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Amateur techniques to align sub-base

A standard router has what is called a sub-base that attaches with screws to the base plate of the router. (You might have heard it called the bottom of the router.) This sub-base is often removed to mount the router to a table or to attach a specialized sub-base.

One of the functions of the sub-base is to hold template guides. For the purpose of this example I will discuss what is often called the PC standard 1 3/8” hole system.

When using template guides the bit of the router must be centered in the open of the guide. Visual inspection may reveal that this is not the case. Even if it “looks” right it maybe off slightly.

Even from the factory these sub-bases do not always align with the bit. Differences in manufacturing, brands and other factors cause these situations.

Aligning the sub-base to the router is something that can be done more accurately using a few simple techniques and readily available aids.

You will need a ¼” shaft to fit in the router with a ¼”collet. This shaft should be drillstock or other material that measures exactly ¼” inch. Kits for “build it yourself” sub-base usually come with one. They also contain a disk that fits in the template hole on the sub-base and has a ¼” hole centered in it. You could make this disk but make sure the hole is centered it fits snugly in the sub-base hole. (Some template sets contain a template and shaft for this purpose.)

Loosen the screws holding the sub-base to the router then insert the ¼” shaft into the router collet and tighten. Slide the disk down the shaft and into the template hole. Now tighten the sub-base screw a little at a time until they are tight.

Unless things are “way out of bounds” the sub-base is now aligned. Remove the shaft and disk and you are finished.

Anytime the sub-base is removed it needs to be re-aligned when it is reinstalled

Stay tuned for “truing the sub-base”.

For round sub-base: “truing the sub-base”.

This is the second part of a series of two so if you have not read “Amateur techniques to align sub-base” please do so before continuing.

You will want to do this if you ever use the sub-base against an edge as a guide.

In the last posting we aligned the bit using the template guide to the sub-base. Now that they are concentric we will attempt to make the outside of the sub-base also concentric to the bit.

Using the same set-up as before, when we did the first alignment procedure, a ¼” shank mounted in the router, and the disk in the template guide.

Select a piece of scrap wood maybe a 1” X” 4 X 12”or similar. Draw a line down the center of the piece full 12” in this example. Measure the Diameter of your sub-base, for example it might be 6” across. Now measure half the diameter + 1 inch down from one end of the scrap wood piece (in our example this would be 4”).

Mark that location on the centered line then drill a ¼” hole through the wood at this location. This hole must be ¼” and as vertical as you can get it.

Take the router and put the shaft into the hole. You want the routers sub-base sitting against the scarp wood, if need be adjust things so they are sitting flat. Now take a sharp pencil and hold it near the sub-base where the wood extends about 1” past the sub-base. This location should be on the centered line. Very slowly rotate the router about the shaft and watch for the location where the sub-base is nearest the pencil. When you have found that spot use the pencil against the sub-base and make a mark across the centered line.

Using the same method locate the spot on the sub-base where it is at the greatest distance from the mark you made. Mark this location.

Lift the router off the scrap wood and carefully cut the wood a so the line closes to the hole is gone (1/32” is good). This cut is perpendicular to the centered line you made and the resulting wood will be about 11” long in this example.

Put the router shaft back in the hole. The sub-base will now extend beyond the edge of the wood where the cut was made. Slowly rotate the router to make sure the sub-base extend over the wood all the way around.

Now depending on the material of your sub-base you can sand, file or scrape the edge of the sub-base using the fresh cut end of the wood as a guide. Remove material of the sub-base by slowly turning the router until the edge of the sub-base and the wood match.

The sub-base should now be concentric with the router bit.

Template or Pattern routing

If you have been reading posts here you will have heard a lot about this subject. A lot of you maybe thinking about trying a project but they all look to hard. And then there is that trying to figure out what bit and what template guide to use…….. “Now I made the pattern a ¼” larger so I’ll pick out the…… Oh to heck with it let’s see what on TV”.



The following might help with some of those decisions. In attachment 1 you see a cut away sub-base with labels. Those labels are important; they will help you with the table that is attachment 2.



