This was prompted by a reply on another forum about not being able to drill HSS to make homemade woodturning tools.
Of course the observation is correct if we're talking normal HSS drill bits because drill and material are the same... but what about different drilling methods and drill bits?
After doing a bit of on-line searching I decided to conduct some experiments with a piece of 1/2"x1/8" HSS (4" long for about $5). I also bought a 5mm diamond core drill which I thought may do the trick.
So, first of all I tried the diamond core drill with water as a coolant/lubricant. In a drill press with 300rpm it started ok but even with a pecking approach and a putty dam filled with water the diamonds soon wore off and I was left with an annular groove about 1mm deep.
I then tried to use a dremel with a small pointed AlOx grindstone. This was very slow but effective, provided I kept dressing the stone on a devil stone frequently to remove the glaze build-up. Grinding from both sides I managed to meet in the middle but the hole was too small.
One of the tips I read on-line was that tungsten carbide masonry drill bits would work, particularly if sharpened, and so I tried a Bosch multiconstruction bit in the dremel'ed hole. This type of bit has a sharpened carbide insert to permit it to drill wood masonry and metals. With drilling and tapping fluid it worked just fine. First a 4mm followed by a 5mm bit went straight through!
OK so that's enlarging an existing hole but what about a fresh hole?
First of all trying the 4mm multiconstruction bit gain... It required a dremel ground dimple to stop the bit skating around but progress was really very slow - Too slow. The problem seems that the bit just isn't really sharp enough at the point to get an initial "bite". So the bits are ok to widen a pilot hole but not to form a new hole.
So, the final experiment was to try a spear-point tile drill and, as luck would have it, this turned out to be the solution. These bits have no flutes but are just a teardrop shaped piece of tungten carbide on a shaft. They have sharpened edges. It still needed a dremel'ed dimple to start off but a 5mm spear point tile drill taken slowly (~300 rpm) in a drill press with cutting and tapping fluid cut a nice clean hole through the toolbit. Unfortunately the bit I had was already used and not of very high quality and chipped during the process but was still able to make it all of the way through.
The good news is that these bits can be obtained pretty cheaply and you can pick them up for about $2-3 each and so I think that it is possible to make your own cutters with 5mm holes. My 4" toolbit will easily make 4 cutters (dremel cut-off wheel to separate them) and even at a new tile drill bit per hole, they'll work out at about $4.50 each which is cheaper than commercial bits.
I hope this proves useful to someone.
Jon
Of course the observation is correct if we're talking normal HSS drill bits because drill and material are the same... but what about different drilling methods and drill bits?
After doing a bit of on-line searching I decided to conduct some experiments with a piece of 1/2"x1/8" HSS (4" long for about $5). I also bought a 5mm diamond core drill which I thought may do the trick.
So, first of all I tried the diamond core drill with water as a coolant/lubricant. In a drill press with 300rpm it started ok but even with a pecking approach and a putty dam filled with water the diamonds soon wore off and I was left with an annular groove about 1mm deep.
I then tried to use a dremel with a small pointed AlOx grindstone. This was very slow but effective, provided I kept dressing the stone on a devil stone frequently to remove the glaze build-up. Grinding from both sides I managed to meet in the middle but the hole was too small.
One of the tips I read on-line was that tungsten carbide masonry drill bits would work, particularly if sharpened, and so I tried a Bosch multiconstruction bit in the dremel'ed hole. This type of bit has a sharpened carbide insert to permit it to drill wood masonry and metals. With drilling and tapping fluid it worked just fine. First a 4mm followed by a 5mm bit went straight through!
OK so that's enlarging an existing hole but what about a fresh hole?
First of all trying the 4mm multiconstruction bit gain... It required a dremel ground dimple to stop the bit skating around but progress was really very slow - Too slow. The problem seems that the bit just isn't really sharp enough at the point to get an initial "bite". So the bits are ok to widen a pilot hole but not to form a new hole.
So, the final experiment was to try a spear-point tile drill and, as luck would have it, this turned out to be the solution. These bits have no flutes but are just a teardrop shaped piece of tungten carbide on a shaft. They have sharpened edges. It still needed a dremel'ed dimple to start off but a 5mm spear point tile drill taken slowly (~300 rpm) in a drill press with cutting and tapping fluid cut a nice clean hole through the toolbit. Unfortunately the bit I had was already used and not of very high quality and chipped during the process but was still able to make it all of the way through.
The good news is that these bits can be obtained pretty cheaply and you can pick them up for about $2-3 each and so I think that it is possible to make your own cutters with 5mm holes. My 4" toolbit will easily make 4 cutters (dremel cut-off wheel to separate them) and even at a new tile drill bit per hole, they'll work out at about $4.50 each which is cheaper than commercial bits.
I hope this proves useful to someone.
Jon
