MFS guide with patter bit query

[CeeJay]

Hi I’m planning on cutting a router lift base into a piece of laminated MDF using the MFS template.

I only want to cut a 7.5mm deep rebate to take the 6mm plate.

I have ordered a bottom-bearing 5/8” bit which will give me the right radius for the corners I think, with 1/2” depth of cut.

So my question is with a 7.5mm cut, I’ll still have about 5mm of cutter running against the MFS template, with the bearing above on the template. Is this feasible or will the cutter chatter against the aluminium? I assume the bearing is slightly bigger than the cutter - it’s a CMT cutter.

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[Roseland]

It can be done, but I wouldn't recommend it.  I damaged an MFS extrusion once because I wanted to plunge a little deeper, and although I checked the bearing was still running on a face, I missed the fact that the bearing was smaller diameter than the collet, and it scuffed the scale.

Andrew

 

[CeeJay]

Thanks Andrew. Good point but I think I will have enough clearance back to the collet.

Will definitely check though.

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[Bohdan]

Do it with a copy ring.

Just adjust the MFS to the larger size. Then there is no risk to the MFS.

 

[GarryMartin]

Do it with a copy ring.

Just adjust the MFS to the larger size. Then there is no risk to the MFS.

100%

I have damaged by MFS using bearing guided cutters and would always recommend using a copy ring.

 

[Cheese]

It only took one lightly damaged MFS rail before I swapped out the bearing bit for a copy ring.

 

[CeeJay]

Thanks all. Yes my first practice run was with a copy ring. However I can’t get the  corner radius right with the copy rings I have. I need 16mm diameter.

I think I’ll abandon the MFS and make a template which can take the damage from the pattern bit.

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[Bohdan]

Your corner radius is determined by the cutter radius not the copy ring.

If you use a 5/8" diameter cutter you will get a 5/16" radius corner.

You need to use a cutter to suit your required radius and then any copy ring diameter that will allow that cutter to pass thru.

 

[AstroKeith]

Surely you establish the corner radius by the cutter radius, not the copy ring radius.

 

[CeeJay]

Surely you establish the corner radius by the cutter radius, not the copy ring radius.

OK that’s what is confusing me.

It’s possible I’m using the wrong cutter. The supplier of the router lift says to use  a 5/8” bit, which I did, in a 30mm copy ring. This didn’t work, the radius was too large.

So perhaps the suppliers instructions are incorrect.

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[CeeJay]

The plate is from Sherwood (Timbecon).  Their website says use a 5/8” bit.

It’s a standard plate size, so I looked at Jessem’s website which says to use 1.5”  bit to achieve a 3/4” radius.

I guess only one of them is right! I haven’t got a 1.5” bit.

Rockler and Jessem both supply mdf templates but can’t get either to ship to Australia.

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[CeeJay]

The closest matchup to the plate corner radius I have to hand is a 35mm forstner bit. So I think Jessem is correct and I need a 1.5” bit. So I’ve ordered a 40mm copy ring and will try to find a bit big enough!!!

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[CeeJay]

Ordered a 38.1mm bit as well.

Wish me luck.

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[AstroKeith]

Surely you establish the corner radius by the cutter radius, not the copy ring radius.

OK that’s what is confusing me.

It’s possible I’m using the wrong cutter. The supplier of the router lift says to use  a 5/8” bit, which I did, in a 30mm copy ring. This didn’t work, the radius was too large.

So perhaps the suppliers instructions are incorrect.

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Lets be clear, in a square template, the copying ring has no effect on corner radius. It is completely down to the cutter diameter. The copying ring needs to clear the cutter shaft etc, but other than that you can use what ever size you have to hand. You will need to adjust the template opening size to account for the copying ring to cutter diameter, but that is the only impact.

So key here is finding out what cutter diameter you need - measure the table insert to be sure.

 

[CeeJay]

Yup that’s what I got to thanks to all the good advice here.

It’s 38mm diameter, 19mm radius as far as I can tell.

I have advised Timbecon their website and instructions are incorrect!

So pleased I bought the wrong bits first up.....

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[imdking]

So how did this go? Update, please!