For purposes of alignment, and minimizing planing after glue up, it would seem that dowels would work well. They wouldn’t allow for much slipping around during the glue up, would they? I am thinking about doing one board at a time, using a self centering dowel jig and spacing the dowels about one every foot. Does anybody have any experience or comments about this? If you think it is a good idea, should I use 3/8 or 1/2 inch dowels on 5/4 oak?
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Replies
I would not bother using any alingnment aid. Just clamp the boards and tap them with a hammer and a scrap block of wood to knock them into alignment. Glue is stronger than the wood and alignment should be achievable without dowels.
Mark:
Dowels can be difficult to line up accurately in this type of application, even with a decent guide. I would agree that you can do most glue-ups without any type of additional alignment aid, but I personally like to use biscuits, since they are easier to use than dowels, and provide some extra insurance against joint failure. Of course, this involves the purchase of a specific tool to create the biscuit slots.
Kevin
Dowels would work, but I always use buscuits, as they are far less work to do than dowels. I just finished gluing up a table in 8/4 maple that is 48"x120" It weigs a ton, but it went together easy...Now I just have to move it :)
Peter
jpswoodworking.com
I do glue-ups like that, one board at a time, without dowels or biscuits or other alignment aids. I stand the first board on edge directly underneath a light in the ceiling. I use a vise to hold the board, but you could use other means. When I put the second board on the first board, the ceiling light makes shadows along the faces of the lower board if it isn't perfectly aligned. I can see so well what's happening that I generally clean up the joint with just a card scraper.
This may sound counter-intuitive, but I like the panels to move around during glue up.If I use a biscuit or dowel and God forbid, the alignment is not absolutely positively perfect, then the panel will have to be hauled down to the supplier for surfacing.On the other hand, if there are no fasteners between the boards, I can use a slow set glue and tweek and pound the boards into perfect alignment while still in the clamps. Ya'all can't do that with dowels and biscuts.I don't think the dowels and biscuits add much strength to the table top, and even if they do, plain edge gluing is strong enough for me, and the ability to adjust alignment far outweights any strength the dowels give me.Regards,
Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Either dowels or bisquits will add considerable strength. The bisquits will not help with alignment, the dowels will.
And some have experienced "bisquit ghosts" when bisquits have been used. The bisquits swell as the glue soaks in, causing a noticable aberration in the surface of the project. Sanding/planing will solve this, but whyu bother?
3/8 dowells will be fine. 1/2 would also work well, but are overkill.
Unless you're the lead dog, the view just never changes.
So many folks want to take a simple process and make it complicated. No need for bisquits of dowels for edge joints. I use the curved caul method and can glue up a 4' x 8' panel in one set up single handed and get perfect registration. The cauls are slightly curved 1/8" over a 42" span. The crown of each caul top and bottom face each other to put pressure in the middle thus allowing perfect alignment of the boards and no slip will occur so the glue gets scraped off and the panel is done except for finish sanding. No need to allow for an extra 1/8" to be run through a big planer or widebelt. Very simple method and fool proof!
Rick,
I agree with your thoughts about making it as simple as possible but I draw a blank when trying to figure out what you mean by using a "clamped caul". Can you elaborate with a more detailed description of how it works and/or a picture of it in action? I am new to the finish side of woodoworkingand would very much appreciate it.
Mike
Cauls are lengthwise pieces of wood on the top and bottom of the panel - they're clamped to each other (on the ends) and keep the individual boards registered during glue-up.
Basically it's a variation on a veneer press idea. You can use your basic clamps on hand. The diagram shows the application as used as a veneer press. Eliminate part A and the rest is the basis of the curved caul method. I've used all the other methods described by the others and find the curved caul is the simplest and very reliable. I've even worked in factories where we had big revolving clamp assemblies with air powered wrenches for tightening the clamps or radio frequency clamping machine where you can unload the clamp as soon as it's glued up. I don't know of anyone using dowels except the folks on knots. None of the commercial shops around me use biscuits for panels either. There is documented evidence on glue joint strength in the Forest Products Laboratory handbook which is available online in pdf format. A little out of date as there is no updated info regarding biscuits but basically it says the best joint is a freshly jointed butted edge joint. I find that the curved caul method lets me glue up the full panel single handedly and planed to finish thickness so all I have to do is scrape off the glue and sand to a final finish. I have glued up 4' x 8' panels with no problems.
