flattening wood for bowl blank glue-ups

[Dan Gaylin]

Hi all,

Question about glue-ups for turning. It will take me a few sentences to get to it...

I have had some good success using woods of different shades making both vertical glue-ups (wood aligned to make a striped pattern in the bowl as you look down at the bowl) and horizontal glue-ups (wood aligned to make circular pattern in the bowl as you look down at the bowl).

Lately I have been gluing shallow bowl blanks together to make horizontal glue ups. So for example a 4X4X2" piece of maple glued to a 6x6x2" piece of walnut. I might put a piece of thin stock in between. When the blanks are reasonably flat, the result is good. If not, I get visible glue lines (to ensure I am filling gaps I typically use wood glue or sometimes T88 epoxy).

I do not have a thickness planer. Nor do I think it would work anyways (if I am not mistaken, to use a thickness planer with a relatively small bowl blank, I'd have to build some kind of stretchers for it, right? This is not my primary question, but I'd appreciate thoughts on this too).

I am learning to use hand planes and this is an option for flattening and smoothing the blanks so they will glue up better (I posted on this previously).

So here's the noob question: any reason not to simply mount each blank on the lathe, and flatten them up there, and then glue them together? This actually seems about as fast as other options, including a planing sled, which I have considered buying or building.

Thanks for your help,

-dan

[Steve Eure]

I turn segmented items, bowls, vases, etc, and have found that you can indeed use the lathe to true each piece. You can also use a sanding board, a board with a wide strip of sandpaper glued to it and while the lathe is spinning, take the board and apply even pressure across it. i have also made a 12" disc with paper mounted on the lathe. Pressing your work piece up to it while it is spinning, but you have to be careful with this approach because you can apply uneven pressure and it can cause dips in the surface if not careful.
Hope this is of some help. I am by no means an expert on this, but it has worked for me. Hopefully some of the more experienced turners will chime in.
Good luck.
Steve

[Eugene Dixon]

Look at this... https://www.youtube.com/watch?v=oxSxatD2MeU

[John K Jordan]

Flattening on the lathe will work but can be difficult. When I do that for certain glue ups I flatten "mostly" then use a long, thick "stick" with 80 grit sandpaper glued on one flattened surface and press against the wood while turning slowly. But you have to mount/hold each piece some way then maybe reverse and flatten the other side. When flattening on the lathe, I take the time to partially hollow each section so I can just cut through the thin web for each piece and save a lot of hollowing time. (It's a lot easier to flatten a narrow section of the blank then the entire surface, especially with the sanding block method.)

BOC_drawing_A.jpg BOC_drawing_C.jpg BOC_drawing_D.jpg

This is how I do beads of courage boxes like this:

BOC_C_Jack_01_IMG_6687.jpg

But sometimes I simply run the blanks through my Performax drum sander with 60 grit paper and flatten both sides. I think this is a lot quicker, and makes both sides very flat AND parallel with almost no effort. I haven't tried a 4x4 blank but often flatten 6x6x2 and larger this way. To prevent snipe I push down on the trailing edge with my hand then push down on the leading edge when it comes out the other side. I certainly wouldn't try this with a planer - yikes!

JKJ

Hi all,

Question about glue-ups for turning. It will take me a few sentences to get to it...

I have had some good success using woods of different shades making both vertical glue-ups (wood aligned to make a striped pattern in the bowl as you look down at the bowl) and horizontal glue-ups (wood aligned to make circular pattern in the bowl as you look down at the bowl).

Lately I have been gluing shallow bowl blanks together to make horizontal glue ups. So for example a 4X4X2" piece of maple glued to a 6x6x2" piece of walnut. I might put a piece of thin stock in between. When the blanks are reasonably flat, the result is good. If not, I get visible glue lines (to ensure I am filling gaps I typically use wood glue or sometimes T88 epoxy).

I do not have a thickness planar. Nor do I think it would work anyways (if I am not mistaken, to use a thickness planar with a relatively small bowl blank, I'd have to build some kind of stretchers for it, right? This is not my primary question, but I'd appreciate thoughts on this too).

I am learning to use hand planes and this is an option for flattening and smoothing the blanks so they will glue up better (I posted on this previously).

So here's the noob question: any reason not to simply mount each blank on the lathe, and flatten them up there, and then glue them together? This actually seems about as fast as other options, including a planing sled, which I have considered buying or building.

Thanks for your help,

-dan

[Dan Gaylin]

These are super helpful replies. Thanks very much. John alas a drum sander is not in my future anytime soon. I don’t have the space for it. I’m surprised there is not a commercially available jig for trueing up bowl blanks on the lathe similar to the one they have for trueing up pen blanks. When folks say it is hard to true up the blank on the lathe is that simply because you are trying to eyeball it and you are looking for a perfectly square bottom?

What do people think about the planing sled idea?

Thanks,

-dan

[David M Peters]

The difficulty in sanding for "perfect" flatness on the lathe is us - the imperfect human. But I feel that the sanding board technique mentioned in this thread will get you good enough results.

