Threaded dowel and nut....... HELP!!!!

[Redfly]

Haya people.
Sorry my first post is a plea for help but I'm having trouble sourcing a short length of treaded dowel.
I'm building a work cabinet that has a small set of drawers that lift out of the top when a handle is turned.
Turning the handle also opens the doors. The doors and running gear are finished which leaves me with the lifting mechanism for the drawers.
I have tried a 16mm threaded nylon bar but the thread pitch means it needs to rotate sixty times to travel just 13mm. I have twenty turns available from the door action but by the time I gear it upto 60 I lose all power and the gears can't manage the umph.

I would like to replace the nylon threaded bar with a wooden screw (obviously with a much bigger thread pitch) so I can lift the drawer unit the 13mm in less turns. That way I can gear down a bit and give the screw a bit more umph ( can't spell torque)

So my question is, without spending a fortune on a lathe or an American tap and die set, how can I get my hands on a 200mm length of hardwood threaded dowel and a matching nut. Thickness isn't critical but it would be nice if it was around the 16-20mm to keep the modifications down.

Any ideas....

 

[MickCheese]

Axminster sell the tools for doing this. I don't think it is too expensive.

Welcome by the way.

Mick

 

[gwr]

Sorry cant help with the threaded rod but would like to see some pics of this table.

 

[rxh]

Tilgear have threadboxes and taps, at half price until 31/01/13. Available sizes are 1/2", 1" and 1 1/2".

 

[baldpate]

I think this is what Mick means:
http://www.axminster.co.uk/axminster-axminster-wood-thread-cutting-kit-prod21303/

The 3/4" (19mm) kit will produce a thread with a pitch of 6 tpi (threasd per inch).

I'm a little confused by your saying it takes 60 turns to move the threaded nylon rod through 13mm (!). Do you really mean 13 millimeters? If true, that would imply a screw thread pitch on the nylon bar of about 120 tpi, which cannot be right. I wonder if you actually meant 13 centimeters, which would imply your nylon rod is threaded at about 12tpi - a far more reasonable thread for a 16mm nylon rod!

Assuming you actually want 13 cm of movement, the 6 tpi of the 3/4" thread cutter would require about 30 turns. However, you should also remember that each turn will require twice as much to effort (possibly even more because the internal frictional resistance of a wooden thread in a wooden nut is likely to be greater than nylon on nylon), because each turn has to do the same amount of work as did two turns of the nylon rod.

In other words, your gearing mechanism needs to deliver twice as much torque! Do you think your gearing mechanism is up to it?

Chris

 

[Redfly]

Quite right Chris 130mm.

Looks like I'm fitting chain and sprocket. Didn't want to as I'd rather stick with wood but I'm stuck with twenty turns at source. I was hoping to gear down to say ten turns with enough poke to lift the tiny drawer set and possibly make a feature of the turned shaft but I'm not fighting physics. I have already spent months on the project getting the doors to open 180 degrees. They sit flat on the cabinet top and open out like upside down aircraft bomb bay doors at the turn of a handle...... :roll:

 

[marcros]

Tilgear have threadboxes and taps, at half price until 31/01/13. Available sizes are 1/2", 1" and 1 1/2".

cheers for that info- they look pretty good value at those prices. (search threadbox for anybody looking on their site).

might have to invest in one for a future project, although i have to confess, other than vice screws i cant quite think wjat i might use one for...

 

[Argus]

.

I have a ¾” screw box………….. looks like the Axy one, but it didn’t cost that much!

Anyway, the approximate diameter of the threaded part (taken from the tap) are;
19.5 mm to 15 mm - the pitch is 3.5 mm, which come out nearly 8 to the inch.

If you are desperate for just one piece, I could probably make something up for you, if you can get some sketches or drawings organised showing what you want and the wood type in question - some timbers takes thread-detail better than others, without crumbling.

.

 

[baldpate]

... i cant quite think wjat i might use one for...

I've used my 3/4" one to make devices which hold themselves down on the benchtop, where you can't or don't want to use any sort of clamp - for example, low-profile planing stops.

Thread one end of a length of 18mm hardwood dowel (about the length of a bench dog). That's the lower end. The upper end is attached (screwed, glued, whatever) to the bottom of the device you want to clamp to the bench. The threaded end goes down through a dog hole of your choice, and is secured from below with a wooden nut.

 

[Redfly]

Thanks for the offers and help guys. It's a lot to go through if at the end its not going to work. I've sat scratching my head at it all day and the only way I can be sure of it working is with a timing belt front and back with a bar clamped between them.
I can gear it much easier and the whole thing will lift in only two turns of the belt pulley wheels. A 20-2 reduction gear will give it more than enough poke to lift several times the weight I need.
I have just ordered the required parts and at just over fifty quid it could save me a lot of time and wasted expense.
I'll get a picky up when its done for you all to laugh at.
Think of a writing desk with knobs on and you won't be far out.

Happy hammering

Iain.

 

[MARK.B.]

cant wait to see the pics of this,sounds very complicated (hammer)