All,
To add to Rick's description of clamping cauls, I have plastic packing tape on mine and that prevents and glue squeeze out from bonding the caul and the wood. It also reduces the friction so lateral adjustments and vertical adjustments of your clamps and cauls can be accomplished while still apply slight pressure on the piece.
Doug
HAvent tried this curved caul aproach (have used flat ones with even thicknesed pads on the individual planks and recognise that the pressure across the width is a problem only roughly solveable)
How accurate does the curve have to be, ie symetrical across a single board, circular or eliptical curve etc, and mirrored on the opposing caul? What were the starting dimensions of the caul (I probably missed these in an earlier post) What is the radius over (say) 36" for a wide table top.
This definately looks better than the fiddling about with shimming flat cauls to even the clamping pressure.
I have maple cauls 2" x 2" x 48" with an 1/8" crown. The key is to make them exactly the same. You can make one and use a flush trim bit to make the rest of them uniform. I space them in pairs every 18" or so. Waxing them or using packing tape to keep the glue from sticking is important. I sit the cauls on two large beams to give clearance for the clamps. The nice thing with the curved cauls is you don't have to use the pads you have been using and it gives perfect alignment so my stock is at finished dimension plus you can use your regular clamps and even beat old pipe clamps are usable plus you don't have to alternate clamps on top and on the bottom. Just experiment and see what works for you. It's really easy to do complete glue-ups instead of doing two boards at a time and then gluing up the pairs of boards.
Mark,
Contrary to popular belief, neither biscuits or dowells add signifficantly to the overall strength of this type of joint and, as others have stated, the glue does provide a bond that is greater than the surround wood. The primary purpose of dowels and biscuits for a glue-up is alignment. Dowels can be an advantage for certain joints such as joining end-grain rails to long-grain stiles in place of M&T's. The problem with the self-centering dowelling gigs is that between dowels there is zero tolerance for deviation in the spacing whereas with biscuits you have some end-to-end play for slight adjustments. Over the length of a long glue-up, the odds of absolutely perfect alignment among all of the dowels is problematic at best. I agree with the others that simple clamping and adjusting with a mallet and block is usually sufficient.
Doug
I guess I'll play the role of contrarian today. I've recently built some pretty large tables and was glad that I used dowels, not biscuits, as an alignment aid. If you are building a really big table, you most likely will be thrilled you used an alignment aid.
First and foremost, do not plane the individual pieces of stock to be glued up to their finished thickness. Plane them to a uniform thickness, but at least a strong eighth over (I am assuming you are using machine tools in your shop). Then do your dowelling work. Please note, this does not need to be your debut with whatever dowelling jig you decide to use. You should have used it before and have confidence in it and your ability to use it on a glue-up of this size. Glue-up time is not the time to discover a flaw in the jig or your own technique.
I think biscuits are useless as aligment aids on very large glue-ups. Firstly, there is is not enough biscuit projection to be of much help and they slide around too much due to their shape. If you use dowels with hot hide glue you'll have a firm projection that you can actually use for alignment purposes.
I'd use 1/2" dowel pins.
They had dowels long before there were biscuit jointers, didn't they. Like your approach and it has worked well for me when I have needed help with alignment. I havent seen them for a while, but there used to be a metal plug you could get that you dropped into the dowell holes on the first edge and it had a little point on it that marked the position on the opposing edge (you can do the same with a small shallow pilot hole and drop a brad into them then press the two pieces together).
