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Trevor
 
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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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alexy
 
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"Trevor" wrote:

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.


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

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.


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:
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.


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.


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?


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.


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.


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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Trevor
 
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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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