Wood screw threads

[Mike Holbrook]

I was putting together an order for the parts to make a walking cane or two from Lee Valley's offerings. I discovered that the brass handles LV sells are made to accept threads on the presumably wooden shaft of the cane. The only devise I could find on the LV site to make these threads is a router bit & kit. I believe I have read "threads" on work bench leg vise construction, in which posters mentioned threading their own screw dowels. I found a couple threads about posters making devises to thread wood but I am not finding purchasable products suitable for "tapping" dowels by hand, although I think I have read a few. Can anyone point me in the right direction?

I run a dog park and like to have a cane/staff with me all the time. There is a very good reason most pictures of guys herding shows them with a cane/staff. These devices are invaluable when "herding" large numbers of dogs. The ones I have bought frequently break way too easy. I am thinking a 1" maple dowel screwed and locked into a brass handle with a double sided bolt will give me a sturdier tool.

[David Keller NC]

Here's a link to a page on Woodcraft's site for traditional wooden thread boxes and taps. These are problematic for making shop tools like wooden screw thread clamps because the thread pitch is too fine (fine pitch = slow). But because the pitch is fine, the threaded joint would be quite strong, which might be just the thing for your application:

http://www.woodcraft.com/category/20...ding-kits.aspx

[David Posey]

Look at the instructions on LV's website. They're linked to on the page with the handles down where the products are listed. They say the handle is on two parts, a collar and the actual part you grab on to, and the collar is self-threading. If you questions about how they work give LV a call.

[george wilson]

For a 1" diameter,5 threads per inch is about right for correct threads for wooden hands crews. These used to be supplied in the older thread boxes Marples used to make,sold at Wood Craft Supply. You can still fine these older boxes on Ebay,but be sure to get the tap with them.

I believe coarser threads on wood will be the stronger. In metals,fine were invented for steel,and coarse for the weaker cast iron. Since wood is weaker yet,I think coarser threads would be stronger. At least,that's the way old time wooden objects were threaded. Since wood was a primary material long ago,I think they must have had the threads pretty well figured out from empirical use over the ages.

[David Keller NC]

I believe coarser threads on wood will be the stronger. In metals,fine were invented for steel,and coarse for the weaker cast iron. Since wood is weaker yet,I think coarser threads would be stronger. At least,that's the way old time wooden objects were threaded. Since wood was a primary material long ago,I think they must have had the threads pretty well figured out from empirical use over the ages.

I think you're correct from the standpoint of the threads themselves; if plow planes are any guide (their threaded arms tend to be very fine pitched compared to hand clamps). But what I meant was that the joint will probably be stronger with finer pitched threads since the length of thread engaged in the joint per length will be considerably greater.

And yeah, don't I wish that I'd cracked open my wallet a few months ago when a tool dealer had a set of 5 Marples thread boxes and their corresponding matched taps in nearly perfect condition! That was really dumb - now I'm going to have to make the taps on a small milling machine that hopefully will arrive shortly. I'd much rather make lever cap screws.

[Harry Hagan]

I recently watched a segment of The Woodwright’s Shop titled: Two Screws for You!

Chris Schwarz was showing Roy Underhill how he used the twin-screw Moxon vise in his shop. About twenty minutes into the show Roy and Chris discuss and demonstrate how to use a “thread box” and tap to make wood threads.

Here’s the link:http://www.pbs.org/woodwrightsshop/video/3200/3205.html

[Jeff Heath]

Another option....

http://www.highlandwoodworking.com/m...r1-126tpi.aspx

Jeff

[Mike Holbrook]

Yeea, good info. guys!

I missed the info. in the Lee Valley instructions which states that the handles are designed to self thread onto the shafts. I am not sure how good a connection I might expect via a self threaded connection though? Even if the connection is not all that great it might be compensated for by the ease of replacement. The problem I have had with the canes I have used to date has been broken/bent shafts and handles separating from shafts. The dogs I work with can break the handles or shafts of most canes like tooth picks. I should have thought to check Highland Woodworking, great to know my local store carries threading and tapping devices in a nice range of sizes. At 46-$54 each, I will have to think on what sizes I might actually get significant use of.

[Jim Belair]

I think if you backed up the self threaded connection with a bit of epoxy you'd have a joint that was as strong as anything you or the dogs could throw at it. For a belt and suspenders solution, also drill a hole through the handle and shaft and put a steel pin through the whole works.

[george wilson]

It isn't just the length of the thread that will be engaged,it's also the shear strength of the material being threaded. Cast iron uses coarse threads because it hasn't the shear strength of steel. I'm pretty sure the same applies to wood,and it needs even coarser threads. The old timers had hundreds of years to work this out. Finer threads on plow planes are an exception: their arms aren't made to take a lot of sideways force like wooden clamps are. They are made finer to facilitate more precise adjustment.

In large steel threads,by the way,it has been found that 12 tip is the strongest thread. I was examining a 350 ton press with 2 1/2" posts in it,and sure enough,12 tpi were used on the posts that take the force of the press.

Those Highland threading boxes make a too fine thread,too. I'd keep looking on Ebay for an OLD set of box and tap. The taps on the old Marples thread boxes have a very tapered tap that does 5 tip for a 1" dia. shaft. The trouble is,with the crude old rapidly tapered tap(which looks like it is made of cast iron or cast steel(cast something?),the tap takes skill to tap squarely through a hole with. It used to come with a crude tap handle with a slot in the center to slip over the flat end handle of the tap. Last time I had to use one of those things,I turned the tapered tap handle straight,chucked it in a metal lathe,and fed the wood I was threading against the tap,using the face of the tailstock ram to support and keep square the wood I was tapping. The large tailstock ram's hole was a lot larger that the 1" tap,though,unlike the #2 Morse taper of a standard wood lathe tailstock. I was making a book stitching frame for the book bindery,and had to tap about 6 nice,squarely tapped holes. It worked fine. I did not have the missing tap wrench,and didn't care to make one for this 1 shot job. The stitching frame was needed quickly,like everything else.

They had wasted money on a modern Scottish made stitching frame. It was crappy,having too fine threaded shafts,and a base made of MDF,totally unsuitable for a museum shop. Also,shiny lacquered finish,another no no. They should have asked us to make it. We had it ready in a day or so,IIRC.

[David Keller NC]

The problem I have had with the canes I have used to date has been broken/bent shafts and handles separating from shafts. The dogs I work with can break the handles or shafts of most canes like tooth picks.

Mike - Perhaps riving a cane blank out of hickory might help with this - I'd think with such a narrow diameter and long length a cane blank would almost have to be riven rather than sawn out.

[george wilson]

Riven definitely would be stronger. How do your dogs break the canes? What kind of monster dogs do you have?? The older I get,the smaller my dogs get,it seems!