The other recommendation is to make the dowell holes deeper than the dowel is long so that there is no risk from differential shrinkage along / across the grain. If their only purpose is alignment (compared with a dowel joint) they do not need to be glued in. The glue along the edges is plenty strong enough.
I use dowels in large thick panels. They offer positive allignment unlike bisquits, and Sam Maloof believes they add strength thats good enough for me. Prep stock as cstan advices. The holes have to be spot on no fudge factor. Holes should be drilled a bit deeper than 1/2 the length of the dowel. Cut a piece of scrap that is equal to 1/2 the length of the dowel and set it next to the hole, place dowel in hole(after you have spread glue along edge) and tap dowel till it is flush with the top of the scrap. On the adjoining edge I use one of those cone shaped counter bore bits and chamfer the recieving dowel openings this helps the dowels in the other board find the holes. You need to chamfer the holes before gluing up. There is really no way to check your allingment except by eyeballing so its pretty much trial by fire. Stagger your dowels. Accuracy in laying out and drilling is paramount.
It is almost astonishing to read the various replies with almost completely contradictory advice about this relatively simple process.It's also surprising to see how long myths and misundertandings about this sort of thing hang around and even grow.Neither dowels nor biscuits add any strength to a correctly prepared edge joint such as this. The joint will be stronger than the wood. If stressed enough, the surrounding wood will break before the simple undoweled, unbiscuited joint. There is no way to improve that behavior with dowels or biscuits in there. They can't make the surrounding wood any stronger.The furniture industry has long used dowels, then biscuits predominately for the last 20 years for alignment purposes. But their techniques and their end result is far different than for a small-shop craftsman.First, their doweling jigs were industrial strength and far more accurate than hand drilling even with excellent small drilling jigs. It is very hard to space dowels accurately along the length of two boards. Try it. It's really not worth the effort. Large machines do it very accurately and very fast.Biscuits are even faster and more suited to production work. It doesn't matter in big production facilities if the board surface alignment isn't perfect. The panels, table tops, whatever, are run through huge thickness sanders and the job is done. (Small shops have no such facilities and need glue ups to be almost perfect.
American woodworkers have fallen in love with biscuit joining (plate joining) for all the wrong reasons.)Biscuits swelling and telegraphing their presence are not a problem if the glue-ups are set aside to equilibrate for a few days.Working without huge production facilities is an entirely different matter. The techniques do not translate to the small shop. Dowels are very difficult to do right. Try it. Why suffer the frustration? Try biscuits. Dry clamp. Nothing's perfectly lined up. Why bother with that either?For the small shop, arched clamping cauls as described above answer more of the needs and present fewer problems than any other method. For a large production facility they are much too slow and cumbersome. But in the small shop, everything is calm and under control with cauls. Dry clamp everything first and there will be no surprises. The glueup will go well and if all the boards were milled to the same thickness, the panel will need only scraping or very light planing when done.Second best is clamping without cauls. In may be possible to coax boards into alignment with a mallet and blocks. Unfortunately, it's just as easy to adversely affect one spot while correcting another.Rich
Wow, if I had known dowelling was so difficult I never would have done it.
Edited 12/7/2004 7:45 am ET by cstan
See how much one can learn here?Rich
Since it's harder to break wood by trying to bend it along the grain than across the grain, how is it that a dowel doesn't "add any strength at all"? The rule of thumb used to be that the dowel should be 1/3 of the wood thickness so the area outside of the hole wouldn't be weakend in case the board was stressed across its width. If it's done right, the glue joint will be stronger than the parallel wood fibers and should tear the wood just outside the glue line. The dowels will add some strength, just not a tremendous amount since the dowel won't necessarily break if it's a lot stronger than the wood it's in or the diameter is too large and the wood over it is too thin. Use a metal rod instead of a wooden dowel and see how much strength is added. Biscuits are another story.Also, consideration has to be given to how the piece will be used and what stresses will be applied to it. If there will be a lot of support across the width and length, a simple glue joint is fine. If it will be under a lot more stress in an unsupported place, reinforcement will be needed. With practice, as was said before, dowels can be used with good results. I don't think I would count on them for a huge increase in strength or as a crutch for skimping on material, though. In high production furniture manufacturing, speed is usually more desired than quality. At least from the examples I have seen.
