Basic question

[Bill Pealer]

FINALLY started turning a bowl (1st), it is dried aromatic cedar from Arkansas. Did well until the screw stripped. Decided to change to the faceplate & used #8 X1.5" screws to mount it. When I was trying to turn a dovetail in the bottom, the bowl goes sailing. Slow speed on lathe, tools sharp. What am I doing wrong.

[John Hart]

I'm just guessin' cuz I really don't know the dimensions of a number 8 screw....but isn't it less than .200" in diameter? Anyway...just guessin'....your screws are too small.

Now..this is just me....but I use stainless steel 1.5" Lag screws for most everything....sometimes larger for really big pieces. But even on the smaller pieces...I go with the 1.5" Lag screws. Lost too many pieces and got fed up.

[Alex Elias]

Are you trying to hold the piece from the end grain? That is not the best idea. Ende grain does not do a good job holding screws, glue, ETC bigger deeper screws could be the answer

[Bill Pealer]

Thanks John, I was afraid that it was because of the wood being dried rather than green. As some of you know, being chased by a block of wood flying from a lathe is not a fun experience. I'll get some lag screws. Should I also use dbl sided tape on he face plate?
Alex it is end grain but i figured 1.5" would be long enough.
But on the positive, shopsure does smell great.

[John Hart]

I don't use double-sided tape Bill. I know some people do though with good results. My key point would be to drill small holes for the screws. Small enough that it's a pain to drive the screws in with a socket. That'll give you the best bite. Like Alex says....end grain isn't friendly to screws so it's best to get all the bite you can from the threads.

[Jim Becker]

And for a bowl or vessel, consider using a tenon, rather than a recess. You don't have a lot of support in a recess as you typically make your form. I only will use a recess for something like a platter where there is a lot of material outside of the recess to provide support.

[Gordon Seto]

Bill,

You didn't say how big a piece you are turning.

Start with a smaller bowl first. The number of screws is more important than the size and length of screws. End grain doesn't hold screws well. Punky wood won't work either.

The largest & longest screw in CSUSA catalog for face plates is #12 X 1¼". The screw holes on some of the faceplates that I have are not even large enough for #12 screws. I believe if bigger screws are needed, then the screw holes would be larger.

May be you need a bigger faceplate.

You can find the instruction from the 1st DVD by Bill Grumbine "Turned bowl made easy". Bill just did a demo for our club last week end. He just used some skinny deck screws. He emphasis that those screw looked like dry wall screws; but they are not. He ran out of the German Spax screws; he has been using the exterior deck screws instead. The blank was maxed out on the Powermatic 3520.

Gordon

[Richard Madison]

Been using deck screws for years with no problems. They are apparently not as brittle as "drywall" screws. Bill did not say how many screws. Have a 6" faceplate with 18 screw holes, and for a big, unbalanced chunk I use 'em all.

Ditto what Jim said about using a tenon. I actually split a piece one time tightening the chuck into a recess.

[Steve Campbell]

Bill I don't know how big your blank was. I only have a General maxi lathe so you blanks may be bigger. What I do z lot of the time is just start turning the blank between centers. Get it round then turn a tenon on the end. I then turn the outside of the bowl. Then finally I put it in the chuck and turn the inside. I haven't lost many that way.
Hope this helps some
Steve

[Bill Pealer]

Thanks for all the info. Will try the tenon when I return home. The blank is about 7' dia. Started off a lot bigger but there has been several design changes :D

[Bob Hallowell]

I different than most, at least that's what I have been told:D

but for bowls even big heavy out of balanced ones up to 14" I drill a recess in the top 2 1/4" and stick my chuck in it, bring up the tail stock and see how I like to positioning lock everthing down once I am happy. the key is turning with the tailstock until all that is left is cleaning the tenon down some. The wood's not going to fly if it is attached both front and rear.

[Bill Wyko]

You might try adding some 3-M double sided tape between the faceplate. Then put the screws in. I've done this before and had the wood break before it came off the plate. The nice part about the 3-M is that when you remove it, it leaves no residue.

[Gordon Seto]

The blank is about 7' dia. Started off a lot bigger but there has been several design changes :D

Bill,

I guess you meant 7", not 7 feet in diameter.

The success of recess depends on how much wood is outside the jaws.

For a 7" bowl, if you aim for 1/3 foot size, there is not much wood left. Even if the foot is ½ the bowl size, deducting 2"+ for recess, the wood on the outside of the recess would be well under 3/4". There is no room for design change. That's may be why recess is more often used in large platters.

Gordon

[Reed Gray]

The problem, as others have said is the screws into end grain, think of splitting wood with an axe, you split down the end grain, not cross grain. As far as a tenon or recess, both work well when properly done.

I prefer the recess. I mount the bowls for turning the base with a recess drilled into the top with a forstner bit that is the same size as the jaws on my chuck. I turn the outside of the bowl, and then make a recess. I only use a face plate with natural edge bowls.

General rule of thumb is the foot or bottom of the bowl is between half to 1/3 the diameter of the top of the bowl (a 12 inch bowl should have a foot about 4 to 6 inches). If you are using a tenon to contract onto, you want a tenon at least 4 inches, otherwise there just isn't enough wood to get a secure grip on. A 2 inch tenon on a 12 inch bowl won't work. Also, you want fairly wide jaws on your chuck. With a recess it is about the same thing, a foot that is 4 inches across will work. You want to make the recess as close to the diameter of your chuck jaws as you can. A chuck with 2 inch jaws, needs a recess about 2 1/8 inch wide max. If the recess for the same chuck is 3 inches wide, you have very little metal on the wood, and don't get a very secure hold. Also, you need some wood outside the recess to keep it strong. If you only have a 1/4 inch shoulder to expand into, this isn't strong. With 4 inch foot, and 2 inch recess, that is a good amount. I can safely turn and core bowls up to 18 inches this way. You need to experiment to find out what will work best for you.

Another thing is the surface the chuck sits on. It Needs to be dead flat, and you don't want the chuck to bottom out. By that, I mean that the jaws need to sit on the wood, but not the body of the chuck.

You can also over tighten the chuck. I broke a few tenons and recesses by doing the old armstrong thing. Get it snug, move the key to the other hole, and get it snug again, some times I will go around a few times, but never get it really as tight as I can. Also, if you have it too tight, if you do have a catch, then it is more likely to fail where there is a lot of stress.

The recess or tenon also need to match your chuck jaws for shape. If you have dove tailed jaws, you need a dove tailed tenon or recess the same angle as your jaws. There are specialized tools for this. If you have straight jaws, then you need straight sides of the tenon or recess.

Depth of your recess or tenon is another thing to consider. For my recess, with the drilled one on the top of the bowl, I usually go about 3/8 inch deep. For the turned recess in the bottom, I go 1/8 to 1/4 depending on the size of bowl. I use the dove tail because I feel that it holds better. With straight sides to a tenon, or recess, I would make it deeper, like my drilled hole, 1/4 inch minimum. Again, this depends on bowl size.

robo hippy