Thanks: 0
Likes: 0
Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 7 of 7
-
24th August 2012, 02:13 PM #1
cove cutting question - basic geometry
i have a small table saw 2hp x left tilt 10" blade
i need to cut a radiusing block for sanding fingerboards on the guitar necks i build
10" radius is easy, carefully feed the stock at 90deg to the blade from left to right
the 80 tooth carbide blade should make a neat job
i will make up a jig to steady the stock as it goes through the blade and ensure my pinkies are a safe distance from the blade
my question is this [in two parts] please pardon my ignorance of geometry
1. if i tilt the blade to the left x deg and feed the stock across the blade at 90deg will i get a bigger radius cove say 12" or some weird eliptical cove
2. if a larger radius is the result of the above cut, how do i calculate the angle of tilt to obtain a given radius ? - 10" is the minimum obviously
i have looked at a few cove calculators but none seem to address my questions
thanksray c
dunno what's more fun, buyin' the tools or usin' em'
-
24th August 2012 02:13 PM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Age
- 2010
- Posts
- Many
-
24th August 2012, 02:30 PM #2
Look at the blade side on, when its vertical it is a circle.
If you tilt it and look from the side it is an elipse.
If you are talking about a fingerboard 2 inches across cut with the top edge of the elipse you could approximate it to a larger circle (that you have a segment from), But it is still not a circle segment exactly.
If you are talking about 1.5 Inches its a better approximation of a circle segment.
Do you still want the maths done?
Peter
-
24th August 2012, 02:39 PM #3Member
- Join Date
- May 2009
- Location
- Geraldton
- Posts
- 71
I find it easier when coving to use arc width and arc height inputs.
To your first question tilting the blade will affect the shape of the cove not the radius as such.
Back to the calculations. Once I have the arc width and the arc height which can easily be converted to a radius using one of the many calculators on the net I use Blocklayer.
With the arc height I take the radius of the blade that I will be using for me that is generally 127 mm and work out a new arc width for an arc height with the saw blade radius and arc height. This is used to work out the angle for passing the timber across the blade.
I treat the width of the cove I want to create as one side of a triangle and the saw blade arc width as the hypotenuse.
Just a word in general on coving take it about 3 or 4 times slower than you think you need to. For a cove 6 or 7 mm deep I you usually be making between 12 and 15 passes. It also puts quite a strain on your saws bearings I have had to replace those on my carbatec tsc10hbr.
I hope you can understand this waffle
Ben
-
24th August 2012, 02:54 PM #4
apologies
i have a 10" diam saw that can only cut a 5" radius cove
been thinking about this for days and just suddenly realised my initial premise is completely wrongray c
dunno what's more fun, buyin' the tools or usin' em'
-
24th August 2012, 06:47 PM #5Member
- Join Date
- May 2009
- Location
- Geraldton
- Posts
- 71
Old picker I have never passed the timber over the blade at 90 degrees to the blade and thinking about it at 90 degrees the cove would be symmetrical even when tilting the saw blade this would enable you to have a bigger arc width for less arc height. I am not sure of the exact shape you would end up with but it wouldn't be far off
-
24th August 2012, 07:10 PM #6Member
- Join Date
- May 2009
- Location
- Geraldton
- Posts
- 71
I just calculated that tilting the blade to 45 degrees and passing at 90 degrees to the saw blade would give a arc width 75 mm for arc height of a smidge under 4 mm if that helps at all.
Ben
-
24th August 2012, 07:38 PM #7
the idea came from here
from the venerable oztradie master guitar builder who is a forum member
i thought that extending this out a little and using the bigger blade of the table saw would give more accurate sanding blocks
if i can't get a decent job out of it i am going to have to import specialty sanding beams from the states at around $300 for the pair inc freight and a couple other lil pressiesray c
dunno what's more fun, buyin' the tools or usin' em'
Similar Threads
-
Cove cutting jig
By bluekingfisher in forum WOODWORK - GENERALReplies: 6Last Post: 28th November 2010, 09:27 PM -
Basic geometry instead of measuring?
By Skew ChiDAMN!! in forum WOODWORK - GENERALReplies: 46Last Post: 3rd September 2006, 11:37 PM -
Cove cutting on a table saw?
By Skew ChiDAMN!! in forum WOODWORK - GENERALReplies: 15Last Post: 4th May 2006, 05:08 PM -
The most basic wood cutting question??
By Acrapone in forum WOODWORK - GENERALReplies: 15Last Post: 3rd January 2005, 02:28 PM