Woodworking Screw Box Tap

[Martin King 2Participant @martinking2]

Hi All,

I have quite a few wooden screw boxes for threading male & female wooden items, most have the associated taps but ther are several that need taps and they are REALLY hard to find.

I thought that I would have a go at making a larger size 4tpi one as I have a proper one for a pattern.

My Super 7 has a gearbox but only goes to 8tpi.

Can anyone please advise how I might go about doing this? The tap has a slight taper and the die box is marked 1 (&quot. I presume that the material is turned, the thread cut and then the 4 grooves milled at 90 deg but keeping the thread on the taper is a mystery to me?

Cheers , Martin

[Martin King 2Participant @martinking2]

How to make a large tap 4tpi ?

[Martin King 2Participant @martinking2]

Sorry about the smiley, typo!

[Brian OldfordParticipant @brianoldford70365]

I would suggest the use of a taper turning attachment or throwing over the tail-stock might be a first step. I suggest the problem of cutting a very coarse thread be solved by adopting the solution proposed many years ago for the column of the Dore-Westbury mill. Set your gear train and rig up a drive to the end of the lead-screw and drive the spindle through the change-wheels.

[Michael GilliganParticipant @michaelgilligan61133]

The "interesting" feature is that the threads are full form all the way down the taper [the original appears to be cast] … 'though I doubt if this is useful.

MichaelG.

[Martin King 2Participant @martinking2]

Posted by Brian Oldford on 19/01/2017 16:36:45:

I would suggest the use of a taper turning attachment or throwing over the tail-stock might be a first step. I suggest the problem of cutting a very coarse thread be solved by adopting the solution proposed many years ago for the column of the Dore-Westbury mill. Set your gear train and rig up a drive to the end of the lead-screw and drive the spindle through the change-wheels.

Sounds a bit beyond me , what would the gear train be please?

M

[Martin King 2Participant @martinking2]

Posted by Michael Gilligan on 19/01/2017 16:47:23:

The "interesting" feature is that the threads are full form all the way down the taper [the original appears to be cast] … 'though I doubt if this is useful.

MichaelG.

I agree, certainly cast. The thread points are very blunt and show no signs of honing at all.I almost always find them like this yet they cut nice threads in hardwood if used carefully. The othet (femal) parts always have a very sharp vee cutter.

[Neil WyattModerator @neilwyatt]

Posted by Martin King 2 on 19/01/2017 17:07:07:

Posted by Brian Oldford on 19/01/2017 16:36:45:

I would suggest the use of a taper turning attachment or throwing over the tail-stock might be a first step. I suggest the problem of cutting a very coarse thread be solved by adopting the solution proposed many years ago for the column of the Dore-Westbury mill. Set your gear train and rig up a drive to the end of the lead-screw and drive the spindle through the change-wheels.

Sounds a bit beyond me , what would the gear train be please?

M

Choose the 8tpi gear train, and if possible, double the size of one of the driven gears.

You may need to rig up a toolpost spindle for thread milling as I doubt change gears can transmit anywhere near enough torque to cut such a large thread, even with minute cuts.

Neil

[Martin King 2Participant @martinking2]

Neil, OK I get the idea of doubling to get 4tpi, would it be OK if taking very small cuts and using the front edge of the tool only (a la Tom's Techniques)?

Which one should I double?

I am getting the feeling that this may be beyond me…. More trouble than its worth possibly.

M

[Neil WyattModerator @neilwyatt]

Posted by Martin King 2 on 19/01/2017 17:31:28:

Neil, OK I get the idea of doubling to get 4tpi, would it be OK if taking very small cuts and using the front edge of the tool only (a la Tom's Techniques)?

Which one should I double?

I am getting the feeling that this may be beyond me…. More trouble than its worth possibly.

M

You might get lucky, a cut about 3/16" long is quite a large one to take geared up 2:1 even shaving a thou at a time (which will drive you quietly insane as that's about 180 passes…)

Any gear that would normally be the driven one of two meshing gears (when working normally i.e. driving the leadscrew)

[Jonathan GarsideParticipant @jonathangarside40968]

Surely there is an article on this very subject using a Myford lathe in the latest (No 250) issue of MEW

Jonathan

[John ReeseParticipant @johnreese12848]

Don't worry about making a tapered tap. Most modern taps for wood are not tapered. Some do have a tapered lead similat to a metal cutting tap. Google is your friend.

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