Question about Derby bolts
Road Warrior
Joined: Jan 2007
Posts: 1,276
Likes: 8
From: Minneapolis Area, MN
RE: Question about Derby bolts
The major diameter on a 1/4-20 helicoil tap is .3187" and the major diameter of a 5/16-18 tap is nominally .3125". These are pretty much identical as far as radial wall thickness around the fastener is concerned.
Given the choice...a 1/4-20 helicoil will hold up much better than a 5/16-18 tap in aluminum. Not to mention retaining the original fastener, maintaining the same "look" as the other fasteners and keeping the original counterbore size for the fastener's head.
Keep in mind that to install a 1.5X length helicoil (for a 1/4" fastener that's 3/8" thread engagement into the helicoil) a minimun tap depth of .430" is required. As a general rule of thumb for a blind hole helicoil, the tap drill depth is: the required thread depth + 1.5 times the thread diameter. A 1/4-20 X 3/8 long helicoil for example: .375+(1.5*.25)=0.75 deep tap drill. Now if you use a bottoming tap, you reduce that tap drill depth some. Not sure how much without the books at work.
The fastener itself should run completely through the helicoil. It is common to have a 1/2" of fastener going through 3/8" of helicoil. (The helicoil tap drill is always larger than the major diameter of the fastener threading into it.)
Given the choice...a 1/4-20 helicoil will hold up much better than a 5/16-18 tap in aluminum. Not to mention retaining the original fastener, maintaining the same "look" as the other fasteners and keeping the original counterbore size for the fastener's head.
Keep in mind that to install a 1.5X length helicoil (for a 1/4" fastener that's 3/8" thread engagement into the helicoil) a minimun tap depth of .430" is required. As a general rule of thumb for a blind hole helicoil, the tap drill depth is: the required thread depth + 1.5 times the thread diameter. A 1/4-20 X 3/8 long helicoil for example: .375+(1.5*.25)=0.75 deep tap drill. Now if you use a bottoming tap, you reduce that tap drill depth some. Not sure how much without the books at work.
The fastener itself should run completely through the helicoil. It is common to have a 1/2" of fastener going through 3/8" of helicoil. (The helicoil tap drill is always larger than the major diameter of the fastener threading into it.)
Outstanding HDF Member
Joined: Jun 2006
Posts: 3,432
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From: SW Ohio
RE: Question about Derby bolts
A real good trick is put the wrench head on each bolt .. give each one 4 or 5 good raps with a hammer before you try to take them out . works even on old bikes most of the time..learned this from my old honda days and they were even worse . then i put some anti sieze on the bolts before i put them back in. good luck .
Road Captain
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From:
RE: Question about Derby bolts
Use a handheld impact driver. If you are not familiar http://www.kk.org/cooltools/archives/000723.php
Thread Starter
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From: Orange County, CA
RE: Question about Derby bolts
ORIGINAL: Dynamite17
I'd like to replace the Torx with chrome Allens, do you know the bolt size?
I'd like to replace the Torx with chrome Allens, do you know the bolt size?
Size is 1/4-20 5/8" long for an '06 dyna.
Their part number is 9425 - that is a box of 10 socket button head screws, grade 8 chrome, 1/4-20 x 5/8. They also sell them individually.
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From: Orange County, CA
RE: Question about Derby bolts
ORIGINAL: mtnlvr
The major diameter on a 1/4-20 helicoil tap is .3187" and the major diameter of a 5/16-18 tap is nominally .3125". These are pretty much identical as far as radial wall thickness around the fastener is concerned.
Given the choice...a 1/4-20 helicoil will hold up much better than a 5/16-18 tap in aluminum. Not to mention retaining the original fastener, maintaining the same "look" as the other fasteners and keeping the original counterbore size for the fastener's head.
Keep in mind that to install a 1.5X length helicoil (for a 1/4" fastener that's 3/8" thread engagement into the helicoil) a minimun tap depth of .430" is required. As a general rule of thumb for a blind hole helicoil, the tap drill depth is: the required thread depth + 1.5 times the thread diameter. A 1/4-20 X 3/8 long helicoil for example: .375+(1.5*.25)=0.75 deep tap drill. Now if you use a bottoming tap, you reduce that tap drill depth some. Not sure how much without the books at work.
The fastener itself should run completely through the helicoil. It is common to have a 1/2" of fastener going through 3/8" of helicoil. (The helicoil tap drill is always larger than the major diameter of the fastener threading into it.)
The major diameter on a 1/4-20 helicoil tap is .3187" and the major diameter of a 5/16-18 tap is nominally .3125". These are pretty much identical as far as radial wall thickness around the fastener is concerned.
Given the choice...a 1/4-20 helicoil will hold up much better than a 5/16-18 tap in aluminum. Not to mention retaining the original fastener, maintaining the same "look" as the other fasteners and keeping the original counterbore size for the fastener's head.
Keep in mind that to install a 1.5X length helicoil (for a 1/4" fastener that's 3/8" thread engagement into the helicoil) a minimun tap depth of .430" is required. As a general rule of thumb for a blind hole helicoil, the tap drill depth is: the required thread depth + 1.5 times the thread diameter. A 1/4-20 X 3/8 long helicoil for example: .375+(1.5*.25)=0.75 deep tap drill. Now if you use a bottoming tap, you reduce that tap drill depth some. Not sure how much without the books at work.
