Considering a drum sander - help please

[Ken Casser]

I make frames - 20 at a time - size is about 9 x 12. The wood face is 1" and the sides are 1 1/4" wide. The wood is poplar and I mill it myself from 5/4 rough. Final finish is glossy black nitrocellulose lacquer. I've had issues with grain showing through the lacquer. My customer doesn't mind, but I do. So I keep trying to refine my prep work not only to make it more precise, but quicker if possible. I've been sanding with an RTS 400 starting at 120 and going up to 400. I tried my RO 90 because every post I've read says an RO is the best solution for sanding frames, but I've found the RTS 400 to be more comfortable and faster sanding. So, I was considering getting a Jet 10-20 drum sander. Now my quandary is that I've read that a drum sander is good at 120 grit, but then you should go to the RO and back down to 80 grit and then progress up to whatever you want. My thought is that I would use the drum sander to give me a very smooth surface on the wood while keeping all planes very flat, but if I then revert to an RO or even the RTS and drop down to 80 or even 120, I'll end up taking too much wood off the middle of each rail. I had tried starting with 80 grit on the RTS once and it took way too much wood off the inside surfaces and they weren't straight anymore. Any suggestions? Sorry there aren't any paragraph breaks, but my carriage return key doesn't seem to work here.

[Andrew Fleck]

Are you using a primer under your lacquer? I use General Finishes primer when I spray tinted poly and it hides all of the grain from poplar. No reason to go crazy sanding going this route. GF even makes a black primer if I remember right. Here is something I just built. The base is poplar that I first sprayed GF white primer and then white poly over it. I only sanded up to 180 and it is very smooth.

[Ken Casser]

Thanks, Andrew. Maybe this is in the wrong forum then, but I do shoot black lacquer undercoater and give it a light sand - 400 wetordry usually, but when I shoot the topcoats, the grain usually comes back. I tried filling the grain with NitroStan but that didn't do any better. I generally shoot three topcoats, but I've tried shooting six and still no improvement. The wood looks great after the undercoater is applied and I always expect the finish to turn out great but I'm usually disappointed.

[Andrew Fleck]

I shoot 3 coats of primer and scuff sand with 400 between coats. By the time the third coat dries I can't see the grain any longer. I follow this up with three coats of poly scuff sanded the same way. It takes a little longer, but it works well for me. I'm not sure that sanding differently will help out with your grain issue. On poplar that is to be painted I use 120 on the RO and then finish up with 180 by hand.

[Bruce Page]

To answer the DS question; I often run 220 in my Woodmaster DS with very little need for follow up sanding. I have never gone from finishing with 220 to paint but I would be willing to bet further sanding would not be necessary. As long as your frames are flat to begin with and you are just taking a cleanup pass the DS should be all you need. Do you know anyone with a DS so you could run a couple of test pieces?

[marty shultz]

Another answer to your drum sander question. I didn't have very good luck with a Powermatic dual drum sander. The belts took a long time to instal and they often overlapped each other after they were installed which caused grooves in the material. It was also easy for the belt to burn from a glue line. For me, the drum sander was more of a problem than a solution.

I went to a 37" wide belt sander which may be overkill for you but it works pretty well.

[Ken Casser]

I shoot 3 coats of primer and scuff sand with 400 between coats. By the time the third coat dries I can't see the grain any longer. I follow this up with three coats of poly scuff sanded the same way. It takes a little longer, but it works well for me. I'm not sure that sanding differently will help out with your grain issue. On poplar that is to be painted I use 120 on the RO and then finish up with 180 by hand.

How much time do you allow between primer coats? Time is a factor with this job. I get an order and have to mill the wood, do the assembly and paint in a week or so.

[Ken Casser]

I should look around to see if there's one nearby to try it out.

A belt would be nice but pricey.

[Andrew Fleck]

How much time do you allow between primer coats? Time is a factor with this job. I get an order and have to mill the wood, do the assembly and paint in a week or so.

With the GF primer I wait 30-45 minutes to start scuff sanding and one hour after spraying I am applying my next coat. This is with good drying conditions though.

[glenn bradley]

Not that I would deny anyone a new tool but, your telegraphing grain sounds like a surface prep or a primer issue. If you see the grain "topographically" then they need to be smoother. The film thickness of the finish you are using cannot fill in the irregularities and self-level. If it is strictly visual due to absorption variance, I would try a different primer method, shellac seals very well.

I have a SuperMax 19/38 and love it. This would be large for your requirement and these things do take up a whopping footprint so if you aren't going to use it, a lot, consider your space availability carefully. I run all the way up to 320 on it for certain tasks. You can change paper in about 5 minutes so doing batches of 20 I would have no problem in starting coarse and working up through 4 or 5 grits. However, mine is not an oscillating head so no matter how fine you sand, it is all one direction generally resulting in cross grain lines that need attention before a clear / translucent finish is applied. This would not be the case with your painted frames.