# Wood screw threads



## oughtsix (Nov 3, 2014)

Am thinking about making butt plate screws for an old rifle.   Do you make wood screws the same way as metal screws? The one I'm looking at is ~ 6 tpi,  but there is a lot of root between the teeth.  Is there some trick  or is it just basic thread cutting?

Thanks, 

-06


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## Bill Gruby (Nov 3, 2014)

The 6 TPI is the easy part. It's cutting them at the taper that throws the monkey wrench in the gears, I hope someone comes forward on this one as I think everyone would like to know ho it's done.

 "Billy G"


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## OldMachinist (Nov 3, 2014)

Yes you just cut the threads with a tool with a wide root. The threads on the main body are the easy part, getting the threads to come out right on the gimlet point is the hard part. 6 TPI seem very coarse, how big are these screws?


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## OldMachinist (Nov 3, 2014)

I got distracted looking for a image of a gimlet point while I was writing my response and see Bill responded with almost the same answer.

Commercial screws are either cut on a tracer type machine or roll threaded. 

Thomas J Sloan patented a machine in the mid 1800's to form and thread wood screws.


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## oughtsix (Nov 3, 2014)

I had just grabbed an old screw out that measured 6 tpi,   an actual screw I hope to copy is about 12.  Although I suppose the actual  tpi may not be as important as the height of the thread is big enough to bite the wood.  I was hoping someone would have a home shop answer to the  gimlet point and taper.  
Looks like playtime in the shop.


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## dave2176 (Nov 3, 2014)

Make the point using a file or your compound. Grind a cutter with the right profile. Mount the cutter upside down in the tool holder. Lathe in reverse, cutter on the front side. Start cutting left to right. When you get to the start of the taper turn the compound in to follow the taper. A little tough but doable. Follow up with a file to clean up the tip.
 Dave


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## 12bolts (Nov 4, 2014)

I have seen a video of someone making wood screws but for the life of me I cant find it.
In the meantime, if you turned a taper on your stock that matched the TPI you should end up with a tapered thread form that had equally spaced, but also sharp vee crests for the length of the screw. Not sure if the taper would be too fast or slow for "technically correct" woodscrews.

Cheers Phil


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## oughtsix (Nov 5, 2014)

Nothing good to report yet,  first two I turned, the taper diameter was too small,  and as the threads were cutting  the screw shaft bent.  You would think I wouldn't do it twice, but I tend to be a slow learner.  Back to the drawing  board.


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## benmychree (Nov 5, 2014)

I have seen gun screws that do not have a gimlet point; if the pilot hole for the screw is drilled to the root diameter of the screw, there is no need for the gimlet point.  In screwing into hard wood, such as is used in gunstocks, the pilot hole is necessary to avoid splitting.  For a grist mill restoration, we needed big long lag screws; they were screwed into big timbers, with pilot holes drilled; I cut the threads with a form tool with a wide nose and steep included angle, and it worked fine.  I suspect that wood screws for gun work are, or were,  mostly cut with an automatic die head, and I have seen a set of chasers for the purpose.


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## Andre (Nov 5, 2014)

I made a wood screw on my 109 for the watchmakers lathe project, forget the pitch but it was a standard straight thread, worked fine. Just with straight threads it might be a good idea to drill a pilot hole first.


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## silence dogood (Nov 6, 2014)

I'm not sure if this will work in your  case,  however, there was an article in Fine Woodworking(Sept/Oct 1997) on threading wood for machine screws.  You just drill and tap the wood just like metal.   Here is a chart.
Machine screw sizes         Pilot hole sizes        Thread hole size
3/8-16                            3/8"                       5/16"
5/16-18                          5/16"                     1/4"
1/4-20                            1/4"                       13/64"
#10-24                           13/64"                   9/64"
Mark


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## Bill Gruby (Nov 6, 2014)

silence dogood said:


> I'm not sure if this will work in your  case,  however, there was an article in Fine Woodworking(Sept/Oct 1997) on threading wood for machine screws.  You just drill and tap the wood just like metal.   Here is a chart.
> Machine screw sizes         Pilot hole sizes        Thread hole size
> 3/8-16                            3/8"                       5/16"
> 5/16-18                          5/16"                     1/4"
> ...



 I have a question on the drill sizes. First, the pilot hole must be smaller that the screw size thread for it to have the threads hold. Question, "How does a 3/8 thread hold in a 3/8 pilot hole." The 5/16 is correct though. Maybe I'm reading it wrong?

 "Billy G"


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## OldMachinist (Nov 6, 2014)

Bill,
Looking at the sizes for using machine screw threads in wood I assume the pilot hole is in a different piece to act as a drill guide.


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## middle.road (Nov 6, 2014)

I for one enjoy tapping machine threads into hardwood, best to use a polished/ground tap though.
I've made fixtures and repaired items with threads up to 1". If it's a jig or fixture I use mineral oil when tapping, paste wax on finished pieces.
I've even tried threading hickory and maple dowel rods for a clamp, still have to perfect this operation... :biggrin:

_Dan


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## Tony Wells (Nov 6, 2014)

Now see? Who said metal and woodworking don't belong on the same forum? :roflmao:


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## Bill Gruby (Nov 6, 2014)

I agree, but a pilot hole in wood must be smaller than the thread size for it to hold.

