Screwdriver bit material

[Keith MathesonParticipant @keithmatheson47708]

Hi, I’ve decided to make my own hex screw driver set. One reason is I take apart carbs apart for my motorbikes and never have a slot driver which is a really good fit. There is always the risk of damage or throwing up a bur. I’m thinking of getting some hex bar and grinding the slot to suit. ( Ive just purchased a universal tool and cutter grinding machine as it happens so a nice little side project).I’m sure I will find lots of other screws in the future which will need a specific slot to avoid damage.  What material should I chose to make them out of. Regular steel, stainless or tool steel and harden them.I’m sure I could find a set of a billion slots but like the idea of having a little wooden holder with specific types eg, dellorto bits , Weber bits, imperial slots, metric slots. oK hopefully you get the idea.  Many thanks in advance to my question.

[JasonBModerator @jasonb]

You will want a carbon steel so that they can be hardened. Silver steel is the usual option but you will have to find something in hex.

Might be easier to buy some long allen keys and machine them.

[SillyOldDufferModerator @sillyoldduffer]

Screwdrivers that don’t fit do a lot of damage.   They need to be dimensionally correct in the first place, and then hard and tough enough to resist deformation.  Otherwise they’re likely to chew the screw head, or slip and scratch the bodywork.  Dimensionally correct is achievable in a home-workshop, at least slot drivers are, but suitably hard and tough is more difficult because screw-drivers are highly stressed.  For regular use the steel needs to be suitable.

At minimum a hardenable steel.  If chilled too quickly, all hardenable steels become brittle, so it’s best practice to temper them.   That’s two heat-treatments that might go wrong!  Silver steel is good stuff, but it’s formulated for ease of use rather than best possible performance.   Manufactured screw-tips are often made by grinding drop-forged Manganese Steel, which is harder and tougher than most steels.   Judging by my collection of screwdrivers, not all of them are that well-made.

I like Jason’s idea.  Allen keys are made of a suitable steel and can be ground to shape.

Slotted screws look good but are a pain because they come in hundreds of slot sizes making it necessary to own lots of different screw-drivers when it’s important not to mangle slots.   The end-shape of the driver can be important too – some slots prefer a wedge shaped tip, many others demand parallel tips.   Gunsmithing, clocks, instruments, and anything else where screw-heads are part of the look are usually parallel.

Dave

[SillyOldDuffer]

On SillyOldDuffer Said:

At minimum a hardenable steel. …

 

anything else where screw-heads are part of the look are usually parallel.

A third vote for a 1/4″ allen key. You might get more usable material for your money if you pick a T-handle version as it is one long, straight shaft.

The difficulty with allen keys is that the really cheap ones just corkscrew when subjected to too much load. Better quality ones will twist considerably before they permanently deform.

The other option might be standard 1/4″ hex bits but in 100mm or 150mm long versions. Remove the OEM tips and you have another long, straight piece to play with.

I have found that even in the cheapest versions (e.g Toolstation 83011), unlike allen keys, the heat treatment of screwdriver bits is adequate.

I do not think the bits need to be very hard as such. They need to be tough, with a high yield point. That might rule out straight carbon steels and require other more exotic alloys, which are not so easy to home-heat treat.

As above, for straight screwdrivers, a hollow ground shape is much kinder to the screw head than a straight taper grind.

[mgnbukParticipant @mgnbuk]

As you have the T & C grinder, could you not purchase oversize branded hex bits & regrind them to suit your  requirements ?

That way you get  quality chrome vanadium steel bits correctly hardened and tempered – not overheating the bits when reworking should retain the original properties.

Nigel B.

[Anonymous]

Screwdrivers and Allen keys are not particularly hard. I’ve just measured both and they are around 45 to 50Rc. That is easily machinable; an ordinary carbide milling cutter will be fine.

Andrew

[Martin Johnson 1Participant @martinjohnson1]

Traditional screwdriver material in apprentice days was silverv steel.  Harden out and temper to light blue.  You could leave the tip a bit harder (straw) if required.

Martin

[jaCK HobsonParticipant @jackhobson50760]

I fancy making some lower bainite screwdrivers. Need deeper hardening steel than silversteel. O1 would do – quench to about 230C then hold for a couple of hours.

[Keith MathesonParticipant @keithmatheson47708]

Thank you all so much for your wise words and suggestions. I must admit Nigel B’s suggestion of just buying some larger slotted hex bits and grinding them down to suit seems the most quickest and efficient way forward for me. It will also provide some (hopefully!) straightforward activities on the tool and cutter grinder machine when it comes at the end of the week. Thanks for taking the time to educate and inform me. Keith MM

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