Replies

1. 
   UncleDunc | Dec 09, 2003 09:45am | #1

   >> What kind of pitch (TPI) does one use on a 2" diameter screw?

   3 TPI sticks in my mind from somewhere.

1. 
   SailingRandy | Dec 09, 2003 06:36pm | #2

   Hi Dunc,

   Roy Underhill has a book out called "The Woodwright's Workbook" University of north Carolina Press, 1986. The third chapter is "Screwboxes and Taps" which deals with very thing. Although I have done it, it looks do-able.

   Good luck!

2. 
   user-301582 | Dec 09, 2003 07:44pm | #4

   Thanks for the suggestions, everyone. I do have Scott Landis's Workbench book (beautiful BTW), and have scoured every line of text.  Unfortunately it makes no mention of the pitch for a 2" screw.  The only reference I could find was that Frank Klause said he would have prefered the wooden screw's action (faster).  The largest metal screw I have is 1-1/4" @ 4 TPI.  Actually, that just gave me a thought about a really easy way to cut the screw.  The tail vice I have for the new bench could be fastened to the rough wood screw blank and used as a feed screw through a block with a 2" hole.  The block would have the router attached to the top like the Beall jig. 

   I still have the issue of cutting the internal threads in the nut block though.  I looked into buying a Grade 8 bolt and filing it into a tap, but the coarsest one I can get is 4.5 TPI... but they are almost as expensive as just buying the metal hardware in the first place.  ;-)

   I really want to make the screw, if for no other reason that the challenge of it.  So my plan is to try it unless it ends up costing something crazy.  If I don't like the action of it for my shoulder vice I will either put it on the shelf or use it in a front vice elsewhere so that the screw isn't the aligning object.

   Thanks to everyone For their help.

   Kirk

   NB.-I am looking for Roy Underhill's 'Woodwright's Workbook' now too.

1. 
   ETG | Dec 09, 2003 07:54pm | #5

   Back in the early days of FWW - when it was trying to live up to its goal of being the Scientific American for woodworking - there were several in-depth articles on wood threading.  Issue 5 sticks in my mind but you would be wise to do a search of the FWW archives - those very early issues discussed all the details you are interested in.  Unfortunately FWW's audience today is different so those kind of articles are found only in the early archives (prior to issue 100).

1. 
   ETG | Dec 09, 2003 10:38pm | #8

   FWW Issue 6 has a 6 page article by Richard Starr on making your own screwbox and tap - excellent article that covers all the issues you raise.  The FWW issues is no longer available but I would be happy to copy and fax it to you if you need it.

1. 
   OneStepatatime | Feb 02, 2011 09:53pm | #18

   Copy of Richard Starr's article
   I'm pretty new to woodworking and I really like the idea of hand tools. I kinda see it as a logic puzzle imagining how a woodworker 200 years ago would have done something. I am having the hardest time finding the issue 6 article about making your own screwbox and tap. Any chance you could help me out? Even the Internet seems to be pretty useless for this! Thanks!

2. 
   UncleDunc | Dec 09, 2003 08:33pm | #7

   You could make the nut by boring the hole through the blank, splitting it, and carving the threads with chisels, rifflers, Dremel tool, etc. Mark the high spots with chalk or something on the screw, shave off the marked spots, and repeat till it fits. Then glue it back together. Slow and boring, but it'll work if you can't come up with something more elegant.

3. 
   eddiefromAustralia | Dec 09, 2003 10:41pm | #9

   Kirk,

   was 5 tpi, if I recall correctly.

   But, 6tpi is a more commonly available size - they make 1.5" threading dies and taps in this size/pitch.

   eddie

4. 
   JohnWW | Dec 09, 2003 10:43pm | #10

   Kirk,

   On page 123 of The Workbench Book there's a plan for making a jig for cutting internal wood threads, the device is simple and would seem to do the job.  It seems to be exactly what you are looking for.

   On page 127 there's a picture of a wooden vise screw that's identified as being two inches in diameter.  Using a caliper to take the dimensions off the photo, the threading is 4 TPI.

   We have a shoulder vise on a bench in our shop and it's jaw does drop a bit, it's the nature of the design.  The drop doesn't seem to affect its use however.

   You wouldn't need to use a grade 8 bolt for a tap for wood, a mild steel bolt would do the job well enough for cutting a few nuts.  You might try stopping by a heavy equipment repair shop and ask if they've got a bolt of that size in their scrap pile.

   John W.

2. 
   JohnWW | Dec 09, 2003 07:01pm | #3

   Kirk,

   If you don't like the fit you get with a metal screw, you won't like the fit of a wood one.  The clearances needed to make a wood screw run smoothly are even looser than an average quality metal screw. 

   In a good vise design the threaded rod is only responsible for generating the clamping pressure, the alignment is supplied by some other components.

   By the way, I love wooden screws and I don't want to discourage you, but I didn't want you to start the project without understanding their limitations.  A classic vise well suited to a wooden thread is the leg vise. 

   If you don't have it, take a look at the "Workbench Book" by Scott Landis, it has a lot of information on vises and a section on making wooden threads for vises.  It's a Taunton Press book, I think you can order it on another part of this web site.

   John W.

   
   

   ---

   Edited 12/9/2003 11:16:34 AM ET by JohnW

3. 
   Steinmetz | Dec 09, 2003 08:15pm | #6

   Hillman, Archemedes made his first wooden screws just like Leonardo Di Vinci He wrapped a flat tape and a thin wire together (Side x side)  around the round 'Billet' After securing the tightly wound tape, they un wound the wire. This left a narrow groove in which to carefully incise a fine line with a knife .The resultant (Spiral,) was enlarged using a triangular rasp/file. With continual filing, the screw thread was made. The nut was made by inserting a wood 'Tap' which held two adjustable 60 degree hand filed cutters wedged in place.

