Making A Jig

The whole point of the Stots Dovetail Template Master is to use it to MAKE a tool. There are actually many ways to construct a jig as well as several considerations for materials and methods.

Template Material
Solid wood could be used as long as the grain is oriented properly (running WITH the comb fingers) but the overall width (of an individual section) should be less than 6 inches wide. A hardwood such as Hard Maple would be best, preferably quarter-sawn.

The instructions indicate that plywood could be used, I do not recommend common plywood because of the use of softwood for the inner plys. Baltic Birch or something similar that is made entirely of hardwood veneers would be a far superior material.

MDF could also be used, although the inner core of MDF is not especially hard it would probably serve far better than softwood or common plywood. The advantage that MDF has is that it is easily machineable and inexpensive. MDF of ¾" thickness will be stronger and the material should provide a reasonable amount of service life.

One could also make the comb out of phenolic. This would make for a very durable jig, many commercial dovetail jig combs are made of this material. Phenolic is a plastic lamination that is relatively easy to machine and quite strong. If phenolic were used ½" thickness is probably more ideal (and less costly) than ¾". The disadvantage of phenolic is its high cost. I haven't tried it but Corian might be an interesting choice of material, particularly if it could be obtained at low cost as scrap from a counter top maker.

Template Thickness
The material thickness of the template has a very important impact on the design of the system as a whole. This is due to two factors. The first is a "strength of materials" issue. Mainly, the stronger the comb material, the thinner it could be. For instance, ½" MDF is not nearly as strong (or durable) as ½" phenolic therefore it might not be the best choice for the template material.

The second aspect relates to the depth of cut required AND the available cutters. Assuming one is going to use bearing guided bits, there are limitations in the standard size cutters that are useable and the placement of the bearing relative to the thickness of the template. For example, if the stock thickness is ½" and the template thickness is also ½", the standard dovetail cutter would not allow it's guide bearing to touch the template. In the situation above there are several common options:

1. Make a thicker template that allows for bearing engagement and the proper cutting depth.

2. Find a cutter with a smaller cutting height which ALSO allows a bearing to be used (there are few if any).

3. Switch to using a guide bushing.

4. Increase the thickness of the router base.

5. Offset the stock in the jig by spacing it away from the template.

I want to make it clear that ALL template based dovetail jigs that use bearing guided bits will suffer from this same exact dilemma. Different jig makers have different official "solutions" for the problem but the problem is the same. There are pro / cons associated with all the above solutions, here I'm just pointing out the impact template thickness has on the system.

Template Length
The beauty of the Stots template is that you can make a jig of what ever size you want, you are not limited or hindered like you are with some other commercial jigs. For example, with a ready-made jig such as any of the Keller dovetail jigs, you may find it a bit too long to run on the router table when used to make small boxes. The Katie jig has exactly the opposite problem, it is smaller than one would wish when used for case joints. Even the Keller Journeyman may not be as long as desired for some case work. With the Stots you can make a range of templates to cover your needs at a tremendously lower cost than these commercial jigs.

Most drawers and small boxes are probably less than 8 inches wide. An 8 or 9 inch capacity jig will be easier to maneuver on a router table or clamp to the workpiece if used freehand. Something of around 16, 18, or 24 inch capacity would probably take care of most of your needs when used on case-work. For long jigs you will probably prefer a wider spacing like 2 inches. A 12 or 14 inch capacity jig is a good in-between size. It is large enough to be used on some case work and small enough to maneuver on a router table. This size would also allow you to "double-up" small parts (like drawers).

Cutting The Template
The instructions mention making starter holes in the subject template material then plowing out the pattern using a bearing guided router bit. I prefer to lay out the pattern on the stock then cut away as much material as possible with a saw. The result is that when the router bit is used to complete the pattern both the stock and the router bit have significantly less stress applied to them. I think this noticeably improves the pattern accuracy and lessens the wear on the bit as well. The down side to this technique is that it takes more time and more care. Just as when using the jig to cut joints, the router should be run at some high speed setting.

I also think it is important to mention cutter placement. Ideally absolutely NONE of the cutter would be in the area of the master template. Ideally the cutter and bearing are exactly the same diameter. When a lot of side stress is applied to the cutter it is possible for it to deflect. If the cutting portion of the bit protrudes into the zone of the master template it is possible(even with the bearing) that it can cut into the master.

Although this may be obvious, it is also important to firmly fix the template and stock during cutting. The template is fixed to the stock using two screws - make sure they are tight! If the whole assembly were clamped to a bench it would provide a very stable surface. Spacer blocks could be used to keep the bit from cutting into the bench. Remember that it is important to cut as accurate of a copy of the master template as possible, all these small suggestions help to do that.

Layout
Using the template master one can easily create spacings on multiples of one inch. For example a two inch spacing would probably look a lot better on a large piece like a blanket chest. The instructions describe the process. Spacings other than on multiples of one inch can be made but it will require a bit more figuring out on your part.

I'm of the opinion that it would be best to stick with the "easy" layout options (multiples of one inch) for fixed templates. There are well documented ways of getting a true variable layout using a jig of this type so creating numerous iterations of fixed spacings would seem to be a waste of effort. I do see value in having separate one and two inch spacing templates though.

The master template is made with dovetail fingers laid out on a one inch spacing in an offset pattern. I say the pattern is offset because a jig made in this "stock" pattern would have the pins and tails board edges in different planes. This isn't good or bad, it's just the way it is laid out

Another aspect of layout would be to create a template that is not "offset". This would yield a jig of the pattern like the Katie jig with a pin finger centered on the slot of a tail guide. This is actually very easy to do by routing one side of the jig, moving the template ½", then routing the other side. There isn't a great deal to be gained by doing this and it does create an opportunity for error. I recommend either using the stock alignment method mentioned in the manual or making an offset stop to compensate for the offset stock placement.

