A Couple More Auger Bit Quotes
Some more information on the topic of auger bits that I came across.
quoted from ALF at, http://cornishworkshop.blogspot.co.uk/2013/02/lead-astray.html
Occasionally I delude myself that I've got a bit of a handle on this old tool business - and then I clean up some auger bits and confusion descends like a familiar cloud.
Auger bits are not simple. Auger bits are complicated little blighters. F'rinstance, early in your auger bit orientation you've probably come across the revelation that lead screws can come in coarse, medium and fine. You may have tripped and fallen in the quagmire that is the uncertainty over whether coarse lead screws are for soft woods and fine for hard woods, or... not. But it's not even as simply confusing as that. Take the lead screws on these two Cornelius Whitehouse and Sons Jennings pattern bits. At least I thought they were Jennings pattern, although they surely don't look like it in the picture... But that's not the point. #11 on the left, #10 on the right.
The lead screws appear to be much of a muchness, no? Yes, the one on the left needs a little attention, but that's not the point either. Well it is the point, but it's not the point.
Wrap a length of cotton thread round those screw points, why don't we? Top tip of the day there, incidentally, and possibly the only useful thing you may glean from this blog entry. Having wrestled and sworn over trying to trace the spirals with a marker in the past, it dawned on me that a piece of thread wrapped round the, um, thread, did the job in a fraction of the time and inconvenience. Unless it occurs to you that the nearest piece of thread is the loose one on your shirt and you start pulling, at which point your inconvenience quotient can increase dramatically. So don't do that. Anyway:
Can you see it? The cotton goes round every spiral on the left like a kiddie on a helter-skelter; it only goes round every other one on the right. Yes, the blighter on the right is a double thread. Cunning swine. Which means...
Well that's where I get confused. More confused. It means the thread pitch is coarser than it appears. I think. But the number of threads is doubled for better grip, maybe? If so, in what exactly? Which lead screw is preferred for what type of wood? Does it matter? Do I even need to know? Most books, however ancient, and the few catalogues I have are all oddly silent on lead screws and the differences in same, so maybe it's no big deal. But I can't help wanting to know, and so I wonder. In circles.
again quoted from ALF at, http://cornishworkshop.blogspot.com/2013/02/leading-by-nose.html
Leading by a nose
Partially prompted by the comments, something of a follow up to the last post. Some 19/20thC advertising blurb to ruin your confidence in what you think you know about lead screws:
Quote:(from a Russel Jennings Box)
"The bits in this set are our Fig. 100 and have our standard double thread point, and are unsurpassed for accurate work in seasoned woods not extremely gummy or hard. It is the thread used by cabinet makers.
"We also have a similar bit, our Fig. 101 with single thread point for quick boring which is especially adapted for hard or gummy woods, end grain boring, mortising doors, etc."
And from Josh Clark via the Old Tools List:
"The 1911 Sargent catalog says that the RJ bits with the double lip, double twist, and double thread screws (the bits everyone wants these days) are "not adapted for rapid boring or in hard wood where fine lead screws tend to clog. .. fine double thread screws are intended for pattern-makers and are for use in soft wood"
"Sargent is also quite definitive as far as the distinction between the double and single thread bits: 'It should be clearly understood that the double thread bit is intended for soft wood, the single thread for hard wood, as the latter will not clog up as readily as the former.'"
So if, like me, your initial introduction to auger bits was an all encompassing "coarse for soft woods, fine for hard woods", like me, you're probably either a) Grumbling a little about this, or b) Going "Ahhh, so it's not just me then" as personal experience is finally explained.
Going through my Irwins yesterday, they threw me another loop. Bit after bit, pretty much, was single thread - and then the numbers 6 and below all went double thread. Didn't see that coming at all.