Some Thread work

[auscab]

I have the threading tools I did my workbench with in 1996 .
Long story short is I haven't used them since 1996 because I had no need for more threads. And I chipped a tooth on the Tap in 1996 and it needed fixing . That was a complex thing . Weld back the missing tooth with some fancy hard welding rod on a hardened and tempered tool steel and risk it not working, maybe loose the tool. Or make a mess of it . Or grind the tool back to fresh meat and re form a tooth . Ugly repair but safe. I did the later a few weeks ago .

Just recently I added a steel handle to the tap . This tool was a tough one to get to go through the hole drilled for the threading to make the nut back in 96 . We all believe it was because of sharpening the wrong way by a previous owner. The teeth cut their way in and should leave enough room for the body to pass . This wasn't happening and the body binds in the hole . That's how I broke a tooth . Using the wrong part of the tool for leverage to get it through with me and another guy on a pipe for leverage.

So with the tooth repair I gave it a go on some 50mm Oak . It still binds . Nothing worse than trying to get a tap through and you cant get a good enough purchase on its end. Previous owner had re ground that as well . So the T handle with all that leverage was great. The T handle was added by me heating a small length of pipe and hammering it over the end of the tool quenching it to shrink it on and leaving it 8mm high to Mig weld it as well to the very end of the tool steel on the inside. I then joined another length on to that by tack welding and mounting it in a lathe and turning by hand to get it centered before a full weld . Then the Top short T piece was added . After that a 800 mm length of Gal pipe slides through to give a handle that comes off for storage.

I did the nut first in the Oak then got the Die sharp and did some Beech thread . Had some problems to sort with that and this first one will be re done or shortened. I was getting large chip out . Solved it by reducing the size a little , I had it to big, and using lube . Oiling the wood . Ill have a go on the tap with the oil next time . It makes a big difference.



Adding a handle to the tap .
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Its a work out getting it through that tough Oak . Even with 800mm of leverage. Chewed the end grain a bit . A good oil and wax next time should make a very noticeable improvement.

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My Jarrah bench thread done with the same tooling . I took it out for dimensions . The battered part of its thread is whats seen when using the vice . Its nice to see the thread when opening the vice but that part of the screw does not need to be threaded. From the shoulder on my bench the screw goes though 75 mm of vice face , then 80 mm of Bench timber before it engages with the nut . 150mm of wood from the shoulder could be kept plain . Something I must have considered when making the bench. I forget now though . What ever hits it is not going to stop the thing working unless it goes all the way through . I think Id still rather see thread when looking down at it for the first 150mm .
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I showed the best side of this first one for pictures. The block was left square just in case it didn't work out . Ill turn it later . Ill probably still get to use this one . I'm working on doing two threads for a clamp to the table big Moxon style twin screw vice.
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I sanded up the T piece and will paint I think . This stuff will need a special box at some stage .
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Rob

[hiroller]

That’s a big tap. I’m curious as to what might cause the binding.
Does it just need a larger diameter hole?

[auscab]

The drilled hole size could be larger but wouldn't do a thing to help.

The material being removed by the cutters are leaving a thread slightly too small for the rest of the thread to pass . The cutters cant be made larger without welding stuff on them . I don't want to try that. The rest of the thread could possibly be ground back a little but its as hard as glass. A file wont touch it . I dont really want to try that either .

The two pics on the right are the broken tooth before and after grinding . The one on the left is the final tooth . That to me looks fully formed and not over sharpened on the outside like the first one was before the break . So the thread dimensions that follow that are different some how .

[auscab]

It may be that the the thread dimension after the final fourth tooth is different some how or

The thread dimension that follows the last tooth is just exactly the same size, the friction builds as the tool goes further in and adds up . I measured it . It adds up to being 260 mm long in a 50mm thick piece of Oak . 260 mm of steel in tight contact with the wood . It polishes the inside thread of the wood with pressure .
Maybe they just come that way and its always been hard to get through ? Its working good now though . Takes some pushing but its good .

Rob

[hiroller]

Maybe it is intentionally tight to burnish the wood so the finished product works better!

[auscab]

Maybe it is intentionally tight to burnish the wood so the finished product works better!

It could be ? I took some more pics .
Its a little hard to see the burnished shiny bits without being able to move the piece in your hand with the light hitting it .
There in there though .
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I did a Blackwood screw today . Very nice . Its firmer timber than the Beech and came up better .

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And here's an instagram action video of the Die cutting one of the Beech threads . As well as the Wadkin lathe tool carriage at work and a few other pics . If you play the video you have to stop it to progress through the other pictures.

Here

Rob

[IanW]

Rob, one problem I see is that your "single tooth" tap has to cut the full thread profile right off. The force required to do this will be compressing the wood quite a bit, and you'll get 'spring-back' which is probably the source of the binding. Some linseed oil should help to get a cleaner cut. I find it eases my taps a huge amount, I can't turn my 2" tap on my own when dry (using a tommy-bar about 500mm long!), but can do it if I use a little linseed oil to ease the passage. My tap was made by a friend and we used metal taps as our model. It has four lots of 'cutters' which step up from nothing to full depth over several turns of thread, so it's cutting the full thread by a series of 'cuts'.

