MDF Repair For Holes Cut Wrong

I posted this on Facebook and posting here for the non-fb users. Need the following assistance please:

Ok guys and gals. I need some help correcting a problem when I was cutting dog holes for my compression clamps. I designed a single bore that was the size I needed with the material and bore the same size. The bore was .8" in diameter and .7" deep. I was using this to manually cut each dog hole. There are 12 dog holes in each strip of MDF. This was a tedious method so I redesigned it. I set up a strip 30" long with all 12 holes laid out. The first strip I cut was wrong. All of the holes came out .9" instead of .8". No changes in toolpath parameters other than cutting 12 holes instead of 1. I ended up deleting the design and starting it over from scratch. This time it worked correctly. Anyway I need to fill up the bad holes and re-cut them correctly. Any recommendations on mixing saw dust with wood glue and making a paste? Ratios of saw dust to glue? Some other type of material? Glue? The spoil board is 3/4" MDF. Any help appreciated.

@Heyward43 H: I would use another piece of MDF and cut plugs that are .9" - a wee bit (don’t you just love that technical talk?) in diameter. Slather them with glue and press them into the holes.

@gwilki, lol, thanks for the chuckles. I do have some scrap MDF left over from my spoil board build. I may have to try that instead of sawdust and glue. Glue them in, let set and re-drill the right sized holes. Only other choice is a whole nuther sheet of MDF, ugh.

@Heyward43 H: I’ve done the sawdust and glue trick in real wood, with some success. But, in MDF, I think you’re better off with a plug. The plug does not need to be MDF, really. It could be anything. In fact the more that I think of it, you may be better off enlarging the already-too-big holes, then making plugs. If you glue in .9" plugs and cut them to .8", you are not leaving much in the new “walls” of the holes.

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@gwilki, good point Grant. I think I will enlarge them to 1.5". That will leave me about .7" of wall when I recut them. Hopefully that will be enough. If you think I need more please, by all means, throw it out there. Worst case I go buy another sheet of MDF.

@Heyward43 H: I think that will work. That leaves you about 5/16" all round. That should be plenty. As you likely know, use lots of glue. MDF sucks the stuff up. I suggest that you paint both the plug and the hole with glue and let it dry. Then, put another coat on each surface and press them together. We do this with end grain glue ups with good success.

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