 "Billy G"


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## Eddyde (Nov 6, 2014)

oughtsix said:


> Am thinking about making butt plate screws for an old rifle.   Do you make wood screws the same way as metal screws? The one I'm looking at is ~ 6 tpi,  but there is a lot of root between the teeth.  Is there some trick  or is it just basic thread cutting?
> 
> Thanks,
> 
> -06



 You could also use a threaded insert in the wood and use a machine screw to attach the butt plate.


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## mzayd3 (Nov 6, 2014)

I think somebody confused pilot hole and clearance hole?


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## silence dogood (Nov 6, 2014)

LOL,  a couple of you of caught the mistake of the pilot hole and the clearance hole. The article in Fine Woodworking had it written as pilot hole instead of clearance hole.   The writer of the article, editors of Fine Woodworking, and me should had caught that error.  Oh well.  things happen. and sadly I know better.   I'll try to do better next time.
Mark


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## ronboley (Nov 6, 2014)

Maybe this will help....the most successful (hobby) wood threading device is the Beal Wood Threading system...it uses a 60 degree V bit in a router with a plastic jig to cut threads in round wood dowels and comes with matching taps...the picture is of two of the taps with a scale so you can see the threads they would make...

The resulting threads seem to be deeper and wider than "standard" machine threads in metal....which would make sense as the strength of the holding power of the thread is the shear thru the root of the thread...

Good luck!  and let us know your results....


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## Bill Gruby (Nov 6, 2014)

silence dogood said:


> LOL,  a couple of you of caught the mistake of the pilot hole and the clearance hole. The article in Fine Woodworking had it written as pilot hole instead of clearance hole.   The writer of the article, editors of Fine Woodworking, and me should had caught that error.  Oh well.  things happen. and sadly I know better.   I'll try to do better next time.
> Mark



 Thank you, I thought I missed something. Just the opposite, I caught something.  :lmao:

 "Billy G"


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## mzayd3 (Nov 6, 2014)

ronboley said:


> Maybe this will help....the most successful (hobby) wood threading device is the Beal Wood Threading system...it uses a 60 degree V bit in a router with a plastic jig to cut threads in round wood dowels and comes with matching taps...the picture is of two of the taps with a scale so you can see the threads they would make...
> 
> The resulting threads seem to be deeper and wider than "standard" machine threads in metal....which would make sense as the strength of the holding power of the thread is the shear thru the root of the thread...
> 
> Good luck!  and let us know your results....




Does Beal make taps other than 8 series threads?  I have a few of theirs, but all are 8 series.  My Oliver wood lathe is a real peculiar size- 1-1/8"-8.  That is actually what lead me down the road of machining.  Try finding any accessories with that thread size...I ended up making my own.


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## middle.road (Nov 6, 2014)

Tony Wells said:


> Now see? Who said metal and woodworking don't belong on the same forum? :roflmao:



That is so true. Anyone here remember the Pattern Shops in the old factories that made the patterns that created the pieces that were destined to be machined?
I had the privilege to meet two of the Makers just before the Pattern Shop was closed up and all the patterns discarded.
Those patterns showed magnificent woodworking craftsmanship. And the wood - pheeeeeeew.
So the two 'hobbies' have really been together a very long time...

_Dan


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## oldgoaly (Nov 6, 2014)

I've been working at metal spinning and watching Terry Tynan's  dvds he threads his wooden spin forms to directly go on the lathe spindle. I had never threaded wood before with a standard tap. Well it works, work even better if you wax your tap!  Fine grain wood is the key, drill size is the same as metal.  I would practice on a scrap pc 1st then go for it! A couple of pic to prove it. wood is maple I believe, from a pc of 50's or 60's furniture under side of a chair?  Type of wax? toilet wax ring.


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## benmychree (Nov 7, 2014)

mzayd3 said:


> Does Beal make taps other than 8 series threads?  I have a few of theirs, but all are 8 series.  My Oliver wood lathe is a real peculiar size- 1-1/8"-8.  That is actually what lead me down the road of machining.  Try finding any accessories with that thread size...I ended up making my own.



Special taps are not difficult to find, I got one for my Oliver patternmaker's lathe from KBC, I think.  The catalog has a section for special taps.


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## jgedde (Nov 7, 2014)

oughtsix said:


> Am thinking about making butt plate screws for an old rifle.   Do you make wood screws the same way as metal screws? The one I'm looking at is ~ 6 tpi,  but there is a lot of root between the teeth.  Is there some trick  or is it just basic thread cutting?
> 
> Thanks,
> 
> -06



The same way you do machine threads except:
1) The thread profile is different.  You'll need to grind a cutter to get what you want.
2) Wood screws are tapered.

I've made tapered threads on my lathe before.  I thread the item between centers with the tail stock offset to generate the required taper.  You won't get a gimlet point this way, but I don't think you need one since your stock holes already exist.  Or if they don't, you can just predrill to the root diameter say midway up the thread.

John


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