"I cut this piece four times and it's still too short."
Edited 12/7/2004 11:15 am ET by highfigh
Dowels work great because one never:
Uses them to join stock that is at finished thickness.
Uses them to join stock that is at finished length.
Uses them to join stock that is at finished width.
Which means, gasp, one has some room for error.
Anybody doing glue-ups, aligment aids or not, with stock at finished thickness and without allowances for trimming in length and width, is courting disaster.
I would say that a dowel would add a little shear strength to a glue-up, but it is of secondary concern.
Dowels as an alignment aid for panel glue-ups is a well tested technique with a lot of history.
I'm certainly not advocating dowels as a joinery method, say as a substitute for mortise and tenons.
Room for error? I though we all went for the same precision as machinists! Now, I'm disappointed. lolThinking about how long ago dowels came about and what the craftsmen were working with at the time, if they didn't have a place in all of this, they wouldn't be used today. I agree, it's a matter of installing them correctly and for the right reasons. Courting disaster or they think they do everything perfectly. Either way, not a good thing.
"I cut this piece four times and it's still too short."
cstan,
With all the allowance for error, I wonder, why bother with dowels at all?
I don't use dowels for edge gluing, don't allow for thickness for cleaning up afterwards, other than enough to remove the machine marks with a smoothing plane. This translates to about the thickness of the mark on my tape measure.
If I have more than 3 or 4 boards in the glue up, I'll do it in two steps, then join the two halves together.
Alternate the clamps on top and bottom of the stock, over its length. Start clamping at one end, aligning the boards, and gently tightening each clamp as you go from one end toward the other. Snug all the clamps when done. Unless one piece is bowed, or twisted, it's pretty straight-forward. If the glue has started to get grabby when I get to the far end, occasionally I'll use a wooden clamp to squeeze the ends flush. Usually, though, hand pressure is sufficient.
It's surprising to me, the number of different approaches to the best way to glue up a panel... Almost like the best way to hang a door, fit a drawer. One of those "Well this is how I was taught, so it must be the right way!" deals. To each his own, I guess.
Cheers,
Ray
Highfigh,You're misunderstanding the contribution of the dowel within the glued joint. The strength of the joint is achieved by the adhesion of the glue to the long grain fibers along the edges. There is no strength in a joint that does not have long grain to long grain orientation.When an edge joint is properly prepared and a glue is used that has both adequate adhesion to wood fibers and adequate cohesion within its own structure, the resulting bond will be stronger than the wood itself. If enough stress is applied to the glued-up assembly, it will break anywhere but at the glue joint. This is stress across the grain orientation. (I don't know why you bring up the subject of stress applied lengthwise - that has no revelence here.) It may break next to the joint, half way between two parallel joints, anywhere but right in the glue line.The limiting factor is the wood's own structure, not anything about the joint structure. Since the glued joint is stronger than the whole assembly, nothing that you do to theoretically "improve" the glue joint can change where stress-induced fractures will occur. Even if you made the glue joint twice as strong, nothing would change. The joint would survive any stress that breaks the wood, because wood strength is the limiting factor. So, in that sense, even if dowels did improve a glue joint, they can't improve the behavior of the assembly.A dowel does not impart to the assembly any greater ability to resist a destructive stress applied across the assembly's grain . The dowel itself, being subjected to that same stress in the orientation of its longitudinal grain, may be better able to handle such stress than it could if the same stress were applied to it in its own cross grain direction. But that's simply irrelevent. The dowel will simply fracture the wood of the boards even sooner that the wood would otherwise fail, because the dowel is now acting like a lever. In panels glued up with dowels, the wood in the location of the dowels is in even greater danger of failing under stress than anywhere else.More importantly, though, is the fact that the dowels, along their length within the dowel holes, make contact with the boards almost exclusively as end grain to long grain joints. If you analyze the dowel to board contact by looking directly at the jointed edge of the board, which then gives you a cross section view of the dowel, you realize that the only long grain/long grain contact is at tangents to the dowel at the 2 points where the dowel hole is closest to each board surface. As you move away from those tangent points, around the circumference of the dowel, more and more of the board's endgrain comes in contact with the side of the dowel within the hole, until at 90 degrees from the tangents, only endgrain touches the dowels. The dowel to board glue joint is very weak, conferring no strength to the surrounding glue joint. It is actually weaker than the joint would be if the dowel hole weren't there at all and just the long grain of the 2 board's edges were in contact. Dowels actually weaken joints by taking away potential good gluing surface.RichEdited 12/7/2004 11:49 pm ET by Rich14
Edited 12/7/2004 11:51 pm ET by Rich14
This has been a fascinating discussion, great pondering material for a novice like myself. Have only one thing to add, and that's a source for those dowel centers. Click here for these:View ImageYou can probably get them at places like Rockler and Woodcraft also.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
That's the beast.
