Replies

1. 
   Wdworker | Jan 31, 2011 09:27am | #1

   Straightedge

   I suggest that the first step is to buy a master straightedge from which a suitable straightedge suitable for use with your router can be made or purchased.

   How to find that "master" straightedge? Of course one could just buy a straightedge that is manufactured and sold as a straightedge, but these are quite expensive. For a less expensive alternative, what I did when I needed a straightedge I could trust to adjust my jointer, I went to the hardware store with a feeler gage and checked out the four foot levels for straightness. They all seem to have some deviation from straightness, but some are better than others. I put two levels of the same design together with the bottom of one against the bottom of the other and checked for gaps between them  with the feeler gage. I found some designs straighter than others. As it is likely that both levels were made with the same process, it is likely that both will deviate from straighness by the same amount. Therefore any gap measured would be approximately double the deviation for either of the levels. I then purchased the level of the design with the least deviation.

   Once you have a reference straightedge, you can use that to either:

   • Go to the structural aluminum or steel bin in the hardware store with your level and feeler gage and try to find an aluminum or steel angle, channel or bar with the required straightness, or if none has the desired straighness,

      

   • Make up a hardwood straightedge to match the "master" straightedge (the level) in straightness using the feeler gage

2. 
   oldusty | Jan 31, 2011 09:47am | #2

   It's not rocket science

     Gregg,

          All you really need is a straight board or a straight  piece of 3/4" plywood to use as a straight edge for the work you are attempting .

      Lots of folks only have a top with a router in it that they clamp over saw horses or whatever .

     Go to the local Formica counter top shop and get a sink cutout to use for the top , that's one way .

      Lastly , go to a local cabinet shop and ask pay them to make the few cuts you need on your own materials , they most likely will be happy to help you for about a 6 pack .

                    good luck             regards   dusty,boxmaker

3. 
   RalphBarker | Jan 31, 2011 11:26am | #3

   flat vs. FLAT

   For most router table purposes, the top just needs to be "pretty flat" (like a well-made table saw) as opposed to FLAT (as in Starrett granite reference plate flat).

   Depending on the weight of the router you'll be mounting in the table (presumably on an aluminum or phenolic insert plate), the desired level of rigidity of the top can vary. Many recommend laminating two sheets of (good quality) 3/4" MDF, or two sheets of 3/4" phenolic covered Baltic Birch ply. Covering both surfaces of the MDF with plstic laminate (Formica) is often recommended, as well. A thinner top with a support matrix built into the cabinet, or attached to the top, can also suffice. The phenolic-covered Baltic Birch ply doesn't require the Formica, of course.

   I also agree that a good quality 4' level can be used as a "straight edge" for checking work surfaces for "flat". A level with machined surfaces is a good indicator that the manufacturer has attempted to be sure the surface of the level is reasonably stratight and flat. The level can then be used to check the top supporting surface of the router table cabinet to make sure it is supporting the top properly. A block plane can be used to shave off any high spots.

   "Machinist" level precision isn't required here, unless you're building things that require that level of precision.

4. 
   forrestb | Jan 31, 2011 01:17pm | #4

   try a scale instead of a level

    I had a problem routing several flutes for bookcases not too long ago that needed a straightedge almost 6 feet long.  I did what was suggested above:  take a feeler gauge to the hardware store but instead of  4 ft levels I checked 72 inch aluminum scales at ACE Hardware.   They had several and I found 2 that were straight within a few   thousandths.

   Bought them a lot cheaper than a level and they came in different lengths.

   Of course, a really straight 4 ft level comes in handy.

   Forrest

5. 
   Saville | Jan 31, 2011 01:22pm | #5

   "scale"?

   Hi Forrest,

   What is a "scale"?

   thanks,

   Gregg

1. 
   BruceS | Jan 31, 2011 08:29pm | #7

   scale

   Another name for a ruler,  generally made of steel.

6. 
   Saville | Jan 31, 2011 01:26pm | #6

   "pretty flat"

   Thanks to everyone for their replies.

   Ralph:

   Not sure I know how flat a well made table saw table is ;)

   I bought a Triton 3 hp router (TRC001) and the Bench Dog aluminum plate.

   If I understand your comments, a double later of 3/4" material is enough to keep it all flat by itself? The support structure is of less consequence (so long as it doesn't pull it out of flat)?

   With that router and plate,how close must the support structure be before it begins to sag the top?

   thanks!

   Gregg