Rick Thom and I improved the fences on our inexpensive router tables

Frank Pellow

Member
Messages
2,332
Location
Toronto, Ontario, CANADA
Early in 2007 Rick and I both purchased inexpensive tops for router tables at Busy Bee Tools:

Router Table Top.jpg

We both also bought Triton 2.25 hp routers and built cabinets to support the table tops and to house the routers. Here is a picture of mine:

Router Table Top on cabinet.JPG

Please observe that the fence is held in place by a two wooden clamping blocks, one at each end of the fence. These proved to be inadequate and the fence shifted when pushed. Rick dealt with this by also using a couple of quick clamps to hold the fence in position. I glued sandpaper strip underneath the table along both sides and this helped quite a bit –but when I really needed to be sure, I also need to use auxiliary clamps.

Yesterday, we got together at Rick’s place to make some improvements. The first thing that we did was to install two 10 inch strips of t-track near the edges on the back of our tables. In the photos below, Rick is attaching a template then routing one of the grooves in his table top:

Router table upgrade 1 -Rick with template -small.JPG Router table upgrade 2 - Rick routing groove -small.JPG

We installed the t-track in the grooves using glue and screws, drilled holds through on the horizontal surface at the back of the fence and installed a cam locking mechanism for each track. Here Frank is tightening a cam lock:

Router table upgrade 3 Frank adjusting a cam-lock to hold the fence in place -small.JPG

We found that, with applying only very little pressure to the handles of the two cam locks, the fence held very solidly.

Next, we acted upon a suggestion by Mack Cameron, we next built a micro-adjust gizmo to fit into one the tracks. The micro-adjust is a short piece of aluminum bent at a right angle and fitted (1) with a knob to hold it in place on the t-track and (2) with a thumb screw threaded through the aluminum. The thumb screw is used to push against the wooden block screwed into the back of one end of the fence. This is best shown by pictures a couple of pictures:

Router table upgrade 4 -micro adjust gizmo -1 -small.JPG Router table upgrade 5 -Router table upgrade 4 -micro adjust gizmo -2 -small.JPG

In the first picture, the thumbscrew has not yet been threaded through the micro-adjust and the micro-adjust has not been tightened onto the track. In the next picture, the micro adjust is fastened in place on the t-track behind the end of the fence that we want to adjust and the thumb screw pushing against the wooden block in order to adjust the position of the fence.

Here is a picture of my table top with the modifications complete:

Router table upgrade 6 -Upgrade completed on Frank's table -small.JPG
 
Why the nut on the Micro-Adjust?

There is a nut on the outside of the vertical surface on the micro-adjust gizmo. What is it's purpose?

Hey, I thought that no one would ask.

The aluminum on the micro-adjust is not very thick and, although we tapped it, there is not much thread for the thumb nut to grip. We placed the nut there (with apoxy) in order to provide a more thread. But, we are not sure how effective this will be. Mine is still in place, but Ricks has fallen off.
 
There is a nut on the outside of the vertical surface on the micro-adjust gizmo. What is it's purpose?

Hey, I thought that no one would ask.

The aluminum on the micro-adjust is not very thick and, although we tapped it, there is not much thread for the thumb nut to grip. We placed the nut there (with apoxy) in order to provide a more thread. But, we are not sure how effective this will be. Mine is still in place, but Ricks has fallen off.

I could send you a larger bolt with a hole to fit your thumb screw tapped in it. Install bolt and nut in larger hole then thumb screw thru hole tapped in bolt.


However I suspect the threads in the Alum will work fine. Another option is to double up the alum and thread thru two thicknesses.
Garry
 
Using the same concept I'm assembling components to make an edge guide for a router. What thread pitch on a lead screw would be good? For a fixed fence or an edge-guide?

Gary Curtis

For things like this where we are usually working in fractions I like 3/8x 16 tpi.
That makes 2 rotations 1/8 inch. Some prefer 1/4 x 20 but though that is finer it causes my mind to hurt on some of the fractions, and is fine enough it takes a long time to count to 2 inches. Using the so called coupling nuts helps with backlash or tap some man made material for your nuts.

I would actually like something in 8 tpi but then you are into more exotic threads in smaller sized rod.

Garry
 
For things like this where we are usually working in fractions I like 3/8x 16 tpi.
That makes 2 rotations 1/8 inch. Some prefer 1/4 x 20 but though that is finer it causes my mind to hurt on some of the fractions, and is fine enough it takes a long time to count to 2 inches. Using the so called coupling nuts helps with backlash or tap some man made material for your nuts.

