Thread: Fitting router base properly

Hi Jill

It's not an uncommon issue with routers, if you put a sub-base on it you not only will solve the concentricity issue, but have the ability to use the Porter Cable style templates have a look at the Jasper Plate as it comes complete with a centering pin and fits a heap of routers.

Regards

Grahame

The key to getting the sub-base perfectly centered around the bit is to use a centering cone as suggested, and to use mounting holes which are slightly oversize, and pan head screws rather than countersunk.

Mark out the sub-base as accurately as possible for drilling, then drill flat bottommed counterbores that are about 2mm bigger than the screw heads (forstner style bit or similar), just deep enough to recesss the heads below the surface of the sub-base. Then drill through holes 2mm bigger than the the screw threads using the counterbore center dimple to locate the bit.

Assemble the sub-base to the router but do not fully tighten the mounting screws. Install the centering cone into the collet and adjust the 'depth' so that the cone contacts the aperature in the sub-base (some cones might need a template guide installed in the aperature). Tighten the mounting screws once the sub-base (or sub-base and guide) is centred on the cone.

This method allows about 1mm of movement in any direction to centre the sub-base, drilling 3mm oversize would allow about 1.5mm, but the screw heads would start to apply uneven pressure to the sub base.

Not sure with your D handle 3601, but if it is a fixed base style router, where the motor screws up and down in the base to adjust depth, the centre position might vary with the depth adjustment as these units tended to use a cast thread rather than a machined one for the depth sttting, and maintaining concentricity with the base was not a major design consideration.

Hope this helps, could draw a cross section sketch if you need help.

many thanks for this, Malb, much appreciated. Looks like the key points are accuracy in marking out, and allowing enough play in the fixing screw holes. Agree with your comments , now you mention it, about lack of accuracy in screw type depth adjustment where the whole motor is moved up and down in a sloppy arrangement, just like the Makita 3601B

I purchased the same router second hand about 7 years ago and then obtained a poly carbonate sub base from Carba-Tec that had multiple holes drilled. This fitted perfectly and using the porter cable style guide bushes and a centering cone was able to center it perfectly. Not sure if they stil sell the base, but one can always make one quite cheaply. What Malb said is true especially about the fixed base depth setting and centering. It is only a minute or 2 to center it when the depth is set following Malb's directions.
Les

Originally Posted by JillB

many thanks for this, Malb, much appreciated. Looks like the key points are accuracy in marking out, and allowing enough play in the fixing screw holes. Agree with your comments , now you mention it, about lack of accuracy in screw type depth adjustment where the whole motor is moved up and down in a sloppy arrangement, just like the Makita 3601B

Hi Jill, I refer you to my subscription in Router Forum back on 30th Aug 2010 under " Has this happened to you'' which was on the same suject. In my case the problem I discovered was the locking plate that is located between the motor housing and the outer metal case. The locking handle bears against the plate when you tighten the handle. In my case I replaced the Locking plate with a new plate Makita part no 342290-2. Do you have a hand book on the router to refer to as this shows the part. The parts are available through any good tool shop and or can be ordered in.
Mac

I'm in the same boat here...
have three Makita 3600BR plunge routers, 1980s vintage, and tremendous machines.
Bought a 3601B, with a router table of some unbranded name, and the bit can never be got 90 degrees to the table top, not concentric nor plumb. The problem is not the base plate, but the knob.
The more or less you tighten the black knob, to stop the engine falling out when it's upside down, and to lock its depth, the more it pushes the router bit out of plumb or the body backwards away from the thread on that side..."Not Happy Jan!"

Maybe there's a bracket that's been lost over the years before we bought it...but it's totally unacceptably useless-variably inaccurate- the way it is. Maybe it's missing that lock plate also...perhaps I can make one up easily enough.
Part 33 here:
Makita 3601b parts breakdown on ToolPartsDirect.com

Originally Posted by Stewey

I'm in the same boat here...
have three Makita 3600BR plunge routers, 1980s vintage, and tremendous machines.
Bought a 3601B, with a router table of some unbranded name, and the bit can never be got 90 degrees to the table top, not concentric nor plumb. The problem is not the base plate, but the knob.
The more or less you tighten the black knob, to stop the engine falling out when it's upside down, and to lock its depth, the more it pushes the router bit out of plumb or the body backwards away from the thread on that side..."Not Happy Jan!"

Maybe there's a bracket that's been lost over the years before we bought it...but it's totally unacceptably useless-variably inaccurate- the way it is. Maybe it's missing that lock plate also...perhaps I can make one up easily enough.
Part 33 here:
Makita 3601b parts breakdown on ToolPartsDirect.com

As I had previous written the problem I found was that the Part no 33 (342290-2) which in my case was missing was the main cause of the problem as this part controlled the positioning of the motor with the base, The knob engages this part when tightening ( I did try to make my own out of a narrow piece of Stainless steel but it was not quite successful) The part is available and can be ordered from any trade tool shop for a few $. When fitting this part you could have some difficulty as you virtually have to pull the motor completely from the outer sub assembly fit the part in position and then reassemble.
Even now when I use the router I always check before turning on to see if the bit is central in the router guide bush.
Best of luck
Mac

Thanks for the reply. I ordered that part-and a new collet/chuck while I was at it, as postage wasn't that dear on the two items.
I did make up a copy of that part-out of some sheet brass, in the meantime. It was better than without it, but still room for improvement.