This table is for the set of template guides we can call “oak-park”. (If you have a set that might be called “PC” let me know and I'll post a table I personal use.) The first column has the OD or outside diameter of the template guide. The second column is the maximum bit size for that guide. Looking at the rows under “BITS” for the size of bit. Below that is “C” or the distance between where the template guide meets the template and the router cut.



Let’s try one:



The ½” guide and ¼” bit. Locate the guide size then go across until you are under the ¼” bit. That box contains 1/8”, see attachment 3.



The 1” guide and ¼” bit. This time the box contains 3/8” see attachment 4



One more time, 1” guide and ½” bit. The box says ¼” see attachment 5



(If anyone spot an error in the table please mail me right away so I can fix it.)

Hope this helps,



Ed

Amateur’s Night building a template

This will be done in a series of posts. First we will discuss the “project”. (This is describing the task being done with a hand held fixed based router and straight bit.)



(You can really make this or do it mentally, your option.)



For some reason you decide to make 20 nest boxes for Daffy Ducks. Most of the cut are easy but when looking at the pattern you see that it requires an oval that is 3” tall and 5” wide. You see this as an opportunity to use your router but now you have the issue of how do I make a template and how do I use that template with a template guide. (See attachment 1)



The book has a nice picture of the oval but for some reason they made it some smaller odd size when they printed it. What to do, how do I draw that shape????? Well maybe you don’t have to. Maybe you have a scanner or home copier that allows you to enlarge the image or maybe a local store has a copier that you feed money into and out comes copies.



For now we will assume that the local store is the option. You take the book, a ruler/scale and head to the store. The object is to make a copy then measure the oval to see if it 3” high and 5” long. Doing a 110% is almost right when you measure the copy. You try again at 111% and it right on! (See attachment 2)



So we now have the right size for the hole, but then you remember that when you use a template and a template guide the pattern will have to be larger. (This is where a table of template guide to router bits as {seen in a previous post) comes in handy.)



As efficient as you are you pull out a copy of a table and see that if you use a 1” guide and a ¼” bit (both of which you own) you will need the pattern to be 3/8” larger all around. Remembering the flash cards from back in 5 grade you add the 3/8 and 3/8 and getting ¾”. Now you go back to the copy machine and change the settings to get the hole to be 3 ¾ by 5 ¾. A couple tries later you have it. (Check out attachment 3 and 4 for a view of how this works



On the way home you stop by the hardware/lumber/what-ever-store and pick up a sheet of ¼” thick hardboard and a 1” x 12” x 24” pine board. (You may choose to use some other material like plywood or a routable plastic and you might already have something at home in place of the hardboard).



To be continued

Amateur’s Night building a template pt2

Back safely at home we can start the layout process. Take the hardboard (or what ever you are using for the template) and size it as shown in attachment 1.



Select the smooth side of the hardboard (some have both sides smooth). Add the pencil lines as shown in attachment 2. You will notice the longer line is not down the center of the “template”, you will see why later.



Trim the copy of the 3 ¾” X 5 ¾” hole that you made at the copy machine so it is more manageable. Then carefully fold the paper so the two long ends of the oval match each other and crease the paper. Unfold and do the same with the short dimension of the oval. (See attachment 3). You have just created a centerline for the oval.



Take a piece of “carbon”/tracing paper and trim it to the same size as the copy you have just been working with. Look at attachment 4 and position the creases of the paper to align with the marks. Tape in place then trace the oval shape (making sure the tracing paper is positioned to leave a mark on the hardboard). Remove the tape and papers, the oval you might want to save for some other use or recycle it.



The next step is cut out the oval shape in the hardboard. You can pick a method that you like but make sure you stay within the lines. Unless you have a really smooth cut and stayed right next to the line you will need to sand away until you are right to the line. An osculating spindle sander works well for this but hand sanding works fine. The smoother the job on the template the smoother the finished hole turns out.



Now attach two strips of wood to the template (yes you have made a template) as shown in attachment 5. Make sure the strip along the long edge is to the side with more space between the oval and the edge (“A”).





