Tongue and Groove - How Tight Should the Fit Be?

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Forum topic by BetTheFarm posted 02-18-2012 04:19 PM 6123 views 0 times favorited 10 replies Add to Favorites Watch
View BetTheFarm's profile


15 posts in 2639 days

02-18-2012 04:19 PM

Hello all. I recently upgraded from a router table to a shaper and have begun making tongue and groove raised panel doors for a cabinet. I am having some anxiety because the tongue does not fit into the groove as tightly as what I am used to with my router table bits (they were 1 piece as opposed to stackable).

How tight should the tongue and groove fit be? Mine is not what you would call a “friction fit”, just ever so slightly loose. Will the glue correct this issue or will the doors not be as strong as they should be? Thank you for your advice!

10 replies so far

View Sawkerf's profile


1730 posts in 3061 days

#1 posted 02-18-2012 05:12 PM

I like mine to just be touching the grroves (i.e. no visible gap) without having to apply more than a slight amount of pressure. If they’re too tight, they can split the groove, and if they’re too loose the panels will rattle.

Space balls are a good way to hold the panel while allowing for some expansion and contraction. I’ve also used screen spline to do the same thing.

-- Adversity doesn't build reveals it.

View waho6o9's profile


8187 posts in 2570 days

#2 posted 02-18-2012 05:18 PM

What Sawkerf said, +1.

View casual1carpenter's profile


354 posts in 2468 days

#3 posted 02-18-2012 08:54 PM

My router bits came with several thin washers that can be removed or added to adjust the tightness of the T&G joint, perhaps there are similar adjustments you can make with your stackable cutters.

View ELCfinefurniture's profile


112 posts in 2313 days

#4 posted 02-19-2012 01:43 AM

I would say use spaceballs if you cant tune the fit better. I wouldnt get then so tight that there is the risk of splitting but like was already said, to loose and you risk the panel rattling from the start or eventualy if the wood shrinks the right way.

-- {Current North Bennet street school student}

View HorizontalMike's profile


7754 posts in 2907 days

#5 posted 02-19-2012 03:01 AM

I used space balls on my recent paneled bookcase and they work well. Panels are meant to float so I would not get to worried about that prospect. As a matter of fact my rear panels called for 1/4in veneer ply and that ply came in at 0.20in so with a 1/4in router bit there you have it… rather loose fit. Space balls worked wonders in taking up any slop and they all sound snug.

BTW, I cheap trick I was turned on to is to run a bead of silicon caulking along some wax paper, let it dry, and then cut/slice the string of hardened silicon to your own perfect sized spacers for much, much cheaper.

-- HorizontalMike -- "Woodpeckers understand..."

View BetTheFarm's profile


15 posts in 2639 days

#6 posted 02-19-2012 04:28 PM

Thank you for the replies. For whatever reason, the tongues still don’t fit snugly into the grooves even after some additional attempts at setting up the cutters. I thought that the shaper spindle may not be perpendicular to the table, but this does not appear to be the case either. I think the Freeborn set I purchased is just calibrated this way, but I don’t know why.

I am making the doors out of hard maple with mdf raised panels. I am glueing the panels so I hope this will compensate for any weakness in the tongue and groove joints. I glued up one door to see what happens…

View Mitch's profile


6 posts in 2282 days

#7 posted 02-19-2012 08:29 PM

I have to fine tune my stack set with some homemade shims, to make the tounge slightly bigger. Business cards or just some paper work real well for this…...i stack up some business cards, maybe 4 or 5 and sandwich them inbetween a couple pieces of scrap wood. Run some screws in to make sure the paper or cards are sandwiched between the wood really tight and wont move. Then i take a 1” hole saw( because i have a 1” spindle on my shaper) or forsner bit and dill a hole all the way trough the wood/paper/wood sandwich. Unscew the sandwich and you are left with papershims with a perfect 1” hole in them. Scissors will clean up the outside diameter and make some cheap liittle shims that you can insert between your stack to bump up the size of tounge you stack produces. Try one shim…..check the fit…...try two check the fit etc. Its nice to have a few made from business cards and a few that are just plain paper, so you have a little different thickness to fine tune with. Hope this makes sense and helps!

-- Hardwick Construction and Woodworking

View HorizontalMike's profile


7754 posts in 2907 days

#8 posted 02-21-2012 02:59 AM

Wud SAID: ”...Space balls are only going to help your width and height expansion….”

Uh, yeah… Isn’t THAT the point… (redundant, no answer required nor requested).

-- HorizontalMike -- "Woodpeckers understand..."

View HorizontalMike's profile


7754 posts in 2907 days

#9 posted 02-23-2012 02:36 AM

A little testy eh Wud?

And Wud that be on a humid day, or Wud that be on a dry day?... Or are you NOT even thinking that far ahead in your quest to give advice?

-- HorizontalMike -- "Woodpeckers understand..."

View HorizontalMike's profile


7754 posts in 2907 days

#10 posted 02-23-2012 02:03 PM

Wud, I have you blocked for good reason and your attitude shows why.

RE: how tight—I disagree with your assessment. I have had T&G joints (while also creating grooves for panels and their inserts) fit when routed and then NOT fit the following morning, all due to changes in humidity that prevented, yes prevented, me from fitting the very same pieces together. They were THAT MUCH TOO TIGHT. My own experience tells me that it is safer to have a looser fit to begin with to insure against future problems of cracking due to swelling. I have also consulted with a master craftsman about this as well because of my very same concerns.

If noise/rattles from time to time are bothersome, then the use of such things as spaceballs or bits of silicon chalking can be used to minimize/eliminate such panel rattles if one feels they are undesirable. Regardless of how you or anyone else were to fit the panels originally, seasonal shrinkage WOULD STILL allow those panels to rattle on occasion unless you or anyone else were to use something flexible to take up the space created by the shrinkage. At least by being a bit generous/loose originally, does prevent cracking from the swelling of panels.

-- HorizontalMike -- "Woodpeckers understand..."

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