Converting Spade Bits-How I Do It.
Posted: Sat Aug 28, 2010 7:18 am
I decided to make myself a new parallel bit and thought some of you might like to see how I do it.
WEAR GOGGLES AND GLOVES
When choosing your blank take into consideration the length of the bit you want to make, Dublin and Parallel bits need to be longer because of the taper. Quality is also important, you need some good steel to hold the edge, the ones I use are Swiss made.
Mark a centre line on the bit.
Use a computer drawing program to create a pattern, print it and cut it out.
Glue the pattern in place and leave to dry.
Although best done on a bench grinder the bit can be shaped using a disc mounted in a drill, the drill needs to be firmly held.
Once you have trimmed down to the line on the bit shorten the shank, a short shank means less vibration.
The fun part begins........
Mount the shaped bit in the drill and spin it up, if you have another drill use it with the disc (spinning) to balance the bit, an angle grinder is better. This is easiest on a lathe with an angle grinder.
Once you are happy that the bit is shaped and balanced properly it is time to set the edge at an angle of 10-20 degrees. There are a lot of ways of doing this, on a bench grinder you angle the rest and work with the fine stone, in a vice you can use files or a Dremel and cut by eye, the important thing is to go slowly and accurately. Work your way down until you are almost at the edge and switch to a sharpening stone of some type, I have a diamond ‘stone’ somewhere which is great for this.
Once you are happy with the edge, the sharper the better, mount the bit in the drill or lathe and spin it up, do a visual check to make sure it is still balanced. If all is ok you should be able to drill with it, on the first drill take it slowly and take note of any spots on the bit which judders. If you have any judder or burning it means the two edges need to be checked for high or low points and sharpness.
After this first drill it is obvious that something needs checking, the burning is the giveaway.
Much better, a bit more sharpening was needed, fine shavings and no smoke.
The finished bit and holes.
Have fun trying this.
David.
The Next Instalment
Reduced shank blacksmith drill
WEAR GOGGLES AND GLOVES
When choosing your blank take into consideration the length of the bit you want to make, Dublin and Parallel bits need to be longer because of the taper. Quality is also important, you need some good steel to hold the edge, the ones I use are Swiss made.
Mark a centre line on the bit.
Use a computer drawing program to create a pattern, print it and cut it out.
Glue the pattern in place and leave to dry.
Although best done on a bench grinder the bit can be shaped using a disc mounted in a drill, the drill needs to be firmly held.
Once you have trimmed down to the line on the bit shorten the shank, a short shank means less vibration.
The fun part begins........
Mount the shaped bit in the drill and spin it up, if you have another drill use it with the disc (spinning) to balance the bit, an angle grinder is better. This is easiest on a lathe with an angle grinder.
Once you are happy that the bit is shaped and balanced properly it is time to set the edge at an angle of 10-20 degrees. There are a lot of ways of doing this, on a bench grinder you angle the rest and work with the fine stone, in a vice you can use files or a Dremel and cut by eye, the important thing is to go slowly and accurately. Work your way down until you are almost at the edge and switch to a sharpening stone of some type, I have a diamond ‘stone’ somewhere which is great for this.
Once you are happy with the edge, the sharper the better, mount the bit in the drill or lathe and spin it up, do a visual check to make sure it is still balanced. If all is ok you should be able to drill with it, on the first drill take it slowly and take note of any spots on the bit which judders. If you have any judder or burning it means the two edges need to be checked for high or low points and sharpness.
After this first drill it is obvious that something needs checking, the burning is the giveaway.
Much better, a bit more sharpening was needed, fine shavings and no smoke.
The finished bit and holes.
Have fun trying this.
David.
The Next Instalment
Reduced shank blacksmith drill
