There are a number of off the shelf and DIY solutions to the problem of connecting a fixed pipe to the rotating spindle on the lathe. I decided against the method of building a sealed box around the handwheel end of the spindle because I wanted to maintain access for using a knockout bar for drive centres and I wasn’t sure how airtight the bearings on my lathe would be. Of the other methods I found, there was the airpress rotary adapter that simply screwed on to the spindle nose at £ 162; the Oneway rotary adapter at £ 100 which attaches to the outboard end of the spindle and a choice of two makes of through spindle adapters, the Holdfast at £ 35 and the E-Z adapter at £ 50. Both of these work on the same principle, namely a 10mm (3/8″) hollow threaded rod through the MT2 spindle with a bearing in the outboard end for the hose outlet. I also found some DIY plans for making my own using a length of hollow lamp rod, a bearing and some home made bits to join them together.
I decided to go for an off the shelf adapter and as the threaded rod types looked like they could be removed in seconds without any tools, it seemed like the obvious choice. From the catalogue photos, it looked like the main difference between the Holdfast and E-Z adapters were that the Holdfast was made from fibreglass reinforced plastic and the E-Z was aluminium. I selected the Holdfast adapter as it was considerably cheaper.
Selection of chuck heads
Having researched what was available off the shelf, the choices were different sizes of cup chucks, designed to hold bowls, boxes, hollow forms etc. from Airpress, Oneway, Vicmarc and Holdfast and faceplates from Airpress and Vicmarc which are used to hold a reversed bowl by its rim or possibly a box in the same way. I also found a number of articles explaining how to make your own cup chuck or vacuum faceplate using an existing faceplate or suitable bolt and some mdf or plastic pipe.
Here I opted for a mixed approach. I had a couple of spare faceplates so I thought I could use those to make my own cup chuck and faceplate but I also decided to buy a couple of chucks to get me started. I bought the 90mm (3 ½”) and 150mm (6″) Holdfast chucks at £ 35 and £ 42 respectively. The theory was I could see how much I could do with the two chucks I bought and make other ones as needed. The Holdfast chucks are moulded plastic with an aluminium spindle thread section whereas the Oneway and Airpress versions are all aluminium but this is reflected in the price. Holdfast also sell packs of the round neoprene seal material that can be used to make your own cup chucks so I bought some of this too for £ 5.60. Other materials that can be used to give a good seal between the chuck and the wood include foam mouse mats, wetsuit material and thick walled airline hose.
Vacuum Chuck Rotary Adapter
I bought the rotary adapter, seal kit and the two chucks from Packard Woodworks. They had the M33 threaded chucks in stock to fit my Wivamac lathe. If (like me) you are ordering from the UK, VAT will be charged on arrival along with a collection fee.
One thing to bear in mind is that the holding force is proportional to the area of the chuck so the smaller the chuck, the less force holding the wood to it for the same vacuum pressure so there is a minimum effective diameter for a vacuum chuck of this type given the vacuum obtainable with the pumps generally used. Most manufacturers seem to start with 90mm (3.5″) as the minimum, presumably for this reason so I assume a cup chuck smaller than this will have a very limited grip.
Next – Assembling the Vacuum Chuck
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