The last aspect of layout I'll cover is that it is entirely possible to create a movable finger jig very much like the Katie Jig; this would be more work though. However, ShopNotes Magazine Volume 8, Issue 43 has a good article describing a process similar to how this could be accomplished. I'm of the opinion however that if this is what is desired, you should either buy a ready made jig that does that and more (like the Leigh) or just go ahead and build the ShopNotes jig from scratch; ie: if you can imagine how to do it using the Stots template you already have the skills to do it without it.

Alignment
All through dovetail systems (yes, even the Akeda) require some kind of alignment, the Stots system is no different. First, it may be useful to know what causes a dovetail jig to need alignment. Note that only the pins side of the jig needs fine alignment, the tails side is gross enough to qualify as simple assembly.

1. Initial alignment. Most jigs (and of course the ones you build) do not come fully assembled thus the parts that form the critical relationship between the reference face of the stock and the position of the "wedge" shape of the tail section of the guide template are not in the proper relationship.

2. Cutter change. If one cutter were used during initial alignment, it is possible that another cutter (or a re-sharpened one) could be just a little different even though it has the same catalog specifications. If the differences are big enough (a few thousandths) it can cause a difference in fit prompting a re-alignment.

3. Stock density / hardness. Even a change in the workpiece has a small effect on fit, this is due to differences in the compressibility of the wood fiber. The best example of this is the change from something like Hard Maple to Pine (a softwood). A joint that goes together with moderate hand pressure in one specie may produce a fit that either needs a mallet to join or is a bit "loose" in the other species; this is an easily observable phenomena.

4. Stock width. Although it doesn't affect the individual pin/tail fit, the wider the joint the more opportunity for an interference fit situation. To illustrate, consider that the odds of success when assembling a 2" wide joint that is tight are much greater than on a 24" width of the same tightness. Meaning that on wide joints you may wish to have a looser fit than on smaller ones.

5. Backer boards. In the common #1 and #2 designs of a Stots-made jig the important consideration for the backer boards is that their thickness effectively controls the relative position between the workpiece and the template - which is in effect alignment (in this sort of design). Meaning, that if the backer board thickness changes (on the pins side) by even a small amount it will affect the joint fit.

The alignment described in the instructions is really the same as those used on similar jigs such as the Gifkins, Katie, or Keller and effectively others like the Leigh although it may not look like it. Through trail and error test cuts the pins (or pins side) of the template is moved relative to the backer section of the jig. The Stots instructions provide a good starting point for this alignment. After the first test cut or two you are into the domain of alignment #3 & #4 above and are presented with a decision to make.

Do you:

1. Align for a "best compromise" fit between hardwood and softwood and or joint width.

2. Create a separate "loose" and "tight" (pins) jig.

3. Create some form of method that allows one to minor adjust the template to compensate.

The decision above is somewhat predicated on what you consider a "good fit". Consider first though that there is another factor affecting fit - glue; because glue takes up space. For example "gap filling" glue with a high solids content will make a looser joint go together more tightly. For joints that are already tight, chair glue (which is about as thin as water) has the ability to wick into the joint that would otherwise be starved.

In alignment, the first real issue I believe is the tedium of the trial and error process. To make this a much more controlled, I install two small blocks on one side of the template; these accept small #10 jack screws. With these it is possible to adjust the template in fine known & repeatable increments to the desired level of "fit". Using these devices it possible to easily implement whichever of the decisions above are selected.

Using The Jig

The whole point of making a jig is of course to use it. A Stots-made jig can be used for making evenly or variable spaced through type dovetails quite easily. With a little more effort, variable size dovetails can also be made. In addition, a half-blind effect can also be achieved.

Reference
Actually using the jig it somewhat anticlimactic after having built it; this is mostly due to it's ease of use. There are two common methods for lining up the stock to be cut using a jig like this. The first method (I'll call Mark Reference) is to position the tails joint by eye, cut the joints, and position the the pins joint to match it (this is described in the instructions). This works fine for a few joints or if you are doing a true variable layout.

The second method (I'll call Edge Reference) is to use some form of stop system. The stop can either be immovable or allow re-positioning to be done. A stop system worth using will locate both the pins and tails boards. This is fairly easy to accomplish on a jig that has both pins and tails sections, not as easily on separate pins and tails jigs.

An important consideration for template dovetail jigs is what guides the router. With a Stots-made jig it is possible to use either a router mounted guide bushing or a bearing guided bit. The problem with using a guide bushing is that it may not be exactly centered on the cutter. This can result in a joint where the edges do not line up perfectly. A bearing guided bit does not suffer from this phenomena.

Bearing guided bits also seem to require less effort to guide and they are more accurate. The down side of a bearing guided bit (in these template based jigs) is that the stock thickness and template thickness have an interaction.

Tearout
Tearout is a common problem on many through dovetail jigs, both on the front and back, a Stots-made jig is no exception to this. The remedy is the use of a sacrificial board both in back of and in front of the stock. Backer boards are commonly used, fronter boards are not.

In addition, technique can also play a part. When cutting it is preferred to use a "climb cut" action, this tends to reduce tearout a little. On a standard Stots layout, this technique is possible on the pins because there is room to maneuver the bit side to side. For the tails though this is not possible, there is no side-to-side movement allowed - you have no choice but to go straight in and out. It is possible however to orient the stock so that the tearout will only (hopefully) occur on the inside of the joint where it will be less visible. A very important aspect of preventing tearout is to use sharp bits as well.