WHAT DOES “RIGHT-HAND ROTATION” MEAN IN MORTISE BITS?

(And how to choose the right bit for your mortising machine)

When purchasing mortising bits, if you don't opt directly for the spare parts provided by the manufacturer but choose from the tools available on the market, it is essential to check some technical parameters for compatibility with your mortising machine:

• Connection diameter
• Useful length
• Compatible speed
• Direction of rotation

These four elements determine whether the bit can be mounted correctly and whether it will work efficiently. Among all of them, however, there is one that is often overlooked: the direction of rotation .

The direction of rotation: the most overlooked (but crucial) parameter

Many users check the diameter and length, but ignore the direction of rotation. Yet it is precisely this parameter that determines whether the bit will cut or jam.

What is right rotation?

• Right rotation = clockwise rotation, top view.
• This is the most common direction in modern mortising machines.
• The tip flute is designed to evacuate the chip in that direction.

And the left rotation?

• Left rotation = counterclockwise rotation.
• Less common, but present on some older or special machines.

Why is it so important?

Because a drill bit designed to rotate in one direction won't work if mounted on a machine that rotates in the opposite direction. Typical problems are:

• missed cut
• vibrations
• overheating
• risk of damaging the tool and chuck

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How to Check Your Car's Direction

You can do this in three ways:

• Direct observation : turn on the machine and look at the spindle.
• Technical manual : often indicates RH (right hand) or LH (left hand).
• Tip already mounted : the propeller “goes up” to the right → right-hand rotation; to the left → left-hand rotation.

Attention: left rotation exists even if it is rarer

Some mortising machines use counterclockwise rotation bits. Always check the rotation direction of your machine before purchasing. A bit with the wrong rotation will not cut and may be damaged.

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Other parameters to check

Once you have clarified the direction of rotation, you can move on to the other three fundamental elements.

1) Diameter of the connection

The diameter of the shank must match that of the mandrel. The most common are:

• 10 mm
• 12 mm
• 16 mm

If the diameter does not match, the tip cannot be mounted.

2) Useful length

This is the part actually used for cutting. It must be compatible with:

• mortise depth
• car race
• thickness of the piece

An incorrect length can cause:

• incomplete cut
• flexion
• vibrations

3) Compatible speed

Each bit has a recommended working speed. If the machine is running too fast or too slow:

• the cut gets worse
• the tip overheats
• the duration is reduced

Always check:

• RPM of your mortising machine
• Recommended rpm for the tip

In summary

To choose the right mortising bit you need to check:

• Connection diameter
• Useful length
• Compatible speed
• Direction of rotation

Only when these four parameters match is the tip truly compatible with your mortising machine.

Not sure about the compatibility of mortising bits? Before making a mistake, contact us and we'll help you choose the right replacement part for your machine.

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