Thread Boxes


Hi all,
Maybe some here can help me. I am in the mists of making some book presses and I am having trouble with threading the wooden spindles for the vice jaws.
I have turned a tap on the metal lathe, but I am lost as how to secure the cutter in the threadbox. I have cut the threads into the box but don't know what angle to mount the v cutter or how to retain it.
I done a Google search awhile ago and found a good site with pictures and detailed instruction for making a threadbox, but I didn't save the info. Does anyone know of a site address, or have information on how I might proceed with mounting the V cutter in the threadbox?
I know that I could probably buy one somewhere, but I like to make my own tools. The spindle is 1 1/4' Dia 18" long, hardwood.
Many Thanks,
Trevor Australia
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First of all, turn off the mister while in the midst of a woodworking project, since those mists will cause wood swelling and rust your tools! <g>

Wouldn't you just set it at the angle determined by thread pitch? E.g., if you want 4 TPI on your 1.25" spindle, you will want a pitch of 1" rise for every 4*pi*1.25 = 15.7" run, or and angle of arctan(1/15.7) = 3.6 degrees.
Caution: This is just a guess, and how I would approach it. It is NOT based on experience, so proceed at your own risk!
BTW, I made wooden bench vise screws using a commercially available tap and die set, and found the screws almost impossibly tight until I ran them though the female part several times with a little pumice or fine silicon carbide grit on the threads. You might want to tend toward tightness in your set. Easy to loosen the end result as I did, but not so easy to make the end result tighter.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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Trevor wrote:

By angle to mount it I assume you mean the angle of attack at which the cutter meets the wood. For a shearing cutter, one that cuts like a plane blade, I'd think that a 45 degree angle would be as good a guess as any.
Since you have a tap, why not _tap_ the hole though the threadbox, then rout a slot in the front face of the threadbox at a depth such that the point of the cutter lies inline with the thread. One way to hold the cutter in place would be to rout a shallower cross slot accross the cutter slot and screw a metal bar accross the cutter to clamp it in place.
Then cut away any threads forward of the cutter and add a face plate with a tapered hole in it that will guide the dowel into the cutter. I have a purchased threadbox that is made that way and it works great. However I do not recall lthe angle of attack it uses. You will need a space alongside the cutter to allow the shaving to exit the threadbox as you cut.
I _think_ in mine the cutter is secured by passing it at right angles through a hole in a metal dowell that is threaded on one end. That dowell sits in a hole drilled through the body of the threadbox with the treaded end protruding thorugh the back face. There it is secured with an acorn nut. The cutter is adjusted for depth of the thread root (and maybe to some degree for angle of attack) then the acorn nut is tightened to secure it. The unthreaded end of the dowell and the cutter are covered by the faceplate with the tapered guide hole.

In one of his books Roy Underhill describes how to make thread boxes and taps. ISTR these used scraping cutter with a near 90 degree angle of attack for both the threadbox and the die, and the threads were cut in several passes, advancing the cutter in depth a bit each time.

Good for you. I'm impressed that you made your own tap and would like to read a description of how.
--

FF


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On 19 Jul 2005 06:45:25 -0700, the opaque snipped-for-privacy@spamcop.net clearly wrote:

The Woodwright's Workbook Further Explorations in Traditional Woodcraft by Roy Underhill 259 pp., 81/2 x 11, 239 illus. $18.95 paper ISBN 0-8078-4157-9
    Table of Contents for The Woodwright's Workbook
Annotated Text of The Debate of the Carpenter's Tools Making Workbenches Making Screwboxes and Taps for Wood Threading Constructing Springpole and Treadle Lathes Building a Carpenter's Tool Chest Rustic Chairs Hickory-Bark Chair Bottoms Turned High Chair Weaving a Cattail Reed Chair Seat A Loom-Back Chair Ladders, Folding Bookstands, Eggbeaters, and Music Mills Making a Rowboat A Field Guide to American Tool Marks Building a Colonial Fort, a Barn, and a Blacksmith Shop
--

-- Friends Don't Let Friends Eat Turkey and Drive --

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Thanks to all for replies.
I will try to obtain the book references.
As to making the tap. It was straight forward. I just chucked a 1 1/4" X 8" length of steel in the metal lathe, turned a 6" section down to 1/2", then set the gearing up for 6 TPI and cut the thread (60 degree) in about 6 or so passes. I then used a pointer on the spindle gear and divided the threaded portion into 3 equal section. I used a grinding wheel 3/8" X 2" on an arbor in the milling head and ground 3 slots across the threads about 5/16" deep to make the recess. I caseharden the tap with Hardenite in my homemade furnace, tempered to dark straw\brown, and slip stone the cutting edges. I then ground 4 edges on the 1/2" section end, attached tap handle and presto, one 1 1/4" X 6 TPI wood tap.
It helps when you have metal lathe, milling head, furnace, etc. Otherwise it can be done without the machines "IF" you can find a 1 1/4" X 6 or 8 TPI bolt. Just grind/chisel/cut the recesses in the threads, harden and temper with propane torch. Give it a go, a bolt doesn't cost all that much. I have done it with smaller bolts and they work ok where you can't obtain a tap when you want it. Of course good quality tools make it easier to produce quality results.
Just my two cents worth!
Regards, Trevor
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