Toolpost screws

In article , John writes

John,

It might be worth trying a tough alloy steel such as EN24T, or EN19T. I have never tried either to make screws, but have used the former where toughness was required; it is much tougher than mild steel, but reasonably easy to machine.

David

An unusual beginning?

Annealed and tempered ??? no - and silver steel is entirely the wrong steel anyway, it's really for cutting tools.

You may be able to quench-and-temper that, but I'd check. Iirc it needs to be above 0.4% carbon, and "medium carbon" steel may or may not be quench-and-temperable.

EN9, or maybe EN24 if you don't want to heat-treat it?

Guy is still in business, worth a try.

-- Peter Fairbrother

Try here.

You can search their stock online. They seem to do every conceivable size of square headed set screws.

[...]

Of course, it might be easier and cheaper to buy some 8:8 HT hex head bolts and grind the heads square?

-- Peter Fairbrother

It all depends on te kit you have but I would go for round EN8, mill the square and heat treat. Peter

Try here for the finished article

Charles

To buy them you can usually get some from Steve at Premier Tools AKA Fazerblazer on fleabay. There's also:

who will do them in 50's I think

If you are going to make them, I wouldn't bugger about with alloy steel from Parkers or whoever, just go an buy a box of M10 cap heads and machine them down. It's 12.9 (120MPa tensile, 90% yield), made for the job and reasonably cheap and easy to get.

Richard

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I have used normal Allen cap screws in the past with the heads machined square. There is usually sufficient metal in the head to do this, and these screws are very tough.

de quoted text -

Thanks to everyone for their replies.

I now have some screws on the way from Premier Machine Tools who were very helpful. They are running out of their stock so I was lucky to get what I needed.

Interestingly (I thought it was interesting) I was told these 'tool post screws' with the reduced diameter end, were originally for locking levers to shafts and not for tool posts. They were used where a hole of the minor diameter was drilled through the lever into the shaft and only that part of the hole which was in the lever was tapped.

John H

Hide quoted text -

Can someone enlighten me why normal socket headed screws like on my toolpost wouldn't've been suitable?

Robin wrote: [...]

I have no idea why the OP wanted toolpost screws, but they have two main advantages over socket heads for some circumstances - first, they don't have sockets to get filled up with swarf, and second they can be packed closer together.

-- Peter Fairbrother

Peter,

Good point on the first, but I'm confused on the second. How? Surely the need to put a spanner round them, as opposed to a hex key inside the socket type, is quite decisively the other way.

I always imagined they were less likely to get damaged and become unusable than hex socket screws. I notice my little Myford size 00 ones have hex socket screws but my mid-size T1 ones have square head screws.

David

No - it's one of those things which is quite easy to show with a diagram, but quite hard to describe in words - I'll give the ascii-art a try:

. __ __ __ __ __ __ __ __ . | | | | | | | | | | | | | | | | Allen heads . || || || || || || || ||

. . . . || . | | Spanner . | | . . || || || || || || || || Toolpost screws

HTH.

It's because the space between two screws has to fit in two Allen shoulders, and only one spanner shoulder, if that makes sense - told you it's hard to put into words!

That too :)

-- Peter F

I notice my little Myford size 00 ones

Just occurred to me, are you thinking about grubscrew size socket heads?

The problem there is then that the actuating area is very small, and a) it can't give enough torque and b) the socket gets worn down quickly as it's highly stressed.

For a toolpost screw the head can be about the major diameter A/F and still be about the same overall cross-sectional area as the minor diameter, thus still giving full strength for torquing purposes.

In order to increase wear resistance the heads of toolpost screws are made square, not hexagonal. They can't be a very accurate fit to the spanner, so square is better.

-- Peter F

In article , Peter Fairbrother writes

No - could only imagine using those where it's unavoidable - i.e. where the head needs to be sunk and can't be counterbored for some reason. The sockets chew up too easily.

How I was misleading myself was imagining the use of a conventional spanner rather than a socket - which is surprising, as my larger set has square headed screws and a socket spanner! Must have been too late.

David

Fairbrother

May have been covered before as I've not followed the whole thread, but socket cap screws are not very good in a tool post as the recess gets filled with swarf - hence the use of square screws

AWEM

Prompted by this and the fact that I could use some as well, I asked for a quote from Non-Standard Screws Ltd, they offered me a minimum order of 100 (OK) for £208 + VAT & carriage, almost £2.50 a screw by the time you're done.

I will come as no great surprise that I declined thier offer .....

Richard

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