I receive this question in my inbox at least once a week so I decided it was time to make my response more official. Because I value your time, let me start off by giving you the short and sweet answer: it depends on the kind of work you do.
The Domino DF500 is great for small to medium-scale projects including panels, frames, cabinetry, boxes, and small furniture. The Domino XL DF700 is well-suited for large scale furniture projects such as entry doors, beds, big tables, and larger structural components. In my opinion, the majority of users will be best-served by the Domino DF500.
Of course, the tools have a bit of overlap on the high end of the DF500 and the low end of the DF700. To elucidate this gray area, we need to dig into the details.
The Festool Domino is functionally similar to the classic biscuit joiner. You simply plunge the tool into the work and seconds later you have a mortise. But there are some major differences between a biscuit and a Domino tenon. Most folks believe biscuits are fairly weak and they typically aren’t used in applications where joint strength is critical. Part of this comes from the thickness of the biscuit itself but also from the shallow penetration and the fairly loose fit. A Domino tenon suffers from none of these issues. The solid wood tenon is strong, tight, and penetrates deep into the adjoining boards.
The Domino now comes in to two flavors: the original Domino DF500 and the Domino XL DF700. To help you decide which Domino is right for you, let’s evaluate three important attributes: mortise sizes, weight, and cost.
Cutters available for 4, 5, 6, 8, and 10 mm thick tenons.
Max depth 1 3/32″ (28mm)
Cutters available for 8, 10, 12, and 14 mm thick tenons.
Max Depth: 2-3/4″ (70mm)
When looking at the resulting joint made by a Domino, the two most important factors are penetration depth and tenon thickness. As you can see, the two tools overlap in the 8mm – 10mm range. So if you are the kind of woodworker who makes a lot of smaller craft items and you occasionally delve into small furniture and casework, the DF500 is an obvious choice. If you primarily make full-size tables and chairs and you occasionally delve into large-scale work like conference tables and entry doors, the DF700 is the clear winner. If you tend to focus solely in that middle range of small to medium-sized furniture (the one that makes frequent use of the 8-10 mm tenons), you’re in the gray area. And if you’re like me and your work tends to span the entire range, you’re in even more of a pickle. Of course the ideal solution is to have both tools but most budgets just won’t allow for that. So here’s how I break the tie.
For me, it comes down to a fundamental woodworking component: panels. Nearly all woodworking eventually requires you to take two boards and glue them together to create a wider board (table tops, frame and panel doors, etc). Because I like trouble-free glueups, I use the 5mm x 30mm Domino to assist with alignment. Unlike a biscuit, the domino has zero slop and ensures I have very little flattening work to do after the glueup. It’s like having another set of hands (or cauls) working for you behind the scenes. As a result, the 5mm x 30mm Domino is the most frequently-used size in my shop. And that’s a size I can only use with the DF500. While thicker tenons would still work, I find the 5 mm size to be ideal for the task.
What makes the Domino tool so special is the fact that you can take the tool to the wood. This is incredibly helpful whether you’re on a job site or working in a cramped shop space. So no matter how large the workpiece is, you can always make your marks and cut your mortises easily. But all of this movement means there’s a potential for wrist fatigue. The DF500 weighs in at 7 lbs and the DF700 weighs in at 11.4 lbs. While both tools are ergonomically designed and are probably about as comfortable to use as they can be, an additional 4.4 lbs is a lot of extra weight to sling around your shop. Not a deal breaker by any means, but it’s something to consider if you’re on the fence.
For the tool alone with no accessories or Domino tenons, the DF500 costs $825 and the DF700 costs $1200 (as of November 2013). If you specifically need one size range or the other, the price isn’t really relevant. But if you’re on the fence, the cost savings of the DF500 is certainly something to think about.
Frankly, I don’t follow the Festool rumor mill very closely but I have heard that smaller cutters are going to be made available for the DF700. These are not Festool cutters and obviously Festool recommends against using them. Having no specific knowledge of these cutters myself, I can’t really comment.
As you can probably tell by now, the DF500 would be my choice if I had to pick only one unit. I have used the DF500 for years now and there were only a few times I thought to myself, “I wish they made a larger version.” Part of that stems from the fact that I still make a lot of traditional mortise and tenon joints in my work. Since I teach woodworking for a living, I can’t exactly whip out the Domino on every project.
No doubt someone else will provide a well-reasoned argument for the DF700 as the only Domino you need. Since each of us represents a different use-case, it’s hard for anyone to make a one-size-fits-all recommendation. And being realistic, most of us would ultimately be happy with EITHER tool. The fact that they have a bit of overlap in the middle range means that many of our joinery needs can be met by both tools.
My hope is that you’ll review the facts and specs and decide for yourself what would be best for your shop. Be sure to read the resulting comments below as your fellow woodworkers are likely to chime in with their personal opinions on the subject and they may very well sway your opinion.