When sawboards go bad

So I cut a length off a full sheet of 3/4" MDF. Being too large to feed through my table saw I used my long sawboard[1]. Normally I am just breaking down a big sheet so I can machine it further, but this time was actually cutting to finished size.
When I checked the cut part in the middle, I thought "that's odd, its 2-3mm too wide". Then I checked both ends, and they were spot on. So a bit of further investigation showed that the trusty sawboard had a very slight bend along its length! Not sure if its always been there, or for some reason it had warped.
Anyway, to fix it I clamped it to the factory edge of the MDF sheet, and used a router with a fence to trim the face part of the board parallel to the edge of the MDF sheet - vutting just deep enough to take the face edge flush to the top of the board. Then I re-cut the board edge with the circular saw to make it match the now slightly shifted (and straight!) fence on the board. So it works ok again now...
[1] http://wiki.diyfaq.org.uk/index.php/Sawboard
--
Cheers,

John.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/5/2017 10:48 PM, John Rumm wrote:

Weird! Mine (4 foot and 8 foot) are both two bits of 9 mm ply, I would be surprised if they distorted that way. A very elegant fix though, I will try to file that away mentally. Will check my boards when they come back from loan too.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 05/02/2017 23:34, newshound wrote:

This was one made from 6mm ply, so perhaps that's part of it. Come to think of it, I did wax it the other day...
--
Cheers,

John.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 06/02/2017 00:19, John Rumm wrote:

I suppose one should invest in plastic but it's so damned expensive. I suppose narrow strips might get chucked by fabricators.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 05/02/17 22:48, John Rumm wrote:

For some reason my circular saw has has a bit of an occasional startout wobble and taken some material out of the start and end of my aging thin MDF sawboard.
It's a mm or so, so me using either end to match measured points on the workpiece doesn't work out that well for accuracy. I now prefer to align further down the sawboard against straight drawn pencil lines, where this sawboard damage hasn't happened.
--
Adrian C

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This has happened with my MDF one. I noticed when I cut some strips of ply off the long edge of a full sheet. I suspect that when used on a full sheet, because it can only be clamped at the ends, pushing the saw against the guide bends it a little. After a few goes this bend sets in. I had hoped that switching to ply for the sawboard would solve this, but your experience suggests not.
--
Jón Fairbairn snipped-for-privacy@cl.cam.ac.uk
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2014-04-05)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 07/02/2017 10:46, Jon Fairbairn wrote:

Well mine was bent in the other direction - bowed against the direction of push...
I think 6mm base board, and 9 or 12mm ply fence is probably a better combination.
--
Cheers,

John.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/7/2017 11:53 AM, John Rumm wrote:

Certainly a bit easier to use with a thicker fence. I had spare 9 mm when I made mine. You lose a bit of cut depth with a 9 mm base board, but not a problem if you are mainly cutting sheet up to 18 mm. With 9 and 9 or 9 and 12 it is easier to screw and glue to make a very robust board.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.