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epoxy for mortise and tenon joints

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Forum topic by thebigvise posted 02-20-2012 07:19 PM 2183 views 0 times favorited 8 replies Add to Favorites Watch
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thebigvise

190 posts in 1554 days


02-20-2012 07:19 PM

I just viewed a video from AskWoodMan.com about using a chisel to square up mortises. On the audio track, the guy said that he swears by using PC-7 epoxy for the adhesive in his MT joints, citing its gap-filling properties and its longer working time to check for perfect alignment. I plan soon to glue up 32 MT joints with Titebond yellow glue. I’d be interested in others’ thoughts about using epoxy instead. Thank you.

-- Paul, Clinton, NC


8 replies so far

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Napaman

5346 posts in 2730 days


#1 posted 02-20-2012 07:23 PM

dont go offf my advice for a joint like this…but I have been building TWO sail boats this past year and I love epoxy…it will definitely fill the gaps…and be strong joint…

The only word of caution that I can think of off hand would be that you could NEVER take the joint apart…when making furniture sometimes there is good reason to take an assembly apart…with epoxy there is no way…

Okay…back to boat building…

-- Matt--Proud LJ since 2007

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crank49

3421 posts in 1624 days


#2 posted 02-20-2012 09:48 PM

That’s how I attached the legs for my workbench. It’s solid as a rock after 2 years.
I used System 3, slow setting. Not a good choice for winter time. Had to heat the joints to get them to cure.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

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waho6o9

4917 posts in 1230 days


#3 posted 02-20-2012 09:57 PM

I haven’t used it but read that the slow setting epoxy is golden, as stated above. Don’t breathe that stuff though.
Use plenty of fans, open windows, or what ever you have to avoid breathing that stuff.

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Danpaddles

537 posts in 965 days


#4 posted 02-20-2012 10:15 PM

Don’t breathe it. and wear gloves.

It costs more to use, I always feel like I am wasting half the glue to the (jar lid) I mix it in, and the stick I use to apply it. With PVA- no gloves, no fumes, little waste, and I can spread it with my finger.

How good are your joints? Sloppy, like mine? Use epoxy. Outside furniture? Use epoxy.

BTW- gorilla glue also fills gaps, it too is waterproof, but it can make your parts move if they are not secured. And you still need gloves.

-- Dan V. in Indy

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ChrisK

1148 posts in 1735 days


#5 posted 02-20-2012 10:31 PM

The epoxy is water proof and can be slow setting. If the joints are nice and tight the Titebond is a very good choice. Use III if waterproof is needed. Epoxy is a pain to clean up. Wear gloves and have solvent handy for spills and tool clean up, or sand off later.

The PC 7 Epoxy from PC products is a paste. It will be hard to wipe on a thin film. There are several other types that are easy to flow. Also, they can drip. Mixing the epoxy in the correct proportions is need for maximum thickness. The paste type can be hard to do this with.

The polyurethane glues are not really gap filling. They will foam if the parts to be joined allow for an air space. The foam is very brittle compared the tight joint surfaces.

-- Chris K

View David Kirtley's profile

David Kirtley

1281 posts in 1651 days


#6 posted 02-21-2012 02:15 AM

Only down sides are that the epoxy doesn’t do well clamped too hard and it’s thickness can be a bit of an issue if you don’t give it time to ooze out when you put the joint together. I would suggest not using it straight for that type of gluing. I really like System 3 Gel-magic for that. It is one of the pre-mixes that has fillers in it. Great stuff. Their other premix that would be good is EasyFillet which is much thicker but tends to be a bit too colorful unless it doesn’t bother you.

-- Woodworking shouldn't cost a fortune: http://lowbudgetwoodworker.blogspot.com/

View PurpLev's profile

PurpLev

8476 posts in 2302 days


#7 posted 02-21-2012 02:25 AM

I use epoxy from time to time when the application calls for it.

I’m sure it’ll work great for M&T, but I absolutely see no reason to use it for this purpose. it’s more expensive than yellow glue, more messy to work with, fumes are toxic, and for M&T where you have plenty of long-grain-to-long-grain surface it will not be any stronger than yellow glue (thats right – it will NOT be any stronger).

especially if you have so many M&T to do, yellow glue will be easier to work with, cheaper, will will result in just as strong of a joint.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View JAAune's profile

JAAune

796 posts in 970 days


#8 posted 02-21-2012 02:37 AM

I try to get all joints cut with a nice, friction fit. If for some reason every joint ends up being a little on the sloppy side I’ll often go with epoxy if I don’t want to put shims on the tenons. My preference though, is for a tight joint and pva glue since it’s quicker to apply, less messy and less toxic.

The reason epoxy is so slow for me is due to the fact that I always give the glue plenty of time to soak into the wood fibers before clamping parts into place. On a mortise and tenon joint, epoxy can easily soak right into the end grain and leave a dry joint if it is assemble immediately after spreading the glue. Three applications of epoxy over a 45 minute period is typically enough to prevent that from happening.

-- See my work at http://remmertstudios.com and http://altaredesign.com

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