This is a 1 inch tap beside a factory-made bottoming tap: 1 inch.jpg

I'm always impressed by the cleanness of internal threads made by any of the taps I have, they invariably turn out well in any wood I've tried from pine to Spotted Gum. The "archaic' tap I described in AWR does a grand job, and you can easily adjust the cutter to get the threads as tight or loose as you want. It's easy to make & easy to use (but slow!).

I early-on tried a few threadboxes for making screws but found they were limited in the range of woods they'd handle, so when I first saw a router being used to make screws I was quick to try it and very pleased with the results. One advantage of cutting threads this way is I can adjust the cutter by the tiny fractions needed to get the threads running just right - not too tight & not too loose. I suppose you can do that with a threadbox, too, but I found sharpening & adjusting that cutter to be a very tricky business, so I would advise anyone who wants to have a go at wooden threads to think about making a router jig, particularly if you only want to make a couple of bench-screws. They are very simple to make, and though they do need bit of fussing to get set set correctly, once you've got it right you can churn out screws in no time, The router bit also causes less chipping, as long as it's adjusted properly, but I have found that a bit of chipping seems to make little difference to the smooth running or durability of the threads, so it's more of an aesthetic problem than a functional one...
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Cheers,

[auscab]

Rob, one problem I see is that your "single tooth" tap has to cut the full thread profile right off. The force required to do this will be compressing the wood quite a bit, and you'll get 'spring-back' which is probably the source of the binding. Some linseed oil should help to get a cleaner cut.

Nice taps you did Ian . How do you adjust the Tap to make a tight or loose thread ? Bend those side cutting bits in?
What steel were they made from?

The oil helps . Im using a mix of linseed and turps . Then rubbing a candle into that to get a bit of a thin paste .

Mine is 4 teeth not a single tooth .
The line of the thread as it goes around has been ground into three other lower stages from a full bite. So that full tooth you see only takes 1/4 of the bite . The three before it having already removed the other 3/4 of wood in stages. The 800 mm bar I turn with is good . I was first using it 400 mm out each side but once I get it going, shifting the pipe out so 800 mm is hanging out one side makes it even easier.

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Blackwood is nice timber to cut for the screw. I remember the Redgum I used on my bench screws being great too . Clean cutting and an impressive out come .
I'm wondering how Ironbark would go ? To Hard or very nice ?

Rob

[IanW]

Nice taps you did Ian . How do you adjust the Tap to make a tight or loose thread ? Bend those side cutting bits in?
What steel were they made from?

Rob, I think I confused you, the taps pictured aren't at all 'adjustable'. Like yours, they cut what they cut, the only way I've found of easing a nut made with these is to wait a while & run the tap through the nut from the opposite side. That picks up the fibres a little & eases the fit a fraction. They are turned from mild steel, or something near to it. I read somewhere that that's all you need and it seems to be fine, some of my taps have cut hundreds of feet of thread & show no appreciable signs of wear. The commercial (wood) taps I have are certainly not hardened, either.

The tap I was referring to is the 'mediaeval' one described in my AWR article of a few years ago (#92). It consists of a shaft turned to the minor diameter of the screw, a hole is cut through the tip for the cutter (& a wedge to hold it in place), and a helix cut on the shaft at the desired pitch of the thread: Tap made.jpg

You make up a jig which is slotted to take a piece of saw-plate or something similar which engages the helix on the tap, and this is clamped to the piece in which the thread is to be tapped. As you turn the tap, the cutter is driven through the hole to be tapped at the correct pitch:
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After each pass, you back out, advance the cutter a bit, and run it through again. This is the cutter emerging on the 2nd or 3rd pass: Tapping.jpg

Sounds cumbersome, but it only takes 5 or 6 passes & you only only likely to want to tap one or two nuts at a time, so it's not really much hassle. The thread you get from this primitive setup is surprisingly clean: Nut.jpg

....Mine is 4 teeth not a single tooth....

My mistake - I thought it was just one. Yes, stepping up in 4 stages makes much more sense. My taps 'step up' too. There are two grooves, and the thread goes from zero to full over about 3 turns, so that's roughly 6 steps.

....Blackwood is nice timber to cut for the screw. I remember the Redgum I used on my bench screws being great too . Clean cutting and an impressive out come .
I'm wondering how Ironbark would go ? To Hard or very nice ? .....

I can see Blackwood being good for threadbox cutting & I've threaded Red gum with the router cutter & it responded well. I can't imagine Ironbark being too good though, unless the IB down your way is very different to the stuff round here, which is highly siliceous. I'd expect the cutter to dull quickly & you'de get a lot of chipping? My solid carbide cutter would take it in its stride though - I've threaded Bull Oak & Gidgee with no problems...

Cheers,