T&G tight or loose?

Re: T&G tight or loose?

Tim of San Leandro

>Steve,

In my experience, the fit depends heavily upon the wood being joined. If I'm tongue and grooving cedar....the fit is very tight. If I'm doing the same joint with jatoba, I have a teeny bit of slop....barely able to feel the slop with the joint put together...but enough slop that you've got to be careful when clamping.

I'd design a matched set for a very tight fit. It is always possible to remove wood - either from the tongue or the groove - but much more work to try and add back wood.

Tim

ps....I really like the planes I received : )

Mr. Knight...

Scott Burr Ben Lomond,CA

>I for one would never believe you would ask such a question. Is that realy you...If so yes to a point. I'll comment later...

Re: T&G tight or loose?

Adam Cherubini, NJ

>Steve,

I have many sets of match planes are all are ridiculously tight. I thought there was something wrong, maybe the grooving cutter was originally tapered and subsequent sharpenings have made it too narrow. That could be.

What I've learned is that the fit is so tight you can't put the joint together edge to edge without breaking something. Now I slide them together end wise. The result is a very fine wide panel made in moments. If your planes were intended for flooring, my answer would be different.

Were I you, I'd make the grooving iron perfectly fit the gap in the tonguing iron. Mine have some slop which means an interference fit. That works in Pine, but probably wouldn't in Maple (though I wonder why anyone would be T&Ging maple).

Good luck

Adam

What I would do

jim_reed@marietta

>I use T&Gs frequently and make them with an old #48. The joint works better loose because most boards are not exactly straight. The #48 makes a 1/4" tongue to ride in a 5/16" groove. Works very good for me.

Re: punt!

paul womack

>If you make the groove cutter a little too wide, the joint will be loose (since the groove will be bigger than the tongue).

People have already pointed out reasons for this being desirable elsewhere in the thread.

If the customer, now or in the future, decides that (s)he would like the fit to be tighter, grinding the groove cutter to be a little narrower is fairly easy.

(going from a tight fit to a loose fit by widening the 'U' shaped tongue cutter is more difficult)

This appears to be a good way to cover all the possibilities, and would allow you to make a batch of T&G planes without having to know your customers' preferances ahead of time.

BugBear

Agree with Jim

David Miller from Iowa

>Make them loose enough so they go together easily. The variations from board to board will lock it in quite satisfactorily.

I know use guys know this, but for the lurking readers - Always match plane from the same side of the board (i.e, always put the fence on the front or the back - do not mix) The tongue may look like it is in the middle, but you will have unhappy reslts of you don't keep track of this.

Re: Agree with Jim

SteveC

>It all depends on what you are doing. I've used T & G for interior decking on a boat that was to be glued with epoxy and you definately want it loose in that instance. If I was trying to make a panel for a carcase then I would probably want tight. I think I would want it no tighter than the same kind of slip fit you get with a well fit M & T joint. As said before, it is always easier to remove wood than to add it on.

Re: Agree with Jim

steve knight

>great info. I will make the irons match perfectly then the male can be modified if needed. Or they can get a couple of them for different uses.

now I just need the plane irons milled and work out the design. I also want to redu my plow plane idea's and I am making a wooden side rabbet plane from a really old design.

Correction and something forgotten.

Adam Cherubini, NJ

>If the customer, now or in the future, decides that (s)he would like the fit to be tighter, grinding the groove cutter to be a little narrower is fairly easy.

Okay. Grinding the grooving iron makes a narrower groove.

(going from a tight fit to a loose fit by widening the 'U' shaped tongue cutter is more difficult)

What? Widening the U in the tonguing plane makes a wider tongue and yet a tighter fit. I know of no easy way to modify the plane to increase joint slop. I've tried tapping the tonguing blade cold to close the U to no avail.

But increasing slop with T&G is a simple procedure that I had forgotten. David Miller reminded me.

Since the tongue is never perfectly in the center of the board, you simply redo the tongue from the other side of the board. The result is a narrower tongue and looser fit.

One other thing:

I disagree with my friend Jim. I think loose T&G planes are worthless. Its easy to make a loose joint, even without my reversing T-plane trick. A simple rabbet will work away a fat tongue. A plow plane can stand in for the groove in a pinch, either by having a slightly wider iron or taking a pass the removes a tiny bit more material.

But in general I've learned to value my fit fitting match joints. I've used T&G'ed boards to quickly make very sturdy carcass tops and bottoms, drawer bottoms, and in the case of my laundry room, entire closets and bead board paneling.

I'm glad you are making these planes, Steve. Please pass on my tips to your customers. Also don't forget to give your planes a good loose mouth. Your typical wispy shavings are not desirable here! I don't know if I've ever mentioned but I used your planes recently and was impressed but in no way surprised by their performance. I appreciate your effort and craftsmanship.

