What can I use my vacuum chuck for?
Hopefully by now, we have a reasonable idea of what a vacuum chuck is capable of but there are certain limitations imposed by the nature of the material we use. Wood is a porous material and all those pores can allow air to flow through. For vacuum chucks this can be bad news because too much leakage will reduce the effective vacuum and the holding force, potentially to the point where your latest pride and joy becomes airborne! For this reason, it would be advisable to continue wearing your protective headgear and also to try not to stand in the line of fire just in case. The thickness and type of wood will also influence how much air leakage through the wood there will be, not to mention cracks, worm holes, bark inclusions etc. The thickness, type and shape of the piece of wood will also influence its strength and care must be taken not to exceed what the wood can withstand or you will find your bowl might collapse under the pressure.
As discussed earlier, each of the vacuum chucks relies on a good seal between the chuck and workpiece so a textured or carved surface might inhibit a good seal. Common sense would apply here as to what can and can’t be successfully held in the vacuum chuck. If your bowl or vase has changed shape since it was turned, it may no longer be round enough to make an effective seal. This is more likely to be an issue with turning green wood.
When applying finishes while mounting on a vacuum chuck, bear in mind that liquid finishes may be drawn through the wood by the vacuum. This may cause differences in the appearance of the wood after finishing so it’s one to watch out for.
During my tests, I also found the chuck provided a good grip on an unturned bowl blank so the system could be used to grip pieces of wood instead of a screw chuck or faceplate while a chucking spigot or recess was formed. Obviously this depends on there being a flat surface on the blank but I found the seals still performed well on a sawn surface as you would find on many blanks. If in any doubt, it would also be possible to supplement the grip from the vacuum chuck by using a live centre in the tailstock. I think common sense would also dictate how big a blank would be safe to use with this method
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