   I don't remember how(I was just a lad) they arrived at the matching pitch, however I think they installed one cutter, then juxtaposed it to the screw and fitted the second one. Stein. 

4. 
   jako17 | Dec 10, 2003 02:50am | #11

   As you seem such a glutton for punishment .Get some steel and make a pair of chasers .One inside ,one outside and hand chase them on a lathe.If you have a slow enough speed it is relatively simple.Make the nut out of lignum vitae as it is self lubricating

1. 
   user-301582 | Dec 10, 2003 11:32am | #12

   What species would be ideal for the screw?  Also, I have heard a few times before that the old timers would wet the blank with either wather or oil prior to cutting the threads which prevented chipping.  Any thoughts?

   I think I have devised a way to cut a nice 3 TPI thread on the screw, and I couple use the same feed system on the nut.  The only problem is that one would need to make a cutter cutter for a rotary tool that operates at 90 degrees to a regular bit as used on the Beall system.  In this case I wouldn't be likely to use a router as the tool since this cutter would be long and prone to whipping and vibration.  Sort of a more 'modern' version of what they show on page 123 of 'Workbench Book'.  I would use my existing screw as the advance mechanism and the rotary tool instead of the beam and cutter.  This might actually work...

   Kirk

1. 
   JohnWW | Dec 10, 2003 07:54pm | #13

   Kirk,

   I'd be careful going to too coarse of a thread for at least three reasons:

   1. The coarser the thread the less "leverage" you get, you have to pull harder on the handle to get the same amount of pressure on the workpiece.

   4. At some point the thread becomes so coarse that it is no longer self locking, the screw won't hold its position after you let go of the handle, it will back off especially under vibration.

   3. The coarser the thread, the less contact area there is inside of the nut, wood threads are inherently weak, you need to spread the load as much as possible to keep the threads from shearing off.

   The choice of thread is primarily related to the diameter of the screw and 4 TPI looks about right for a 2 inch diameter screw, I think that 3 TPI will create problems at that diameter.

   John W.

1. 
   user-301582 | Dec 10, 2003 10:05pm | #14

   I was up way too late last night doing more research on this pitch issue.  It looks like the Shaker bench in the 'Workbench Book' was 3.5 TPI (assuming the drawing is correct).  My current bench incorporates screws which are both 4 TPI and I find that a little slow.  The tail vice hardware for the new bench is 3 TPI.  Since I plan on using the metal screw as part of the jig for cutting the threads I will try 3 TPI for a test.  I might also temporarily mount the new tail vice to see what I think of it's action compared with my existing one.  If there are problems associated with 3 TPI being too coarse/weak/fast I will likely follow the Shaker's lead and try 3.5.  It sounds like I will have a number of test screws in my shop by the time I finally have a shoulder vice on my workbench.  :-)

   Kirk

1. 
   adrienne4468 | Dec 11, 2003 10:09pm | #16

   The only reason for using a coarse thread on a screw is the material that it is made out of. A coarse thread is deeper so there is more material to support each individual thread when compressed. A faster thread can be a double start, or four start thread which is a thread that is double the pitch (8 rather than 4 tpi)which is cut at the same lead as the 4 tpi only there are two of them started 180 deg. apart, or in the case of a four start thread 90 deg apart. If your material is solid and not prone to chipping you can use a finer pitch which is easier to thread but will take more turns to travel the same distance as the coarser thread. What other people have done is not as important as material choice and preference. A finer thread produces more pounds per square in with less effort.

   TonyWe already have enough youth, how about a fountain of smarts.

2. 
   user-301582 | Dec 12, 2003 08:21am | #17

   Tony,

   My decision to go with the coarser pitch actually had everything to do with what I prefer.  In this case I don't believe I will be short on clamping force, but I do find the 4 TPI on my current vices a tad slow.  Since there is no quick release on my wooden screw design I am willing to give up what's in my humble opinion an acceptable loss in power.  The reference to what is in the past is a simple step in logic.  Well tried and tested principles are found in a piece of hardware that not only worked but did it for many decades, sometimes hundreds of years.  The example that comes to mind immediately is that huge Shaker bench in the 'Workbench Book'.  I may not know the PSI that screw can generate before failure but I can tell you that they wouldn't have let it be if it wasn't practical and functional. 

   As to your point about using a multi-lead thread, it's simply not something I had concidered until you mentioned it.  One query though, doesn't a screw with more leads actually work faster than one with fewer?  IE, should an 8 TPI double-lead travel twice as far as an 8 TPI single-lead with the same number ov turns?  Not having any experience this isn't a criticism at all, I honestly don't know but  my 'common sense' tells me it should be.  Mind you, it is late and I only just thought about it long enough to write this...  ;-)

   Wait a minute.  I just re-read your post, Tony.  I think I am making your point for you.  Sorry about the confusion.

   Kirk

   Edited 12/12/2003 12:23:46 AM ET by hillman88

5. 
   10fingers | Dec 11, 2003 09:38pm | #15

   I read an article in FWW the other day on wooden screws.  The type of thread is called a "Buttress" thread I believe,  I can't remember which issue it was in and I had to put my magazines back in the garage to keep peace & quiet in the house.  If I fing the article this weekend I will post what issue it is in.

   Chuck