acme thread for large wood screw

I want to make a wood screw for a vise(2in. dia). I have tried using dried and green oak and 3 tpi. The threads for the nut cut very nicely
but the outside threads are a mess. Lots of chipping and tearing. Is it the wood, the tool grind ,or me? I have also tried cherry and it was worse than oak. My brother ground the tool for the inside threads and I ground the tool for outside and am a relative clutz so I hope it is just the grind. Anyone with experience doing this? Thanks, Bob
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bob wrote:

nicely
it
I
Hello Bob, you are cutting the male thread? I have heard [not seen] of it being done, using a Dremel with the appropiate shaped cutter burr,mounted on the toolpost and cutting at whatever t/p/i needed. Worth a try? All the best for now, John.
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bob wrote:

Perhaps do a search on wooden screws ("wood screw" makes me think of a screw to go into wood) -- anything that's easy to split won't make good threads, because you're asking them to hold along the grain, where the wood is very weak. I think you're right in trying different woods, but you haven't looked far enough afield to find the right one.
I'd try Elm. Elm was used for wheel hubs because it has a dense interlocking grain -- apparently it was a bitch to work with because you simply could not split out blanks but had to saw everything. Assuming the grain is fine enough that should be just what you want for this part.
Obligatory disclaimer: I haven't actually done this; I've just watched a lot of episodes of "the woodwright's shop" and read a couple of Roy Underhill's books.
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Tim Wescott wrote:

I'd try Maple, or one of the various IRON woods (every state and country has one!). Purple Heart might be ok - it is hard.
Cell size and material composite is important. A little Si in the wood helps but will eat the cutters - use carbide or regrind.
Martin
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If you look at the cutters in a typical wooden screwbox, you'll find that their geometry is quite a bit different from that of the cutting edge of a tap.
A woodworking tap presents the cutting edge to the wood in essentially a scraping orientation. There may be a slight amount of rake, or there may not.
A screwbox uses a V shaped cutter, presented to the work on a tangent. Think of a wood carver's V tool - V on the outside, V on the inside, with the edge razor sharp. Or, a piece of angle iron with the end cut at, say, 60 degrees (with the points longer than the heel), and the inside edges then sharpened. Again, the cutter does not scrape, but is presented to the work pretty much at a tangent - and it slices. It produces not chips but a continuous curl. A larger screwbox will usually have two cutters, so you will want to make several passes on the lathe.
John Martin
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I made the mistake of trying to split some elm for firewood once. Karl

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Hydraulic only!! Ever see a 24 ton splitting ram come down on a 16" block of straight grain elm, bury itself in a couple inches, and STOP? Sheesh! Had to use a sledge hammer to get the ram out of the log.
The new sapwood for each year grows in a spiral pattern. But not necessarily the same pattern each year so you could have a left hand spiral one year, right hand the next, straight the third year.
Karl Vorwerk wrote:

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bob wrote:

nicely
it
I
Oak is probably going to be a non-starter. You need a close-grained, tough wood, like hickory, maple or ash. They make threadboxes for doing the male threads, the thread isn't much like a metal thread. Several woodworking books I've seen tell you to shape the threadbox cutters and make the threadbox itself. Or you can go to some of the specialty places on the internet and buy them and the matching taps. I've used threadboxes on <1" stock, they work OK with the right wood.
Another method is to use a router jig, this company, http://www.bealltool.com /, makes jigs. If you're tooled up, you could probably make one yourself. The owner also has a book out on wood threading.
See http://www.woodshopdemos.com/beall1.htm for a how-to with the jig. Stan
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Go to a firewood pile and select whatever species of wood is common to your area that is a pain in the ass to split with a maul. If the cutting tool is not razor sharp with no rounding of the edge forget turning it with no tearout. Dampening the wood with a moist but not dripping sponge may help.
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take a look at wood turning tools, 'wicked' shaaap
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Try http://www.bealltool.com /

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I find it very difficult to single point a wood "screw".
What does work well is to mount a router on the toolpost and user that to cut the threads. A 60% v bit in the router, and a slow back gear works well. If you want some other tread form then the proper router bit may be harder to find.
Single point inside works better.
Tom Gardner wrote:

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Seems to me that using a wooden screw for a vise is something you would do if metal were not available. The only time I have seen wooden threads is on broom handles painting poles and that is the usual point of failure.
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Roger Shoaf wrote:
"Seems to me that using a wooden screw for a vise is something yo would do if metal were not available. The only time I have seen wooden thread is on broom handles painting poles and that is the usual point of failure."
I've seen such threads on "decorative" nut crackers. It's a wooden cup roughly the size of a coffee cup, for the nut, and a wooden threaded ra for cracking the nut.
Can't help with the wood type however
-- J. Mark Wolf
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On Fri, 17 Dec 2004 20:43:06 +0000, J. Mark Wolf
|| ||Roger Shoaf wrote: || ||"Seems to me that using a wooden screw for a vise is something you ||would do ||if metal were not available. The only time I have seen wooden threads ||is on ||broom handles painting poles and that is the usual point of failure." || || || ||I've seen such threads on "decorative" nut crackers. It's a wooden cup, ||roughly the size of a coffee cup, for the nut, and a wooden threaded ram ||for cracking the nut.
I have a 3-legged stool with adjustable height via a large wooden acme thread. Blonde finish, almost looks like pine. Whole thing cost me $10 new, so it couldn't be anything exotic. Texas Parts Guy
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I made one of those, I used a 55 degree thread, 3.5 threads per inch. turn the tap out of high speed steel, mill in three flutes. The tap was so large I easily relieved it with a file, after blueing it. After hardening, it was sharpened with a fine stone on a die grinder. I cut very sharp threads in clear maple for the nuts useing beeswax as a lubricant. The screws were made with a router mounted in a metal lathe, I ground some 55 degree cutters, I calculated thread depth, and cut the thread one pass in slowest backgeared speed. Dennis
On Fri, 17 Dec 2004 10:03:26 -0800, "Roger Shoaf"

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Cheat; use plywood. Or even metal (plastic) painted with wood grain ;)
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"bob" wrote: (clip) Anyone with experience doing this? (clip) ^^^^^^^^^^^^ I am a woodturner, not a machinist, so I will tell you what little I know: 1.) You can sometimes help with tearout by waxing the wood, treating it with lacquer sanding sealer, or thin C/A glue. 2.) You need to use very sharp tools. 3.) Woodturning practice is to turn the wood fast to get better surface finish. I don't think this is applicable to turning threads in a metal lathe. So the suggestion to use a router mounted on the carriage would likely be the best way to go. There are woodturning tools designed to work this way--it seems to me that a machine lathe would do this easily.
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Leo Lichtman wrote:

A look at a wood working web site that has thread cutting hand tools might help in the physical cutter and angles. e.g. a wood working supplier...
Martin
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On Sat, 18 Dec 2004 05:01:36 GMT, "Martin H. Eastburn"

One of the Tauton books has a couple of articles from Fine Woodworking on making a screw box to cut screws out of wood. Unfortunately I can't find the exact reference.
IIRC the design of the screw box was pretty simple.
--RC Projects expand to fill the clamps available -- plus 20 percent
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