|Project by MJCD||posted 10-16-2012 02:45 PM||1929 views||9 times favorited||15 comments|
Outdoor Bench – Jatoba, Mortise & Tenons
The plan is from the May/June 2008 Fine Woodworking magazine – I found it critical to use the purchased full-scale drawings ($19.95) – these are two large schematics, which provide all dimensions, full-scale views of different joints and miters. One item which is clear on the plans, which is not mentioned in the accompanying article, is that some of the tenons need to be 45⁰ mitered.
The plan calls for 40 Mortise & Tenon joints; and, is considered ‘Intermediate’ skill level by our friends at Fine Woodworking. When I first saw the plans – my wife loved the design, and I was left to figure-out the rest – my thoughts ran to the book title ‘A Bridge Too Far’.
I’m relatively new to fine woodworking, and I’m slow as molasses – the project required about 150 hours, and tools which I had to purchase; which is to say, this is the first time I’m 1) using these tools; and, 2) performing these operations.
The Bench is to be used outdoors (Northeast USA), and to remain without varnish or sealant – my wife’s request. As such, I was limited to one of Teak, Jatoba, White Oak, and Ipe – these are the natural oil woods available in my area. Teak was outrageously expensive; White Oak quantities were too limited (dimensionally), so the Jatoba & Ipe were the only real choices I had. I went with the Jatoba.
Jatoba is twice as hard as Teak (Janka Hardness Scale), quite heavy; and machines and finishes smooth. It has a nasty tendency to ‘chip-out’ – guide bearing router bits can ‘catch’ the wood; and I had a piece vibrate off my router table, the splinter-off a 3” piece when it hit the concrete floor long-end first. This wood is very hard, brittle, and requires attention when being milled. Carbide cutting tools are recommended; though, I used HSS for planning (DW735) and Bi-Metal on the Bandsaw – both of these will be changed-out, now that I’m done.
I found the dust to be very fine; an almost sweet aroma; and, necessary to capture as much at-the-source as possible.
The Jatoba was less expensive than the Teak, yet I still had approximately $320 worth in the project.
Wood Dimensioning; Cut Diagram, & Purchase
Jatoba, in my area, is approximately $8/bf – while much less than Teak, this is still expensive. One goal is to limit the amount purchased and the amount wasted.
To accomplish this, I setup an Excel file which contained the dimensions for each of the 30 pieces; and concurrently, I visited my local hardwoods supplier to determine the available rough dimensions for individual lumber. You can see this in the scanned file.
For 4/4, 5/4, and 6/4 pieces, I determined the amount required; and then set-out to find the most economical way to garner these pieces from the good stock I found. In all, 7 boards were necessary, and the cutting diagrams for each board can be seen in the accompanying scan. I strongly recommend something like this process to the Forum Members. The key is to determine how to efficiently use both the length and the width – if a board is 6” wide, you may get only one usable cut; while at 7” you may get two. Conversely, paying for width you don’t need is wasteful.
It may be difficult to tell, but on the attached cut diagram, I purchased individual lumber pieces wide enough to always allow two project pieces (you can see the solid lines running horizontally).
There are 30 individual pieces which comprise the Bench – some of these are glue-ups from 5/4 & 6/4 stock to make a single 10/ or 12/4. On the exploded drawing, I numbered each piece, then used an Excel (Microsoft) file to catalog & sum the piece dimensions for a ‘cut-diagram’ – this was used when I went to my wood supply store. This numbering was very important, as later I used these references to catalog the 40 M&Ts (as intersections of wood pieces). Virtually all pieces are orientation-dependent – left or right, front or back. You have to have your wits about you.
I found the jointer to be a valuable friend. Previously, I’ve used the jointer primarily for glue edges and straightening. Now, I see it as a means to a precise dimension. By all means, purchase a high-quality digital caliper, and use it on every piece, and use it often.
Mortise & Tenons
This is my first real M&T project – I’ve done some Festool Domino projects before. Of the 40 required, 8 could be performed by my Domino (6mm, ¼”); with the remaining 32 cut with either the Router (mortises) or on the Router Table (tenons).
Mortises where done with a homemade 1/2” MDF template, with guide holes for ether 2.5”, 2.0”, or 1.75” x ¾” wide (using a forstner bit), and typically 1.25” deep. The guide bushing approach was great when it worked, and a disaster when it didn’t – centering the mortising bit within the guide bushing within the router proved problematic – I ruined two guide bushings, and chipped the mortising bit in the process: getting everything centered, and keeping them centered during the mortising operation was impossible—- for my current skill level. Next Time, I’ll find a different way of doing this.
Tenons were accomplished on the Router Table. Most sources recommended the Table Saw; though, I’m comfortable with the Incra-based fence, and used it effectively in fine-tuning both the width and length of the tenons. The Incra system allows micro-fine dimensioning – in my opinion, it is hands-down the most precise, stable fence on the market. One troublesome area was the exact shape of the M&Ts – the MDF template system provides a rounded Mortise, while the Router Table approach to the tenons yielded a squared-rectangle. I devised a simple solution …
I mounted the Tenons upright in a Jorgenson-style clamp, which was held to the workbench; I then used a razor knife and sandpaper to: a) carve away the pointed corners, then half-mooned the remainder with a 10” or so long strip of sandpaper, whittling down the edges into a perfect half-moon. The experienced Forum Members will have a chuckle on this approach, I’m sure.
