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Jig for threading turned box and lid

STB

My version of A shop-built jig for threading lids on turned boxes. The picture is of a box and lid used for proof of concept, and it works but needs a couple of tweaks for the final version. Suggestions wood be helpful.

JPG

A courser pitch feed screw?

I like what you have done.

BuckeyeDennis

That’s pretty slick! What’s the material that you’re threading? I understand that fine-grained hardwoods are best for threading.

What are you looking to improve with the tweaks?

If tearout on the threads is the problem, you could try stabilizing the wood prior to milling the threads, using multiple passes to cut the thread to full depth, or maybe experiment with different thread mills.

STB

JPG wrote A courser pitch feed screw?

I like what you have done.

That's definitely on the tweak list.

STB

BuckeyeDennis wrote That’s pretty slick! What’s the material that you’re threading? I understand that fine-grained hardwoods are best for threading.

What are you looking to improve with the tweaks?

If tearout on the threads is the problem, you could try stabilizing the wood prior to milling the threads, using multiple passes to cut the thread to full depth, or maybe experiment with different thread mills.

I tried several things spindle speed, feed rate, cut depth, applying minwax wood hardener, and a few other things. That's the reason the test pieces are so short I cut off the failures. One of my problems was that I used 5/8 all thread and it is a little under 5/8 diameter so my chuck was not stable. I think a 3/4 all thread with the end turned to the Quill diameter might work. I was also thinking CA glue to stabilize the threads but mine is dried up. The cheapest thread mill is around $45 and go up from there. Some harder wood with a denser grain is a good suggestion.

algale

I like that too! What kind of bit are you using in the chuck to cut the threads??

STB

algale wrote I like that too! What kind of bit are you using in the chuck to cut the threads??

It is a thread mill bit typically used in vertical mills.

Hobbyman2

Very nice, how are you doing with the threads and chip out with that bit ? if it is excessive would a less aggressive bit make any difference ?

STB

Hobbyman2 wrote Very nice, how are you doing with the threads and chip out with that bit ? if it is excessive would a less aggressive bit make any difference ?

As for chipout All my trials have been with the workpiece at 90 to the bit. I think my next try will be with the workpiece canted so only the face of the bit is cutting. I do not understand less aggressive bit. Do you mean less flutes?

BuckeyeDennis

I just thought of another issue. Studying the pic of your setup, it appears that the bit is climb cutting. I’ve experimented with both climb and conventional cuts on my CNC router. The best technique for me seems to be to do roughing passes with a climb cut, followed by a light finishing pass with a conventional cut. So you might try a light finish pass while threading out — that should give you a conventional cut on that pass.

STB

BuckeyeDennis wrote I just thought of another issue. Studying the pic of your setup, it appears that the bit is climb cutting. I’ve experimented with both climb and conventional cuts on my CNC router. The best technique for me seems to be to do roughing passes with a climb cut, followed by a light finishing pass with a conventional cut. So you might try a light finish pass while threading out — that should give you a conventional cut on that pass.

I hadn't thought of that Thanks.

JPG

By 'conventional" thee be referring to plow cut?

john_001

When Woodsmith Shop used a similar jig (with a router rather than a Shopsmith) to make threaded-lid canisters, I recall that they warned that the lid threads (the "male" part) were a climb cut and urged caution. They cut the threads in three or four passes.

BuckeyeDennis

JPG wrote By 'conventional" thee be referring to plow cut?

The article below has a pretty good illustration and explanation of “climb” vs “typical” milling/routing direction. In Fusion 360, Autodesk uses the term “conventional” instead of “typical”, and that does seems to be the more common terminology. I don’t know if “plow” cutting is synonomous with “conventional” cutting.

https://www.woodmagazine.com/woodworking-tips/techniques/routing/climb-cutting

For any beginning woodworkers reading this: The reason that climb cutting is generally discouraged in woodworking is that if either the router or the workpiece is handheld, there’s a real risk of the cutting tool biting too deeply into the workpiece, and launching one or the other across the room. The dynamics are very much like a base-ball pitching machine. Almost exactly the same, in fact, if you try to rip a board on a radial arm saw and feed it from the wrong side. But when using a CNC machine or a jig like STB’s, both the cutter and the workpiece are secured mechanically, so inadvertent launching isn’t a concern. Thus you can choose the feed direction based on cut quality alone.

In CNC metal cutting, climb cuts are used almost exclusively. Cutting-direction advice for milling wood is mixed, and results reportedly vary with the type of wood. In my own experiments, tearout on heavy roughing passes was much more likely with conventional cutting. But on a very light finishing pass that removes only 0.010” or so of material, a conventional cut left a better finish than a climb cut.

JPG

Re plow cutting: Think about it(farming history might help). Back when I took machine shop practices(before acquiring my Goldie) it was climb/plow with climb being reserved for unique situations(it be hazardous). However insufficient tie down is hazardous either way with metal milling.

BuckeyeDennis

JPG wrote Re plow cutting: Think about it(farming history might help). Back when I took machine shop practices(before acquiring my Goldie) it was climb/plow with climb being reserved for unique situations(it be hazardous). However insufficient tie down is hazardous either way with metal milling.

That terminology actually does make sense, when I think about a horse-drawn plow with a single share. Which unlike my father, I've never used. But I've watched them in action behind some huge Percherons.

Hobbyman2

STB wrote
Hobbyman2 wrote Very nice, how are you doing with the threads and chip out with that bit ? if it is excessive would a less aggressive bit make any difference ?
As for chipout All my trials have been with the workpiece at 90 to the bit. I think my next try will be with the workpiece canted so only the face of the bit is cutting. I do not understand less aggressive bit. Do you mean less flutes?

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I was thinking the bit looked coarse maybe for a larger thread , I am learning from your thread , was wondering if you were having chip out and how a cutter with a fine teeth would work, I have a thread box and taps for 1" diameter threads , however depending on the grain of the dowel chip out seem unavoidable , even when soaking the dowel on linseed oil .