fine vs coarse thread - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 04-29-2010, 10:26 PM
Registered User
 
Join Date: Apr 2010
Location: Vadodara
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
fine vs coarse thread

Dear Sir,

Can anyone suggest me what is better a fine thread or coarse thread? Why?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-30-2010, 01:23 AM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 47
Posts: 8,925
Wiki Edits: 0

Thanks: 19
Thanked 370 Times in 339 Posts
Fine thread is stronger than an identical course thread bolt of the same size and hardness grade because the course thread cuts away more of the total original uncut diameter of the bolt that was there before the threads were cut. This is called the minor diameter, the smaller fine threads leave a larger minor diameter on the bolt.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-30-2010, 05:30 AM
Member
 
Last photo:
Join Date: Feb 2002
Location: Agua Dulce Calif.
Posts: 328
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
will it make a differance to what the tapped material is, if aluminum is course harder to pull the bolt from Ed
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-30-2010, 10:07 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 47
Posts: 8,925
Wiki Edits: 0

Thanks: 19
Thanked 370 Times in 339 Posts
No fine thread will still be stronger even in aluminum. Just as an example think of it this way - if a threaded hole has 10 course threads in it or 20 fine threads the fact that the fine thread has twice as many holding points is the strength gain: the load is spread out to more of the aluminum and not as concentrated as it is with the fewer contact points of the course thread. That is a crude analogy but you get the idea...

Threaded into aluminum you have to follow certain basic machinist rules. To get correct strength in aluminum the tapped holes depth has to be at least 1-1/2 times the diameter of the fastener, and 2 times or more the diameter is even better if the material is thick enough. On the other hand steel is fine with the basic rule of the tapped hole depth being just at least equal to the diameter of the fastener. These rules are basically the same for fine or course thread.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-01-2010, 07:47 AM
Frisco's Avatar
Glad To Be Here
 
Last photo:
Join Date: Nov 2002
Location: Canton, North Carolina
Age: 72
Posts: 2,244
Wiki Edits: 0

Thanks: 0
Thanked 8 Times in 8 Posts
Quote:
Originally Posted by Ed ke6bnl
will it make a differance to what the tapped material is, if aluminum is course harder to pull the bolt from Ed
It definitely will make a difference.

Using fine threads in non-ferrous metals (brass, aluminum, copper, etc.) and cast iron will 'strip' much more easily than if the same size was done with course threads. This is especially true when the diameters are below 1/2". When designing components made from non-ferrous materials or cast iron where threads are required, the general 'rule of thumb' is to utilize course threads. If fine threads are necessary, then heli-coils or threaded inserts should be employed.

For ferrous metals (steel, stainless, etc.), fine threads are indeed a better choice in many applications.

Here are four links for you to consider.

Link 1

Link 2

Link 3

Link 4

Last edited by Frisco; 05-01-2010 at 08:27 AM. Reason: added four links for your consideration
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-01-2010, 10:46 AM
Registered User
 
Last photo:
Join Date: Dec 2009
Location: north dakota
Posts: 53
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I don't think that a fine threaded hole is stronger it has just as much material contacting do to the height of the thread but male fine threads are stronger because the root is not as deep it also a little less likely to strip out course theads when cutting them. The fine thread is less likely to loose up because the pitch is not as steep. They each have their own uses. There is also have national super fine threads out there I've had to cut them before
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-02-2010, 04:13 PM
cranky1's Avatar
Just stuck
 
Last photo:
Join Date: Apr 2008
Location: Pasagetdowndena, TX
Age: 63
Posts: 436
Wiki Edits: 0

Thanks: 14
Thanked 0 Times in 0 Posts
For most applications, course threads offer these advantages:

* Easier and faster assembly, providing a better start with less chance of cross threading.
* Nicks and burrs from handling are less liable to affect assembly.
* They are less likely to seize in temperature applications and in joints where corrosion will form.
* Less prone to strip when threaded into lower strength metals.
* More easily tapped in brittle materials and or materials that crumble easily.


Fine threads may make for a superior fastener for applications with specific strength or other requirements.

* They are about 10% stronger than coarse threads due to their greater cross-section area.
* In very hard materials, fine threads are easier to tap.
* They can be adjusted more precisely because of their smaller helix angle.
* Where length of engagement is limited, they provide greater strength.
* Thinner wall thickness can be used because of their smaller thread cross section.

From http://www.tapmatic.com/tech_manual/drill_depth.html
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-03-2010, 02:17 AM
Hippie's Avatar
Analog man in a digital world.
 

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,255
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
In addition and on a less technical level, coarse threads are more forgiving of debris, cross thread less easily when starting and installation and removal is faster. On the other hand fine threads take longer to back out if loose giving you more detection time before a total failure. US Military equipment uses primarily fine threads and I was told it was because of increased resistance to vibration.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-03-2010, 05:57 AM
Registered User
 

Last journal entry: 50 Ply wagon
Last photo:
Join Date: Oct 2008
Location: Pottstown,Pa
Posts: 615
Wiki Edits: 0

Thanks: 0
Thanked 28 Times in 27 Posts
simply put ....fine threads are less likely to come loose. example .all motorcycles have fine threaded nuts and bolts due to vibration.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-03-2010, 07:52 AM
Frisco's Avatar
Glad To Be Here
 
Last photo:
Join Date: Nov 2002
Location: Canton, North Carolina
Age: 72
Posts: 2,244
Wiki Edits: 0

Thanks: 0
Thanked 8 Times in 8 Posts
Quote:
Originally Posted by sunsetdart
example .all motorcycles have fine threaded nuts and bolts due to vibration.
This statement is just NOT true. Most motorcycle engine cases are made from cast aluminum. They have course threads (metric for the Japanese manufactured bikes, Whitworth for older British bikes and SAE for American made bikes) in them so that the assembly screws will have less of a tendency to strip when being tightened. Some older Harley Davidson cases used a 1/4-24 tpi for the tappet block mounting screws and for the oil pump studs as well as the cam cover screws. This is neither a course (1/4-20 tpi) or a fine (1/4-28 tpi) series thread. It is a National Special. Later models used 1/4-20 NC.

To combat vibration on motorcycles, there are several methods employed besides using fine threads to prevent the premature loosening of fasteners. Using the correct torque being the first. Thread sealants (such as RTV), Loctite, self locking nuts, etc. Safety wire. Locking tabs.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-04-2010, 06:27 PM
Registered User
 
Last photo:
Join Date: Aug 2008
Location: Melbourne, Australia
Posts: 113
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
The fact that you can buy both coarse and fine threads ought to tell you that neither is "best" for every single application. They each have advantages and disadvantages, mostly depending what is being threaded onto the end.

Fine threads are definitely stronger and give a higher clamping force for a given tightening torque. They are also less likely to come loose. Fine pitch threads are always the best choice where a nut is to be used.

Coarse threads are better when a blind hole is tapped into soft material. You will always find coarse threads going into aluminum castings, because fine threads would tear out of soft material much more easily.

The problem is not the bolt itself, but the strength of the material the bolt goes into. So we need both coarse and fine bolts depending on what screws on the end.
Reply With Quote Quick reply to this message

Recent Hotrodding Basics posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
bolt will not thread into hole ran a tap through several times hotbrat Garage - Tools 32 03-23-2010 07:59 PM
New toy for mikey powerrodsmike Garage - Tools 47 12-09-2008 01:28 PM
New Thread Preview Boxes Jon Hotrodders' Lounge 9 02-14-2004 02:18 PM


All times are GMT -6. The time now is 06:29 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.