router bit is "too small"

[slanckma]

Hi,

I'm just starting with woodworking and am wondering if I'm doing something wrong when using my 1010. Let's say I want to make groove in which I want to slide another mdf board. The board is 12mm wide so I take my 12mm straight router bit and make the groove. All's works fine but when I now try to insert the board it won't fit. I could start using a hammer to force it in, but this would damage the board and the groove (especially when using mdf). So I need to adjust my router to move it about 1mm to the left or right of the groove and make another pass.

This procedure feels a bit awkward as I need to do everything twice and I need to readjust my setup every time. My guess is I'm doing something wrong or I need to invent a 12.5mm router bit.

Thanks,
Sven.

PS: I tried some other router bits (6mm,..) and it give the same problem.

 

[JJ Wavra]

sven,
If you are using the guide rail and stop get the fine adjuster and use that to move the bit over about .4 mm that has worked well for me.  You could also do that with the parallel stop and the fine adjuster for that.  This seems to be more accurate for me and is much easier.

JJ

 

[Per Swenson]

Sven,

You are going to have to make the adjustment.

All plywoods are not a standard size thickness.

As JJ said, use the adjuster.

per

 

[Jesse Cloud]

Welcome to the world of woodworking.  Your next batch of MDF may be 12.8 or 12.3 mm.....

Advice above is the way to go.  If you are making several cuts like this, it may be worthwhile to make a thin piece of wood or cardboard to use as a spacer.  Set the mdf against a stop, route the groove, insert the spacer between the stop and the mdf and route again.

 

[Tim Sproul]

The board is 12mm wide so I take my 12mm straight router bit and make the groove.

This is the problem.  In theory, you should be golden.  In reality, you have to introduce a slight amount of 'slop' to allow for a fit.

If you use an adjustable width dado jig and a template bit, you set the width of the jig using the actual stock that will fit into the dado or groove.... PLUS the thickness of a US dollar bill or similar.  This added width of the groove provides the necessary extra space to allow you to assemble without providing so much extra width that the joint is sloppy or loose.

 

[semenza]

Hi,

      If indeed the two are both exactly  12mm it will make for such a tight fit that the piece won't go in.  Same goes for drilling holes for hardware. If you drill a 1/4" hole and try to put a 1/4" bolt through - it is no problem. But try the same thing with a 1/4" piece of steel rod, it will be very tight. I find that in the US bolts are actually made slightly undersize so that they will go in the size hole specified.  Plus even if the MDF or ply manufactured right on it won't take much humidity change to alter it a slight amount and then the exact size just won't go.
      None of that solves your problem though.  As has been said you can use the fine adjuster on the guide rail unit to move the router a little and not have to reset the rail and all. 
        I do not know if 12.5mm bits are made. But you could get a 1/2" bit  which is slightly more than 12mm and try that.

Seth

 

[richard.selwyn]

I have a set of slightly oversize router bits specifically for this job - they were quite cheap and work OK.  I can cut grooves in a single pass.
I'm in Frnace but I get the feeling the place I bought them sourced them from the States.

 

[slanckma]

The fine adjuster is indeed the answer to my problem. I should've known Festool already had a solution for this. 

Many thanks,
Sven.

 

[The Woodentop]

I have a set of slightly oversize router bits specifically for this job - they were quite cheap and work OK.  I can cut grooves in a single pass.
I'm in Frnace but I get the feeling the place I bought them sourced them from the States.

Just how much larger are they richard.selwyn? And from where did you obtain them?

Sorry to be a nuisance.

Larry

 

[mhch]

This may not what Richard uses, but the online vendor HM diffusion sells
straight and slot cutting bits which are 5.2mm, 8.2mm and 10.3mm
to be used for rabbetting and making dadoes to receive 5mm, 8mm,
and 10mm plywood.

Unlikely to help the non-metric folks, anyway, apart the 0.2mm or 0.3mm
slack size.

 

[dltflt]

I have a set made by CMT for plywood.  They are made to fit snuggly on a standard plywood sheet.  That being said if you buy cheap plywood they don't work very well but for all the Baltic birch and Oak that I've used it on they work well.

before I purchased these bits I did what Tim said except I used two boards sandwiched the plywood then installed a cross member on each end with screws.  Guaranteed perfect every time.

 

[Grinding One]

Check out Wood Magazines Video section on jigs ...they show a jig where you route out your groove to exact dimension every time