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Thread: Epoxy for M&T joints for Mahogany Screen Door--first time user needs advice

  1. #1
    Join Date
    Sep 2012
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    Greater Manor Metroplex, TX
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    Epoxy for M&T joints for Mahogany Screen Door--first time user needs advice

    I appreciate all of the great advice I have been getting on a number of projects.


    I am building the first of 3 mahogany screen doors for the house. We like a more modernist look, so the door has 6 "stretchers" between the 2 rails, resulting in 5 smaller screened panels. I have done M&T joiner for everything and had planned on using Titebond 3, but now I am considering using epoxy as the glue for the joints. Aside from the great exterior properties, Some of my joints are a little looser than I would like and there are some gaps at the top of the tenons (i.e. some tenons are narrower than the mortise).

    I have never used epoxy before, so I start researching on the internet and now I am confused. Most of the information I am finding is about stabilizing cracks or doing epoxy river tables

    Some comments have said not to use epoxy on any structure joints. Seems weird to me, but is that true?

    I have been looking at West Systems with the 206A hardner to get a longer open time....are there other recommendations?

    I have seen some comments that if I using the epoxy as an adhesive, I need to add a thickening agent to the mix. True/false?

    I am in Central Texas, with summer temps generally in excess of 100F, do I need to worry about the epoxy becoming brittle?

    Any good reference sites?

    Thanks

  2. #2
    System Three T-88 Epoxy is what you want. Long open time, excellent results.

    51cAUXUZ-OL._SL1000_.jpg

  3. #3
    I've used epoxy on wood joinery with great success and I know many very experienced woodworkers who do the same.

    The benefits are most obviously the incredibly long open time compared to regular glue. I've had some complicated glue-ups that need at least 45 mins and epoxy works beautifully for that application. Just as strong as wood glue. Seems to flow better too which helps it apply more evenly in joints in my mind. Just as strong too. Since it's not water-based it won't swell joints, and actually acts as a lubricator so you can run tight joints that go together better with epoxy than just dry. Lots of benefits to epoxy.

    Only downside is cost really, and also the reason wood glue has such a strong stance in the glue-up world. Also I've heard to be a little careful when mixing to ensure the right ratio, however I've never once had an issue. I do use the West System's pumps though so that does all the work for me.

  4. #4
    Join Date
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    Quote Originally Posted by Phil Gaudio View Post
    System Three T-88 Epoxy is what you want. Long open time, excellent results.

    51cAUXUZ-OL._SL1000_.jpg
    I agree with this recommendation. T-88 is a structural epoxy and designed for this kind of operation.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
    Join Date
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    Not all epoxies are structural adhesives, but several are. Go to Systems Three and West Systems websites. A wealth of info. at both. I've only used System Three's T-88 for the exterior doors I've made and can vouch that it's easy to work with and 5 years in all is well. You definitely do not want to use TB III for a structural joint that gets any direct sun on it. Even non structural joints that get stressed don't fair well.
    Titebond Polyurethane glue would be another excellent choice and requires no mixing. The working time is not as long as T-88 but it doesn't require mixing and has equally impressive water resistance and high temperature strength.

    Oh yeah, epoxy cleans up easily with plain white vinegar. Also, you don't want tight fitting joints with epoxy. An easy sliding fit is best.

    John

  6. #6
    Join Date
    Dec 2007
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    I just used epoxy for the first time over the weekend. I was gluing up a bed that had 16 spindles on both the headboard and footboard, housed tenon's, and they were they were four different lengths. So it was very fiddly getting everything together.

    I went with the west epoxy and the hardener you mentioned. With the pumps west supplied, the ratio for the two parts was easy. I did a little experimenting on Friday to see what it was like, but my experimenting showed it to be like any other glue up, just with a long open time.

    I really liked it, and no way I could get the glue ups complete with parts swelling and a short open time. It is expensive, and I won't use it for every project, but I was really happy I used it this time around.

  7. #7
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    The only other downside to epoxy is it's not as easy to clean up as wood glue when wet.

  8. #8
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    Quote Originally Posted by Alex Zeller View Post
    The only other downside to epoxy is it's not as easy to clean up as wood glue when wet.
    White vinegar is your friend...
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #9
    Join Date
    Apr 2008
    Location
    Edmonton, Canada
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    I used west system for this 42"x96"x2.25" door out of Mahogany:
    https://sawmillcreek.org/showthread....s-)&highlight=

    In our harsh climate (with +30C to -35C in winter) it is holding up pretty well after 6 years.

  10. #10
    Join Date
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    WEST System epoxy is virtually all I have used for wood glue for over 40 years. Nothing better. 206 hardener will be fine. Take time to cleanup excess squeeze-out before cure takes place. I like acetone for cleaning up.
    "Anything seems possible when you don't know what you're doing."

  11. #11
    Join Date
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    I have only ever used West system products. Besides long open time, you can mix some of your saw dust in it for color matching as well as thickening, and it has excellent gap filling properties.

    When you think it is dry and fully cured, give it another 24 hours before you sand. Sanding green epoxy is hard work and hard on your lungs. Get a respirator.

  12. #12
    Join Date
    Oct 2018
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    New Boston, Michigan
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    Yup....T-88
    Ask a woodworker to "make your bed" and he/she makes a bed.

  13. #13
    Join Date
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    Quote Originally Posted by Phil Gaudio View Post
    System Three T-88 Epoxy is what you want. Long open time, excellent results.

    51cAUXUZ-OL._SL1000_.jpg
    Exactly!!
    Admittingly the OP referenced loose joints, and T-88 is designed to fill gaps.

    To the OP
    Epoxy is not difficult to use, and is used in zillions of wood working applications world wide,every day. Many, many of them high stress structural joints. There are though, many formulations that have different properties, for different applications. For the application you have detailed, you need a "gap filling" structural epoxy, and T-88 is a one and done product. It is very easy, and forgiving to use, and easy to get. You don't need "micro balloons", or wood flour. The thixotropic, or thickening agent, is already in the resin when you buy it.
    Epoxy is not "glue". You don't need pressure on the clamps for it to work, and in most cases, to much clamping pressure is the cause of an epoxied joint failure. You need only enough clamping pressure to hold the pieces in alignment. You're not looking for "squeezeout". Epoxy does require an initial "cure time", usually 12-24 hours before the joint can be stressed, and it may take up to a week for 100% strength. The initial cure will be about 80% of strength in the first 24 hours.
    If you want to prove it to yourself, cut an M&T joint to fit more loosely that it should. Apply the T-88 epoxy and set the joint up in a vise so that only gravity is holding the tenon piece in the mortared piece. Align them with blue painters tape and come back the next morning. That joint is not coming apart.
    Most epoxies available to the general consumer have a shelf life measured in years, so don't be worried that it will "go bad" if you buy the bigger kits.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  14. #14
    Join Date
    Apr 2013
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    I started using epoxy for M/T joints because I've rarely had a good tight joint. I've used T-88 for several years with inside and outside projects. I start I have a oak bench with all the joinery done with T-88 and its held up for several years in the extreme cold and the extreme heat. One advantage is that its a bit slick, as opposed to PVA glue which can start swelling the wood and making it a tight fit in assembly.

  15. #15
    Join Date
    Dec 2014
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    Eastern KS
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    I'll go against the grain a bit and support West Systems. You can use an additive to increase strength, workability, or filling depending on what you use.

    https://www.westsystem.com/filler-selection-guide/

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