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  1. #1
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    Default Wooden Threads For A Twin Screw Vise

    Hi All,

    I posted a thread (pun intended) earlier about what thread profile to use for wooden threads.
    I'm reposting the pictures of the tap, just to keep it all together..
    (The previous post was in the metal work section)

    This is the next stage of that project.

    I finally got the new tap made, it's 2" 3.4 tpi 90 degree profile.

    The only critical dimension is the root diameter should be made to suit whatever hole size you can easily drill, in my case that was an 1 3/4" forstner bit. The cutting flutes are offset slightly when milled so as to create a slight angle to the cutting edge

    None of the other dimensions are not especially critical. The bar is a 3/4" drive and I welded a 1" 3/4 square drive socket on the top.

    It takes three teams of horses and extension handles to cut a thread in dry english oak.. but it works...


    The next stage was to cut the male threads, I started making a screw box, but I never even got it finished, I went for a router with a chamfering bit instead, mounted on the lathe cross-slide.. (an idea I borrowed from George Wilson over on Sawmill Creek. thanks George! )

    This is the general set up.. for those who are squeamish about killing electrons look away now...


    The router is a Makita laminate trimmer with a chamfering bit.


    After cutting the thread I sanded off the peaks of the thread to round them off a bit.
    The finished diameter, I went for a fairly loose fit, to allow for moisture expansion.

    Ok, the squeamish ones can look again...

    And finally the threads and shoulders cut, it's ready for a few final finishing touches.
    Then I can put the vise together..



    More to come later, when I get the jaws made.

    Regards
    Ray

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  3. #2
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    Ray, that is just beautiful work!

    Totally makes my effort using the Carba-tec Chinese set with the Moxon vise look pitiful.

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, many handtool reviews, and my trials and tribulations with furniture builds.

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    yep ...looking good

    your making two tight...one for you and one for me....right

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    That tap looks splendid, Ray.

    I did warn you it takes a husky bloke or two to drive a 2" tap through hard wood! But to be fair, I don't think you need to choose super hard wood for nuts, because the grain orientation ensures the threads are much stronger than the screw threads. I have even used crapiata for nuts (clamp jaws), and they worked fine.

    I think I'll stick with my simple router threading jig for now. Your setup is very elegant & I can see it has some advantages, but the carriage on my little lathe would barely hold a Dremel, let alone any serious machine like that!

    The amount of 'slop' to build into the threads is a matter of experience & fine judgement. I used to make screws only when I thought the wood was at its minimum MC, but over the years, I've learnt to adjust to where I think the wood is at, & just make them a bit tighter if the weather is wet. Mostly I get it about right, & occasionally I cock it up badly, but since I'm usually using scraps that aren't good for much else, it doesn't matter if a few have to go in the kindling box. The screw on my shoulder vise was one of the first really biggies I made (> 20 years ago, now) & more by good luck than good mangement I got it just right. It usually runs very nicely, and about the first time I have noticed it being a bit tight was mid January this year, but we had had an exceptionally humid time of it up here, as you may be aware...

    A note of warning to would-be wood threaders - don't try forcing the scew if it is too tight, as it is likely to lock-up, & you'll strip the screw threads trying to back it out. Similarly, make sure you oil & wax the threads before use, especially for handscrews - one drop of spilled glue in a raw thread & you have a joint that makes a mortise & tenon look wimpy! (DAMHIK )

    You've got me fired up to get my 1 1/2" 4 tpi tap made - must get onto it soon.

    Cheers,
    IW

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    Quote Originally Posted by RayG View Post
    Hi All,

    I posted a thread (pun intended) earlier about what thread profile to use for wooden threads.
    I'm reposting the pictures of the tap, just to keep it all together..
    (The previous post was in the metal work section)

    This is the next stage of that project.

    I finally got the new tap made, it's 2" 3.4 tpi 90 degree profile.

    The only critical dimension is the root diameter should be made to suit whatever hole size you can easily drill, in my case that was an 1 3/4" forstner bit. The cutting flutes are offset slightly when milled so as to create a slight angle to the cutting edge

    None of the other dimensions are not especially critical. The bar is a 3/4" drive and I welded a 1" 3/4 square drive socket on the top.

