Cox's Patent Winner

[Boringgeoff]

You'd think that Mr Cox would have made one first to make sure it was going to work on the species of wood he was intending to use it on prior to going to the trouble and expense of patenting it.
The bits you find with fine or coarse lead screws are referred to by the manufacturer as being intended for "hard woods" or "softwoods" but this reference is irrelevant with a lot of the woods I've used them on. My experience is, you can't expect the threads to be self feeding but do have to keep a lot of force behind them to stop the threads stripping out in the hole.
Cheers,
Geoff.

 

[AndyT]

That point about still needing to press down on a bit with an ordinary lead screw comes up in Cox's patent claim. He says that his version is properly self feeding.
I looked at the patent yesterday, having rewatched the film of the manufacturing process. I was surprised that the patent claim wasn't for an improvement in the ease of manufacturing, as you pointed out in post #7.

Is your example in good enough shape to try it out?

 

[Boringgeoff]

I gave the 3/4" Cox a trial on the end grain of a piece of structural pine and it pulled itself in very aggressively with minimal pushing form me. On the side grain it was that aggressive I stopped through fear of damaging it. A similar diameter Scotch bit with coarse thread didn't go so well on the end grain and needed a helping push but was pretty well self-propelled on the side grain.
Three images taken from a 1928 Greenlee booklet on making of an auger bit, concentrating on making of the threaded lead screw. I tried to scan these three pages and attach which was a disaster and an hour of my life I'll never get back. I photographed them instead and apologise for the poor quality, but hope they may shed some light on that part of the process.
Cheers,
Geoff.

 

[toolsntat]

Going by the picture of the bit side on and not accounting for any after purchase sharpening, what strikes me is the angle of the cutting edge.
This seams to roughly follow the screw pitch and I wonder if this angle draws it into timber just a great big screw?
That screw point looks familiar to me and I should go straight to my boring bit storage section and look but apart from a hundred or so I picked up many years ago there scattered in box's everywhere...
Cheers Andy

 

[AndyT]

Thanks Geoff. I share your pain with scanning - but now you have shown us that the pamphlet exists, I can provide a link to the whole thing here:

https://archive.org/details/GreenleeTheMakingOfAnAugerBit/mode/2up
so any other boring tool enthusiasts can enjoy the complete 52 page booklet.

 

[Cheshirechappie]

I gave the 3/4" Cox a trial on the end grain of a piece of structural pine and it pulled itself in very aggressively with minimal pushing form me. On the side grain it was that aggressive I stopped through fear of damaging it. A similar diameter Scotch bit with coarse thread didn't go so well on the end grain and needed a helping push but was pretty well self-propelled on the side grain.
Three images taken from a 1928 Greenlee booklet on making of an auger bit, concentrating on making of the threaded lead screw. I tried to scan these three pages and attach which was a disaster and an hour of my life I'll never get back. I photographed them instead and apologise for the poor quality, but hope they may shed some light on that part of the process.
Cheers,
Geoff.

View attachment 91915View attachment 91916View attachment 91917

Performance sounds good, but that's for a smallish bit in softwood. I'd imagine the same bit in hardwood, or a larger bit in almost anything, may be a problem, the force required being enough to worry the operator about damage to workpiece, bit, brace, operator's anatomy, or some combination of all four.

The Greenlee booklet was interesting, in that it seemed to indicate a slightly more mechanised, jigged and tooled approach than the Footprint Tools video Andy mentioned. Given the larger population of the US and consequent larger potential market, that's not entirely surprising, perhaps.

 

[Boringgeoff]

Once again, well saved Andy, your link is much better.
In my boring trial I was using an 8" brace on the end grain, but couldn't turn it on the side grain , so went up to a 12" which produced serious tear-out and made me abandon the test. This bit is a far from new or sharp and I'm reluctant to do anything to it that might degrade it any more.

One thing that impressed me in the Footprint Tools video, was the synchronisation by the two blokes on the eye forging stamp. The chap pulling the rope activating the stamp wouldn't want to upset the chap holding the white-hot piece of steel.

Cheers,
Geoff.