Sawing MDF

MDF can be cut successfully with hand saws without splintering or breakout of the core fibres. Most companies will, however, use powered machines, ranging from small portable types to fully programmed panel cutting machines.

As the wood raw materials for MDF are relatively free from grit or other abrasive materials, cutter wear is not likely to be a problem when sawing MDF. Nevertheless, the relatively high density of MDF combined with the resin binder does make MDF slightly more abrasive than commonly used hardwoods. Carbide tipped saws are therefore recommended for most production work.

When large volumes are to be cut the use of polycrystalline diamond (PCD) tipped saws should be considered to take advantage of their substantially longer cutting life. For highly intricate pattern work, high energy laser beams can be used to cut MDF providing charring is acceptable or can be removed by sanding.

Saw blades which have been developed for particleboard will cut MDF with reasonable success, but the adoption of alternate top bevels of 15° and an increased tip clearance angle of 20°-22° will further extend the life of the saws between sharpenings, thereby reducing costly down time.

The following general recommendations based on research and experience gained over twenty years working with MDF will help to ensure smooth cut edges, minimal breakout and long saw life.

Running speed

The running speed (RPM) of the saw is calculated as follows:
 

Thus a 400 mm diameter saw blade with a recommended rim (peripheral) speed of 60-70 m/s should be operated with a running speed in the range 2800 - 3300 RPM.

Feed speed

Chipload which is the amount of material removed by each tooth should be in the range 0.15 to 0.25 mm. The feed speed required to produce this chipload is calculated as follows;

Feed speed (mm/min) = RPM x No. of teeth x chipload (mm).

When using a 40 tooth saw blade, irrespective of diameter, operating with a running speed of 3000 rpm, the feed speed should be in the range 18 m/min (0.15 mm chipload) to 30 m/min (0.25 mm chipload).

At low feed speeds, the saw crushes and abrades the MDF rather than cutting it and the frictional heat generated by pressure on the tips can seriously reduce saw life. At higher feed speeds, the quality of the cut edge will be diminished. The production of fine dust is a sure indication that the feed speed is too low whilst a ragged cut indicates too high a feed speed.

Saw geometry

Saw geometry is important. Small increases in the clearance angles used on general purpose saws are recommended to ensure effective disposal of the fine dust produced when machining MDF and to prevent resin build up.

The following tooth geometry has been found to give satisfactory results:
 

Sawing veneered MDF

For production cutting of veneered MDF, saw blades with alternate 5° face bevel and alternate 15° top bevel are recommended. In addition, a scoring saw should be used on the underside to prevent breakout.

Resharpening

All original angles should be maintained when the saw is serviced. Reduced angles will increase the amount of resin build up whilst increased angles will reduce the saw life between sharpenings. The gullet should be reground periodically to maintain dust elimination efficiency. Chip clearance and resistance to resin build up can be improved by finally polishing the teeth with a 600 grit diamond wheel as part of the sharpening process and periodic treatment with a PTFE spray during saw operation.

Work piece rigidity

The MDF should be firmly secured while sawing and the saw blade should be free from vibration.