*
I’ve not used a biscuit machine, but I
know it is a very useful beast. In the
Nov/Dec 98 FW Robert Lang uses one for
building a quick set of shelves/cabinet
out of plywood. Is strength of shelves
held together with biscuits a problem?
If a large bookshelf were made this way,
could the joints break?
Thanks for any info.
Jeff
Replies
*
Yes, the joints could break. Biscuits make excellent butt joints in sheet goods
b provided
that the case is lateraly braced. If your bookcase/shelves have a back, that is sufficient. If you intend for the biscuits to provide all the integrity of your construction, they will fail.
*In cases where I've used biscuits for sheet good shelving, I've also dadoed the shelves. Granted, the depth was only about 1/8" to 3/16", but I'm sure it provided more strength to the joint. No complaints from the clients...
*Fred,In the case of an open bookcase without a back or a face frame to prevent racking, dados would also be subject to failure as well as biscuits. An open case relying on just 4/4 shelves is probably bad design. If anything, I' try sliding dovetails. Consider using thicker shelves with wedged mortise and tenon joints. It would seem that if you had enough shoulder area per shelf and enough shelves that racking could be controlled somewhat.
*A useful test I have done several times when using biscuits in a new (for me) situation- put some joints together with biscuits, let them dry thoroughly and then beat them apart with a hammer. I think you will be amazed at the amount of force it takes. I would not rely on them in every situation, but they compare very favorably with much more time consuming joinery.
*Jeffry,How do you use biscuits with dados? Do you cut the slots 1st then the dados? Do you cut slots for #20's and use #10's or do you trim the biscuits to compensate for the loss of depth in the slots?
*A #20 biscuit is only a little less than a 1/2 in wide (12 mm) on each side, and only at the apex. The area really is not much.If biscuits are as strong as M&T, they have lived too long. I think either a plywood back that is a structural part of the case, or brackets are necessary.Biscuits are good here since they allow the structure to form, without the intended load, so you can be entirely sure about the goodness of fit of your work. Personally, I don't like to use brackets because of cost and appearance. I would use a sheet of plywood for the back. I would rabbet the inside of the case and fit the plywood, as well as put screws through the plywood back into the back edges of the shelves. 1/4" plywood would be enough since the plywood does not bear the direct load, but is a means to keep the load bearing part true without twisting. To reinforce the biscuits, I would use pocket holes on the bottom of the shelves, assuming that they are at least 3/4" thick. People in the USA seldom use pocketholes for case joinery, but in Canada they are common for newly built furniture. Since the sides are only 3/4" thick, the screws used in the pocketholes can penetrate into the sides only 5/8". Particularily for solid stocks, three 5/8" of penetrations each side of each shelve would be good to reinforce the biscuits.
*Can anyone tell me why, when I use a biscuit joiner (mine is a Black & Decker/ Elu)to join timber, the joint is often out of line? The timber I use is machined with a thicknesser and so all the timber is of an identical thickness, but when I dry fit the two sections, they often do not meet in quite the same plane. I am as sure as I can be that I am holding the joiner flat onto the piece into which I am about to cut the slot, so the cutter goes in horizontally,nor is there dust on the section to alter the height of the cut,but I still often get a slight difference in height when I put the biscuit in place to try the fit. Maybe half a millimetre, no more. I have had the problem since the machine was new. HELP!! Robert.
*If the blade of your machine is out of parallel with the horizontal plane but the guidance system is not, then your cut would be a little wide and the fit may be loose, but there will be no mis-alignment. If the guidance mechanism (in the Dewalt it consists of gibs) of your machine is out of parallel with the horizontal plane, then what you discribed would be the problem. To test out your machine, you need a perfectly flat surface. You need a feeler gauge, the kind for checking valves for automobile. Get the kind that is folded up like a Swiss army knive, and by unfolding each sheath you reduce the thickness of the stack. Clamp the body of the joiner. As you expose just the very tip of the blade, check the distance from the flat surface by inserting the adjusted stack of the gauge. Pick a tooth. Now extend the joiner fully. If there is a detectable difference, then your gibs are possibly tapered. Dewalt sells replacement gibs.
*John -So sorry I didn't get back to you sooner. I changed jobs recently and was away from the computer for a long time.You started off describing my technique fairly accuately. I cut biscuit slots first, then dado for the shelves. Both slots (on the shelf and in the case) are cut for #20 biscuits, then I use #20 biscuits as well - believe me, there's room in the slots for it.I find that the biscuits fit tighter in the slots for that reason with less slop. Since you're only cutting your dado about 1/4", you're really not taking away significantly from the biscuit's required depth. If I cut the dado to 3/16", then I may switch to a #10 biscuit. In addition to the biscuits getting glued, the shelf is also glued into the dado. I almost always use a backing board for shelving of that nature, as well. Hope that helped!
*I have an Elu biscuit joiner and have been frustrated with the accuracy. The solution was to cut the biscuit slots on top of my table saw which has a very flat face. While cutting slots, ensure the fence on the jointer is set correctly and press down on the left hand side of the tool to maintain a flat and parellel orientation between the tool and the wood. The right side is not secured as the left is. There is nothing worse than banding solid oak to oak plywood and have to run your belt sander around the joint to level it. Ugh
*The first biscuit joiner I bot was a DeWalt. Its blade cutting was not horizontal. I experimented immediate trouble on its first job. Then I took clean and squared pieces of 3/4" MDF and made a few test cuts. I adjusted the square to draw a center lines through the biscuit cuts along the long side. I was surprised to see that all cuts were cockeyed visibly. I took the sample cuts to the store and I was refunded my money. Then I bot the more recent model from Poter Cable, which did not have that problem.
*Can you use double biscuits to join 3/4" red oak rails to 1 3/4" posts (writing desk) and have good joint strength? I am confused by the conflicting info on biscuit joinery.
*Manilio, how do you like your new Porter Cable biscuit jointer?
*I think I detect some confusion here.Biscuits and dowels are not structural devices, they are alignment devices. Use them only to hold two parts in alignment while glue sets or screws are sunk or other structural support pieces are put in place.The last message from DLCBRADY indicates planning to butt join a rail to a leg with just biscuits between them. The common and correct joint would involve some form of mortise and tenon or dovetail.Joint strength is a function of area joined and two skinny biscuits ain't makin' it.
*I have just found out that Delta has stopped making it's bench biscuit joiner. Are there any other non portable biscuit joiners around? Any thoughts or suggestions would be appreciated.
*A couple of years ago I built stairs for my son's bunk bed using T joints with biscuits on 3/4 plywood. The stairs were just three progressively narrower shelfs open on both sides, the long end was attached to a wall and the bottom to the floor with no other support.After two years of a 8-10 year old stomping up and down the joints are as good as new. However most of the loaded joints are in compression so it may be the design that's doing the job rather than the biscuits.
*b WHAT IS THE BEST BISCUIT JOINER TO BUY?
*I recently acquired a Freud Model JS102 and find it very satisfactory considering the low price.
*I am intending to glue several 8 foot red and white oak boards, edge to edge I/biscuit joiner. Which glue would you recommend? State of the art?in advance ... thanks
*Titebond II.
*Hi all,I have been tossing up whether or not to buy a buscuit joiner. They seem very handy. My only concern is about the strength of the joins. Can anyone shed some light on the matter? What type of joins/uses are they good for, or not so good for. Uses I would be looking at are edge to egde joining (table tops), edge to end grain joins (rails), edge to edge (frames). I realise that they are not as strong as MT joints, but are they good enough? Any tips also appreciated.Cheers.Ray.
*Biscuit joinery is simply a more convenient method of spline joinery. It is spline joinery for all intents and purposes, with some resemblance to loose tenon joinery as well. A simple rule of thumb is that biscuit joinery can be used wherever one might have used spline joinery, and in some instances where one might have used loose tenon joinery (if the joint can accomodate the somewhat lesser strength of biscuits than loose tenon joinery.)
*Dclbrady, I used biscuits to joint a computer table i built. the 3/4 ' skirt to the 1 3/4" legs. Charles is right when he said that biscuits and dowls are used for alignment purposes. They do however have some strength qualities but not as much as a traditional m/t joint. What i did was reinforce the corners wih blocks pocket holed and screwed this added support seems adequate. thewhole process was fairly fast and simple .Ive been using it for a while now and have no problems.
*Reference to Charles Christensen (#14 of 23)You comment is most knowledgable one ever precisely described about the strength of the biscuit joint.As you mentioned, as the joining area increases the joint get stronger.However, consider the time it takes to make mortise and tenon or dovetail, and loss of stock materials.I do not agree to your opnion: "dowels are not structural devices".I found a doweling jig from http://www.smartdoweling.com, that is too easy to use, fast to set up, and most of all it does not require any marking prior to drilling hole for alignment.For critical joint area where strength is required, I used 3/8 inch diameter by 2 inch long dowels per 0.50 to 0.75 inch spacing, which is even stronger than dovetail or mortise and tenon joints.I strongly suggest you to try if you have any prejudice against old day doweling jigs. You can drill holes for dowel pins as a pair-1.0 inch spacing without moving jig, but by unclamping/clamping you can have 0.50, 0.62 or 0.75 whatever spacing.Setting spacing as 0.50 - 0.75 inch is not difficult at all because it has built-in visual markings. Very efficient tool for edge-to-edge, edge-to-surface and miter joints. Young [email protected]
*Robert I had the same problem with the Dewalt Plate jointer when I ought my new Porter Cable the problem stoped the Porter Cable just has a better system for aliging material.
*I have been using biscuits with success for a couple of years now. It is a topic worth going into in some detail, as there seems to be a lot of debate about the use (or misuse) of biscuits.BEST USES:Sometimes, biscuits really do add strength and efficiency to your woodworking projects, and there are other times where biscuits simply are not adequate. Biscuits are fine in non-weight-bearing situations (such as cabinet face frames or decorative edges). When I use biscuits for weight-bearing joints, I ALWAYS add reinforcements. Generally, you should not use biscuits where you are doing edge-to-edge joints in which there is pressure bearing on the edge of the biscuit, or where the joint receives a lot of dynamic pressure. For example, I recently built a kitchen table and a floor cabinet, and I used mortise and tenon to join rails and legs. I also recently built a large cheval mirror (the swivelling type) and used mortise and tenon, along with small dowels, to join the corners. In both of these examples, I would not trust biscuits -- there is much more strength in the mortise and tenon because it creates a large surface that is excellent for a face-to-face glue joint. Also, let's face it, mortise and tenon is much more attractive if anyone ever looks closely at the joint (especially in the case of the mirror).Biscuits are effective when you are doing edge-to-face joints and the pressure is bearing on the face of the biscuit, as in a bookshelf. However, biscuits used this way should still get reinforcement. I build a lot of custom bookshelves and I use biscuit joints to attach the shelves to the sides. But I also strengthen the unit with 1/4" backing brad-nailed to both the sides and the shelves, and I build face frames in the front of the shelves that are nailed into both the sides and the shelves. With all of these elements in place (biscuits, backing, and face frame) I can assure you that the bookshelves are extremely strong and attractive. In this instance, I actually trust biscuit-joined shelves much more than dadoed ones.It is also true that biscuits are great for alignment. I use biscuits to glue up table tops or butcher blocks. In these examples, biscuits are just adding some additional strength to a simple edge-joining operation.WHICH MODEL TO BUYI own the DeWalt joiner. Before I purchased mine I read everything I could get my hands on about biscuit joiners (and about biscuit joinery in general). I also tested the Porter+Cable and the Makita. In my opinion, the DeWalt feels better to grip. Also, its non-skid system (little teeth) works very nicely. I have not had a chance to use the Lamello models, but have heard very positive things about it. In my opinion, I don't use a biscuit joiner enough to justify spending three times the amount to obtain a Lamello.CHOOSING BISCUITSI've seen a lot of discussion about biscuit joiners, but not much about biscuits. But it is important to consider the quality of the biscuit as well as the joiner itself. I used Porter+Cable biscuits for a while, but found that I was routinely throwing away about 50% of them (they were broken, cracked, or improperly sized). I switched to Lamello biscuits, and it has made a big difference, with only about 10% waste. This saves you time and frustration, which is the whole attraction to biscuit joinery.TECHNIQUEDepending on the size (#0, #10, or #20) you should leave between one and three inches between the edges of each biscuit. Also, the outermost biscuits should be at least an inch from the edge of the panel.Mark and cut all your biscuit slots, then dry fit every slot with a different biscuit. You should not use biscuits with broken corners. When you insert the biscuit into the slot, there should be some resistance, but it should not be so tight that you have to shove the biscuit into the slot. The biscuit should not be too loose in the slot either. If you need a pair of plyers to remove the dry-fitted biscuit from the slot, it is too tight; if the biscuit falls out when you hold the panel upside down, it is too loose. If biscuits are too tight in the slot, you will have a very difficult time pulling the two panels together during glue up. Also, over-tight biscuits may cause your panels to crack (remember biscuits swell when they absorb glue). If the biscuits are too loose in the slot, your joint will be weaker.When you're done dry fitting, you should have a pile of biscuits sitting beside you that you know fit snugly into the slots. Do not attempt to select your biscuits after you have put glue into the slots. This may sound like a small matter, but remember that in any box of biscuits (even good ones) several will be broken, or will be too tight or too loose for the slots, and you don't want to be first figuring this out as your glue is drying up right before your eyes! * * *With all this in mind, I would say that being able to rely occasionally on biscuits adds a modicum of flexibility to my woodworking techniques.
*i Also, over-tight biscuits may cause your panels to crack (remember biscuits swell when they absorb glue). The first time I saw a biscuit joiner, this guy used a Lamello (Top 10, what a fine machine) on a MDF paint grade window seat that was over 8' in length. He sanded the joint shortly after glueing it up, and when the painters got through, you could "see" the biscuits in the top. Charlie
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