Drilling advice needed

[ChrisCar6]

Working on current project http://www.borderbogie.co.uk/

Trying to ream out M14 thread on bearing cups of BMX hub to fit on 14mm axle. Hard as fun! HSS bit doesn't touch it, nor does file. Any suggestions as to how to get rid of the thread? One shattered while drilling, so brittle too.

[Fingers]

Do you know anybody with a lathe? Might be a bit tricky if it is still laced up to the rim though, but that's easily fixed. That would be the best way I can think of, drilling may get it off centre, then you'll be in for a bumpy ride.

[AndyH]

Hi,
Masonry drills have a tungsten tip. If you can get hold of a 14mm Masonry drill and re-grind the tip from Chisel to HSS, this should cut through the hardened M14 threads.
The tungsten tip is only held in with some sort of solder, so don't let the drill tip overheat or the tip will come off.
Just a little bit at a time.

I've done this before (albeit on a smaller thread) and when traditional HSS won't touch it the tungsten tip worked a treat.

Good luck
Andrew

[ChrisCar6]

It's the removable outer cups I'm working on, so that's OK.
I'll try the masonry bit idea as I've got one already.

[ChrisCar6]

Hi,
Masonry drills have a tungsten tip. If you can get hold of a 14mm Masonry drill and re-grind the tip from Chisel to HSS,

What exactly do you mean by that Andrew? Is it the undercut edge on the HSS rather than the vertical face on the masonry?

[Stableblock]

....if that doesn't work three other suggestions.
1) find a 14 mm diameter carbide burr,
2) wrap emery cloth round a mandrel and use in a power drill - this will take ages but should get there in the end
3) I have seen special cobalt alloy tipped drills at car shows and these are demonstarted by brilling through files etc. These might be hard enough. Somthing like...http://www.toolstation.com/shop/Power+Tool+Accessories/Cobalt+Drill+Bits/d80/sd1230 - dont forget to use some coolant - even a little oil will help to keep temp down.

Peter

[Nigel]

You should be able to drill thru hardened steel with HSS drills if you keep the speed slow enough.(15 sfm or 5 Mm is only about 100rpm for 14mm) the problem with using a drill as a reamer is the tip is unsupported and will grab and chatter. Try screwing in a piece of soft bolt thread(allthread is even softer), put something underneath to stop it turning and then drill to the size you need, - this will support both cutting edges and stop the chatter.
Hope this helps
Nigel

[AndyH]

What exactly do you mean by that Andrew? Is it the undercut edge on the HSS rather than the vertical face on the masonry?

Hi,
I took a standard Masonry drill bit and sharpeneed the tip as you would a HSS drill bit. Cuts through hardened threads easily so long as you take it nice and easy.
The standard profile on the masonry is more of a point than an edge and the hammer action helps it to chisel through stone. No good for steel steel.
Andrew

[GrahamH]

spark erode, lots of places do it.

[Fingers]

A proper cobalt drill should work too, probably available from a good engineering supplier. We have them at work and they chew through titanium and hardened steel fasteners like they're butter if you keep the speed and feed rate slow.

[ChrisCar6]

Thanks for the suggestions. I left them with my local engineer who was going to try lathe or grind or (most likely) turn up new ones.
The bogie is almost finished, the race is on Saturday and I'll need to fit the bearings, bed in the brakes and get a handle on the handling before then! Had a drive up & down the course this evening and it looks straightforward unless they put chicanes in.
It shouldn't hurt too much!

[Fingers]

Sounds like a great project and a lot of fun. Looking forward to seeing some video, hopefully with the wheels pointing down the whole time.

[Griff]

I take it you are going to post some pictures of the missile in all its glory?

[Sando]

Hedge 2:1
wall 3:1
finish line ..evens
;) Hope it all went well Chris......and you took pictures before the start ! ;-)
Rob

[ChrisCar6]

Oh ye of little faith!
Wasn't last, didn't crash, nothing broke! That's a first! Roll on Abingdon.
Good fun - touched 50mph on the way down. First run I didn't wear goggles, and between wind and vibration couldn't see well enough to go too close to barriers and edge of tarmac - sorted for subsequent runs. There were a couple of big crashes, but not me.
Aerodynamics seem to be the big thing. and weight. i loaded up the (genuine) soapbox on mine with 25kg ballast, on the basis of momentum through corners, but the top two carts were lightweight carbon jobs - one built by the Lola factory, and the other by a university advanced materials carbon fibre research unit. Bet they didn't use hammers. So, maybe a new approach needed next year.
I haven't found any video yet, but it's on Dave on the 11th July I think - probably not me though!
I failed scrutineering on some sharp edges - hence the rubber balls taped on strategically. The name is a bit contrived - mu is the coefficient of friction - a curse of gravity-powered machines. And everybody knows that bogies are made of mucus......

466246604661

[ChrisCar6]

Here's a vid from the luge race - gives an idea of the course. Mad bastards.
http://www.youtube.com/watch?v=Oo2rI_1c3zE

[Fingers]

Nice vehicle, maybe all you need is a good fairing then? I bet that was a lot of fun, I'd love to have a go at that. That luge looks good too, that's one thing I always wanted to try on ice.