Graphical Construction Glossary >> Tools. >> Power Tools >> Chain Mortiser

Chain Mortiser

In woodworking: A machine that uses an endless chain to cut mortises in timber.

A Makita 7104L 12 Amp Chain Mortiser from Amazon.com

I can remember the very first time that I saw one of these portable chain machines. In 1966 I was hitchhiking around Japan and I wandered onto a building site in Kyoto. The guys were building a traditional Japanese timber frame house, with the frame being about 6" thick. All the joints, studs to plates were mortise and tenon and while the guys did a lot of hand work, they had one of these little beauties. In the time span between then and now, I have no doubt that Makita have improved the mortiser no end, but I mention it here do dispel any ideas that you may have that Makita is a lightweight company. (they were founded in 1915)

At that time I had never seen a portable machine like this in either the UK or Australia. I had seen and used very heavy solid cast iron framed workshop machines, but what amazed me was the fact that the portable mortiser was performing as good as a workshop machine in respect of the cutting, but it has the advantage or being portable.

• It takes up less space in a small workshop and it can be packed away when not needed.
• Like a portable magnetic electric drill, it has the tremendous advantage of allowing one person to work on large and heavy timbers without needing extra help to move the timber to the machine.
• This particular machine weighs 17kg
• It has a plunge capacity of 155mm so we can say that it will do a through mortise in 300mm stock.
The cutter chain is 16.5mm wide but by using pre-set stops wider mortises can easily be cut.

While chain mortisers are a lot faster than hollow chisel mortisers they are slightly rougher. The downward side of the chain leaves a clean cut, but the other side, the upward cut leaves whiskers or sometimes splinters.

The trick to stop this is to do a shallow cut first so the the upward end is angled say 45deg. then cut to it but not quite. So that maybe 1/16" of the bevel is left showing.

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