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The Proper use of biscuit joiners

Biscuit Joiner IGM Fachmann MJS104K

The biscuit jointer is one of those power tools which has been around for a number of years, having first been developed in the early 60s by Swiss woodworker, Hermann Steiner who formed Lamello, unquestionably the market leader for these extremely versatile machines.As most know, the basic principle is very simple, being similar to the way in which an angle grinder works. Rather than a diamond or abrasive cutter, there’s a slot blade instead and the addition of a couple of fences turns it into a very rudimentary biscuit jointer.

Biscuit Joiner IGM Fachmann MJS104K - history
One of the first Swiss-made models

Although biscuit jointers are nowadays capable of very sophisticated ways of joining and hinging, the basic operation remains the same: a very quick and easy method of construction.

How to make the most of the biscuit joiner?

The motor assembly slides along a machined aluminium base and it’s always worthwhile ensuring that the sliding parts are well lubricated before use.

Use a dry lubricant to make sure that both sections of the machine run smoothly together.

Biscuit Joiner IGM Fachmann MJS104K - maintenance

The biscuit jointer can be used to join two pieces of timber edge to edge but the main purpose of the biscuit in this instance is to provide alignment. Provided the edge joint has been made correctly, it will be strong enough and adding biscuits may provide additional problems as well as entailing extra work. The real advantage is when joints at 90° need to be made; with biscuits a simple butt joint, as might be used in a box, can be turned very quickly into something far stronger. Most machines have the facility on the fence setting for mitre joints cut at 45°, but biscuits work best when the machine is perfectly aligned. If the two slots are even a fraction out, the error is doubled and the resultant joint won’t be accurate. Most of the errors with a biscuit jointer come from holding and using it incorrectly which results in misalignment of the slots. The small discrepancies in alignment as the tool is used account for nearly all the errors that a user is likely to come across, but there are a few strategies which make life much easier and also ensure complete accuracy.

Biscuit Joiner IGM Fachmann MJS104K - tilting stop

1. The Cutter doesn’t have to be centred in the thickness of the material; somewhere around the middle is good enough. Some very sophisticated machines do have the facility to adjust the blade and it can be advantageous when thinner boards are being joined. Fachman offers 6 preset depths which is a useful feature.

Biscuit Joiner IGM Fachmann MJS104K - depth stop

2. The Pencil indexing lines aren’t crucial as there’s always a certain amount of lateral ‘give’ (arrowed) in the slots.

Biscuit Joiner IGM Fachmann MJS104K - centering

There’s no need for them to be positioned with pinpoint accuracy and it won’t make any difference if there’s a little variation in the distance from slot to slot, however, the joint should never be positioned too close to an edge as it wouldn't hold properly.

Jigs and other helpful tools

A very useful jig can easily be constructed from oddments of workshop ply or MDF which will allow the machine to be used so that it’s indexed off the base (and thus used flat) rather than the fence.

Biscuit Joiner IGM Fachmann MJS104K - guiding accessories

The jig also enables both hands to be used to keep it flat; one on the handle pressing down and the other pushing the blade into the workpiece which allows much greater control over the machine. Gripping the work with one hand and holding the machine with the other sacrifices half the control. In the first example, section ‘A’ is firmly clamped to the bench and the jig, whilst section ‘B’ is held vertically against the large central stop whilst the second slot is machined. As can be seen, the simple box corner shown is perfectly aligned.

Biscuit Joiner IGM Fachmann MJS104K - step by step proccess

Placing a board in the middle of the workpiece, such as a fixed shelf in a bookcase, poses another difficulty which is easily overcome by using a guide block, in this case, a pair of accurately made left and right-handed squares which can be clamped onto the edge of the job.

Biscuit Joiner IGM Fachmann MJS104K - accessories

In the second example, the slot is made in the shelf ‘C’ using the jig and the ‘shop made square clamped against the exact location of the underside (arrowed) of the shelf on cabinet side ‘D’. The jig registers the cut and allows precise location of the shelf.

Biscuit Joiner IGM Fachmann MJS104K - accessories

The two fences that are supplied with all biscuit jointers are used when the machine needs to be used on a larger workpiece, where it’s impossible to use a jig. As before, both hands should be used, one on the motor casing and the other on the handle. In the vertical position, it’s essential to keep the extraction hose attached to the machine as, without it, the debris is blown vertically into the operator’s eyes.

Dust extraction

All machines are equipped with a port for dust extraction. Machining without efficient extraction will clog the machine’s interior very rapidly with the result that it will need to be taken apart and cleaned more often.

Biscuit Joiner IGM Fachmann MJS104K - dust extraction


Depending on the application, biscuits are available in a number of different sizes and the depth of slot for each can easily be regulated on the machine. They’re compressed during manufacture and are a loose fit in the slot when inserted dry. The application of a water-based glue causes the wood to immediately swell after assembly, but this also has a disadvantage as if they’re stored in damp or humid conditions, it then becomes very difficult to insert them. Biscuits should be kept in an airtight container together with a silica gel bag or a few grains of rice which will absorb any moisture in the air.

Biscuit Joiner IGM Fachmann MJS104K - biscuits

Fixing Mistakes

It’s inevitable that an alignment mistake will occur from time to time, but with biscuit jointed construction, it’s quite easy to rectify. Glue a biscuit into the offending slot and allow to thoroughly dry, then remove the upper half and plane flush, after which it’s an easy matter to re-cut the slot in the correct position.

To sum up

In recent years, the biscuit jointer may have become sidelined by another jointing system. Nonetheless, the biscuit jointer should not be discounted as it’s still a valuable, quick and more importantly, a very economic method of joining material together. If you haven’t got one in your workshop, it definitely deserves a place in the power tool cupboard.

The IGM Fachmann MJS104K Biscuit joiner was used when making this article.
To achieve a firm biscuit joint, IGM recommends using the Titebond Extend wood glue.

Related products
Titebond Extend Wood Glue - 473 ml, Plastic Bottle
6.20 €
7.50 € incl. VAT
Order Code: 123-9104
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