08-14-2022, 02:02 PM | #1 |
Not Yet Wild
Join Date: Aug 2021
Location: Chicago area
Posts: 16
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420 tips for drilling crankshaft?
Working on a 420 going into a G9. Planning to drill / tap for 1/2x20 to use the existing clutch bolt. Got to the part where I drilled out the existing threads in the new engine, planning to drill deeper using the old hole as a guide, and then just came to a dead stop when I hit solid steel at the bottom of the existing hole. I haven't cut the crank yet, because I'd rather keep the old hole as a guide unless I have no choice.
What's the trick... drill a smaller hole first? But then, using what as a guide to keep it centered? Or suck it up and spend $$$ at a machine shop? |
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08-19-2022, 01:32 PM | #2 |
Searching for The Way
Join Date: Oct 2009
Location: Medina, Ohio (NEOHIO)
Posts: 11,436
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Re: 420 tips for drilling crankshaft?
I used small bits and graduated to large using taping oil. No issues. I cut my crank first.
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08-19-2022, 02:01 PM | #3 |
Born to be Wild
Join Date: Feb 2019
Location: Palm Harbor Florida
Posts: 2,767
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Re: 420 tips for drilling crankshaft?
A real carbide drill bit? With slow speed, lots of pressure and plenty of oil.
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08-19-2022, 05:26 PM | #4 |
Gone Wild
Join Date: Oct 2016
Location: Dundee quebec
Posts: 3,190
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Re: 420 tips for drilling crankshaft?
Cranks are relatively easy to machine/drill. I've done a few over the years for retaining bolts. KEEP the existing hole as a pilot unless you are drilling this on a mill or drill press, and even then. The only reason that a decent drill wouldn't do the job is if it encountered an inclusion, not unheard of in china iron.
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08-19-2022, 11:27 PM | #5 |
Not Yet Wild
Join Date: May 2022
Location: Ocala, FL
Posts: 35
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Re: 420 tips for drilling crankshaft?
Do you guys drill out the hole with a drill while the crank is still in the engine? Or, do you remove the crank and drill it out on a drill press?
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08-20-2022, 08:05 AM | #6 |
Gone Wild
Join Date: Oct 2016
Location: Dundee quebec
Posts: 3,190
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Re: 420 tips for drilling crankshaft?
I'd just bolt the engine to an angle plate and clamp/bolt the plate to the drill press. Add something to stop the crank from turning, and Bob's your uncle.
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08-20-2022, 08:01 PM | #7 |
Not Yet Wild
Join Date: May 2022
Location: Ocala, FL
Posts: 35
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Re: 420 tips for drilling crankshaft?
[QUOTE and Bob's your uncle. [/QUOTE]
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08-20-2022, 08:52 PM | #8 |
Searching for The Way
Join Date: Oct 2009
Location: Medina, Ohio (NEOHIO)
Posts: 11,436
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Re: 420 tips for drilling crankshaft?
I always thought it was "Mums your uncle"
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08-28-2022, 10:50 AM | #9 |
Not Yet Wild
Join Date: Aug 2021
Location: Chicago area
Posts: 16
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Re: 420 tips for drilling crankshaft?
Thanks everyone. I didn't want to cut the crank first, since I wanted to use the old hole as a guide to help me stay on center. Several carbide drill bits, lots of oil and a sore elbow later, and I'm done. Cut, drilled, and tapped.
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