I previously attached a top to sides with dowells (dont ask why, but the tops are still secure after 14 years and four house moves between temperate and tropics) on a pair of bedside tables and couldn't find any shops open at 9pm that sold these so used pilot holes and brads. I have used them reproducing dowel joints in chairs (only to match the original) with some success. In both of these applications there is no relationship between the pieces with respect to matching edges, so positioning with a dowel jig or marking guage is not a viable solution.
Like a lot of the others, I don't think you need either biscuits or dowels for strength. But if you do decide to go with one or the other for alignment purposes, I think there's one small advantage that biscuit jointers have over doweling. If your stock is flat and held tightly (face side down) to a flat surface and the jointer base is against the same surface, you'll get consistent placement of the slot height across all the boards. Most jointers (maybe all?) cut the slot to be in the center of 3/4" stock when just resting on their base (without using the fence) so you'd end up with the slot 3/8" O.C. down from the face surface. Using the biscuit jointer fence still allows you to get tippy and end up with slot height variations. You're better off just registering off the base.
The self centering doweling jigs work well, but if you've got the inevitable thickness variation, you'll end up getting misalignment on both sides of the glue-up. The biscuit joiner method means you only have one side misaligned if you have thickness variations.
The only purpose for dowels for me is alignment.
I have made a few smaller tabletops, for coffee tables, end tables and cabinets using the adjustment by mallet method, but I could never get one spot to stay level without another popping out of alignment. I made a half-hearted attempt to use cauls but they didn't work, probably because I didn't (and still don't) want to devote the time and energy it would take to build a set of decent cauls. In any event, in both instances, there were large areas that needed to be levelled way too much. I don't own a bisuit joiner and don't want to buy and learn how to use yet another power tool.
For a dining room table glue up, that leaves dowels. It sounds like they would work fairly well -- the biggest concern being accuracy. I think I can solve that problem by building a simple jig out of a long strip of wood, with a bunch of spacers screwed on for the for the self centering doweling to align with. As long as I anchor the jig with a dowel after drilling the first hole, the rest of the holes should line up ok. If I find that some of the dowels don't line up perfectly, I can still glue up with the rest of the dowels, which should be better than using no dowels at all.
thanks for the comments. Mark
Mark
another option is to use a tongue and groove joint. If it is cut accurately, you get a massive increase in glue area compared to a plain glue joint, perfect alignment of the boards, and minimal post glue-up flattening. the joint can be cut with a table saw, router or by hand.
Ian
Do you actually use this tongue and groove joint in your glue ups? I've been in the business 35 years in custom shops and factories and no one does this. Very labor intensive and if you read the research from Forest Products Laboratories you would find in theory the part about the increased glue area is interesting but when you factor in the labor and the strength of glues today, it's actually better to have a simple butt joint. Not to mention the waste of material factor. The problem with most of the posters claims about joints is there is no documented information to back up the claims. That's why I refer to the experts at FPL in Wisconsin other wise it's just undocumented opinions!
