So why did it take me so long to figure it out?! :doh:
A friend who is a much more capable driver of metal lathes made me a couple of whopper-sized taps for wood-threading (2" & 1.5"). They cut a good thread, but there are two issues with them 1) they are very difficult to start & 2) it takes the strength of 2 (fit) men to drive them though any of our harder woods.
Today I was trying to make some 1 1/2" nuts in Forest Red Gum, which is not only hard, but 'gummy'; it leaves a sticky residue on plane soles, chisels, or whatever rubs over it, greatly adding to friction. The taps we made are hard to start, for reasons we haven't quite figured out, and unless you apply a lot of pressure to get them to 'bite', they just chew away the edge of the pilot hole, and go nowhere fast. I was trying to tap these nuts on my own, & getting very frustrated, so I quit for a while and attended to some other parts of the job.
Then a potential solution suddenly occurred to me. I had a piece of pre-threaded wood which I use for testing screws, and I reckoned if I clamped that to the piece to be tapped, it might help to drive the tap into the new hole. So I tried it & it worked like a charm! Tapping.jpg
But there was still the problem of turning the thing - it takes some very serious torque to cut large threads this way - look at the size of the shavings that come out the bottom of the hole being tapped: Thread shavings.jpg
Somewhere in an old thread someone mentioned using some Linseed oil or similar when tapping. I didn't give it much credence at the time because I have tried paste-wax in the past and it didn't help at all - seemed to make matters worse, if anything. But in desperation, I grabbed some boiled linseed oil, hoping it might do something & used a a toothbrush to I slather it into the partially-cut thread and on the tap. Lo & behold, it improved matters immensely. I was able to turn the tap with about a quarter of the effort it was taking to tap the 'dry' hole, and as the tap came round across the grain each half-turn, it gave this lovely, satisfying crunching sound as it sheared the wood fibres.
Result, a much less fatigued chap, and a very cleanly-threaded hole: Thread.jpg
So why has it taken me 30 years to figure out that such a simple addition to the process would give such spectacular results? :C
Cheers,
A friend who is a much more capable driver of metal lathes made me a couple of whopper-sized taps for wood-threading (2" & 1.5"). They cut a good thread, but there are two issues with them 1) they are very difficult to start & 2) it takes the strength of 2 (fit) men to drive them though any of our harder woods.
Today I was trying to make some 1 1/2" nuts in Forest Red Gum, which is not only hard, but 'gummy'; it leaves a sticky residue on plane soles, chisels, or whatever rubs over it, greatly adding to friction. The taps we made are hard to start, for reasons we haven't quite figured out, and unless you apply a lot of pressure to get them to 'bite', they just chew away the edge of the pilot hole, and go nowhere fast. I was trying to tap these nuts on my own, & getting very frustrated, so I quit for a while and attended to some other parts of the job.
Then a potential solution suddenly occurred to me. I had a piece of pre-threaded wood which I use for testing screws, and I reckoned if I clamped that to the piece to be tapped, it might help to drive the tap into the new hole. So I tried it & it worked like a charm! Tapping.jpg
But there was still the problem of turning the thing - it takes some very serious torque to cut large threads this way - look at the size of the shavings that come out the bottom of the hole being tapped: Thread shavings.jpg
Somewhere in an old thread someone mentioned using some Linseed oil or similar when tapping. I didn't give it much credence at the time because I have tried paste-wax in the past and it didn't help at all - seemed to make matters worse, if anything. But in desperation, I grabbed some boiled linseed oil, hoping it might do something & used a a toothbrush to I slather it into the partially-cut thread and on the tap. Lo & behold, it improved matters immensely. I was able to turn the tap with about a quarter of the effort it was taking to tap the 'dry' hole, and as the tap came round across the grain each half-turn, it gave this lovely, satisfying crunching sound as it sheared the wood fibres.
Result, a much less fatigued chap, and a very cleanly-threaded hole: Thread.jpg
So why has it taken me 30 years to figure out that such a simple addition to the process would give such spectacular results? :C
Cheers,
Sometimes the solution is so simple..
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