Dealing With That Pesky Snipe- Question of the Week

February 20, 2007 | Filed Under Blog, Question of the Week 

This weeks question comes from Tom. He writes, “I am having a problem with very light drum sander marks showing up on my tops (usually QS white oak), but they only become evident after several coats of wipe on poly. I have had this happen before, so after sanding with a vibrator sander, 100, 150,and 220, I hold the piece at different angles to the light and have even wet the wood to simulate a finish, NOTHING. Even the stain doesn’t reveal the dreaded drum dip. Any tips on making the flaws appear before the final finish goes on?”

For anyone who doesn’t know, snipe is a term for the little dip that is created at the beginning and/or end of a board after passing through a drum sander, planer, and sometimes even the jointer. Its usually happens when the board is under only one pressure roller. The board actually sits up a bit higher until it encounters the second roller, and the result is a board that is just a hair thinner at the leading and trailing 3-4 inches.

Now on to my reply, “Hey Thomas. Don’t you just love that? I have a table that I made and didnt notice the marks until it was finished for about a month and I saw it while watching TV. The light hit it just right and I was pretty upset. But, thats the way it goes sometimes. Since it really is hard to see while still in the shop, I usually make an effort to sand that little bit extra on the last 6″ of the board. I make sure that if that snipe is there, it will be nullified by my sanding. Thats the fix. Now lets talk prevention. One thing you can do is make sure you cut your piece about a foot longer than you need. Although wasteful, it ensures that you can cut off the sniped ends later. But what I find the easiest is to run a small length of scrap after your board. Back it right up against your workpiece as it goes through the sander and it will support the pressure rollers while you workpiece passes safely under them. This should alleviate the problem all together. But you have to make sure you have a piece of scrap to use for this process. Which isnt a bad idea anyway since you can use it to size up your joinery later.”

And I would like to add a few comments. The best way to inspect a board prior to finishing is with something called a raking light. Any light shining over the surface at a very low angle is essentially a raking light. This will make any flaws in the surface very obvious. The reason why is because the low angle of the light creates a very wide shadow, which is very easy for our eye to see and creates what our eye sees as a third dimension. This is very handy before, during and after finishing and will improve the overall quality of your finish. But it sounds like Tom’s snipe is so subtle that he cant even see it with a raking light. If thats the case, then prevention is really the best option.

Here is a great article from DIY that talks about surface prep. DIY Article

Comments

3 Responses to “Dealing With That Pesky Snipe- Question of the Week”

  1. Matt Berger on February 20th, 2007 5:05 pm

    Another way to inspect a surface before applying a finish is to wipe it with a rag soaked in Mineral Spirits. It simulates an oil finish but evaporates without a trace in just a few minutes and doesn’t raise the grain. I’m not very patient at the sanding and planing stage so I do this a few times to check my progress.

  2. Tim on February 21st, 2007 9:19 pm

    Yup I agree use Mineral Spirits not water!

  3. John Reinecke on February 24th, 2007 5:06 am

    A trick I use to avoid snipe is to slightly lift the back end of the wood as it starts to feed into the planer. Ususally after about 6″ is in the planer you can let go. That seems to stop snipe for me.

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