Hi rick,
Not to disagree with your contention regarding the relative strength of butt vs tongue and groove joints. Just a note that in the small factory I worked in years ago (Virginia Craftsmen) they typically used a special jointer that produced a sort of tongue and groove lock joint for table tops. The thickness of the stock was critical, because the joint was achieved by passing alternate top and bottom sides against the fence of the machine. Variations in thickness produced an offset in the alignment of the stock. As you say, it was a PITA to use. But "That's the way we've always done it" so it must be right!
Regards,
Ray
Dowels have a long history of being used to register stock in large glue-ups. This is an indisputable fact. They are a viable alternative. They offer more positive registration, which is what you are looking for in the first place, than biscuits.
New dowel jigs, like the kind you find at Home Depot, are junk. If you're interested in owning a quality jig buy an old Stanley or Woden unit.
"Dowels have a long history of being used to register stock in large glue-ups. This is an indisputable fact."
You have me curious now. No expert by any means but a lot of the antiques I've seen have butt joints on the panels. Seems that the dowel joint came into being during the machine age so I'm curious about the indisputable fact. Got any documentation sources on this? Would be interested in reading more on the history of dowels! Thanks. I'll check my Forest Products Lab sources in the mean time.
Sport, you need to acquaint yourself with the dates of the beginning of the Industrial Revolution in Great Britain.
While certainly not the first thing 'invented' in industrial age Britain, rest assured that dowels have been around for many, many years.
Don't have time to do your homework for you.
Check out the production dates for the Stanley 59 on Patrick's Blood & Gore and you'll start to get an idea of what I'm talking about.
Might also want to take a peek at Joyce.
Edited 12/8/2004 10:43 am ET by cstan
rick,
I've seen "dowels" on one or two period (pre-industrial revolution) tables that were in my shop for conservation. These were hand whittled, you could see the facets running their length. Hickory, and the table was walnut. The glue lines had let go, and the pins were holding the two boards of the leaf together. Guess this is proof, as cstan says that they add strength to the joint! They held up longer than the glue in this instance, at least;-)) This technique is certainly the exception to the rule, but I've seen it more than once.
Regards,
Ray
I think Egyptian boat builders also used what essentially amounted to dowel joinery.
Dowels were used, before the modern, "machine" furniture building era primarily to pin M&T joints and in the form quasi M&T joints themselves. They were not used as extensively as they came to be in mass-produced goods.The fact that 2 pieces of wood, whose glue joint has finally failed after an exceedingly long time, still stay fairly close together because they are hanging precariously on the friction of some dowels does not show that the dowels either strenghened the joint or that the dowels provide any usefulness as the piece now stands. The piece can't be used as intended until the glue joints are re-established and the fact that that one piece has not actually dropped away from the other is convenient, but otherwise not particularly useful.Rich
In a panel glue-up, ceteris paribas, dowels must add some amount of additional strength, albeit miniscule, along the joint line. However, as has been said the main purpose of the original poster was for registration of work pieces in an unwieldy panel glue-up.
This is absolutely a very legitimate use for dowel joinery.
Viking longboat. All the lapstrakes were doweled, as was much of the other joinery. The Vikings used to dis-assemble them for portages on rivers, that's how they got from the Baltic to the Black Sea.Several years ago some marine engineers looked at the design of the longboat and couldn't come up with any significant improvements. Now that's design longevity!Leon Jester, Roanoke VA
I would always prefer to use dowels to ensure alignment during glue-up of large panels, as well as alignment of cabinet facings .... where they most definitely add to the strength. I prefer the Stanley No.59 jig, or one similar, where you can align one face and let the differences in board thickness run-out on the back side.
Some of the negative comments in this thread almost make me sorry I've enjoyed using dowels for the past forty years! The only biscuits around my house are sourdough, warmed, with butter and honey!
John
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