Casting – off center hole correction

[colin hamiltonParticipant @colinhamilton16803]

I’ve bought a cast iron handwheel for a project. It was supplied with a small (8mm) center hole. I need to open this up to 20mm for my application, which I was intending to do on the lathe. The only problem is the existing hole is way off (approx 3-4mm) and I was thinking was too far out to drill successfully.

What would be the best way to get the hole back centered?

Thanks Colin

[JasonBModerator @jasonb]

Bore it.

Depending on the size of your boring bar you may need to first open up the wonky 8mm hole which can be done by using a milling cutter in the tailstock chuck, say 10mm then 12mm before starting boring.

[Andrew CrowParticipant @andrewcrow91475]

Hi Colin, as the hole in the casting may be a bit rough you could mark out where the hole should be and then use a round file to get it approximately back on centre before boring to size.

Andy

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I’ve done what JasonB has said a time or two.

Regards Nick.

[cogdobblerParticipant @cogdobbler]

If you don’t have a milling cutter to hand, you could mount the job off centre on the faceplate or 4 jaw so the existing 8mm hole is running roughly true, then drill it out to, say, 12mm or so. Then set the handwheel rim to run true and bore out the now offset hole with a boring bar.

With your final hole being 20mm , you have plenty of “meat” to play with. If you mark out the 20mm hole to start with, you will know exactly how close to it you are drilling.

 

[noel shelleyParticipant @noelshelley55608]

Bearing in mind this is a casting I would be loath to use a milling cutter lest the casting had hard spots that could wreck the cutter. Grind up a tool bit to open up the hole, or try to drill out 1/2″ on a pillar drill then bore out to size. Good luck. Noel.

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