Router Table Dilemna

[blind bill]

I'm trying to make a rabbet on a 3" x 23" mdf board that will fit into a 1/4" slot in the adjacent board. The rabbett will be 3/8" x 1/2" leaving a tongue that is 1/4" x 3/8".

Now the problem: The insert on my router table is 1/2" polycarbonate about 12" long and 9" wide. It is leveled with the table top with 8 leveling allen screws, 3 on each side and 1 on each end. The problem is that I can't keep the insert level with the table, thus the tongue ends up being either more than 1/4" thick or less than 1/4" thick on the next board in line. Since I have 16 boards to cut on both ends, setting each cut individually is a pain you know where.

I thought for a while that the insert fit a little tight in the opening in the router table so I sanded the edges so it had a skoch of clearance. The thought was that the boards on the table and the insert were expanding and contracting at different rates. When I tried it again, no luck struck.

Now I'm suspecting that the leveling screws are vibrating out of level. After a cut the plate is out of level by as much as a 1/16". This would be enough to throw the slot and tab out of alignment. How about a bit of Locktite" on the allen screws?

Any ideas or suggestions will be warmly appriciated. Blind Bill

[Jim - TEG]

How about a bit of Locktite" on the allen screws?

There's your answer, right there. Some of the manufacturers of router lifts (Bench Dog specifically) include a similar product with the lift and include its use in the instructions as part of the setup.

[Bob D.]

If you use Loctite be sure it is the temporary formula (colored blue I think). The permanent stuff can be overcome but many times it takes heat to do so.

From the Loctite website FAQ:

Q: What do colors mean?
A: Many times Loctite anaerobic materials are called " the red or the blue stuff". With threadlockers, colors designate strength. Generally red means high strength and blue means moderate strength, and purple is low strength. Other colors do indicate strengths in relative areas.

[blind bill]

Hoorah! I used some "threadlocker" blue to keep the allen set screws from working loose and throwing my router insert out of level. I was concerned because the instructions said not to use it on plastic. I presumed polycarbonate doesn't qualify as plastic and did it anyway.

It works like a charm and I heartily recommend it to others in the same pickle. Thanks for your help, guys.

Blind Bill