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Discussion Starter #1
Hi,

I'm working on my first project with joints. I'm using blind mortise and tenon building my night stand. My questions is, how tight should the joint be before I apply the glue, I don't have any idea on this. my first several joints seems too loose, it has some space between mortise and tenon. Should I make it tighter?

Thanks,
Jue
 

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I may be wrong (it would'nt be the first time), but IMO tenons are there just to keep a joint from slipping. not to hold it together. Therefore it doesn't need to be tight enough to adhere with glue, just enough to keep it in place. Am I wrong guys & gals?
 

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I hope you're wrong

I may be wrong (it would'nt be the first time), but IMO tenons are there just to keep a joint from slipping. not to hold it together. Therefore it doesn't need to be tight enough to adhere with glue, just enough to keep it in place. Am I wrong guys & gals?
I use mortise and tennon joints quite often and I thought they were used to hold the joint together. I hope I'm correct because I've built several projects with no other fasteners. I hope they don't fall apart.
 

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It sounds like you are new to the hobby. Congratulations. Woodworking is great!

Get ten woodworkers together to answer this question and you are likely to get ten opinions of how tight a joint should be. Some say hand tight as above - that is the tenon should slide easily into the mortise, and some say it should be tight enough to require some kind of pounding to get it together. Most will argue that it should be at least snug. Visible gaps are not good. I favor the hand tight opinion. Here are some things to consider. I will usually test fit the joints without glue, and I hate to whack my nicely machined wood with any kind of hammer. Second, the yellow glue many woodworkers use is in of itself not strong, and has no gap filling properties, so a nice snug joint without any play will give the best bond. Too tight and you may starve the joint and actually weaken it.

Finally, water based glues can expand the tenon slightly after it’s applied. This takes a few minutes. If the joint is very snug at the dry fit and you are slow about assembling the joints that have glue sitting on them, the tenon could swell just enough to crack the joint that did not crack during a dry fit. I made that mistake once and it cost me a finely carved cabriole table leg.

With respect to previous posts, I am reasonably certain that the glue does have a role in keeping the joint together, but the mechanical fit of the joint is important as well. For example, the shoulder of the mortise mechanically prevents racking (wracking?) and makes the glue’s job easier. If you hammer a tight mortise and tenon joint together without glue it will eventually come apart because of seasonal wood movement. The glued mortise and tenon has been holding furniture together for hundreds of years. Pinning a mortise and tenon probably adds some strength, but is in my opinion is optional and mostly decorative, and won’t rescue a sloppy fit. Try this some time - prepare a snug fitting mortise and tenon joint, glue it, then after a week try to break it apart. The wood will usually break rather than the glue joint. If the joint fails, you probably did not prepare a snug enough joint. If you are new at this, it might be worth playing with sacrificial joints to get a sense of how tight is tight enough.

If you have already cut the joints and they are too loose, you don’t have to start over. You can glue veneer or other thin wood to the tenon, clamp it to get a good long grain to long grain joint, then after the glue dries in about a day, re-trim it to a snug fit. I’ve done this (too many times I’m embarrassed to say) and the joints are going on 30 years without problems.

Hope the post isn’t too long but I wanted to share this with you.
 

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Discussion Starter #7
It sounds like you are new to the hobby. Congratulations. Woodworking is great!

Get ten woodworkers together to answer this question and you are likely to get ten opinions of how tight a joint should be. Some say hand tight as above - that is the tenon should slide easily into the mortise, and some say it should be tight enough to require some kind of pounding to get it together. Most will argue that it should be at least snug. Visible gaps are not good. I favor the hand tight opinion. Here are some things to consider. I will usually test fit the joints without glue, and I hate to whack my nicely machined wood with any kind of hammer. Second, the yellow glue many woodworkers use is in of itself not strong, and has no gap filling properties, so a nice snug joint without any play will give the best bond. Too tight and you may starve the joint and actually weaken it.

Finally, water based glues can expand the tenon slightly after it’s applied. This takes a few minutes. If the joint is very snug at the dry fit and you are slow about assembling the joints that have glue sitting on them, the tenon could swell just enough to crack the joint that did not crack during a dry fit. I made that mistake once and it cost me a finely carved cabriole table leg.

With respect to previous posts, I am reasonably certain that the glue does have a role in keeping the joint together, but the mechanical fit of the joint is important as well. For example, the shoulder of the mortise mechanically prevents racking (wracking?) and makes the glue’s job easier. If you hammer a tight mortise and tenon joint together without glue it will eventually come apart because of seasonal wood movement. The glued mortise and tenon has been holding furniture together for hundreds of years. Pinning a mortise and tenon probably adds some strength, but is in my opinion is optional and mostly decorative, and won’t rescue a sloppy fit. Try this some time - prepare a snug fitting mortise and tenon joint, glue it, then after a week try to break it apart. The wood will usually break rather than the glue joint. If the joint fails, you probably did not prepare a snug enough joint. If you are new at this, it might be worth playing with sacrificial joints to get a sense of how tight is tight enough.

If you have already cut the joints and they are too loose, you don’t have to start over. You can glue veneer or other thin wood to the tenon, clamp it to get a good long grain to long grain joint, then after the glue dries in about a day, re-trim it to a snug fit. I’ve done this (too many times I’m embarrassed to say) and the joints are going on 30 years without problems.

Hope the post isn’t too long but I wanted to share this with you.
thanks a lot for the detail answer. It helps a lot.
 

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Hi,

I'm working on my first project with joints. I'm using blind mortise and tenon building my night stand. My questions is, how tight should the joint be before I apply the glue, I don't have any idea on this. my first several joints seems too loose, it has some space between mortise and tenon. Should I make it tighter?

Thanks,
Jue
the tenon should be a tap in fit. The end shouldn't botton out. Also instead of the end staying flat take it off at a slite angle so that the glue has some where to go. If not it will act as a piston pushing the glue trying to get out. Now just knock the ends off don't . The tenon is also to hold the iten togother. If not glue will not hold wood flat to end grain. Yrs ago they used to drill and pin the tenon. Now that is the best joint you can get. I make mine so that you have to tap it togother but you can get it apart again. This is for a dry fit. Also so that you can tap it up or down to make both or all the tenon's equal from the botton of leg ect. Hope this help's
 

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i always try to get the fit to where i can push the tenon in all the way by hand but i have to really strain to do it. if you have to hammer it with a mallet it is too tight and you risk splitting the mortised piece.

if the fit is a little loose try epoxy over wood glue.

if it's really loose, like the tenon can rattle around in the mortise, your best bet is to start over, although you can experiment with glueing veneers or wedging.

wedging blind tenons can be a tricky game, you should know exactly what you're doing with that joint.
 

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del schisler said:
the tenon should be a tap in fit. The end shouldn't botton out. Also instead of the end staying flat take it off at a slite angle so that the glue has some where to go. If not it will act as a piston pushing the glue trying to get out.

That's how I do it. Leaving the mortise slightly deeper than the tenon to give the glue somewhere to go.

I prefer to have them fight snug enough to hold together on a dry fit, but loose enough so I can push them in without hammering. then alittle struggle to pull them apart. Once the joint swells a bit from the glue, they'll be very tight.
 
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