The issue with planing small parts is that they won't contact the infeed roller, cutter head, and outfeed roller all at the same time, leading them to get stuck. I don't feel that a sled would help here unless it had sacrificial rails for the rollers to grip onto...

[Dan Gaylin]

Thanks David. I wasn’t clear what I meant by the planing sled. I was referring to a router based system with rails. Like the woodpeckers slab flattening mill.

[Alex Zeller]

I've been keeping my eyes open for a used open end drum sander for some time now and either they go so fast or they are priced like new. I have been toying with the idea of making a sanding disk for the lathe. I think the video Eugene posted shows the concept. A face plate with a piece of good quality plywood or maybe MDF screwed to it (using countersunk screws and nuts) for the sandpaper. I've never looked but if you could get a Morse taper to threads (that fit what ever chuck you have) you could mount your chuck in your tail stock and use it to hold the wood flat. It seams like the cheapest way. But I have a set of cole jaws for my chuck so I can hold wood up to about 20" in diameter. It wouldn't require a new piece of equipment in the shop.

[Kyle Iwamoto]

In my opinion, if you want to get perfect, by this I mean little to no visible glue lines, you need to cough up the money and space for a drum sander. I think the drum sander is the only tool that can make something flat on both sides, and flatten small irregular pieces and flatten end grain. I think any cutting tool would tend to grab and fling end grain pieces. If you're doing glue ups, you do know, eventually you will do end grain.
Jet makes a small 10" benchtop drum sander. If space is really your problem. A friend has one, and yes, they are very hard to properly set up, but once you do, it does make flat flat pieces. It's not good for a lot of other duties, but he does love it. I love my 16". I use it all the time. An finally, yes, they are not cheap. As mentioned, even used, they are pricey. And that's a good thing if you choose to invest. You can sell it when you upgrade. Good luck!

[tom lucas]

The supermax 16-32 doesn't take up much space. Mine is on casters with the folding table extensions. It occupies about 18" x 24", and rolls easily.

I also built a homemade version of the sandflea (vdrum sander). It worked quite well. I used a 22" conveyor belt drive roller I bought off of ebay. I sold it when I bought the super max.
If you plan to do a lot of glue-up bowls, the thickness sander is the way to go. I love that thing.

IMG_0058.jpgIMG_0056.jpg

These are super helpful replies. Thanks very much. John alas a drum sander is not in my future anytime soon. I don’t have the space for it. I’m surprised there is not a commercially available jig for trueing up bowl blanks on the lathe similar to the one they have for trueing up pen blanks. When folks say it is hard to true up the blank on the lathe is that simply because you are trying to eyeball it and you are looking for a perfectly square bottom?

What do people think about the planing sled idea?

Thanks,

-dan

[Dan Gaylin]

Thanks for the additional thoughts, folks. So I hear you on the drum sander. Will need to think about fitting it in. Has anyone tried to use a router-based slab flattening mill on bowl blanks?

[John K Jordan]

Thanks for the additional thoughts, folks. So I hear you on the drum sander. Will need to think about fitting it in. Has anyone tried to use a router-based slab flattening mill on bowl blanks?

I haven't tried it with a turning blank but if the rails are all in one plane and the blank is held securely I can't imagine it not working. I'd still probably sand the surface a little after routing, even if by hand with a sheet of sandpaper fastened to a flat surface. The glue-ups I've made with the sanding stick were always perfect with no irregularities or visible glue line.

JKJ

[John K Jordan]

The difficulty in sanding for "perfect" flatness on the lathe is us - the imperfect human. But I feel that the sanding board technique mentioned in this thread will get you good enough results. ...

The method with a sanding block/stick works extremely well if the sanding is confined to a rim. Cutting away the center a bit on both surfaces also makes clamping easier. And by removing most of the inside makes hollowing even hard, dry wood much quicker. (Illustrated in the diagrams posted earlier.)

Harvey Meyer uses this method in this video at about 22:35. https://www.youtube.com/watch?v=6G7j6KikTV4

I do a couple of things different from Harvey - one, I glue the sandpaper to the flattened surface of the block. (I use Klingspor Gold sandpaper, 80 or 60 grit - lasts about forever.) Another thing I think makes it easier - leave the tool rest in place a little below center line and rest the side of the sanding block on the tool rest while sliding the block back and forth a bit.

I'm not sure how this method would work if used to flatten the entire surface on the lathe. Seems like it would not sand well in the center, possibly leaving a high spot on both halves making glue up difficult. No problem if you first removing at least some wood at the center.

JKJ

[tom lucas]

Thanks for the additional thoughts, folks. So I hear you on the drum sander. Will need to think about fitting it in. Has anyone tried to use a router-based slab flattening mill on bowl blanks?

I've done so on end grain cutting boards. Best done with a bowl bit, which reduces chip out and tearing. Works OK, but not as good as the drum sander.

[Dan Gaylin]

Okay thanks for the additional insights. Really helpful. I’m going to have to try the sanding stick/board approach for sure. Gotta start figuring out how to fit in a drum sander.