Friday, August 17, 2012

Modifying Tools - #1 - Fein Multi Master

Much of the time I make use of hand tools - not because they are quaint or traditional, but because they work fast, predictably, and quietly.

Using a spokeshave on during the construction of a Francois Viver Aber. I was not aware that my wife was taking this photo  as I was concentrating on my work, so you can be assured that the photo was unposed.
Despite my preference for hand tools, it is obvious that for certain jobs power tools allow one to get a lot more work done in a given time, and so where there is a real advantage I have no inhibitiions about picking up an electric or a pneumatic tool. Some become real favourites, and close to the top of my list is the Fein Multi Master.

I have three of these tools - two are mains powered electric versions and one (not a Fein, but identical in operating principle) is a pneumatic version of very high quality made by a Japanese manufacturer who's name escapes me. Fein Multi Masters are expensive, and the pneumatic machine was astranomically expensive, but quality is usually worth the money. For those on a tight budget, the are a number of cheaper brands coming on the market.


Two photos of a Multi Master in use on First Mate
The Multi Master performs a number of tasks using a range of fittings including the triangular sanding pad shown in the photos above, as well as cutting and scraping using several different knife and saw attachments. The use to which I put the machines for the majority of the time is sanding.

What makes a Multi Master (and its copies) so good? Well, most triangular detail sanders work on the orbital principal in the same way as 1/2 sheet and 1/3 sheet orbital sanders. The problem with such an operation is that when you run the sanding pad up against an edge such as in the above photos, the orbital action causes the machine to bounce off the adjacent surface in an annoying and somewhat violent fashion.

However, the Fein Multi Master operates on a different principle. The sanding pad (or saw blade, knife etc) oscillates through an arc of about 1-1/2 degrees in each direction at very high frequency. You will note in the photos that the three sides of the sanding pad are slightly convex, and when you run the pad up against a hard edge, the machine continues to operate smoothly despite being in contact with the adjacent surface. In addition, the sanding action is much more effective than that of an orbital version. Make sure that anything you buy has an oscillating action - not an orbital action.

The metal backing plate to which the foam backing pad and the 'hook-and-loop' is attached. Note the convex sides.


My one complaint is that the sanding 'discs' are expensive, and are held on the pad by a fine 'hook-and-loop' material like Velcro. Because the oscillation frequency is high, and the pad is basically contacting the same place, heat due to friction is not removed by constantly rotating pads, and it is very easy to melt the plastic in the 'hook-and-loop' material. To get around both of these problems, I peel the 'hook-and-loop' off the face of the sanding pad, and use sticky-backed paper placed directly against the dense foam backing on the sanding pad. I cut my own sanding 'discs' by tracing around the machine's pad onto 200mm (8 inch) sticky-backed sanding discs which can be bought in bulk from the hardware store at reasonable prices. I cut them out using a utility knife of robust shears, and I think I get about 6 or seven from each 200mm disc.

Occasionally I find that I need a really flat and hard backing for the sanding 'disc' and I have developed a modification which works superbly well. What I do is I peel the factory-supplied dense foam pad off the alloy plate (I keep a number of spares in my workshop) and in its place I glue on a pad of 6mm (1/4") marine plywood which I cut from scrap. Then I simply attach the stick-backed paper in the normal manner. See photos below.


My modified pad, with 6mm (1/4") plywood glued to the alloy plate using contact adhesive
A nice, flat and hard surface to which the sticky-backed sand paper can be applied. The counter-bored hole in the ply is to ensure that the attaching bolt for the alloy plate does not interfere with the sanding surface.
I hand bevelled the edges of the plywood to replicate the shape of the foam pad.
In some future postings, I'll decribe some other tools which are rarely mentioned, but which I find particularly effective.

4 comments:

  1. I see you use a (Stanley pattern?) metal spokeshave. Have you tried the old style wooden ones, with the tapered tangs holding the blade in place? I have found these to be much easier and quicker to use, once you get the hang of adjusting them with a toffee hammer (or similar). More comfortable in the hand, and easier to control with much less tendency to chatter.

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  2. I appreciate this review of the Fein tools. Because of their cost I never looked seriously at them. Knowing the principle of their operation I will research some of the lower priced copies. They sound very useful. Your approach to lower cost replacement pads was helpful too.

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  3. Ross, I looked at the Fein tool and couldn't come at the price but Bosch have a Multitool in both their Green and Blue range of tools. My students and I use the green model for sanding only and the blue one mostly for cutting. The way it cuts is great, especially for locations where a jigsaw cannot get to or when flush cutting/trimming is required. But also because the blade cuts so cleanly and as it is only 0.2mm thick for separating components and relocating them with what is effectively an invisible join.

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  4. this makes a lot of sense. Thank you!

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