Whats the best way to drill out a big hole in ally....

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

Whats the best way to drill out a big hole in ally when a big hole already exists? Im talking about top yoke clamps that go round the forks.Bought a set to fit a renthal bar and found upon closer inspection that they are 4mm too small Crying or Very sad

any good ideas? someone suggested using a hole cutter but clamp the fork clamp to a piece of wood first to make sure it's dead centre.Isnt there an easier way?
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0ddball · World Chat Champion Joined: 15 Jul 2005 Karma :

You mean the holes that the actual forks pass though? It has to be very accurate to get an even clamping pressure. You're best off taking it to a machine shop and they'll do it on a milling machine (take a fork with you or measure the stanchion diameter accurately with a vernier caliper).

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Yep. Five minute job on a milling machine.

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

Ok so just go to a local engineering shop and ask them to do it? will they take a little job on like this?

i know the measurements now and it's exactly the 4mm difference
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0ddball · World Chat Champion Joined: 15 Jul 2005 Karma :

Yeah. It's sometimes hard to find one that can be bothered taking on small jobs. Avoid the big places that mainly do commercial contracts and try to find a little 2/3 man backstreet workshop set up.

Your local bike shop might even be able to reccomment somewhere.

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

Ok thanks very much Thumbs Up

I think i may know somewhere that might just do it.It's a local firm that make small parts and flanges for a pipe company.Maybe they will have a milling machine. Smile

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stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

offer them a tenner on the side you mean? is that enough or more?
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0ddball · World Chat Champion Joined: 15 Jul 2005 Karma :

It shouldn't be more than a tenner. A lot of the cost in an engineering shop is in setting the machines up. Your job doesn't need any special tooling or measurements so as stinkwheels says, it's a 5 min job.

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

Cool thanks guys Thumbs Up

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gixerboy · Borekit Bruiser Joined: 23 Sep 2006 Karma :

If you can do that in 5 mins I would be impressed. In fact if you could bore them within half an hour I would be impressed. The diameters need to be a decent size, you cant just stick a drill down them, the correct way is to bore them out. To do that you will need to clock the yokes up so that you get the bores in the correct relation to the steering stem. Then you have to get them to the correct size. I think there is a good hour or 2 work in them.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

What? You just need to clamp them down to the table, mark out where you want the edge of the bigger hole to finish and mill away.

Last time I had it done on a set of GS500 yokes (took out all four holes an extra 2mm so I could fit some wacky forks to my Jawa), the guy charged me a fiver.

gixerboy · Borekit Bruiser Joined: 23 Sep 2006 Karma :

Thats the difference between doing the job properly and just bodging it like many people seem to do. To line the forks correctly you need to bore the holes at the correct offset from the steering stem. I suppose a gs500 handles so badly you wouldnt notice if the forks were in alignment or not.
To do the job properly it will take at least an hour just to set everything up.

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

owdamer · World Chat Champion Joined: 06 Oct 2004 Karma :

If you mean something like these then its pretty straight forward,
If the clamps are part of the actual yoke then its going to need a bit of setting up to do it right. Make sure that you can afford to lose 4mm from the clamp though. You dont want to end up with the bars breaking off the first time you brake hard...... Shocked

Either way its not a 5 min job and its not just a case of throwing a bigger drill down it. You only need to be a fraction of an inch out on one of the clamps and you bars will be an inch out of line.

https://www.bmikarts.com/shop/images/241.JPG

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

How do i post a pic? i can show you what i mean then
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stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Get your picture on your computer. Reply to this thread, click 'add an attachment'. When the page reloads, click 'browse', find your file and select it. If you want to add another click 'add attachment' if that's it click 'submit'

Incidentally, most handlebars are a standard size, 7/8" diameter. Specialist renthall twinwall, tapered and fatbar are bigger. I presume this is what you are trying to fit?

gixerboy · Borekit Bruiser Joined: 23 Sep 2006 Karma :

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Who's boring anything?

They were milled out in a sideyways fashion on a big f-off milling machine. He scribed the new diameter on the surface, clamped it to the bed with some tool in the hole to make sure it was perfectly vertical then milled away the metal that was no longer needed.

I was probably exaggerating about the fineness of the tolerance, but the tolerance on a pinch clamp leaves a fair bit of room to manouver anyway. He took about 20 minutes to do both yokes. Hence my five minute estimate for bar clamps

gixerboy · Borekit Bruiser Joined: 23 Sep 2006 Karma :

The ONLY way to get a hole correct without it moving is to either use circular interolation on a CNC mill or to bore it. As I said before, he bodged it.

TheShaggyDA · Repost Police Joined: 14 Jun 2004 Karma :

Half round bastard file would sort it.
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stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

I preferr to call it old fashioned engineering myself. If you've got it marked up on the surface, you could indeed do it with a half-round bastard file (and a square), it would just take a long time.

We are also talking about fitting them on a bike that has a twin cylinder engine with pistons that are measurably different diameters and measurably oval (ving a standard vernier calliper). I did weigh them and file the skirt of one to make them weigh the same though

jimbothe · World Chat Champion Joined: 29 Sep 2006 Karma :

The piece i need to drill out is the bottom piece thats sitting on the desk.The hole for the renthal bar is the correct size but the hole that needs to bolt around the top of my fork needs to be 4mm bigger.
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ZRX61 · Victor Meldrew Joined: 05 Nov 2003 Karma :