Spoil Board Surfacing Problem Ridges

So just got my machine setup and was leveling the spoil board. My spoil board consists of 6 pieces of MDF with t-track between each. I made a file that first does a square around the perimeter and then starts going left to right starting at the front left. My problem is that the first spoil board has noticeable ridges between passes. The second has some as well, but less so. Then by the 3rd spoil board it’s flat. So I’m confused, ridges make me think I need to tram, but if so wouldn’t ALL the spoil boards have ridges? Also, each time the router comes back all the way to the left, X 0, the router goes up and then comes back down and then starts the next left to right path.

Any ideas on what to try? Some of the spoil boards were untouched so I need to do another pass anyway and am hoping I can flatten it all out on the next one.

What’s your table top construction look like? To me the variable tram lines across the work area would make me think that it’s an issue with the table top not being flat. I could be wrong though, I’m not an expert by any means.

Hey Ken,

it could be that your milling motor axle has a different angle to the worksurface when the X gantry is on the left than when it is on the right. You should check the perpendicularity at both positions and first also a possible twist of your machine (e. g. with fishing line method).

See also

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I have it on a torsion box which is pretty flat, but I will look into that.

Thanks, going to try the fishing line.

So I did the fishing line thing and they touch together in the center. I moved one over the other, then in reverse and they touched both ways. I run a level along both the top fronts and then the top backs of the Y rails and it lays flat against both sides in both instances. I feel like they are very coplanar and not twisted. I ran the level against the fronts of the y rails and again the level was completely flush against both sides all along both feet.

Hey Ken,

then it looks good for the next step, checking perpendicularity of the router axis to different regions of wasteboard. You need some kind of swing arm that you insert into your router in place of a bit. This will allow you to measure the deviation from a right angle between router axis and worksurface.

Especially if you have a stronger pattern from surfacing bit on one side of the X travel than on the other side, it could be that your X rails are not on top of the other, and this more on one side.

Adjusting this is discussed here:

Do you have two longer rulers with a flat back, or two straightedges? You could attach them to the two X rails as described here, one at each end of X travel, and by looking from the side see if they are parallel.


This would mean using them as winding sticks.

If they are parallel, then the rails are on top of each other at both ends, check passed.

PS: Also what I would check on X rail is this (but you need to remove it from the machine it to check it, so I would check the other things first):


Just a little comment on winding sticks. I wound up temporarily removing two of the t-tracks and used them for winding sticks. I had not cut them to length so their full 36" length worked out great. Since they were the same color blue I used a white paint stick along the edge of one to add visual contrast. I also checked them on the table saw surface to ensure they were flat/not warped first.

The whole process allowed the rails to be dialed in perfectly.


Hoping to do this later today. Not much free time during the week.

I trammed just the x axis on the side with the ridges; other side checked out. Ran the flattening file and have a nice flat spoil board. Appreciate the help.