Machines for Sanding and Working Down

With any job, time invested in initial preparation can often lead to savings in labour and material costs as well as impacting on the final quality of the work. This is particularly true when it comes to preparing timber floors prior to refinishing. This process will invariably involve the use of a heavy belt or drum sanding machine, and an edge sander. These machines vary considerably from model to model and in this article we look at some of their common characteristics.

Drum Sanders / Belt Sanders
Drum machines usually require rolls of abrasives which are cut to size and wrapped around the machines drum. There is a mechanism, normally a clamp. which holds the abrasive in place. Unfortunately this is not a perfect system. If the abrasive is not clamped tightly to the drum it will flap. In some instances it can actually explode when air is compressed between abrasive and drum. Due to the location of the clamp mechanism, there could also be a small missed area q the substrate after each revolution of the drum. Changing the abrasive can also be consuming.
Belt sanders don't have these problems. With continuous belts it is much simpler to change the abrasives.
Some manufacturers produce belts which are bonded on the inside face allowing greater strength. The belts can be run in both directions providing more efficient sanding with no missed areas.
With both systems a padded drum presses the abrasive to the timber surface. Drums can vary in size, between 8n, 10", and 12" widths. Wide drums allow the contractor to sand a floor with fewer passes while a narrower drum will maximise the sanding pressure.
One of the most important considerations for the flooring contractor with both types of machine is the degree of control which he has over the sanding face. It is extremely important that the sanding machine is moving before the sanding face is applied to the floor.
Also the machine should never be started or stopped with the abrasive in contact with the floor because this will produce deep gouges, which can be difficult to remove.
Some machines have a mechanism providing precise control of the sanding face allowing the contractor to lower and raise the drum. thus minimising damage to the floor. Machines without this feature can be problematic.
In this case the machine must be tilted back with the drum clear of the floor before it is switched on. The operator must then walk forwards and gently lower the sanding face.
As sanding machines may weigh as much as 70-80kg this is not easy. If the sanding drum is lowered too rapidly there is a danger that it will bounce, creating 'chatter' or parallel gouges in the timber.

Edge Sanders
All edge sanders have the same basic sanding action although there can be a large variation in the power of the motor and the ability to vacuum dust. The most important aspect when using an edge sander is to ensure that the sanding disc is angled correctly in relation to the floor.
The sanding surface must not be flat to the floor as excessive frictional heat can be generated sometimes burning the timber.
Before edge sanding commences a sanding proof should be made. The machine should be started. and gently lowered to the floor and then lifted. The mark made on the floor should be triangular shaped, like a slice of cake, approximately one third of the whole sanding disc. If it does not appear so, then the angle of the sanding face must be adjusted.
This is done by altering the height of the two back wheels. The process should be repeated until the ideal sanding proof is attained. This makes a significant difference in terms of the effectiveness of the sander as well as the comfort of the operator, because when the sanding disc is in full contact with the floor the machine is more difficult to control.
Some machine manufacturers produce smaller edge machines known as mini edgers. These have the benefit of being not only lighter and easier to use but are particularly useful in those hard to get areas such as below radiators. Generally mini edgers have-a-smaller sanding disc which also makes sanding stairs and thresholds much easier.

Floor Planing
Some floors can present further problems to the contractor when they have years of old treatments of paint or wax on the surface. Sanding will very quickly clog the abrasives used slowing the work considerably. Once the abrasives become clogged they will no longer sand effectively.
One solution is to use a planing machine. Fitted with a steel drum with a set of blades attached, this machine will remove from 0.5mm to 5mm of timber in a single pass. This type of machine is capable of finishing the timber comparable to the level which would be achieved by 60 grit abrasives. With all surface contaminants removed all that is needed is sanding with fine abrasives to complete the preparation of the floor.