Avoiding Sanding Swirls; Adding Dovetailed End Caps
Issue: Issue 328
Posted Date: 6/18/2013
Swirl Marks from Woodworking.com
This poster was having problems finding sanding swirl marks on his projects -- even though he thought he was doing everything possible to avoid that. - Editor
"I typically have problems with swirl marks from my orbital [sander]. I use a [variable speed Milwaukee Orbital (7,000 - 12,000 opm at 3/32 orbit ). After running my stock through my drum sander, I proceed through the grits, usually starting with 80, to knock down the ridges from drum sanding then 100, 120, 150 and 180. Once I feel , or rather see, that my piece is swirl-free I will move on to my RIDGID 1/4 sheet finish sander (14,000 opm at 1/16 orbit ) using a 180-grit paper . My final step is to hand sand with a 220. But once those first few brush strokes of stain go on, there they are! Not a lot, but enough to get my blood to boil! I believe my process of stepping through the grits is acceptable and my gear is working fine, but I must be missing something. Should I be clamping my piece down to the bench to stop any excess vibration? Is there a technique to use to help spot swirls before the stain is applied, like a damp cloth across the surface? Slow down the Milwaukee opm before the RIDGID ? More or less down force while sanding? I've tried so many different ways and I just can't seem to land the proper combination. Help!" - nightryder
He received a couple of suggestions for different processes, including the suggestion not (!) to sand through all the grits. - Editor
"Perhaps you could try using 220 after the drum sander. If you find some marks, use 180, then 220. I don't have 80-grit in the shop. I think the belt/disc sanders have 120-grit mounted. We have 180- to 320-grit for general use. Additionally 600, 800 and 1,200 for special purposes. Also, I find that carefully clearing away all residue of coarser grits prior to moving to finer grits will provide the best results." - bmorto1504
"I can think of two things to consider: 1. Vacuum between grits. A grain of leftover 80-grit that gets caught in the sander when you're sanding with 220 will definitely leave marks. 2. Watch for 'corning' -- a buildup of resin or finish that clogs the sandpaper and creates 'corns,' small spots of hard material that sit 'higher' than the sandpaper grit. This will also leave swirl marks. Bottom line: make sure everything is clean when you're sanding. By the way, I think you can skip a couple of those sanding steps. I go from 80 (if I use it at all---I usually start with 120) to 120 to 180. You don't need (in my humble opinion) to use every grit size." - Jerry M.
Adding Full Width Dovetailed End Caps to a Workbench from Sawmill Creek
Building a workbench is often one of those showcase projects for a woodworker. This one had a question for a finishing touch he was thinking of adding. - Editor
"I'm finishing my workbench and am thinking of adding end caps dovetailed across the full width. My thought is a tight dovetail over the full width will allow me to not have to glue or bolt anything while still providing stability for the top. The top is about 4" thick by 28" wide and hard maple. My question is how? The end cap will be relatively easy, but how do I cut this dovetail on my top? It seems like a circular saw on its side won't be very precise. Thoughts?" - Ben W.
"I did this on my top as well-- a butterfly dovetail cut into the top and cap both. I used a large dovetail bit with router and edge guide, as mine is about 1-1/4 to 1-1/2" deep x about the same width in both halves. It is easier to hog out waste up to layout lines with a 1/2" straight bit, then last pass with dovetail bit. I glued it in the cap piece, but not the benchtop. It is difficult to slide a dovetail that big into a slot that long and tight; have patience." - Peter G.
"You'd get the most precise fit with least effort if you use the same bit to cut both halves of the dovetail joint, with the tail on the bench and the pin side on the cap, and you can approach final fit in the cap in minute increments on a router table or shaper. Cutting the dovetail on the bench will require some gymnastics on your part, of course. Easiest assembly, though, would be with a tapered dovetail, so that the joint goes together with no friction until the final fit right at the end. A bit trickier to lay out and do, though." - Frank D.
"Thanks for all the suggestions. Instead of having three pins, I was thinking of just having a single monster pin on the bench. The cap will be much more easy to maneuver, so I'll do the fine-tuning on that. Once it's snug I'll pound it into place. I'm thinking that having only a single dovetail will make it a little less challenging. After reading some of the comments I started looking at more dovetail bits and found that they do come quite large. With a good edge guide, I'm thinking this shouldn't be too bad..." - Ben W.