Gluing after drum sanding?

[Yuri Strukov]

Hello, I was wondering about what would make a better face gluing surface,
running a board through a planer or through a drum sander?
I have seen many suggest using a planer first and then finish the
board with a 120-180 grit drum sander for face glue-ups. My questions are:
Wouldn't a 180 grit sanding be too coarse for gluing and why sand an
already planted surface, which is supposed to be as smooth as one can go?

Would appreciate any feedback and comment!
Thank you and Best wishes,
YS

[Mel Fulks]

Most planers get some nicks in the knives pretty fast , some are big , they can make for an ugly edge. For gluing two surfaces together,
I just wrap some sandpaper around a piece of scrap and sand quickly across grain to remove the “humps “ , that makes for a thin as
possible glue line.

[Randy Heinemann]

I would think the surface from a drum sander with 120 grit would give a great gluing surface. After all plywood like Baltic birch is sanded to 120 grit off the shelf. However a jointed edge is also gives a solid, strong joint.

[Zachary Hoyt]

I use 80 grit on the disc sander and drum sander for all surfaces, including those to be glued. I also glue right off the jointer or planer. Both types of surface seem to glue just fine.

[Yuri Strukov]

Appreciate all the responses and thanks for sharing the tips! I will experiment with manual sanding with high grit after planing and running through 180 grit on the drum sander for face gluing. I've had an impression that for glues like Titebond, the smoother the surface, the stronger the lamination. For edge gluing, I always lightly finish the edges with a low-angle hand plane for invisible (also the strongest?) glue lines. Good to know 80 and 120 grit sanding still acceptable for gluing. Best, ys

[John TenEyck]

The drum sander always gives a flat, clean-cut surface, which allows the glue to penetrate for a good bond. All planer knives will leave a scallop and dull ones will compress the wood; neither is great for a good bond. If you want to face glue after only planing, make sure the knives are sharp. Hand sanding or a light pass with the ROS is a good idea, too. Purists would hand plane the surfaces.

John

[Richard Coers]

Depends on the drum sander, but I find 180 grit to be a problem. You have to take incredibly light cuts and it's easy to fill the abrasive with some species of wood. It's very rare that I use anything other than 120 grit.

[Bill Howatt]

FWIW:
While this isn't gluing, when staining the exterior of a house for example, the advice is to sand to remove mill glaze which is the result of machine planning so the finish penetrates better.

[John TenEyck]

Depends on the drum sander, but I find 180 grit to be a problem. You have to take incredibly light cuts and it's easy to fill the abrasive with some species of wood. It's very rare that I use anything other than 120 grit.

I agree. I use 80 grit on both drums, or 80 then 100 grit on the second. Anything beyond 120 grit is interminably slow and subject to burning, etc., as you said. I know some folks use 220 grit on their DS, but I don't have the patience. I find my ROS to be the better option for finer grits.

John

[Yuri Strukov]

Thanks for all the responses! It's just that I have never glued up sanded surfaces, and never thought as coarse as grit 120 would even work. Don't PBA-based glues require a planed surface for the glues to work properly through forming a molecular bond?

[Carl Beckett]

This may not be a useful comment, but I have glued all kinds of surfaces that were less than ideal. I can not recall a structural failure, although I do at times have 'gaps' if a board isnt 'flat'.

[Mick Simon]

I've glued straight off of the drum sander with 120 grit for years and never had a failure, including multi-layer bent laminations. I find it's best practice to blow off or vacuum the surface well to get rid of the dust.

[Zachary Hoyt]

I use the drum sander or the planer to flatten lumber and then cut neck sections out of the boards and glue them together. I have not had any trouble with either 80 grit off the drum sander or off the planer. These are critical joints and no "glue line" is tolerated, and I have found that both methods work equally fine. What matters for me is that the wood is flat, and to use plenty of clamps and enough glue for squeezeout all around.

[Kevin Jenness]

As long as the surfaces are flat and cleanly cut a machine planed surface is fine for most wood glues. Snipe, obvious knife nicks and dull knives can cause a problem. Old or glazed surfaces benefit from sanding. Epoxy is one exception that works better with sanded or sawn surfaces and can tolerate a thick glueline.

[Steve Demuth]

I stick to 80 grit on my drum sander for the most part, and use a hand sander if I need to go finer than that. But when I do use finer grits on the drum sander, I spray them with teflon spray frequently. Improves release of the dust and reduces the tendency to burn by a great deal.