I would actually like something in 8 tpi but then you are into more exotic threads in smaller sized rod.

Garry
1/4 x 20 is what we used.
 
From the "For What It's Worth" department, here is some info on how you can get very fine adjustments with not-so-fine thread pitches, using an interesting arrangement called a differential screw. (Click on the thumbnail to see a full-sized image with accompanying text.)

<-- CLICK ON THE IMAGE!!​
If you or a teenager in your life is fascinated by "things that move", I highly recommend the book that this information came from. (The title is at the bottom of the full-size image.) My 1968 hardbound copy has 297 large-format pages (including a 13-page index) and is full of fascinating, easy-to-read information and wonderful illustrations. I've read it cover-to-cover twice, and I think I'm due for a third time through.... :thumb:

There are a couple of copies currently available in the [Amazon Marketplace] ($10.89 shipped).

A [search on AddAll.com] will turn up other editions and other sources, some of which are priced way up there.... :eek:
 
Last edited:
That double screw fixture might do what I want. I'm building a router edge guide and want to save the $200+ it would cost for a Micro Fence. I'm looking for adjustment at or below 1/32" tolerances. Which seems to be the target domain. On my WoodRat (which is powered by a router) I am called upon to adjust making a tenon or box joint and to adjust by another .003" regularly. That is slighly larger than 1/32.

Gary
 
On my WoodRat (which is powered by a router) I am called upon to adjust making a tenon or box joint and to adjust by another .003" regularly. That is slighly larger than 1/32.

Oops! 1/32 = .03125, which is almost 10 times larger than .003 :( (Did you mean .03"?)


I'm building a router edge guide and want to save the $200+ it would cost for a Micro Fence.
That double screw fixture might do what I want.

Yep! If you can figure out how to "join" two machine screws, and you don't mind some slightly odd fractional denominators. :huh:

I guess an alternative to joining two screws would be to tap two different threads onto a single length of steel rod. Instead of $200, now we're in the neighborhood of $30 (+ shipping?) for a tap & die set like [THIS ONE] from Harbor Freight. If you're really shooting for .003", let's see how close we can come, using that set as an example:

But first, let's go back to what would happen with a regular machine screw with 32tpi. Each full turn (assuming super precise threads, of course :doh:) would give you a linear movement of .031 inch. A quarter turn would give a movement of .0078 inch. An eighth turn would go about .0039 inch. How good are you at gauging 1/8 turns? :rolleyes:

If you were to tap a 1/4" rod with 20tpi on one end and 28tpi on the other, you'd have a differential of 1/20 (or 7/140) vs 1/28 (or 5/140) per full turn. That's a total of 2/140" or 1/70" (or .0143") per full turn. Going down only to a quarter turn, we get .0036" ... not bad!

If you used 5/16" rod instead, you could tap one end at 18tpi and the other at 24tpi. The differential would be 1/18 (or 4/72) vs 1/24 (or 3/72) ... for 1/72" (or .0139") per full turn. At one quarter turn, that's .0035" ... so only slightly better than the 1/4" rod options.

If you could procure some "size 10" rod, you could tap 24 tpi on one end and 32tpi on the other. Differential = 1/24 (or 4/96) vs 1/32 (or 3/96) ... for 1/96" (or .0104") per full turn! At one quarter turn, that's .0026" ... so about the same delta from .003" as the others.

Anyway, you get the idea!

Now that I've done all those calculations, if it turns out that you only need movements on the order of .03" instead of .003", I would just use "almost full turns" with a regular 32tpi screw. :thumb:
 
I meant .003". Close to the amount of the typical glueline gap. When adjusting cuts for tolerance, it is easier for me to think in machinist terms and use decimals.

It is too much of a headache to get below 1/32nds and try to calculate in fractions. I've got dies already, but for a clean threaded rod I'll ask a machinist friend to cut a rod with the two different pitches. And since it won't be bearing much of a load, I think brass would provide a smoother movement than steel.

Gary
 
[...] for a clean threaded rod I'll ask a machinist friend to cut a rod with the two different pitches. And since it won't be bearing much of a load, I think brass would provide a smoother movement than steel.

Sounds awesome! Don't forget the "show-and-tell" part when you have this baby working. :thumb:
 
Top