Newbie questions about glue blocks and sanding

[Tom Porter]

I'm still pretty new to turning and have two somewhat unrelated questions. As background, I'm turning green wood from start to finish. I don't have a bowl chuck so sometimes I turn the whole bowl using a faceplate and leave an extra long tenon to account for the screws and sometimes I turn the outside of the bowl with the faceplate on the bowl interior, reverse it and use a glue block to turn the interior. I've been pretty happy with my results; there is certainly room for improvement but I'm learning a lot.

First question, is there any tricks to centering the piece on the glue block (or the glue block on the faceplate) to reduce the amount of work I need to do to bring it back to round? Or is having to true it up again pretty much a cost of doing it this way?

Second question, as one would expect with green would, a fair amount of warping occurs. Typically I turn a piece to about 1/4" or so and let it dry on the lathe for a few hours or overnight just to allow the surface to dry enough to facilitate easier sanding. Even this short dry can make the bowl a bit out of round. When I sand it, I get sections that don't sand as well. Is this a result of the sand paper hydroplaning spots essentially "lower" due to the bowl being out of round? Is there any way to alleviate this or am I stuck with hand sanding those portions? If I bagged the bowl while still on the lathe for the pre-sanding dry, would it still dry enough to sand but limit warping? (I bag them after sanding).

Any thoughts?

[charlie knighton]

Tom,


tricks to centering the piece on the glue block

you might start the blank between centers, that is the revolving center and the drive center, just to extablish the center
next you can use a compass to mark the circle for the glue block or faceplate, your choice, this will give you a center point on each side, i always start hollow forms between centers to establish centers on both ends


I get sections that don't sand as well.

you will have to hand sand warped bowls, or turning so well that it does not need sanding.......part of that is choosing a wood......do not know where you are, but one such wood is mesquite, it cuts very well and is very stable....it will warp over time, but nothing like maple or cherry

[Dale Gillaspy]

I have a couple of thoughts...first....if you turn a bowl with the faceplate on what will become the interior and then reverse it to a face plate, you could turn that faceplate with a small recess, and turn the bottom of the bowl with a matching tenon. When you glue the tenon into the recess, it should be centered.

As far as the sanding goes, it is hard to tell without pictures whether you are running into the problem you are talking about, or if it is just tearout from less than perfect cuts on end grain. Make sure your tools are sharp, and give the best final cut you can, and then look and see where the rough spots are.

[Michael Mills]

This jig may help in finding the center when revering. Just size to where it just drops into the throat of your faceplate and as long as you wish. Make sure you leave a dimple from the tailstock.

I don’t know if you are gluing the waste block on before you reverse it or not. If you are leave a dimple in the waste block, if not leave a dimple in the turning. Make one of the below to just slide into your faceplate; I used a 16p nail but you can use anything. If you scrap wood is already glued on you will have a dimple on it to align the faceplate. If it is not glued on you will mount the faceplate to waste block and then drill through the waste block so that you can use you jig with the pin(nail) going through the waste block to the dimple in your turning.

Oh, the picture is wrong of course. The jig would be inserted from the opposite side when used.

[Tom Porter]

Thanks, guys. In response to comments, I'm pretty sure the warp is leading to the sanding issue because these sections seem to appear on opposite sides of the bowl. I do have issues with tear-out occasionally; I've learned a lot in my short time turning but I still struggle with tool sharpening so they are often not as sharp as I would like.

As for wood species, I've been turning black walnut and cherry because that's what I had. I've worked through most of that and now have a bunch of elm to play with. Basically, I'm using whatever I can get for free that is green.

Thanks for the jig idea. I'll try it. Thus far, I've always taken the piece off the lathe and glued it to the waste block but I like the idea of gluing the block on first. I could then add the hole for the nail in the jig. Cool!

Thanks again.

[Robert Henrickson]

Green wood always has the potential for warping, though the severity can vary from log to log from the same tree, let alone among different species. Turning to finish from green may make this more obvious than twice-turning. That said, I almost always turn green/damp wood to finish; I used to twice turn more often but very rarely do so in the last several years. Well-seasoned or 'dry' wood will tend to be better behaved, but even this may well 'misbehave' some. For example, I've turned some 12"-14" platters from 1" thick planks with centered/symmetrical grain and no obvious flaws (e.g., knots) which had been stored for years in a barn. By the time I was turning the center, the rim had a *slight* wobble, presumably from hidden stresses being released.

[Reed Gray]

One way to true it up when reversing is to turn a small tenon, about 1/16 inch thick on the bowl bottom, and a matching recess on the glue block after it is mounted on the face plate. You may need several face plates, or make sure to mark one screw hole to match with a mark on the face plate when you remount the pair. You can use a compass/dividers to mark each one.

Warping is normal for wet wood. You can leave it for about 2 to 3 days before it is dry enough to sand without it clogging your abrasives, but it will move over night. If you sand with the lathe running, any speed above about 30 rpm will be too fast, and you will hit the high spots and bounce over the low spots. The 3 phase systems can be programmed to run slower than that. Power sanding is better as well. The bowls tend to go oval, and will be long on the end grain direction, and short on the side grain. You have to stop the lathe and hand sand the low spots. If the rough spots are on the end grain, most likely it is tear out related, especially if it is on both inside and outside, and the rough spots will be on different sides of the center of the bowl/tree on inside and outside. More sanding required.

robo hippy

[Wally Dickerman]

I've been using glue blocks for a lot of years. Long before 4-jaw scroll chucks were invented. I use mine with a screw chuck, which of course is a faceplate with just one screw. I mount the blank on a faceplate or screw chuck, then rough turn the outside and true up the bottom for the glue block. After installing the glue block off the lathe I remount the piece and using a drill in the tailstock I bore the hole for the screw chuck. It's perfectly centered to reverse and do the inside of the bowl.

When I'm teaching beginners we always use glue blocks. I want the students to know how to use them and also I want them to know that they can turn bowls without a scroll chuck.

[BILL DONAHUE]

Both Lyle Jamieson and Eddie Castelin have excellent videos on Youtube about glue blocks. In fact, every video I've watched that were produced by both of them has been excellent.