Bandsaw Tension Gage Sketchup Model - Router Forums
 2Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 04-11-2013, 12:03 PM Thread Starter
Registered User
 
GulfcoastGuy's Avatar
 
Join Date: Feb 2012
Country: United States
First Name: Patrick
Posts: 882
 
Default Bandsaw Tension Gage Sketchup Model

I've been messin' around with a model of a bandsaw blade tension gage based on the one on Woodgears.ca. While I was at it I decided to try my hand at Scenes for the first time.

[IMG] tension gage screen shot by pat w1, on Flickr[/IMG]

For those that don't already know the scene tabs are across the top of the edit window.

The gage should produce a .001" reading on the dial indicator for each 2000 psi of tension on the 4" captured section of the blade.
Attached Files
File Type: zip tension gage.zip (135.8 KB, 92 views)

GCG

___
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
___
http://www.routerforums.com/table-mo...table-saw.html
GulfcoastGuy is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 04-11-2013, 06:33 PM Thread Starter
Registered User
 
GulfcoastGuy's Avatar
 
Join Date: Feb 2012
Country: United States
First Name: Patrick
Posts: 882
 
Default

Add the dimension scenes for the clips and the hinge strap.
Attached Files
File Type: zip tension gage.zip (133.5 KB, 34 views)

GCG

___
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
___
http://www.routerforums.com/table-mo...table-saw.html
GulfcoastGuy is offline  
post #3 of 11 (permalink) Old 04-12-2013, 08:44 AM Thread Starter
Registered User
 
GulfcoastGuy's Avatar
 
Join Date: Feb 2012
Country: United States
First Name: Patrick
Posts: 882
 
Default

Added a relief cut behind the blade. I didn't want the possibility of the 4" section of the blade under test to interfere with the gage block.
[IMG] tension gage reliefcut1 by pat w1, on Flickr[/IMG]
[IMG] tension gage reliefcut2 by pat w1, on Flickr[/IMG]
Attached Files
File Type: zip tension gage.zip (139.8 KB, 25 views)

GCG

___
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
___
http://www.routerforums.com/table-mo...table-saw.html
GulfcoastGuy is offline  
Sponsored Links
Advertisement
 
post #4 of 11 (permalink) Old 04-12-2013, 08:55 AM
Registered User
 
Join Date: Feb 2012
Country: United States
First Name: Chris
Posts: 1,298
 
Default

Patrick, I was hoping you wouldn't mind going into how this device works and what is would be used for ... I am having a hard time seeing the physics of the thing.
Chris Curl is offline  
post #5 of 11 (permalink) Old 04-12-2013, 02:23 PM Thread Starter
Registered User
 
GulfcoastGuy's Avatar
 
Join Date: Feb 2012
Country: United States
First Name: Patrick
Posts: 882
 
Default

That's why I gave the woodgears.ca link in the first post. He has an excellent write up.

In short it's a gage for tensioning a band saw blade. It's based on the elasticity of the steel and the use of Young's Modulus to predict the amount of stretch associated with a given tension. The usual implementation is to attach a gage to one point on the blade and a measurement point at a known distance to the previous point. As the tension is applied the blade will stretch a fixed distance for the length of the blade between the two points. You then use Young's Modulus to convert the measured stretch to tension in PSI. This device amplifies the responce by placing a hinge 1" away from the blade and taking the measurement 3.625" on the other side, increasing the response by a factor of 3.625

... So ...

for each .001" on the dial there will be a stretch of .00027582".

- divide that by the 4" of blade captured between the clips and you get:
.00027582/4 = .00006896551724

- multiply that by Young's modulus for steel - 29,000,000 and you get
.00006896551724*29,000,000 = 2000 ... 2,000 psi for every .001" division on the gage.

If not otherwise specified, a rule of thumb spec for band saw blade tension is 15,000 psi so you would tension the blade till the gage showed an offset of between .007" and .008". Low tension blades like Timberwolf call for a lower spec of between 6000 and 8000 psi (I think) so a gage reading of between .003" and .004" would be needed.

Hope that helps.
peterbata likes this.

