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If you don't know this tip for using hole saws, you should.
Hole saws are an effective way to cut large holes... won't do flat bottom closed holes but will do through holes and also make circles and cylinders with the cut off part, unlike a Forstner which basically eats the inside. And larger holes than Forstners.
The problem with hole saws is they make a narrow slot kerf with no escape or flutes for cuttings to be ejected, unlike a Forstner which has flutes to allow cuttings to come out the center. With the hole saw the cuttings are reground by the teeth and literally load up the gullets with tightly compacted sawdust which in turn heats up with friction and burns and prevents cutting. You have to very frequently lift the cutter saw clear and use a stiff brush to clean out the compacted cuttings. This is slow and aggravating, it doesn't take much cutting to completely load up the gullets between the teeth.
The secret to fast hole saw cutting is a relief hole. Depending on whether your objective is the circle cut out or the hole, you put the relief hole intersecting the saw kerf and on the inside if you want a hole, or on the outside if you need a wheel.
I generally make a first shallow cut with the hole saw so put the kerf into the wood. Then I remove the hole saw and put in a 1/2" brad point, and position the drill so that it overlaps the kerf. I drill all the way through the piece and then remove the drill and replace the hole saw, repositioning is easy with the hole saw pilot bit.
Now drill the saw though at least halfway. You'll find that drilling goes much better because now the sawdust falls out of the kerf groove into the 1/2" hole you drilled. I still flip the work over and drill the remaining depth from the other side... pilot hole again lines this up perfectly. You may still need to clear the bit periodically but the drilling will go way faster and not load up nearly so fast. Here i wanted the finished hole rather than the plug so I drilled the relief on the inside.
If you need both the hole and the wheel in the end, then this won't work as you see it leaves a rather obvious hole behind.
Hole saws are an effective way to cut large holes... won't do flat bottom closed holes but will do through holes and also make circles and cylinders with the cut off part, unlike a Forstner which basically eats the inside. And larger holes than Forstners.
The problem with hole saws is they make a narrow slot kerf with no escape or flutes for cuttings to be ejected, unlike a Forstner which has flutes to allow cuttings to come out the center. With the hole saw the cuttings are reground by the teeth and literally load up the gullets with tightly compacted sawdust which in turn heats up with friction and burns and prevents cutting. You have to very frequently lift the cutter saw clear and use a stiff brush to clean out the compacted cuttings. This is slow and aggravating, it doesn't take much cutting to completely load up the gullets between the teeth.
The secret to fast hole saw cutting is a relief hole. Depending on whether your objective is the circle cut out or the hole, you put the relief hole intersecting the saw kerf and on the inside if you want a hole, or on the outside if you need a wheel.
I generally make a first shallow cut with the hole saw so put the kerf into the wood. Then I remove the hole saw and put in a 1/2" brad point, and position the drill so that it overlaps the kerf. I drill all the way through the piece and then remove the drill and replace the hole saw, repositioning is easy with the hole saw pilot bit.
Now drill the saw though at least halfway. You'll find that drilling goes much better because now the sawdust falls out of the kerf groove into the 1/2" hole you drilled. I still flip the work over and drill the remaining depth from the other side... pilot hole again lines this up perfectly. You may still need to clear the bit periodically but the drilling will go way faster and not load up nearly so fast. Here i wanted the finished hole rather than the plug so I drilled the relief on the inside.
If you need both the hole and the wheel in the end, then this won't work as you see it leaves a rather obvious hole behind.
Loring in Katy, TX USA
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