Home made screws

I got a few samples of M1.2 screws for a project and wasn't happy with the quality or material so I decided to make my own. I would have to turn down the head and shorten commercial screws anyway.

It went a lot quicker than I thought. Once I had worked out a "mass production" method I made around 40 ( I need 80+) before running out of silver steel. That took about 6 hours workshop (kitchen table) time.

Here is one on a penny.

This is unfinished - it still needs chamfering, polishing and blueing.

I'm quite happy with the result.

Steve

Edited By Steve Crow on 01/04/2021 16:10:05

Great stuff, Steve

Nice to see some small scale machining.

MichaelG.

Looks great Steve, nicely made.

Wow that is what i call a dinky screw. Nice work.

Steve.

Can you talk us through your mass production process and what tools fixtures you used?

Very nice work Steve. It's not too bad if you can get a rhythm going.

Brian

Hi Ian, I can try.

First of all, I used a Sherline lathe and milling machine to make them from 1/16" silver steel.

I did it in three stages.

First I fixed a turning tool (I used 0.2 radius "ali" type inserts) and a rear mounted parting tool to the lathe carriage about 20mm apart to leave room for the threading.

The material is held in a watchmakers collet and turned to desired diameter and length. Set Y dial to zero for future turning.

Use jewellers cup burr in pin vice to lightly chamfer.

Bring forward the tailstock with thread rolling die/head attached and form the thread. (I bought a Russian made M1.2 thread roller on ebay for £13.01 inc. postage from St. Petersberg. Fantastic value for money.)

Repeat with the cup burr.

Bring in the rear parting tool, index from the screw shoulder and part off.

Withdraw some more rod from the collet and start again.

For the subsequent screws, your Y Is already indexed to zero and you can do it in one cut.

The next stage is just facing the heads after parting. Again you can just set your X and do them all in one cut.

The third bit is the slotting.

I used a homemade square collet block held in a mill vice and a 0.3mm slitting saw.

I hope this is helpful. If you want more clarification, just ask.

Steve

The screw's something I could've done, though with some difficulty and maybe not as neatly.

It's some of the other stuff in your photo albums that's really remarkable - congratulations on your work!

Steve, for slotting, do you hold by the thread or do you have a threaded collet?

Brian

Edited By Brian H on 01/04/2021 18:07:39

Steve

I have just been experimenting with those thread rolling dies with very little success.
I have 1.2 1.4 and 1.6 sizes, I tried the 1.6 first and it just necks the raw material off and the roller box has to be dismantled to remove the broken end, mine was mild steel not silver steel though.

Do you know if the three "rollers are meant to revolve or do they just form a thread as they push forward, mine do not revolve and the friction is just too great for the material to hold up against the twisting force.

I am making longer studs rather than headed screws.

Any advice would be welcome.

Phil

Steve I’m in awe at all that on 1/16” ss

Hi Brian, I just use a 1.2mm collet clamped on the thread.

Steve

Hi Phil, maybe the problem lies in the diameter of the blank you are threading.

The theoretical diameter for thread rolling is the pitch diameter of the thread. This makes sense if you think about it as the tool deforms equal amounts of material in and out.

Pitch diameters :- M1.2 =1.038, M1.4 =1.205 and M1.6 =1.373.

In practice the blank should be slightly less. I've only tried the M1.2 die and I turned down the screws to 1.02mm. It works fine on 1mm rod as well.

For M1.6, I'd give 1.35mm a try.

The rollers don't revolve. The alignment of the wheels forms the thread. Did you get a little threaded rod with each tool? When assembling the tool after a breakage, this is used to ensure the rollers are in the correct alignment when tightening everything up. If you can screw this in and out easily, everything is in the right place.

I hope this is helpful, let me know how you get on.

Steve

I couldn't immediately find your "thread roller" but did see a Cyclo item at nearly £100 and that without rollers; I have put mine in the safe!

I make the penny 0.8" in diameter ie not metric?

.

Then yours may be slightly oversize

They apparently make them 20.3mm maximum

[ no reference temperature stated though ]

**LINK**

https://en.wikipedia.org/wiki/Coins_of_the_pound_sterling#Dimensions

MichaelG.

MichaelG:

Thank you. I'll measure again with greater care!

In accepting the imperial measure I may have been influenced by the understanding that one of the pre-decimalisation coins was exactly 1" in diameter.

Hi Steve

Yes I did get the test piece with each one, and it does screw in easily, I actually measured the remaining bit of plain section on it to find the blank diameter and it seemed to be 1.4 mm so that is what I tested it at.

I will have another play and see if 1.35 mm works out any better, I could not see how it would work with the rollers revolving as they are not retained on the shafts, so it has to be down to the blank diameter I suppose.

Do you use any lubricant on it when forming the thread ?

Phil

PS, Just so others know what we are on about, here is a link to one.

Thread-Rolling-Head-Die-M-1-6x0-35 202976842528

Edited By Phil P on 02/04/2021 12:19:32

Hi Phil

I think that extra couple of thou is critical. If the blank is only slightly larger than the pitch diameter, there is too much metal and nowhere for it to go so it jams and breaks.

It's a bit like tapping a slightly undersized hole - the tap's going to break.

I'm sure that you could go down a bit less than 1.35 mm for safety.

I've done all my threading dry so far. My thinking was that I'm not actually doing any cutting so there is no advantage. I might be wrong on this.

Steve

Hi Steve

You were correct, the blank size was the problem.
I made a fresh attempt using 0.053" (1.35mm) as you suggested and it worked a treat even on a long thread.

It also gave me a chance to try out the ultra slow speed inverter setting I rigged up on my Pultra 1770, I can run a thread up to a shoulder under power and then reverse it off again, I am really pleased with the results.
I just need to set up the capstan attachment now and go into mass production, but that is another story.

Thanks for giving me the advice to carry on, I had all but given up on the roller box but it works very well.

Phil

Hi Phil

Glad it worked for you. Are you using mild steel?

It makes threading a joy. I wouldn't have contemplated making all those screws using any other method.

Also, if you inspect the thread under magnification, the finish is so much better than a cut thread. there is no tearing and the surface has been burnished by the rollers. It's stronger too as the "grain" of the metal has been "folded" rather than cut. I believe it work hardens the material as well.

I also threaded my screws under power even though they are only 2.5mm long. I have to reverse off manually though.

These Russian tools are great value. I've got a few sets of involute gear cutter from the same supplier. I might do a post about them at some stage.

Nice lathe you have there, by the way.

Steve