finish.

Lathe Sanding attachment May 2015

I made this sanding attachment after getting Dale L Nish's book Woodturning with Ray Allen, which features the beautiful work of a segmented turning master.

The sander is also very useful for getting mitre joints absolutely spot on and trimming pen blanks to length.

The main body is a box structure which clamps to the lathe bed. The top has a sliding table mounted on a kitchen drawer slide. These things have ball bearing slides and almost zero side play; in fact ideal for the job. The sliding table has adjustable clamps so that a guide block can be set at the required sanding angle

The sanding disc is made from a plywood glue-up, mounted on a face plate then faced up and turned round to suit off-the-shelf self adhesive sanding discs.

This is a version of the original sander, modified to facilitate coupling to my dust extraction system.