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Post by scootnewb on Mar 11, 2019 13:24:55 GMT -5
Hello,
I am getting a Grom clone and wanted to replace the engine mount bolts with some beefier ones. After reading up I found the best option would be drilling out the pre-existing holes (which accept 8mm bolts) to accept real Grom bolts which are 10mm. I wanted to know how to determine which size and type drill bit to use. I also wondered if drilling it out is as simple as it seems. Any tips would be appreciated.
Thanks
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Post by 190mech on Mar 11, 2019 16:11:47 GMT -5
Easy!Get a 10mm drill bit and a hefty drill and go to it...It may have some very long bolts,so an extra long bit(costly) would be needed..Go only 1/2 way,then go at it from the other side..Good Luck,keep us posted!!
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Post by jackrides on Mar 11, 2019 16:36:37 GMT -5
It's best to get the bolts and measure them so there's no question of diameter. Vernier calipers even cheap ones. Regular new drill bits (preferably titanium coated), cutting oil (wd-40 ok), and see to it the engine and drill are held Really steady! You don't want any cracks starting there.
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Post by scootnewb on Mar 11, 2019 19:01:03 GMT -5
Thanks.
I didn't realize you could use the same diameter bit as the bolts. I thought there was some weird trick like using a slightly smaller sized bit because the friction would make the hole slightly larger or something. I don't know why I thought that.
I'm starting to get psyched up about it now.
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Post by FrankenMech on Mar 11, 2019 23:51:05 GMT -5
A 10mm drill bit will usually drill a few thousandths of an inch oversize. A threaded bolt is usually a few thousandths of an inch undersize. Together they fit fairly well, a solid rod will fit better. A full 10mm solid rod with no threads will be stronger than a threaded rod or bolt. You can cross drill both ends of a solid rod and put a cotter pin through them.
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Post by aeroxbud on Mar 12, 2019 1:53:31 GMT -5
Don't try and force the drill bit through. Take your time and let the drill do the work. Keep stopping to clear the swarf Otherwise you can overheat the bit. Use cutting oil and a slow speed.
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Post by scootnewb on Mar 22, 2019 11:12:15 GMT -5
I've found the engine case (not the block) I'll be drilling through is aluminum and it should be easy. We'll see.
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Post by FrankenMech on Mar 22, 2019 20:51:47 GMT -5
Lube the bit while drilling aluminum with WD-40. It should not be hard at all since you are going from 8mm to 10mm.
I do have a question. Are these holes smooth or threaded?
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Post by scootnewb on Mar 22, 2019 21:33:45 GMT -5
They are smooth.
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