The equipment

The air gun misfires
After having fired a first shot, the air gun is unable to fire a second; the tongue comes back up empty without the wedge. Why?
It probably arises from the air pressure being too low and consequently having insufficient power to push the gun's tongue back up behind the wedges. To overcome this it is necessary to increase the air pressure. The correct pressure for an underpinner is approx. 5 atmospheres.
The cause of the malfunction though, could be due to the non lubrication of the cylinder. In this case it is necessary to insert a few drops of oil into the air socket holes after having disconnected the air tube. In order to let the oil flow into the cylinder it is necessary to fire a few blanks at reduced pressure.
If subsequent to these attempts, the air gun still doesn't work, it means that there is some internal damage. It is then necessary to disassemble the machine and inspect the inside. If you are inexperienced, this last step is inadvisable; it would be preferable to go to your nearest recognised supplier or specialised repair shop.


The blade vibrates
One of the most frequent defects of blade saws is the vibration of the blade itself.
The causes can be:


The pivot on which the saw turns is misaligned: it probably received a knock during cutting; In this case it is necessary to substitute the defective parts.
It is an expensive operation and so always convenient; it might be worth considering the purchase of a new saw.


The diameter of the blade's bore (inside central hole) is greater than the diameter of the saw's bore and so it is necessary to add a reduction ring.


The blade has been made from poor quality steel and has consequently deformed. It is absolutely necessary to change the blade.


Saw or guillotine?
Is it worth buying a saw or a guillotine?
It is one of the most common questions directed to me by beginners. The answer though isn't an easy one. Let's see the pros and cons of each machine. A guillotine's main advantage is its ability to simultaneously perform two 45° cuts with only one operation. In reality though, the cut is better if performed in two steps, as the second cut only removes a thin slice of the moulding. Irrespective of this the second method is still quicker than using electric saw.
Another advantage of the guillotine is that it doesn't create dust. A good aspirator would contribute to overcoming this particular disadvantage of the saw though no aspirator is able to suck in 100% of the dust created.
Another advantage of the guillotine is that it doesn't consume electricity as it is manually operated by a pedal.
The saw though, consumes electricity not only because of the saw itself but also because of the aspirator.
Contrary to what beginners think, the cut resulting from a guillotine is better than the cut from a saw. The frame doesn't tend to tear or burr at the back as can occur with the saw. Only with a double-bladed electric saw is it possible to obtain the same quality of cut as obtained from a guillotine. The saw though starts to have some advantages when it comes to cutting large mouldings. In these situations the guillotine needs to perform additional cuts and although the cut ends up being equally as good, the cutting time becomes greater than the saw's.
The saw has another advantage when the moulding has a hollow back. In these ,infact, cases as the guillotine blades fall vertically, they tend to tear the wood. Another advantage of the saw compared to the guillotine is that it doesn't leave chips under the cut. Another advantage of the saw is in the case of frames with a falling silhouette. In these cases, the blade of the guillotine tends to tear the wood.
In conclusion what advice do we give to beginners? It depends on the type of moulding that one wants to cut. If bigger mouldings are the ones mostly used, then a saw should be preferred; if though the bigger mouldings are only a small percentage of the work performed then it would be preferable to purchase a guillotine.
The price of a guillotine is about the same as a circular saw equipped with an aspirator and measuring table.


A strange humming noise
When starting up the electric saw the blade doesn't move or a strange humming noise comes from the motor. What has happened?
There can be two reasons for this even if the blade is not moving. First of all the motor could be blocked because of a missing electrical phase or there could even be a lowering of the voltage by the electrical department itself. In these cases the first thing to do is to disconnect the electricity and check the electrical box to see what the situation is regarding the phases and the voltage. If these are OK then you should check the integrity of the electrical wires. If these are also OK then you should proceed to call an electrician. If the problem however is of a mechanical nature due to either a broken or loose transmission belt: just open the protective carter and if the belt is loose, tighten it by regulating the appropriate adjusters. If it is broken there is no other solution than to remove the old one and substitute it with a new belt. If the cause is not the belt, then it is necessary to check the integrity of the bearings and change them if necessary. The final cause could be due to the blade being blocked by a wooden cut off; the removal of this will restore the saw to its normal functions.