Woodscrew Thread Cutting

[No1_sonuk]

I need to make a part similar to the attached photo.  I've not been able to find anything about how to cut a woodscrew-type thread. 

The part I want to make needs a longer unthreaded part than the pictured part, and the cross-hole tapped.  Both of those are easy - it's the thread I need help with.  It needs to go into the end of a 1" wood dowel.

Has anyone here done this, or got any ideas?
Thanks.

[Jasonb]

Biggest problem is that you will need something like a 2tpi pitch, not many lathes with that unless you can play about with gear ratios but it can put strain on the lead screw.

I would use a "V" pointed tool with a small flat on the end, cut the thread then move the cross slide along say 0.010" and cut again, keep repeating this until you have the shape you want. Trying to do it in one go with the correct form tool would again put a lot of load on teh lathe.

Jason

[andyf]

Biggest problem is that you will need something like a 2tpi pitch, not many lathes with that unless you can play about with gear ratios but it can put strain on the lead screw.

I would use a "V" pointed tool with a small flat on the end, cut the thread then move the cross slide along say 0.010" and cut again, keep repeating this until you have the shape you want. Trying to do it in one go with the correct form tool would again put a lot of load on teh lathe.

Jason

Yes, unless you have a huge lathe, you would need a ratio to the order of 1:4 from spindle to leadscrew. If it's a one-off, it might cause less strain to crank the leadscrew by hand, changing the ratio to 1:4 from leadscrew to spindle.
 
Given that it's going into the endgrain of a dowel, it will be a weak fixing into the wood. A fairly generous pilot hole will be needed to stop the dowel splitting, unless you put a ferrule round it. Given that the metal to wood joint may not be very strong anyway, what about making the head as a separate item, and brazing it to the end of an ordinary woodscrew?

Andy

[Bluechip]

No1_S etc.

Don't know what it's for but, if you can make the end bit with a M6 machine screw thread and avoid the woodscrew bit altogether, then ..

poke one of these in the end of the dowel.

http://www.screwfix.com/search.do;jsessionid=LFQENLXT4AQ44CSTHZOCFFQ?_dyncharset=UTF-8&fh_search=insert+nuts

I've used lots of them. I screw them in with some epoxy on the 'self-tappy' part.

IIRC the 'tapping drill' is 7.5mm and a 8mm af key drives 'em in .. not sure now, couple of years since I used them.

They are pretty secure, but, as has been said, the end grain itself is not very robust.

If you trawl about for 'Insert Nuts' ( wait for it   ) you may find other sizes more suitable for your needs. I've only used the ones depicted.

Dave BC

Edit.. it's the top picture, not the Nyloc nuts bit  

[John Stevenson]

You want what the trade call wood to metal screws.

http://www.doorfurnituredirect.co.uk/scpro/bernards/productssingle.asp?prodid=6129

Something along these lines and then screw the part you need special onto the 6mm or 8mm metric thread.

John s.

[No1_sonuk]

@ JasonB:
My lathe is a Chester DB7VS.  That's a "fiddle with change gears" type of machine, rather than selectable gearbox, so it's more likely I can make up a suitable ratio.

@andyf:
The objective is to insert this part into a hole in a block, then screw another dowel into the cross hole (using something like John S suggests) through the block, forming a right angle.  Robustness isn't an issue, it's a visual prop that's not going to be strained.
The dowel may be resin coated to help get a glossy finish.  That'd also help split resistance.

It is only a 1-off, so learning/acquiring the brazing equipment is a bit too much, methinks.

@Dave BC:
Your comment about epoxy gives me an idea.  I could make the pin I want with a machine thread then epoxy it into the part you suggest.  That'd also make it easier to adjust the length of the pin - I can keep modifying and trying it until it fits, then epoxy it.
I think we have a winner.  

@John S:
The cross-drilled part needs to be too short to screw on as you suggest.  As said above, I do intend to use something like you linked to screw into the cross hole in the pin I'm making.

[John Hill]

This is what I would do,  make the part with the eye and drill a hole in the base then take a regular wood screw and cut off the head then Loctite the plain part of the wood screw in the hole.

But then I am lazy.

[CrewCab]

Guys I think we are loosing the plot a little, we don't need a wood screw, it's a screw made from wood ........... slightly different  .......... as Jason and Andy said the 2 tpi or whatever is not practical for a metal lathe ................ have a look here

http://www.timberframe-tools.com/shop/tools/joinery/wood.htm

It seems similar to metalworking, but just using that  .............  "brown stuff" 

CC

[No1_sonuk]

Guys I think we are loosing the plot a little, we don't need a wood screw, it's a screw made from wood

Actually, CC, it IS a metal woodscrew that I want.  Threaded wood wouldn't be resilient enough to be assembled and disassembled regularly.

[CrewCab]

Actually, CC, it IS a metal woodscrew that I want.  Threaded wood wouldn't be resilient enough to be assembled and disassembled regularly.  

Dam .......... missed the plot again somewhere along the line,  

Having looked again I can see what you need, the picture reminded me of a wooden screw from a while back, anyway it's one of these I presume



I use a few, long one in the butt and short one in the fore stock

CC

[75Plus]

I need to make a part similar to the attached photo.   It needs to go into the end of a 1" wood dowel.

I believe you missed it again CC.
Bet not many of the items you use a similar device on is made from a 1" dowel.

Joe

[andyf]

Having looked again I can see what you need, the picture reminded me of a wooden screw from a while back, anyway it's one of these I presume



I use a few, long one in the butt and short one in the fore stock

Damn Never thought of that, and I was Range Officer tonight, so could have ferreted round the junkboxes to see if there were any of those still around from the old days of 2-point slings.

Andy

[No1_sonuk]

Gentlemen, I draw your attention to the picture in my original post...

It is a "Deben" screw...  Same thing, just grabbed the photo from a different site.
However, I'm not wanting it for sling swivels.  The hole needs to be further from the shoulder.

[No1_sonuk]

Update:
The "dowel" is actually a piece of broom handle, and is very hard.

I drilled a 7mm hole in a test piece and ran an M8 machine screw into it.  It held very well.

So, I made the part with an M8 thread and it works fine.