I have been using these metal threaded inserts like this:
(https://forestryforum.com/gallery/albums/userpics/13048/insert.jpg)
Even though I bought a special threaded tool to insert them into my wood, this still leaves a lot to be desired. I am inserting this into end grain of mahogany, cherry, and maple. In order to make sure it is secure and as structurally sound as possible, I soak the surrounding wood with woodworkers thin CA after the insert is in place.
I am still cautious about how much these things will hold, especially since they are being inserted into end grain.
Does anybody know how to pre-thread the wood to get more of a secure fit for these things? The method I am using now is to screw about a full turn, back it all the way out, knock off the chips and screw a little deeper repeating this until it is fully inserted. I dont know that this is the proper way or if there is a better way to do it? Any advice would be appreciated!
Have you tryed using a tap from a tap and die set?? Might work
Thanks Alot Mr Mom
I've used a lot of the brass ones on the right...but never in end grain.
Think I would test a few to failure just to see what they will hold. Maybe try a smooth one held in place by JB Weld for comparison?
I recently bought a tap and die for wood. They only come in ½" and ¾". Don't know if that would work for your bigger size ?? I would think you are doing it right.
why don't you try a pullout test? fix up a jig, and use a crow bar or something like that to pull it out?
you'll probably find that what you are doing is fine. I'm assuming that you are using them where the neck attaches to the body? there's probably not a whole lot of stress there, probably 200-300 lb-in which is 16 to 25 lb-ft of torque that the bolt has to hold down.
My biggest problem using those things is getting them in perfectly straight.
If the drilled hole is the correct size, you should be confident they will hold. Especially with your CA treatment afterward.
metalspinner, to install them I use a piece of all-thread with a jam nut in the drill press. I turn the chuck by hand. That ended the problem of getting them started straight.
Ah-ha! Thanks, Larry. I will try that next time.
My impression of those inserts was they were for particleboard, not for solid wood into the end-grain. I think the right size wood screw would be better, as there would be more wood remaining. But not sure what the loads are that you are applying to the joint. A brass dowel that the bolt can thread into the side of, would be another good connector. Or a wood dowel with a wood screw into it's side another method.
Finding the right tap with that thread might be tough. I think boring the pilot hole larger would be the best way, if using these inserts is necessary.
The Wood Handbook, listed in the Knowledge Base, has a good article on fasteners and their ability to hold. A lot has to do with the size of the hole you stick them into.
Thanks for the replies! I guess I am doing it right after all. I would still like to have a tap to pre-thread the wood but I have no clue what size or thread count tap to buy. I am drilling the proper size pilot hole according to the package but it still seems like it would be better to pre-thread them
Thanks again!
Ken
Taps made for wood typically have the threads at a wide angle, because they are made to be used with wooden screws, which need wide threads to be sufficiently strong. Your metal inserts have much narrower threads. Someone may make a tap for a metal insert like that, but it would probably be hard to find. The method you describe sounds like it should work well enough.
You might try using one of those as a tap. You would have to braze or silver solder the modified insert to some all thread rod. File a "v" across the thread so that they will cut the wood, not just deform the wood. Maybe file two "v's" so you will have a two flute tap. I haven't tried that, just thinking out loud. ;)
That's a pretty good idea, low. Might be worth a try.
I've used those ones on the left in an entertainment centre. I put a dab of glue in the hole first then turned in the holding screw. I used those because I wanted to be able to disassemble the piece because it is 6' x 6' x 3' and heavy, made of ash. I never had pull out from end grain. I would say it would be weaker on end grain though because of the way the wood is naturally glued by lignan. You have to pull that screw through several layers of wood on the flat surface and not so many layers out the end grain.
Anyone have a piece of butternut? Turn a #10 1-1/4" long screw on the flat surface about a 1/4" in and pull. Do the same on the end grain. ;D
Here is the results of a quick jerk test with butternut. Tried two different pieces, first pic shows the depth the screws were turned in.
(https://forestryforum.com/gallery/albums/userpics/11009/SD_screwtest1.jpg)
and after a quick jerk of 30 lbs.
(https://forestryforum.com/gallery/albums/userpics/11009/SD_screwtest2.jpg)
I'd say the end grain gave way at 25 lbs.
They may not be exact estimates, but close enough.
Butternut has about the poorest screw holding ability of any wood species. I'm not so sure the screw would budge in ash. I bet the screw breaks first.
I wonder what difference it would make it you soaked the end grain screw with some thin CA (superglue) ?? Neat test SD!
Some Food for thought ;)
Threading Wood (http://www.leevalley.com/hardware/page.aspx?c=1&p=40057&cat=3,41306,41330)
No inserts needed. :P
Interesting! I guess I am just going to have to tap the end grain of some mahogany with a 1/4-20 tap and see where it leads me. I never even thought about doing away with the insert all together. I'm not so sure that it is strong enough either, but you never know... thanks for the tip!
By the way, their prices on the large headed bolts are good too.
Yeah, the big box Maritime hardware store wants $1.50 each, without the insert. That's bad enough, but they first wanted $2.50 each until I let the manager know how much I knew he was ripping people off. ::) Thank goodness for Lee Valley. Get bulk screws up there and save a mint.
saw want you want IIRC in a leevalley veritas catalog...
looked for the book it seems to be missing at the moment...
http://www.leevalley.com/
found this...
http://www.leevalley.com/home/Search.aspx?c=2&action=n
found more...
http://www.leevalley.com/wood/page.aspx?c=2&p=41791&cat=1,43000
WOW that is just what I wanted! Thanks for the lead!!
Quote from: getoverit on September 10, 2007, 12:10:40 AM
WOW that is just what I wanted! Thanks for the lead!!
was what I found was what you needed??
found another site but it was iffy...