If one has tried to tap threads in the end grain of hard woods , of course the threads are destroyed by the tap. I was making some nut crackers like J.R. Bealls. and decided the body of the piece was subject to some high stresses across the grain. To make a thread in line with the grain I first tapped some holes across the grain, then cut and turned these blanks on the mini-lathe, about 1/4 inch larger than the thread o.d., to fit the end grain hole in the body. You know, a good glue fit. Screw the body on a threaded plug in the headstock and finish turn it, using the tail stock for support. I allow the insert to cure overnight. Some of these have been in “service” for several months without failing. Anybody make sense of this?
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Replies
I'm lost on what your doings.... I have those threaders and taps from Beall too... I haven't drill and tap the ends of the hardwoods to see what it does.
Hello.BLUEGILLMAN, For example, try a 3/4' tap in a 5/8' hole in maple or cherry, the hole being drilled into end grain. As the tap enters the hole, it immediately starts to tear out the threads it's trying to make. I guess you'll have to try it to believe it. I've also tried tapping end grain by soaking the hole with Watco to strengthen the fibres,but thread quality was poor and weak. The cross grain insert described before works well and can be made even stronger by making a thicker wall outside the thread. If you wish, I can make a sketch and email it to you. Ernie.
Ernie, use a 11/16" bit for a 5/8" hole in maple. You still get a good bite on the threads. Softer woods can take a 5/8" hole. You will find that none of the crests will break off the thread using a larger bit.
mike
Thanks, I'll try it tomorrow. Sunday is a bad day to make noise in my shop.
MikeK4244's notes seems right. Try rubbing a bar of soap on the tap before it enters the work. I haven't tried that but that gives me the same idea while I use it on screws to drive them into hardwoods. Try to keep the tap straight going in without any tilting. I have a home made fixture for that reason.
Yes I use the drill press to start the tap straight. Thanks, Ernie.
I use candle wax, soap should do the trick too.
mike
I've made some lamps out of apple and tapped it for the 1/8" NPT threaded nipples used to hold bulb sockets, had no problems.
Drilled it on my DP with the spec'd drill, then tapped by hand. Lubed the tap with beeswax.
If at all possible, I'd suggest using Forstner bits instead of jobber's drills or brad point bits.
Lower rpm's seemed to work best for me.
Regards,
Come to think of it, I've often tapped holes with machine screw taps, mostly 1/4-20 both end grain and cross grain, and had no problem. The coarse threads worked best. It's the larger threads,3/4" and 1" that I had no luck with. Thanks to all the response to my first message I'll try the new suggestions.
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