Large MDF Formers
Entry posted by marks265
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Large Case Formers!
Do you really want one? Well, if you do and don't have a big lathe maybe these ideas can help you. I had a smaller cheapy lathe that I bought from a big box store. They don't sell them anymore and I burned mine up trying to make a former that is larger than an 8 inch'er. I contemplated what to do about this and I came up with a solution that went sideways...literally. Instead of laminating blocks of wood and machining them round I decided to take flat sheets and cut them round. Doesn't make much sense does it?
Well it was actually a pretty nice project and the formers work really well. So I'll do a little explaining on how I did this pretty cheaply. My first decision was to use MDF board that is 3/4" thick. I sawed a bunch of MDF into round discs. Then I lightened them up a bit and finally glued all the sections together. So one section looks like the pic below and you can make and glue as many as you want for the length desired. I bought the material new but you could maybe find cheap furniture made of this stuff to use as a donor. This is one section of my 12" former. Maybe now you are getting my meaning! 
Keep reading to see how I made these formers. The smallest former below is an 8" that I made on a lathe. The other 2 are an 8" and a 10" that I made using the MDF material in this blog.
First of all I had to come up with some inexpensive tools to do the job. I found a band saw on Craigs List for $25. I gave it a little attention by getting a couple of new blades for it and adjusting the guides pretty tight. I also changed the table top so that I could clamp a fixture board where ever I needed to.
For the fixture I merely cut some material out of a board in kind of a rounded slot. Then I strategically drilled a 1/4" hole so that I could cut the radius I needed. Clamping the fixture to the table top gave me adjustability. Not really an ideal setup but it worked. Be sure to take your time with a new blade to cut the discs. Any forcing of any kind will not cut nice round discs!
So what I did was I bought the MDF and I cut the sheets down to square pieces that are pretty close to the finish size of the former. For my 10" I believe I cut the MDF into squares that were 9-3/8" which is an 1/8" over a standard 9-1/4" former dimension for making a nominal 10" firework cylinder case. Then I took a straight edge and drew a line from corner to corner in both directions to find the center of each square. The next photo is a practice piece to see how well this project might work.
I used the piece above for a top and another for a bottom. The build was looking pretty good so kept cutting. Before I got a bunch cut I used the center mark to swing an arc to find 3 evenly spaced points where I continued to hole saw out 3 holes from each disc for weight reduction.
What I don't have a picture of is when I glued all the discs together. Take great care in this step to keep the discs clean for final assembly. If the discs have debris between them they might have air gaps between the joints. The center hole that I used is 1/4". After applying Titebond glue or similar to each disc I threaded them onto a 1/4" round dowel. Once all of the discs were thread together I put the stack in a press and applied light pressure to laminate them together without air gaps between discs. Take care to keep well away from the center hole with dowel when applying glue. The dowel hole can act as a vent when done. The catch is that you need to be able to remove the dowel after the glue sets. When I made both my formers I was able to remove the dowel from the center hole.
After the glue dried I sanded to a slight taper and tried the former. Once I was happy with how they functioned I stained them with what ever I had on hand. Then I finished them with spar varnish which is a marine application. Spar varnish also has a little bit a flex to it for expansion and contract for when the MDF gets wet and dries. I never get my large formers that wet so they have not deteriorated in any way. After a several years of use I never regretted making them.
Pics of the finished formers:
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