Several years ago I was introduced in a casual sort of way by one of our Guild members to what I consider to be one of the most useful ideas I've encountered in many years as an amateur wood-turner. So I must start off by stating that the original germ of the idea came from some one else; what I have done is to pick up the ball and run with it.
But this is the way of things . Many great ideas have sprung from a chance remark or simple demonstration.
I refer to the bright shiny wheels found in the scrap bin of every Video repairman. (speak nicely to the man and you will get them for nothing, although it doesn't hurt to take along a small sample of your work as a gift, that way you can always go back again).
The technical term for the item I am told is the "Upper Video Head". It consists of an accurately turned aluminium wheel 62 mm in diameter by 12 mm thick with lots of holes so handy for screw fastening when required. SEE FIG.1. below.
The first use seen for this delightful cast-out was as a substitute for the scrap wood spigot glued to the base of an article to be turned usually for the purpose of obtaining the maximum finished dimensions possible when using valuable or undersized wood blanks. FIG 2 BELOW
In addition to this, who hasn't experienced the difficulty of remounting a piece in a scroll chuck once it has been removed? The crushing effects of the chuck's jaws prohibits in most cases the accurate re-chucking of the work piece This was always something of a problem for me when preparing, at home, a project intended for instructional purposes elsewhere.
At home in my own workshop I could with some measure of success mount and re-mount work on my lathe by making a mark on the turned piece opposite one of the numbers stamped on the chuck. But move to another lathe and success was not always easy to come by.
No problems now, mount and re-mount as much as you will the partly turned article will always rotate truly. Unlike wood, it is virtually impossible to crush the metal wheel and yet it is still kind to the jaws of your chuck. SEE FIG.3 below.
Originally, lacking confidence I guess, the attachment was made with screws but this left those ugly screw holes to be contended with which to some extent was defeating the purpose. So hot melt glue applied with a glue gun was tried and this proved to be most satisfactory.
Another step in the learning process. This was not a case of being unfamiliar with this glue; it was more a matter of being not all that confident in the ability of a small metal disc simply glued on, to support a heavy chunk of wood spinning madly around often out of balance.
Once again, no problem, after many tests it has been found that when correctly applied, even a substantial "dig in"(not by me of course) will rarely remove the glued disc.
There is a proviso. Particularly for larger work. When making the attachment it is essential that both the wheel and the wood are heated with a hot air gun, or small gas torch, prior to placing them together, so that when the glue is applied it runs into all the small holes of the metal disc which in turn should be pressed firmly against the wood so that it sits nice and true with the
bottom of the blank and of course allowed to cool before mounting in the lathe. When in a hurry (and I usually am) I place the work in the freezer compartment of the fridge for a minute or so.
And beware of wet wood. The surfaces to be glued must be dry.
If the usual method of turning a bowl is being carried out, that is, securing the face of the work piece with a screw or pin chuck and turning the bottom and outside first, the video head may be glued accurately to the bottom the bowl whilst still set up in the lathe, by advancing the tail stock so that the live centre engages the hole in the middle of the disc and by having both the disc and the bottom of the bowl pre-warmed, apply the glue to the wood and then quickly wind in the tail stock using sufficient pressure to force the disc firmly against the base of the bowl.
This probably sounds complicated, but it is not. An ordinary hairdryer will provide sufficient heat in most cases and will not damage the wood.
Just get everything ready in advance and give the glue gun time to heat up.
When the job is finished the disc may either be parted off whilst on the lathe, taking care not to damage the metal disc too much as you will no doubt want to use it again and again, or by removing the work from the lathe and applying heat to soften the glue so that the disc can be removed. After scraping off as much of the glue as possible, clean up any residual with a cloth dipped in turpentine.
I have previously discussed the use of Video Heads to secure a turning blank to a scroll chuck. This assumed that the metal disc would be attached to the article to be turned.
Another alternative and one that I personally use many times when turning, is to make up a suitably sized wooden face-plate out of MDF or heavy plywood and secure the metal videohead to this, using either screws or glue. See Fig.4 below.
Having joined the two together, install in the scroll chuck and true up both the edge and the face of the wooden disc.
A word of advice at this stage. When gluing the metal and the wood together, endeavor to keep the glue within the confines of the metal disc. Any glue adhering to the outside of the disc should be removed prior to mounting in the chuck as this will interfere with accurate positioning against the chuck's jaws.
The work to be turned may now be fastened to the wooden face- plate with double sided carpet tape provided that the bottom of the work has been cleaned up and flattened. See Figure 5 below.
This may be accomplished by using the sanding disc to be described later.
The face-plate of course, should be of a suitable diameter for the task in hand. Do not expect to hold a heavy and out of balance blank using this method. In any case, I always bring the tail-stock up against the blank and apply a fair bit of pressure until the work has been trued up. In many cases the tail-stock may be left in place right up till the last minute of finishing off. See Figure 6 below.
Also, don't be stingy with the carpet tape. Use only one layer, but make sure that the whole of the area to be attached is covered.
And again, use only "carpet type" of tape not the thick narrow stuff for sticking objects to the bathroom wall.
Sanding discs of various sizes and grades may be made up simply by constructing the wooden face plate as mentioned above and using disc cement, attach whatever abrasive you require. I even have a couple made up using wet and dry abrasive for grinding and polishing semi-precious stones. See Figure 7 below
In a continuing article we will discuss further uses of the video head and the manufacture of small tools at little cost.