Cutting wood screw threads on the lathe

Hello, I would like to cut my own special brass wood screws / coach screws for models as well as making sime DIY furniture look fancy. Is this something I could do on a S7 or similar? Or is it more specialist? I tried googling but I got mostly info on woodworkers lathes. How would I set up the coarse tpi and what tooling should I use?

thanks

Hi Thomas

You can find the details of woodworking screws in an old copy of Machineries Handbook.

This would be a good starting point.

I doubt the newer versions would have this in them.

regards David

Hi Thomas,
There should be no problem grinding a tool from HSS or finding a combination of gears to give the correct pitch. (The pitch would not even need to be exact.) I initialy thought at a taper turning attachment would allow the thread to be cut on a taper but on closer inspection of a wood screw showed that the taper is not constant. You would need you make an attachment similar to a taper turning attachment but with a shaped guide instaed of a straight one. Have a look at this thread for ideas on this. You may also need to make some kind of steady to support the work if you were making a long screw.

Les.

I made some woodscrews a few years back, I think the screw part was 1/4" dia, and I used 4tpi, after cutting the thread I used a file to taper the first 1/2" or so, the screws went into drilled holes, so a parallel thread not a great problem, the screws had a 1/4 UNF thread on the other end. Ian S C

On a model I would not worry about putting the taper on the end, better to drill a pilot hole to the core dia of the thread as there is a lot less chance of splitting the wood.

I would go for a tool ground like a narrow ACME thread cutting tool and advance the topslide until the peak of the thread is a V form more like the modern woodscrews

If you work slowly (perhaps using a mandrel handle) and use an upside-down tool and cut away from the chuck, you may be able to manually advance the tool near the end of the cut to create some lead in.

This will depend on the sharpness of the tool and the type of brass you use, as some brasses will just bend when you increase the cut.

Neil

Thomas, coming back to part of your original question you do not need anything as exspensive ar big as an S7. You could look at a number of small import lathes if you want new, or various old small ones too. Depends on what else you might want to do one day.

Because it is a coarse thread you might need to wind the leedscrew by hand and have it turn the chuck through the gears. SO look for a lather that allows this.

If you are primarily into woodwork there are a number of simpler cheaper ways to make the screws by thread milling including using an wood lathe or electric drill if you have these already.

Hi Thomas Gude

Below is a CAD sketch of a constant pitch wood screw you can make on the lathe. I have drawn it as countersunk slotted however the head can be changed.

This type of screw is not self drilling you have to drill a small hole at the root diameter first then the helix will cut it way into the wood. As you can see there is no taper.

I learnt about these screws when repolishing a firearm. A Brno .22 that I have had since I was 14. Brno use this type of screw in preference to the tapered kind, I guess due to the superior clamping force and the ability to precisely locate them.

It would not be that difficult to turn them on the lathe. You can make them to scale size.

Cheers

John

It would be worth while making a steel screw as well, use this to screw into the wood first, take it out, then put the brass screw in, you are less likely to damage the brass screw that way. Thats the way a good cabinet maker would do it, even with a well fitting screw driver you can slip and damage the slot. Ian S C

Great post I really appreciate your post.

In the above diagram, I would tend toward a slightly deeper groove, with a sharper crest, make one or two steel ones, use these in the holes first, then use the brass ones in the tapped holes, I like Johns BRNO one, Had a BRNO Fox .222rem, it was good for goats and hares, and long range shots at rabbits. Ian S C

If You are making models, do You need self made screws at all? Perhaps all You need to make is something that looks like screw head. Make brass pins with screw head and use commercial hidden screws to fasten parts together.

Jouni

Ooo, thanks guys, lots to try out. Its the tool that I'm not sure about, I think this will involve lots of retries on the grinding machine.

Bazyle - True but I do have a few other projects in mind that will require S7 capacity but I am yet to make my purchase (yes, I am open to Warco etc, and no I don't want this to turn into a Myford vs China debate)

Im going for about 16tpi on a no.8 - 12 sized screw

Jouni - true enough, but Ive never been one for adding fixtures like that which dont do anything, for me that comes into the same category as decals & miniature handrails etc which Im not really into.

Edited By Thomas Gude on 28/02/2013 16:59:19

Hi Thomas,
As standard 8 to 10 size brass screws are easy to obtain why not just make your special head design and join them to the thread of a bought screw. Drill the shank of the head part you make and turn down the end of the bought screw to fit the hole. Loctite or soft solder should be strong enough to join them unless the are very heavily loaded. I have 1" masonry drill extended this way and held together with loctite that has been used for many years.

Les.

Pierre's drawing is fascinating. It's dated 1935, and it really does seem a very odd screw profile.

Neil

Hi,

The drawing is from a russian blog talking a bout USM1/Garant Carbine

This was also my first wood-screw drawing

pierre

Edited By pierre ehly 2 on 28/02/2013 22:03:39

How do you turn woodscrews?

With a screwdriver

Just finished having a right giggle at Jason`s post. Wolfie me old son you didn`t have ask for that one!!

Suggest you go round to see JS & ask him for a long stand.