LFA Square Hole Master

The LFA Square Hole Master is a UK invention designed to be used as an attachment to SDS Power Tools to produce square holes in all timbers.

The chisel size is 5/8” which is ideal for door lock morticing and it will produce a neat finish without the need to tidy up or trim edges with a chisel and mallet. Larger holes are produced by simply overlapping.

In most cases a door lock mortice can be produced within 3 minutes with the door fully fitted in-situ - no need to take the door to your workshop or employ expensive jigs.

Other uses include exposed timber framing and fencing work.

The SDS power tool should be used in hammer mode for best and quickest results. The SHM can also be used by inserting the SDS fitting into a normal Hammer power tool if fitted with a high quality Chuck such as LFA.

Lubrication
Periodically use some light oil to lubricate the shaft between the main body and the SDS mounting body.

Operating Instructions
1. Attach the SHM to your SDS power tool in exactly the same manner as inserting a SDS bit.
2. Ensure that the power tool is switched to hammer action.
3. Mark out on the timber an outline of the square hole you want to produce.
4. Use a hex key to set the depth stop to the required mortice depth.
5. With the chip ejector slot on the chisel facing downwards, push the four sharp points of the chisel into the timber
at the location you have marked out (if drilling a slot then begin at the top).
6. Chisel the timber to a depth of approximately 25mm, withdraw the chisel and make a second cut to the same depth
immediately below the first one, overlapping if you wish. Repeat this operation before drilling your square hole to
the depth. This will prevent the possibility of the becoming jammed in the timber.
7. To drill larger square holes simply overlap your first hole to the outline you have marked.

Setting the Auger (Chisel)
The distance that the flat edge of the auger projects beyond the tips of the chisel should be adjusted by removing the SDS drive end using two 17mm spanners. This distance should be set between 3mm and 6mm. Once the drive end is removed, undo the locking nut and adjust the screw (LH thread)up or down as required. Use a hex key to loosen the cotter pin bolt, tap it forward with a suitably sized punch to loosen the cotter pin. Replace the SDS drive end. Press the tip of the auger against a firm surface to ensure that the other end is firmly against the setting screw and re-tighten the cotter pin bolt.

Cutting size 16mm (5/8") Square
Cutting depth 75mm
Overall length of Auger 180mm
Mounting shank into main body 24mm
Width of auger shaft 12mm