GCG

___
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
___
http://www.routerforums.com/table-mo...table-saw.html

Last edited by GulfcoastGuy; 04-12-2013 at 02:27 PM.
GulfcoastGuy is offline  
post #6 of 11 (permalink) Old 04-12-2013, 04:26 PM
Registered User
 
Join Date: Jan 2012
Country: United States
First Name: Ray
Posts: 40
 
Default

Does this remain constant with changes in the depth and thickness of the blade?
Ray Y is offline  
post #7 of 11 (permalink) Old 04-12-2013, 06:41 PM Thread Starter
Registered User
 
GulfcoastGuy's Avatar
 
Join Date: Feb 2012
Country: United States
First Name: Patrick
Posts: 882
 
Default

Quote:
Originally Posted by Ray Y View Post
Does this remain constant with changes in the depth and thickness of the blade?
Yes. The force required to achieve the tension is dependent on the cross sectional area but the elasticity and consequently the amount of stretch remains constant. This is why the tension gage in the back of some saws is so unreliable. They respond to the force applied to the tensioning spring and are calibrated to blades of a particular thickness (one source I saw on the net seemed to think it was .019"). Lets say the saw was calibrated with say ... a 3/8" - .019" blade. If the thickness of the blade installed is greater, then it will require more force than is reflected on the integrated gage scale. A 1/2" - .022 blade when at proper tension may display the correct tension for a 3/4" blade or greater.

My Craftsman 10" saw has no such scale and I've never been very confident in the validity of either the 'push the blade with your finger with "reasonable force" for a 1/4" deflection' or the 'pluck for a ringing tone' methods of setting tension.

GCG

___
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
___
http://www.routerforums.com/table-mo...table-saw.html
GulfcoastGuy is offline  
post #8 of 11 (permalink) Old 04-12-2013, 06:50 PM Thread Starter
Registered User
 
GulfcoastGuy's Avatar
 
Join Date: Feb 2012
Country: United States
First Name: Patrick
Posts: 882
 
Default

Oh, forgot to add. I just got home with this:



1" full travel, .001" resolution, with plenty of open space between the ticks. It's not he smoothest action I've ever seen but I am pleasantly surprised for $15 from HF.
peterbata likes this.

GCG

___
"I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit. " - Chuck Yeager
___
http://www.routerforums.com/table-mo...table-saw.html
GulfcoastGuy is offline  
post #9 of 11 (permalink) Old 04-19-2015, 04:54 AM
Registered User
 
Join Date: Jun 2009
Country: United States
First Name: Ragnar
Posts: 2
 
Default Unable to download ketchup file.

Hi.

The download for the sketchup file does not work.
Anybody got the file and can upload again?
Thanks in advance.
Ragnar
ragstian is offline  
post #10 of 11 (permalink) Old 04-19-2015, 11:29 AM
Registered User
 
PhilBa's Avatar
 
Join Date: Sep 2014
Country: United States
First Name: phil
Posts: 1,046
 
Default

Shouldn't be too hard to make from scratch in SU. The only question is how the clamps at the top and bottom work. I'd guess wing nuts would be fine. The woodgears.ca link is pretty helpful in sorting out most questions. I've had this one on my list of shop projects for a while. Might not get to the top as the "tap for deflection" method seems to work ok for me. If I was going to do a bunch of resawing or more extensive BS work, it would probably zoom to the top.

And, the total geek in me says it would be cool to use a cheap chinese caliper with a connection to something like an Arduino for a direct readout of the actual tension. Then you wouldn't have to set it exactly at 4" - the Arduino's programming would compensate for the actual starting point. But that would cut into my time for making things in wood...
PhilBa is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Router Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
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:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Older model Jet 18" bandsaw braunthrax Tools and Woodworking 13 06-28-2012 09:36 AM
Saw Powermatic Model PWBS14 14" Bandsaw Dejure Powermatic Manuals 0 04-12-2011 06:39 PM
Tension On old 1947 Delta bandsaw Gathion Tools and Woodworking 3 05-07-2009 08:32 PM
model 315 17351 = model 735-2 headclansman General Routing 2 04-28-2008 02:13 AM
Bandsaw tension Glenmore Tools and Woodworking 8 07-25-2006 05:18 AM

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 Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome