Replies

1. 
   | Oct 05, 2008 04:09pm | #1

   Hello Jeff,

   Rub joints are great for things like reinforcing blocks. Simply coat your block with glue; hide or PVA seem best because they have a fairly quick "grab time". Use some hand pressure while applying the piece to it's location and slide, or rub, the block back and forth until you feel it "grab". Only a slight amount of movement is necessary, kind of wiggle the piece back and forth about an 1/8".

   Bob, Tupper Lake, NY

   
   

   ---

   Edited 10/5/2008 9:12 am ET by salamfam

2. 
   joinerswork | Oct 05, 2008 04:18pm | #2

   jeff,

   Use hot hide glue for best results.  Used most often to attach glue blocking behind feet, along aprons, or knee blocks to queen anne legs and aprons,places like that.

   1- fit the block so it meets the surface(s) with no gaps.

   2-coat the block with the hot glue.

   3-place the block where you want it, and slide it back and forth a few times, pressing the mating surfaces together.

   4- As the glue cools and tacks, you will feel the friction suddenly increase, or the block will "grab".

   5- Let go, and leave the joint alone til the glue sets.

   Can also use this technique with liquid hide glue, or Elmers, or Titebond, white or yellow glue but I have had these joints open up occasionally, as the glue dries.  With other than hot hide glue, I like to add a spring clamp (made from a section of old upholstery coil spring) to put a little bit of pressure on the joint.

   I've read of using this technique with hot hide glue to join thin panels edge to edge, (where clamp pressure would bow them) but have not tried this myself.

   Ray

1. 
   roc | Oct 05, 2008 08:58pm | #5

   jeffreysherow and
   Ray> using rub joint and hot hide glue to join thin panels edge to edge, (where clamp pressure would bow them)I have done this and it works. Scary to try on an important project but it sucks right down tight if you have a good fit up. Beside the effect of capillary action I think as the glue soaks into the pores a bit the joint closes up even more.Thing is to plane it so there is no "spring" and before applying the glue stack the work vertically and verify it is all in the same plane . Then using magnification look at the match up of the joint and verify it fits together as good as you expect it to look in the finished project with no gaps/twist. Have a light source on one side while looking for light coming through gaps from the other side. If gaps hand plane to correct.( glue, stack and rub in vertical orientation so gravity is working to hold parts in alignment )It seems just too simple to work but it is a fun technique that works great !God I love woodworking ! Why the hell am I typing I could be in the shop.

2. 
   JeffHeath | Oct 06, 2008 11:44pm | #12

   Ray

   I use rub joints to glue cabinet door panels (bookmatched boards for future 'raising') all the time when I run out of clamps.  To my memory (which, granted, isn't what it used to be) I can't remember one ever failing during the panel raising process.  Maybe I'm getting lucky, huh.

   Rubbing also has the added benefit of spreading the glue around pretty well, too.

   Jeff

    

1. 
   joinerswork | Oct 07, 2008 12:38am | #13

   Jeff,

   Gotta try that rubbed edge joint sometime.

   Ray

3. 
   Lataxe | Oct 05, 2008 06:28pm | #3

   Jeffrey,

   What Bob & Ray said; but also ensure that the surfaces to be mated are clean, flat and smooth. Dirt, many hollows/bumps or very rough surfaces will all prevent the glue from entering the wood fibres of both pieces and doing its magical chemical bonding thang.

   Too much glue can make things messy as the excess is squeezed out; and require more rubbing before the joint grabs.

   If in doubt, get a clamp or three on the work once the rub has taken, as Ray mentions. When you do, be careful that lateral pressure from the clamp heads as you tighten them doesn't slide your rubbed pieces awry.

   Ideally the surfaces you make to rub together will be nice and the clamps redundant. I have made edge-jointed small panels like this and, despite no clamping, they do stick strong. I tested one once by breaking it. It broke in the wood fibres not the glue joint, just as with a well-made clamped joint. (This was with Titebond I on beech). Just goes to prove that it really is the molecular bonding of glue at the interface that does most of the work in keeping the joint strong.

   Lataxe

1. 
   forestgirl | Oct 05, 2008 06:58pm | #4

   Lataxe, I've also heard that if you use hot hide glue, you can glue up a picture frame using the rub joint method.  Haven't tried it though.  Is it doable??  Advisable?

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

   Edited 10/5/2008 11:58 am by forestgirl

1. 
   roc | Oct 05, 2008 10:08pm | #7

   forestgirl,howdyI too have read that but have not tried. Seems like this gets tricky because is a good idea to precoat the ends (because it is end grain which absorbs extra glue and starves the joint) then after it sets a bit then add a bit of fresh glue and put the joint together. One joint at a time as I recall. Making up some picture frames for some photos to go in the shop is on "The List" so maybe this winter I will get a chance to put this to the test.I opened my file drawer with folders full of torn out articles and this is what I came across:this one talks about precoating the end grainhttp://www.taunton.com/finewoodworking/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=2735A note to myself says this one is another really good articlehttp://www.taunton.com/finewoodworking/ProjectsAndDesign/ProjectsAndDesignPDF.aspx?id=26378didn't find the rubbed joint picture frame info though sorry.

   Edited 10/5/2008 3:15 pm by roc

2. 
   Lataxe | Oct 06, 2008 12:25am | #8

   Girl,Even this week I've been making yet more picture frames. It seems like a never ending task, as some git keeps taking and printing more pictures!(Oh,it's me). :-)I have tried a frame or two with nowt but glue, giving the mitred ends a good sizing as is mentioned in another post. Them mitres is tight as a chicken'stop lip, too, as I employ the wonderous Lion mitre trimmer after cutting the mitres to a hairsbreadth or three with the TS and its sliding table. I also use one of those steel strip band clamps, which truly squodge the mitres together hard.But.....those glue-only experiments didn't make mitres that were strong enough. I did break the joint deliberately, rather than let it fall apart on the wall, mind. If you stress such a glue-only mitre it does break along the glueline, unlike with long-grain joints where the wood fibres part before the glued bits.The trouble with mitre joints is that the slightest innaccuracy, moisture change or stress can cause the mitre to part. These partings are often tiny - but enough to break that glue joint.I always use the small rectangular sprung steel "nails" pushed into the back side (non-show side) of picture frame mitre joints. In fact, using a magnetic push pin in a dedicated press to put in the nails is much quicker than gluing. These nails make a very, very strong mitre joint for a picture frame, especially if used in pairs at each joint.With larger mitres (pictures or furniture) I use a biscuit. As you know, biscuits are nice, good and superior to all other jointing methods. ;->Lataxe

1. 
   forestgirl | Oct 06, 2008 05:45am | #9

   "I always use the small rectangular sprung steel "nails" pushed into the back side (non-show side) of picture frame mitre joints. In fact, using a magnetic push pin in a dedicated press to put in the nails is much quicker than gluing."  I'm not sure I know what these are.  Have a a link (hyperlink -- computer street sign)??

   And the magnetic push pin?  I might be doing some framed Christmas items, so would love to have more info.  Thanks!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

1. 
   Lataxe | Oct 06, 2008 12:38pm | #10

   FG,Here's a link to an old post on the subject of v-nails et al, which includes some photos.http://forums.taunton.com/fw-knots/messages?msg=7112.25Hope this helps.
   Lataxe

2. 
   zolton | Oct 06, 2008 03:39pm | #11

   I've used many, many rubbed glue blocks when reinforcing various items on furniture. One trick I employ is, before gluing, to quickly plane off the sharp corner on the block where it fits between two pieces on the furniture. With the corner gone, it allows the block to nestle into that junction with no interference. A small detail, but a block that rocks back and forth won't make a good joint.

   Zolton

    If you see a possum running around in here, kill it. It's not a pet. - Jackie Moon

3. 
   forestgirl | Oct 07, 2008 08:27am | #14

   Thanks, Lataxe, there's all kinds of good stuff in that thread!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

4. 
   roc | Oct 05, 2008 09:22pm | #6

   OK I am going to say it finally. Before it seemed with clamped up joints and softer wood I may have been overly detail oriented (they have a phrase for that ) having to do with the posterior regions. This is in reference to the discussion a while back about cleaning glue bottles before putting in fresh glue and cleaning the tip etc.

   This seems a bit fussy or allot fussy depending on how much work you crank out. I admit to being purely a home shop "hobby" dude that futzes around to no end and does not need to make a living from my woodwork. ( in my dreams ! )

   After every glue session I remove the glue bottle(s) tip(s) and wash out (just the tip not the bottle) then put it back on. The reason is if any little chip of old dried glue pops off and falls onto my glue up it can cause fit up problems.

   ESPECIALLY IN A RUBED JOINT ! So there you have it mania or disaster prevention I leave it to better minds than mine to judge.

5. 
   Talma | Oct 07, 2008 07:33pm | #15

   I use rub joints all the time. I even do it for stuff like tabletop glueups. But don't get to cocky with it. only do two boards (until dry) or you'll get yourself in trouble. DAMHIK

1. 
   forestgirl | Oct 08, 2008 06:41am | #16

   My very limited experience with hide glue has been that it "gels" into a somewhat flexible, but not solid, form before it truly hardens ("dries").  How long do you wait before going to the next board?

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

   Edited 10/7/2008 11:42 pm by forestgirl

1. 
   Talma | Oct 08, 2008 03:12pm | #17

   The glue is a firm gel that holds after about 20 min. But when I do a rub joint I place the piece on one edge so the boards weight is pushing down on the joint and I let it sit over night.

   When I have multiple boards to do I do two at a time, then the next day I will join those panels together. Or If I need it done for the next day, I'll wait about an hour then take the panels and do a traditional clamp up.

   Also I think the glue "grabs" better when you run a handplane over the edge, I go from the jointer, to the handplane to the glue up. My jointer has a 4" dia cutterhead so the "waves" from the jointing are pretty flat but I think the waves still weaken the bond a little.

   I usually make glueups a little oversized and after trimming I always snap the cutoff, and, so far, the wood always fails not the glue.

1. 
   bertiesunshine | Oct 09, 2008 09:07pm | #18

   One point to add about rub joints - if board is over 3 foot in length get a reliable helper to handle one end - and make sure they concentrate on what they are doing. Years ago we managed a four foot coopered door for a corner cupboard but the helpers [2] were absolutely dedicated.

6. 
   BurrDodd | Oct 11, 2008 12:05am | #19

   The reason a rub joint sticks initially is to some extent because the glue is sticky. But the main "natural" clamp comes from atmospheric pressure at 15 lbs per sq. inch at sea level (approx.).

   If you can exclude air from getting between any two smooth surfaces, the surrounding air will exert 15 lbs. per sq. inch. For example, a couple of glass microscope slides with a film of water between will stick together surprisingly firmly.

   In a rubbed joint, if the surfaces are smooth and mate well, the glue fills the almost no space between them and excludes the atmosphere and that 15 lbs. per sq. inch takes over.