    It takes three teams of horses and extension handles to cut a thread in dry english oak.. but it works... Thanks Ray very encouraging NOT


    The next stage was to cut the male threads, I started making a screw box, but I never even got it finished, I went for a router with a chamfering bit instead, mounted on the lathe cross-slide.. (an idea I borrowed from George Wilson over on Sawmill Creek. thanks George! )

    This is the general set up.. for those who are squeamish about killing electrons look away now...


    The router is a Makita laminate trimmer with a chamfering bit.


    After cutting the thread I sanded off the peaks of the thread to round them off a bit.
    The finished diameter, I went for a fairly loose fit, to allow for moisture expansion.

    Ok, the squeamish ones can look again...

    And finally the threads and shoulders cut, it's ready for a few final finishing touches.
    Then I can put the vise together..



    More to come later, when I get the jaws made.

    Regards
    Ray

    There in lies the hint I'll soak it in wine ...............or should that be I'll soak me in wine

    I like the router set up using the lathe. One of the OT members has made a specific router jig for cutting thread. There are a number of plans ideas available via google also. Simple to make and adapt to different threads.
    Being down is the low side of being up it shows the road ahead is a steep climb but at the top the view is always special. Then we just coast along till we hit the trough again. Sometimes when coasting we pick up speed and the steep climbs pass by like your on a plain.
    http://woolnwood.blogspot.com

  8. #7
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    Hi All,

    Thanks for the comments,

    There in lies the hint I'll soak it in wine ...............or should that be I'll soak me in wine
    Now there's a plan I can implement...

    My son, cut a few threads in 2" thick Kiln Dried mountain ash today, and was struggling, until in desperation (or exhaustion) he put some of his finishing mix on it. (Turps BLO and beeswax, I think, he mixes it up himself to some secret formula .. )

    It was night and day, much easier to turn and I think cleaner cut. Not sure which one of the secret ingredients did the trick.

    I suspect it was the turps, but the difference between just candle wax and the secret mix was striking.

    Regards
    Ray

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    Quote Originally Posted by IanW View Post
    That tap looks splendid, Ray.

    The amount of 'slop' to build into the threads is a matter of experience & fine judgement. I used to make screws only when I thought the wood was at its minimum MC, but over the years, I've learnt to adjust to where I think the wood is at, & just make them a bit tighter if the weather is wet. Mostly I get it about right, & occasionally I cock it up badly, but since I'm usually using scraps that aren't good for much else, it doesn't matter if a few have to go in the kindling box. The screw on my shoulder vise was one of the first really biggies I made (> 20 years ago, now) & more by good luck than good mangement I got it just right. It usually runs very nicely, and about the first time I have noticed it being a bit tight was mid January this year, but we had had an exceptionally humid time of it up here, as you may be aware...

    Cheers,
    Hi Ian,
    I took it down to 1mm less than the OD of the tap, so I have about 0.5mm "slop" when I clamp the screw in the vise and spin the nut it spins up and down freely, it might be too tight if anything, but if it starts to get sticky during the more humid months, I will put it back on the lathe and take off a bit more..

    What did you use as a cutting lubricant? ... refer to my previous post, for secret ingredients...

    Regards
    Ray

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    Quote Originally Posted by RayG View Post
    ........I took it down to 1mm less than the OD of the tap, so I have about 0.5mm "slop" when I clamp the screw in the vise and spin the nut it spins up and down freely, it might be too tight if anything, but if it starts to get sticky during the more humid months, I will put it back on the lathe and take off a bit more..
    Ray - The beauty of your system is you can easily make a second pass if necessary. With my "Beall" type jig, I have to be very careful trying to recut a thread. I tried re-cutting a couple of screws early in my career & made a right mess. The reason is that if you try a second pass, the pitch of the thread will alter slightly, and after a number of turns, the bit will be cutting out the existing thread land. I discovered the solution after making a few messes, & that is to screw the under-done screw all the way into the nut, THEN start the router & back it out. The router bit doesn't care which direction it's cutting in, & the pitch will remain accurate.