The fastener itself should run completely through the helicoil. It is common to have a 1/2" of fastener going through 3/8" of helicoil. (The helicoil tap drill is always larger than the major diameter of the fastener threading into it.)
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From: Orange County, CA
RE: Question about Derby bolts
ORIGINAL: warren888
Just received mine from www.boltdepot.com
Size is 1/4-20 5/8" long for an '06 dyna.
Their part number is 9425 - that is a box of 10 socket button head screws, grade 8 chrome, 1/4-20 x 5/8. They also sell them individually.
ORIGINAL: Dynamite17
I'd like to replace the Torx with chrome Allens, do you know the bolt size?
I'd like to replace the Torx with chrome Allens, do you know the bolt size?
Size is 1/4-20 5/8" long for an '06 dyna.
Their part number is 9425 - that is a box of 10 socket button head screws, grade 8 chrome, 1/4-20 x 5/8. They also sell them individually.
Road Warrior
Joined: Jan 2007
Posts: 1,276
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From: Minneapolis Area, MN
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Club Member
Joined: May 2006
Posts: 14,564
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From: the 50s & the 60s
RE: Question about Derby bolts
ORIGINAL: cstolp
Use a handheld impact driver. If you are not familiar http://www.kk.org/cooltools/archives/000723.php
Use a handheld impact driver. If you are not familiar http://www.kk.org/cooltools/archives/000723.php
Right on the money cs.
Anytime I remove a torx head fastener from my machine,
I get out the handheld impact driver and the 24 ounce ball pein.
Then I give the torx a couple love taps followed by a really violent smack.
This loosens the fastener, allowing for normal removal without ruining the torx head.
Torx heads are replaced when appropriate, usually with a hexsocket head.
Always with at least blue loctite, or nylon patched threads.
mud
Club Member
Joined: May 2006
Posts: 14,564
Likes: 9,225
From: the 50s & the 60s
RE: Question about Derby bolts
warren, excellent info from mtn.
Problem comes when trying to locate the time and a half helicoils.
Most counter personnel have no idea. Goes right over their head.
Go to McMaster Carr for this sort of thing, quick cheap shipping.
High quality fasteners, helicioils, etc.
They have an excellent online catalog,
and well versed pesonnel manning the 1-800 line.
mud
Problem comes when trying to locate the time and a half helicoils.
Most counter personnel have no idea. Goes right over their head.
Go to McMaster Carr for this sort of thing, quick cheap shipping.
High quality fasteners, helicioils, etc.
They have an excellent online catalog,
and well versed pesonnel manning the 1-800 line.
mud
ORIGINAL: warren888
Mtnlvr - this is excellent information. YOu are obviously a machinist, tool & die maker, or great mechanic. I love this kind of detail. Thank you.
ORIGINAL: mtnlvr
The major diameter on a 1/4-20 helicoil tap is .3187" and the major diameter of a 5/16-18 tap is nominally .3125". These are pretty much identical as far as radial wall thickness around the fastener is concerned.
Given the choice...a 1/4-20 helicoil will hold up much better than a 5/16-18 tap in aluminum. Not to mention retaining the original fastener, maintaining the same "look" as the other fasteners and keeping the original counterbore size for the fastener's head.
Keep in mind that to install a 1.5X length helicoil (for a 1/4" fastener that's 3/8" thread engagement into the helicoil) a minimun tap depth of .430" is required. As a general rule of thumb for a blind hole helicoil, the tap drill depth is: the required thread depth + 1.5 times the thread diameter. A 1/4-20 X 3/8 long helicoil for example: .375+(1.5*.25)=0.75 deep tap drill. Now if you use a bottoming tap, you reduce that tap drill depth some. Not sure how much without the books at work.
The fastener itself should run completely through the helicoil. It is common to have a 1/2" of fastener going through 3/8" of helicoil. (The helicoil tap drill is always larger than the major diameter of the fastener threading into it.)
The major diameter on a 1/4-20 helicoil tap is .3187" and the major diameter of a 5/16-18 tap is nominally .3125". These are pretty much identical as far as radial wall thickness around the fastener is concerned.
Given the choice...a 1/4-20 helicoil will hold up much better than a 5/16-18 tap in aluminum. Not to mention retaining the original fastener, maintaining the same "look" as the other fasteners and keeping the original counterbore size for the fastener's head.
Keep in mind that to install a 1.5X length helicoil (for a 1/4" fastener that's 3/8" thread engagement into the helicoil) a minimun tap depth of .430" is required. As a general rule of thumb for a blind hole helicoil, the tap drill depth is: the required thread depth + 1.5 times the thread diameter. A 1/4-20 X 3/8 long helicoil for example: .375+(1.5*.25)=0.75 deep tap drill. Now if you use a bottoming tap, you reduce that tap drill depth some. Not sure how much without the books at work.
The fastener itself should run completely through the helicoil. It is common to have a 1/2" of fastener going through 3/8" of helicoil. (The helicoil tap drill is always larger than the major diameter of the fastener threading into it.)