Have you tried carpet thread or buttonhole twist? They are heavier than regular thread.

Visit a fabric shop and ask for there strongest thread for sewing buttons on a coat.

When you are sewing buttons on a coat they should be loose not sewn tight to the coat. Put a toothpick under the button when sewing. This leaves a looseness in the button thread. On the last time through the button remove the toothpick. Now to reinforce the loose loop, start wrapping the thread for the button. You just go around and around the button thread until the whole thing is encased in the thread and looks much like a mini rope. Insert the needle into the fabric and secure the thread on the underside of the coat

This technique gives room for the fabric on the buttonhole side and does not put so much strain on the thread.

I sew them on with dental floss. If it is a dark garment a touch of a Sharpie will "dye" the floss.

I use my quilting thread to sew on buttons. The trick for success is the technique by oilpainter. This will give the looseness to the button and it will be secured. Have noticed on my retail clothes the buttons always stay on if they are stitched in this manner.

I remember having coats where the buttons were double secured with smaller, same color buttons on the inside of the coat. So you had to large button on the outside and a small button directly beneath it on the inside. When you sew on the buttons you go thru the holes in the top button into the holes of the underneath button. Clear as mud?

Teresa

Thanks for the suggestions everyone! My peacoat buttons are much happier now, reinforced by the strongest thread from my nearby fabric store as well as by many of your suggested techniques and. =)

Fray Block after sewing too.
Kathy G in MI