Help with CroMo Question!!!
08-20-14 | 12:53 PM
#26
Calamari Marionette Ph.D
Joined: Dec 2013
Posts: 7,861
Likes: 41
From: Coeur d' Alene
Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors
Purchase one of these to mark your holes: Center Punch - Automatic Center Punch with Brass Handle
Then drill a small pilot hole (3/32" or so), then 11/64" for the M5x0.8 tap. Harbor Freight taps are fine. Their drills leave a lot to be desired. Get your drills from McMaster or Fastenal or MSC or Grainger or similar Industrial Supply company.
After drilling, counter sink the holes slightly on both sides before tapping with a 1/4" drill bit by hand, not in a power tool. I have one of these: https://uytit.files.wordpress.com/201...rill-chuck.jpg that I use for holding drill bits for manual operations. Less than $10-
Use lots of oil both when you drill and when you tap. Any light oil is fine - I usually use TriFlow liquid - not spray.
Flush the oil out with Isopropyl Alcohol (from any pharmacy) just before you install the rack, and use blue or purple thread locker. That will protect the cro-mo and retain the screw, while still being removeable. DO NOT use red threadlocker - you will not be able to remove the screw.
Then drill a small pilot hole (3/32" or so), then 11/64" for the M5x0.8 tap. Harbor Freight taps are fine. Their drills leave a lot to be desired. Get your drills from McMaster or Fastenal or MSC or Grainger or similar Industrial Supply company.
After drilling, counter sink the holes slightly on both sides before tapping with a 1/4" drill bit by hand, not in a power tool. I have one of these: https://uytit.files.wordpress.com/201...rill-chuck.jpg that I use for holding drill bits for manual operations. Less than $10-
Use lots of oil both when you drill and when you tap. Any light oil is fine - I usually use TriFlow liquid - not spray.
Flush the oil out with Isopropyl Alcohol (from any pharmacy) just before you install the rack, and use blue or purple thread locker. That will protect the cro-mo and retain the screw, while still being removeable. DO NOT use red threadlocker - you will not be able to remove the screw.
08-20-14 | 01:45 PM
#27
Nigel
Joined: Mar 2011
Posts: 2,991
Likes: 7
From: San Jose, CA
Bikes: 1980s and 1990s steel: CyclePro, Nishiki, Schwinn, SR, Trek........
So that there is not a remnant of the thread sticking up, and to provide a lead in for the screw; also good general practice. Having a thread remnant fall into the chain is not good for the chain or sprockets.
Cro-mo is not the easiest thing to drill, high quality sharp drills required. It is easier to tap than most stainless steels, but not be much. When tapping, turn in 1 turn, turn back ½ turn, repeat. Failure to do so will likely result in a broken tap.
Cro-mo is not the easiest thing to drill, high quality sharp drills required. It is easier to tap than most stainless steels, but not be much. When tapping, turn in 1 turn, turn back ½ turn, repeat. Failure to do so will likely result in a broken tap.
08-20-14 | 02:02 PM
#29
Senior Member
Joined: Feb 2004
Posts: 30,225
Likes: 649
From: St Peters, Missouri
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Well, we bought the bike and it looks like the drilling will definitely be an option and I'm probably going for it! Unfortunately I don't have any bikes to practice on but I'm a pretty meticulous/neat guy anyway. There will be lots of measuring and double checking before any drilling happens, simply to make sure that the holes are in the same spot on both sides.
Purchase one of these to mark your holes: Center Punch - Automatic Center Punch with Brass Handle
Then drill a small pilot hole (3/32" or so), then 11/64" for the M5x0.8 tap. Harbor Freight taps are fine. Their drills leave a lot to be desired. Get your drills from McMaster or Fastenal or MSC or Grainger or similar Industrial Supply company.
After drilling, counter sink the holes slightly on both sides before tapping with a 1/4" drill bit by hand, not in a power tool. I have one of these: https://uytit.files.wordpress.com/201...rill-chuck.jpg that I use for holding drill bits for manual operations. Less than $10-
Use lots of oil both when you drill and when you tap. Any light oil is fine - I usually use TriFlow liquid - not spray.
Flush the oil out with Isopropyl Alcohol (from any pharmacy) just before you install the rack, and use blue or purple thread locker. That will protect the cro-mo and retain the screw, while still being removeable. DO NOT use red threadlocker - you will not be able to remove the screw.
Then drill a small pilot hole (3/32" or so), then 11/64" for the M5x0.8 tap. Harbor Freight taps are fine. Their drills leave a lot to be desired. Get your drills from McMaster or Fastenal or MSC or Grainger or similar Industrial Supply company.
After drilling, counter sink the holes slightly on both sides before tapping with a 1/4" drill bit by hand, not in a power tool. I have one of these: https://uytit.files.wordpress.com/201...rill-chuck.jpg that I use for holding drill bits for manual operations. Less than $10-
Use lots of oil both when you drill and when you tap. Any light oil is fine - I usually use TriFlow liquid - not spray.
Flush the oil out with Isopropyl Alcohol (from any pharmacy) just before you install the rack, and use blue or purple thread locker. That will protect the cro-mo and retain the screw, while still being removeable. DO NOT use red threadlocker - you will not be able to remove the screw.
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