To be continued

Amateur’s Night building a template pt3

At this point we should be ready to “fire-up” the router. I will describe how to make the cut for a fixed base router but those with plunge routers can do the same operation. Make sure it unplugged then put the ¼” bit in and the 1” template guide. Since we will not be doing a “plunge cut” a straight bit will do fine but feel free to use a spiral bit if you wish.



Take the 1 x 12 x 24 piece of wood and select a “top” where the oval cut will be made. Next the template is set it over the board and push into position against the ¾ x ¾ strips. Look at the oval and see if any loose knots will be in the area to be cut, if so they will have to be removed. Mark the oval on the work piece using a pencil.



Since this will be a through cut you will need a flat working surface that you don’t mind cutting into. Make sure this sacrificial surface is large enough to accommodate the material and template.



Using double sided tape/small nails/clamps secure the work piece to the sacrificial surface. Make sure the waste oval area is not going to move as you finish the cut!



Use a ¾” or 1” drill bit to make a starter hole in the work piece. (See attachment 1)

The hole must be into the sacrificial surface, let’s say ¼” into it. The edge of this hole has to be at least 3/8” away from the oval you have drawn. Remember the bit will be cutting 3/8” from the template.



Now you must tape/nail/clamp the template to the work piece making sure it aligned to the strips on the back of the template. Check again that everything is secure and that none of the nails (if you used any) are where the router will be cutting.



Adjust the depth of the cut to be about 1/3 or ½ the thickness of the work piece. You will be placing the router on the template with the bit sitting centered on the hole you drilled in the work piece. Which way are you going to route? (Check attachment 2)



With the router centered in the hole and the depth set, check to make sure the router is turned off. Plug in and make sure you are still centered. Now you can turn on the router and traveling the right direction make a pass keeping the template guide against the template. Take as many passes as required to cut through the work piece.



When you have finished doing this oval hole turn the work piece end for end and do another hole, after all you were not really going to make a daffy duck nest box were you?



That’s all.

reible said:

If you have been reading posts here you will have heard a lot about this subject. A lot of you maybe thinking about trying a project but they all look to hard. And then there is that trying to figure out what bit and what template guide to use…….. “Now I made the pattern a ¼” larger so I’ll pick out the…… Oh to heck with it let’s see what on TV”.



The following might help with some of those decisions. In attachment 1 you see a cut away sub-base with labels. Those labels are important; they will help you with the table that is attachment 2.



This table is for the set of template guides we can call “oak-park”. (If you have a set that might be called “PC” let me know and I'll post a table I personal use.) The first column has the OD or outside diameter of the template guide. The second column is the maximum bit size for that guide. Looking at the rows under “BITS” for the size of bit. Below that is “C” or the distance between where the template guide meets the template and the router cut.



Let’s try one:



The ½” guide and ¼” bit. Locate the guide size then go across until you are under the ¼” bit. That box contains 1/8”, see attachment 3.



The 1” guide and ¼” bit. This time the box contains 3/8” see attachment 4



One more time, 1” guide and ½” bit. The box says ¼” see attachment 5



(If anyone spot an error in the table please mail me right away so I can fix it.)

Hope this helps,



Ed

Click to expand...

Might it not be simpler to remember this: (OD - BD) / 2 = Distance of offset. OD = template guide Outside Diameter and BD= Bit Diameter. Subtract bit diameter from the bushing's outside diameter and divide by 2, that's how far the bit will be positioned from the template.

I'm not familiar with the Oak Park bushings, but for some unexplicable reason, most of the ones I've seen gain in height proportinate to their diameter. I've had 3/4" OD bushings that were 9/16" long, which forfeits a lot of depth of cut and worse, whatever material you use for a template has to be at least as thick as the bushing is tall to keep the bushing from bottoming out on the workpiece. I can see no reason for this, so I addressed it by cutting all of my bushings down to .20" height. This allows me to use 1/4" baltic birch plywood or masonite for my templates.

Also remember that bushings are strictly for defining the edge of the cut, they do not control depth and should not be allowed to touch the workpeice. The router base should ride on top of the template in freehand routing.