DIY screws

The camera is mounted on the cross slide - and so moves with the tool. Its just creates the impression its the chuck that is moving, but if you watch the background you can see the reality.

Reply to
John Rumm
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Yes. Here's a clearer pic:

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here it is all covered up so it doesn't frighten the horses!
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Reply to
Matty F

Reply to
Dave

Excellent thanks. I see there's a hand made screw on page 9, done with a file. I'm starting to think of an angle grinder with a thin blade!

Reply to
Matty F

I don't own any of that, I just work there as a volunteer keeping the machinery going and making parts. I do have a workshop at home with almost every tool I can buy!

Reply to
Matty F

You need 0.8 mm and 1.0 mm cutting discs for the angle grinder anyway. They are cheap, and spectacularly quick and neat on sheet metal compared to the fat cutoff blades. Then you could play with mounting it on a lathe and turning the lathe very slowly (poss. by hand) and grinding the threads...

Note page 10, where they say the conical screws are no good. Made sense to me once they point it out, the "cone" will fall out after a half-turn or so. So feed can be parallel to the stock.

Or could you take modern screws, and machine then down?

OTOH, a chippie I knew threw away a large box filled with screws. They were pretty much all slotted wood screws, remains of boxes of rusty screws of every dimension used that shop for the in the past sixty years. Also decades worth of dumped bottom-of-toolbox bits. And by "large box", I mean about three by three foot, and two high.

So there's probably a stock of whatever you need somewhere. A diving rod, maybe?

Thomas Prufer

Reply to
Thomas Prufer

We already have sorted out huge boxes of screws and bolts. We have to restore and maintain a great variety of old machinery and vehicles dating back to 1891, and bolts and wood screws have to look correct. Many bolts are Whitworth but that is hard to get now so we will use UNC (with the correct nuts of course). Sometimes we need metric bolts. We also have BA. There are coach bolts and countersunk bolts and high tensile bolts and steel, brass and stainless steel bolts. I'm looking after about 250 boxes of different bolts. I don't look after the wood screws but there would be maybe 400 different boxes of slotted screws, in steel, brass, plated, round head, countersunk, cheese head, in all the different lengths and thicknesses.

There's no urgency but for making a few large screws (1 to 3 inch) I'm thinking along the lines of making most of the screw on a lathe then making the thread using a slow fixed thin grinding wheel. I'll hold the screw in a collet chuck and rotate it by hand against the grinder. The chuck will wind forwards and backwards with a screw feed of the desired pitch.

Reply to
Matty F

Like I wanted to say but didn't (what's a "diving rod"? Aaargh!), you need a

*divining* rod...

Or "just file it":-) I have seen a well-trained machinist do thing with files that were amazing. His training with files began with filing a cube, accurate in dimension and angle, checked with a straightedge against the light all ways...

I was at a museum recently where they restored guns and rifles and such. While the mililitary was an early adopter of standarisation, to ensure some interchangeability of guns parts, there were first no standards, then many local standards. The machinist said he tried to set up the lathe to what he though he'd measured, machined a screw thread, checked if it fit, and repeat the whole process until it did... Many of the threads were corroded by gunpowder remains, too.

Thomas Prufer

Reply to
Thomas Prufer

There are moving head lathes, although that is not one - the camera is simply mounted with the tool holder. You can also get lathes where the tools rotate, rather than the head.

Colin Bignell

Reply to
Nightjar

R I C

Thanks Matty

Dave

Reply to
Dave

I must have been thick not to have spotted that, thanks Colin.

Dave

Reply to
Dave

Imagine having to produce a thousand of those at a time. It takes me back to the time I first entered the aerospace industry. We were converting Victor bombers into refuelling tankers and one task was to remove the lower skin of the outer wing to replace it with a new one. In most cases, most of the bolts were in sheer, but the threads were machined too long and being the newbie, it was my job to cut off the excess threads. Well over a thousand per wing were required. You just had to switch your mind to other things.

Dave

Reply to
Dave

I can't see myself holding a 1 inch screw between centres. When I used the die to cut the thread above, it cut a tapered thread. I had to reverse the die in order to tap right up to the end where the diameter gets bigger.

I want to match screws made the old fashioned way, like 100 years ago. I think I will make an adjustable die and see how it works on brass. My uncle made dies out of old files while he was a POW in WW2. I have better facilities than he had!

Reply to
Matty F

I had to look at it twice to be sure.

Colin

Reply to
Nightjar

Curiously the thread on camera tripod mounts is ¼?BSW; I was looking for a die for that and found this site: I haven't tried them out yet, but it might be worth a shot for you.

Reply to
Jon Fairbairn

Thanks. The thread has diverted to the cutting of wood screws. We actually have a full set of BSW dies (dice?). For important bolts like for holding the brakes on we'll use modern high-tensile UNC bolts, since they are fairly hidden and purists won't be able to see them.

Reply to
Matty F

I forget the correct terminology for it, but there is a screw cutting technique that basically uses a comb ended tool to cut several turns of thread in parallel on the lathe. Starting off being the hard bit - since it needs to "travel" along the work at the correct rate for the pitch. However once there is the rudiments of a thread there is can follow it, and deepen it on each pass.

It strikes me that if you cut a parallel thread with a die first, and then had the tool I describe with a matching pitch of teeth on it, you could covert the parallel thread to a taper simply by offering the tool to the work at an angle.

Reply to
John Rumm

Where is it? Looks like MOTAT.

Reply to
Gib Bogle

Have you considered lost-wax casting? There might be local foundry that can do that. You'd still need to machine the head.

Reply to
Gib Bogle

How observant of you :)

Reply to
Matty F

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