Where to send a hardened steel shaft for drilling?

[StreetDragster]

Hi all

I have a gear selector shaft which is hardened steel. I'm modifying the gear selector position, and I need a hole drilling for a roll pin, 4.8mm diameter.

3 local machine shops said they couldn't help as they don't have the tooling. A friend of mine is taking it to a fourth machine shop today.

If they cannot help, does anyone know of somewhere that can definitely drill hardened steel, who I could send it to? (If they are not near preston that is)

Thanks
Matt

[DeadCatWalking]

You need an EDM shop (electrical discharge machining) for hardened steel. Waste of time trying with normal tooling. An edm electrode will go through it like butter. 5 minute job.

https://en.wikipedia.org/wiki/Electrical_discharge...

[StreetDragster]

Thanks for that, not something I'm familiar with but I'll try and find somewhere local that can help.

One of the machine shops said a carbide cutter might do it also but it's nor sounding promising

Cheers
Matt

[DeadCatWalking]

Even carbide won't cut hardened steel cleanly. However if the shaft is only case hardened the hard case can be ground off and then any drill will go through the core. It's unlikely a gearbox shaft would need to be through hardened. That creates brittleness. More likely about 15 thou of hard case and a soft core to give flexibility. It would help if you knew which. An angle grinder or grinding bit in a Dremel would take the hard case off easily. Then it's an easy job in a pillar drill. No fancy machinery needed. The tolerance on a 5 mm roll pin hole is huge, about 5 thou. Centre punch, double drill at 4 mm and then 4.8 mm on a slow speed and job should be a good un. No need for honing or reaming to get tight tolerances.

If it were me I'd mark out where the hole needs to be and grind away with a small spherical abrasive stone and see if I got through to soft core. Or find a spare shaft and cut into it with an angle grinder. If the core is soft you'll be able to mark it with a file or scraper or centre punch.

4.8 mm is a weird size. Why not a standard 5 mm hole? Maybe you mean 3/16".

Edited by DeadCatWalking on Wednesday 8th January 09:23

[finishing touch]

I went to a model engineering exhibition once where on one of the stands they were drilling holes in files to demonstrate their drills.

One assumes you can buy them somewhere ?

[DeadCatWalking]

Do you know for certain if the files had been annealed? Not everyone on this planet tells the truth.

[227bhp]

I think the drills in question had TC tips, the guys been doing the circuit for years.

[StreetDragster]

Thanks for all the help so far.

For context, this is the gear selector shaft from the American t56 gearbox, which needs drilling 3/16", 4.8mm sits right in the middle of the stated tolerance band (which I haven't got with me at the moment)

At the moment, it's with a machine shop that does spark erosion. They are looking at it for me but are really busy at the moment, if they can't do it by Friday I'll pick it up again from them.

I would agree that it's likely to be case hardened, people in the usa insist they can drill it with a carbide cutter which supports this theory.

If I get it back on Friday, I'll grind a small flat spot, and then try and centre punch it. If I can, then I'll try and drill it with the cobalt drills and hss drills I have and see what happens.

Thanks all, very helpful

Matt

[finishing touch]

DeadCatWalking said:

Do you know for certain if the files had been annealed? Not everyone on this planet tells the truth.

They slapped one on the corner of the bench and it snapped.

[wildoliver]

finishing touch said:

DeadCatWalking said:

Do you know for certain if the files had been annealed? Not everyone on this planet tells the truth.

They slapped one on the corner of the bench and it snapped.

These things are always junk, I bought some *amazing super glue" guaranteed to not stick your fingers together but stick everything else like magic. Watched the demo, fell for it. It's just crap superglue. Same stuff you would buy in a pound shop. I still see the bald bd every time I go to any shows.

My dad fell for the "magic drills". They are just drills. The free replacement thing gets old fast due to postage costs.

A friend fell for the "magic spanners". Yes you can indeed grab on to a metal bar with them but they are no better for rounded off fasteners than a pair of stillsons due to awkwardness and are vastly inferior for pretty much everything else.

[finishing touch]

It was hard to argue with these blokes.

They even stuck a bit of plate in the vice and filed a bevel on one edge before drilling the file.

[wildoliver]

I'm not saying don't buy them, but don't believe they do anything that a good quality drill won't do better.

[StreetDragster]

Afternoon all,

Just closing this off, drilled through by a local engineering company in the end with a spark eroded no dramas.

£40 though instead of the 4 pack of beers i was hoping, but i imagine the skills and machines are pretty pricey.

Now to continue with assembling the gearbox and see where the next drama appears.

Cheers
Matt

[DeadCatWalking]

£40 is exactly what I would have guessed for a minimum one-off charge. No doubt if you'd had 100 of them to do it would have been £5 each.