This is an outdoor bench – emphasis on Outdoor. What I know is that everything I’ve made previously for the outdoors looks like crap after two months: the pressure-treated wood warps; joints fail.
I reached-out to the Forum Members, and several web-based individuals on the glue-up process. “AskWoodMan” was very helpful, in both his videos and via e-mails; several Forum Members (Shipwright, for one) also provided expertise. I chose an epoxy glue, rather than the Titebond 3 – the Open (working) time for Epoxy is much longer; I contacted West System for recommendations – their Customer Support was excellent, fairly independent, and knowledgeable – their G/flex 650 has a well-documented track record with Jatoba and other exotic woods; and the West System system provides for thickeners, fillers, and other modifiers which helped offset some of my M&T inexperience.
Epoxy has its own learning curve; and if you go this route you have to buy into the (fairly expensive and 2-part adhesive) process. Use a food scale to precisely measure the Hardener & Resin. It seems to be exothermic, and expands while curing. It’s very tough stuff; your chisels need to be sharp, for clean-up. While epoxy is a great outdoor adhesive, I doubt that I’ll go this route on indoor projects.
The project takes about 20 minutes to glue-up: two dry-fit, dry runs identified a specific sequence; and I had my wife help me with the long pieces. The longer open time from the Epoxy is critical to making this a no-hassle glue-up. With the maze-like M&Ts, knowing exactly how everything needs to go together is critical. Of course, have plenty of pipe clamps available, along with several Besseys.
West System recommends sanding to 80-grit, cleaning with Isopropyl alcohol; once dry, then apply the adhesive – the isopropyl is 30% water, which raises the grain slightly, providing more surface area for the adhesive.
Homemade Floating Tenons/Dominos
Initially, I expected to use the Festool Domino for all M&Ts. This would be my 3rd project using the Domino, and it’s a skill easily learned. Shortly into construction, I realized that most (32 actually) of the required M&T joints were too large for the Domino to cut. On the 8 M&Ts possible, I chose to make my own floating tenons, from the Jatoba scrap. This was fairly simple – having watched ‘HalfInchShy’ make some on his excellent video programs. I saw another person’s version of this, and they cut troughs in the tenons to facilitate both more long-grain surface area and to allow glue in the mortise bottom to squeeze out, if necessary. The decision to make the tenons was one driven by not wanting to expend another $58 for SIPO tenons, which I would probably notr use again. The tenons where easy to make, the grooving worked perfectly – I cut these on the router table, with a v-groove bit – and I’ll be making these from now on.
I finished the Bench with a 150; 220; 600 ‘sanding’; then wiped the final sand with acetone. The 600 finish was to polish the work, nothing more. My wife requested a natural, un-coated finish. Per recommendations from both West System and the Author, I coated the feet with an epoxy layer – this to prevent wicking; and made sure that junction points of the M&Ts were sealed..
The project plans from Fine Woodworking were very good – I found one minor cut error, no great shakes; and the accompanying text was clear and thoughtful. It’s unlikely that I’ll attempt another large project without excellent plans.
Skill-wise & Technique, I will find another way to cut the M&Ts – I found the guide bushing approach too problematic; and I assume this is my inexperience rather than the technique itself. I discovered the ‘scary sharp’ approach to chisel sharpening (I posted a Lumberjocks Forum piece on this), and sold my Tormek in the process. I reinforced my own faith in the woodworking process – Project Selection, Wood Selection, Cut Diagrams, Wood Purchase, Part Details, Cut Execution and Part Precision, Construction and Final Detailing – you have to enjoy the process, to enjoy the project.
Tooling – along the way, I purchased a stronger, higher-precision router – the Bosch MRC23EVS; two Incra Rules (I have an abiding appreciation for Incra products) – laying-out the M&Ts were child’s play for the Incra Rules; and a quality digital caliper – necessary for consistent precision. The Incra LS17 fence provided dead-on repeatable Tenon cuts – the ability to dial-in thousandths of an inch. My dust collector handled approximately 30 gallons of Jatoba dust – this is a single-stage Delta with an Oneida Super Dust Deputy as the particulate separator and Wynn Environmental HEPA filter canister – I’m breathing easier these days, on dust. I discovered within my Festool Domino a handheld router (of mortises, in this case) – I created a 5.5” wide mortise for the backrest. I purchased the Carter Roller Guides for my Delta 14” bandsaw – a great investment.
A great project for me; and my wife is very happy with the results – both of these are important. For my wife, she’ll enjoy this for the next decade, or two (I hope) – we live on the waterfront, and I envision years of good coffee shared with a great friend; for me, an important step along my journey – the project required much more skill than I had before I started.
There are at least a thousand outdoor benches and bench plans to choose from – my wife chose a good one.
A final thanks to the many Forum Members and Web-gurus who took time to answer my many questions. Probably a dozen Forum Members contributed comments, insightful advice, and e-links to specific techniques. For the Web-gurus, when you see a YouTube video by professional woodworkers, with incredible skill – they answer your questions!
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