Adam

Some points of clarity

jim_reed@marietta

>I think we are pretty close in thought, but maybe disagee over the definition of loose and tight. Remember that we are talking GENERAL rules. Certain sized joints and certain woods can break the rules. I still stand my my loose T&G joint theory. By loose, I mean the tongue fits into the groove without heavy pounding. If the boards are 48" or longer, they should be tight enough that the tongue does not slide in the groove without serious blows from the end. The theory of this joint is that it allows major wood movement without cracking. I think if you put a 1/4" tongue into a 1/4" groove, you are asking for cracking at some point because both sides of the groove will be stressed.

Re: Some points of clarity

joel

>don't understand something - how would a tight T+G be stressed if the wood expands. The tongue would expand but so would the space for the groove (the same amount) as long as both parts are made of similar species of wood.

Not exactly that way

jim_reed@marietta

>T&G wood expands as follows: 1)Tongue expands to the right side, to the left side, and to the top side. The side swelling puts pressure on the cheeks of the groove. If the groove is not slightly deeper than the tongue, the top swelling will push the joint apart. 2)The groove cheek expands in and out from the right, the other cheek expands in and out. The outward expansion does not matter, but the inward expansion of the cheeks is a problem. When you couple a swollen tongue with a swollen cheek, the cheeks are likely to crack.

Re: Not exactly that way

joel

>Would not the space between the groove expand also - the exact same amount as the tongue. The inner sides of the groove would move out - because the center bit is expanding.

Re: Not exactly that way

Terry in Denver

>Joel:

Think of it this way: The toungue swells outward on both sides- The piece that the tongue fits into is two tounges. They both swell outward on both sides.

I get into this with shrink in thermoplastics (at work) all the time.

Hope this helps.

Terry

Re: Not exactly that way

joel

>We are obviously talking about different things. I did a little diagram hopefully this will may myself clear. My point is that in similar woods the x dimension expands the exact same amount in both pieces so the parts will still fit perfectly with no stress. THe lips expand but they also move outward.

Re: Not exactly that way

Tim of San Leandro

>I understand you..... :)

I've only had tongue and grooves fail when they are too tight.....then they fail during glue up or within a year as they've got "stress fractures" which are unseen but a single cycle of expansion/contraction makes those hairline fractures quite noticable.....

Re: Not exactly that way

joel

>I'm willing to bet that the reason a very tight T+G can fail during glue up is the tounge and the inner sides of the groove absorb water from the glue and expand. Even if the bottom of the joint gets wet the entire peice can't expand so with thin lips on the groove you get a crack.

I have never seen this behavior but almost all of my grooves are for fitting bottoms and things like that so that they aren't glued in.

Also if the T+G is glued in regular lateral movement in the board (which is a lot more that the thickness movement in absolute terms) could crack something.

THe solution is not gluing in your T+G although there might be cases where you must. Adam does not say if he does and I would be curious what he does for a carcass back.

Re: Rhetorical question

William Duffield on the Cohansey

>But who would glue a tongue and groove? That would be totally contrary to how the joint is intended to be used.

BTW, I agree completely with your analysis that the groove should expand the same amount as the tongue, assuming all the boards are flat sawn, or all are rift sawn, or all are quartersawn, and all have been seasoned the same.

For those considering how tight to make the fit, remember that the two boards being fitted will usually have some amount of twist, warp, cup, etc. If you secure one of the boards to the carcase, or joists, before fitting the next one to it, at least you have removed about half of that part of the stress during fitting problem. The joint components still have to be strong enough to counteract the bends in the second board while you are seating it, and before you have secured it. If the joint is too tight, you will split out the tongue or one of the sides of the groove. If a little too loose, well, that's what the bead or v-profile on the edges is designed to make up for. For floor boards without one of these edge details, you fix it with a floor plane (Hey, another excuse to add to the arsenal!!!) or floor sander after you have completed the installation. The tongue has to be able to move in the groove, in the same manner that a panel has to move in its frame.

If the groove cutter will pass through the slot in the tongue cutter, there is a problem which can only be corrected by adjusting a fence and making additional passes or by replacing one of the cutters.

Wood does not understand theories

jim_reed@marietta

>I agree that glue is out of place in a T&G joint. While you can create a panel this way, you could also just edge glue the boards. I think most of us are discussing a RAW T&G. I understand what you are saying about the board swelling to enlarge the groove. My experience is that wood usually does not follow theory. Most boards are finished on the surface, but not on the T&G joint. The T&G joint also is a crack where moisture can seep and collect. My experience is that the raw tongues and raw groove sides swell more than any other part of the wood. On antique furniture, cracked groove sides are common and the failure always seems to have been caused by a swollen side and tongue combo.