    My method is: turn the blank to a loose fit in a 2" hole, so it would be somewhere between .5 & 1 mm less than the nominal major diameter. Then I judge the "fit" of the screw by how easily it feeds into the 'take-up' nut - you should be able to screw it in easily with finger pressure. If it's too tight, I know I need to lower the router bit a tad. So with a slightly undersized blank, and a free-running thread, all is well. If I think the wood is at a high MC, I'll go for a tighter feel, whereas if it's very dry, a looser fit is better. Experience is my guide, but it isn't foolproof. I can't see how you could gaurantee perfect wood threads, unless you were meticulous with M.C. and did some very fancy arithmetic!

    Quote Originally Posted by RayG View Post
    What did you use as a cutting lubricant? ... refer to my previous post, for secret ingredients...
    I don't use anything. Have tried various 'lubricants' (waxes) but found they only clag things up & prevent free chip expulsion. I read somewhere that taps work better with negative rake, and so that's what mine has on the 'cutters'. I guess I should try your magic mix & see if it makes as big a difference for me. I certainly struggle when threading harder woods (in fact I cannot turn my 2" tap through really hard woods without help). Woods really vary a lot, though, & some cut much more easily, even though they seem equally hard. For instance, Merbau taps really well, and takes much less effort than Vic. Ash, or at least it has for the few bits of each I've used.

    That's the attraction of wood threading - there are so many variables, it's an endless learning experience!
    Have fun...
    Cheers,
    IW

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    Hi Ray. Great work. I have a 1 1/2" threader kit I purchased 6 months ago. Been too busy with backsaws to play with it.

    Stewie.

    Beall's Wood Tapping & Threading Kits - Lee Valley Tools

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    Stewie - the best part of the Beall kit is the carbide bit - it hasn't changed price in 25 years! Mine has cut miles of thread with just an occasional polish-up on a fine diamond file. But I was never tempted to go for their full kit. I managed to pick up taps here & there, and the threading jig is easy enough to make from a block of spare wood.

    Apart from the steep price, I never liked the look of their taps. They are ok in the smaller sizes (I've used the 1/2" size) but they jump up very quickly from root diameter to full thread, so I would imagine the bigger ones are hard to turn when fully engaged, especially when all you have to work with is that little squared-off section at the top of the stem. I reckon you will need a very decent tap wrench to drive the 1 1/2" size!

    Cheers,
    IW

  13. #12
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    Hi Stewie, Ian

    I watched the Beal video, looks like a good system. The only minor point is that he uses a 60 degree profile, rather than 90 degree profile. But I don't think there's all that much difference in reality.

    Here's the latest stage of the project.. I posted in the Metalwork forum, but I'll post here as well, for completeness.



    It's a router mount to suit the lathe tool post, so I get full adjustability and easy of removal and setup. (It's an improvement on the clamps and blocks.. )


    Regards
    Ray

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    Ray

    Do you reckon that you could use a Dremel with a chamfer bit instead of a trimmer?

    If so, some day I might give it a go!
    Cheers

    Jeremy
    If it were done when 'tis done, then 'twere well it were done quickly

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    Hi Jeremy,

    I think a dremel would work just fine, the only thing would be depth of cut, you might need to take a few more passes.

    Regards
    Ray

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    Quote Originally Posted by jmk89 View Post
    Ray

    Do you reckon that you could use a Dremel with a chamfer bit instead of a trimmer?

    If so, some day I might give it a go!
    Jeremy, I'm not familiar with Dremels, & I don't know how much power they can muster, but it doesn't take much to cut a thread on a smaller screw. However, Ray's suggestion to cut the thread in a couple of passes won't work with a Beall type of setup. You could certainly do that with his lathe setup, but with the Beall system, the full depth of thread has to be cut immediately, otherwise it can't screw into the take-up nut.

    Ray - I actually prefer the 60* profile over 90*, because I find the 90 harder to get set up for the right fit in the nut. I always seemed to end up with either too tight a fit or too loose, neither of which is good. But that probably isn't an issue for you, because you can sneak up on a near-perfect thread with the system you have put together. Anyway, I got rid of my 90* tap & have all 60* taps, now, so it's not an issue, unless one opf my old bar clamp screws breaks - then I might have to put in an order.....

    Cheers,
    IW

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