MFS for worktop cut-outs?

[jonny round boy]

I recently did a job which required a stepped opening cutting into a solid timber worktop to fit a Miele flush-fitting induction hob.
[attachthumb=1]
I used my OF1400 with the guide rail, and whilst I was happy with the finished cut-out, it took a good couple of hours to do (mainly due to taking time to make sure rails were correctly aligned, start/stopping points correct etc - I didn't want to make a mistake!).

I've now got another, similar situation, only this time it's a piece of granite (700x500x20mm) to set in. It occured to me that it would be much quicker to do it with an MFS, but it's a lot of money to spend - I'd need the larger MFS700 set plus an extra set of 1000 rails, so that's well over ?400 ($800) worth! One thing that offsets that cost slightly is the thought that I could use the MFS template & router for all my hob/sink cut-outs, in both solid and laminate worktops, instead of the TS55/jigsaw combo (the idea being just set it to the right size, clamp down, and the whizz round with the router in 4-5 passes).

Has anybody used the MFS for this? Is it actually quicker to do them this way?

I know if I bought it it's one of those things that you'd always find other uses for too, but the initial cost is quite steep...

To try & help me decide my local dealer has ordered one of the smaller MFS400's in for demos, so I should be going over there in the next week or two to have a play with it.

 

[woodshopdemos]

It seems to me to be an excellent use of the MFS. If it were just one, I probably wouldn't. But more on occasion -- yes. Question, do you have room away from the back splash for the MFS rail? If not, do your have room for the router. If yes, use MFS to cut a template in 1/2" mdf and hat for the actual installation. So why not just go ahead and create a temple? Cause with the MFS and the right router bit, you should have a perfect template. I say the right bit...just match the diameter to d. of the item and the finished knock out will be perfect.
  By the way, don't set the MFS by measuring whether you measure twice or not. If you router bit has a flush bearing, simply but the MFS snuggly against the cooktop of whatever...and lock the pieces down. If you are using an up spiral bit and a collar, find out the offset and get spacers of the same width and use them when you snug the MFS rails against the spacers and cook top. For me, I go a long way before I trust myself to measure...imp or metric...I am an equal opportunity mistake maker.

 

[greg mann]

It seems to me to be an excellent use of the MFS. If it were just one, I probably wouldn't. But more on occasion -- yes. Question, do you have room away from the back splash for the MFS rail? If not, do your have room for the router. If yes, use MFS to cut a template in 1/2" mdf and hat for the actual installation. So why not just go ahead and create a temple? Cause with the MFS and the right router bit, you should have a perfect template. I say the right bit...just match the diameter to d. of the item and the finished knock out will be perfect.
   By the way, don't set the MFS by measuring whether you measure twice or not. If you router bit has a flush bearing, simply but the MFS snuggly against the cooktop of whatever...and lock the pieces down. If you are using an up spiral bit and a collar, find out the offset and get spacers of the same width and use them when you snug the MFS rails against the spacers and cook top. For me, I go a long way before I trust myself to measure...imp or metric...I am an equal opportunity mistake maker.

I agree about not measuring, John, but you dont want to use the cooktop flange plus spacers, unless you want the cooktop to fall right through the countertop. There should be a rough opening specified by the manufacturer that has some wiggle room already spec'd in.

 

[woodshopdemos]

Greg,
   Thanks for correcting me there. I just dropped in an undermount sink so I was still thinking flush. Fact is for any of these, there is a printed layout that can be used. Tape it in place and move your MFS sides on this with whatever offset you need to use.

Using firring strips to make temporary router guide edge.

Using edge to cut rabett

A perfect fit without measuring...

The page from whence it comes:http://www.woodshopdemos.com/sstat-3.htm

 

[greg mann]

John,

When I first started reading your website I didn't know a pattern bit from a guide bushing, but I did remember a carpenter cutting the wrong sized hole in our brand new countertop back in the 70s. We got an upgrade to a five burner over the four burner we had planned on. One of the first lessons I received as an aspiring toolmaker was the concept of transfering dimensions with a height gage, the toolmaker's equivalent to a story pole.

 

[woodshopdemos]

Don't you just love life experiences? When I was VP of mktg of an audio visual company, we had a gigantic overhead projector for viewing xrays. I stopped down to ask the engineer assigned to it how the alignment was coming. He said he would have 7 done by the end of the day. I was intrigued because we had just introduced lasers in the aligning process. So I went to engineers place at the factory expecting to see laser setup ... not to happen. He had a small trap door open at the side of his office. I said "John", how can you align in here with all that light?" He said that he was using the best pin-light source there was ... the sun?  He didn't have a degree, but he was the smartest engineer we had. I mean really, the massive sun is a pin-light source?

 

[jonny round boy]

The main reason (excuse!) for getting the MFS was 'cos I needed (wanted!) it for the granite insert. Unfortunately, the customer contacted me yesterday to say she's decided not to have the granite, as she needs to shave a bit off the budget.  :'(

Still,that means I'll have to stick with my old method for cutting hob openings (TS55 & jigsaw), so now I've got more of an excuse to buy a PS300  ;D ;D ;D

 

[Jerry Work]

Hi Greg,

The easiest way is to use the MFS set to the outside dimension of the cooktop (router plate, or whatever) and use a straight bit with a router bushing to establish the through hole.  Then use a short flush trim bit designed for hinge mortising without a bushing to establish the step as shallow or as deep as you need (usually the thickness of the top to make the top flush with the field.  The through hole will be offset by one half the difference between the straight bit diameter and the router bushing outside diameter.  If you use a 30mm bushing with a 10mm staight bit the step will be 10mm wide all the way around.  The corner radius showing will be the diameter of the short flush trim bit while the radius on the step will be the diameter of the straight bit, 10mm in this example.  There are router bits made for through holing which feature a drill like tip and a mid shank cutter for the horizontal movement.  Using one of those makes the whole process fast and very accurate time after time.  If the manufacturer needs/wants some wiggle room between the cut out and the cooktop (or whatever) just add shims that thickness between the object and the MFS profiles at set up.  Hope this helps.

Jerry

It seems to me to be an excellent use of the MFS. If it were just one, I probably wouldn't. But more on occasion -- yes. Question, do you have room away from the back splash for the MFS rail? If not, do your have room for the router. If yes, use MFS to cut a template in 1/2" mdf and hat for the actual installation. So why not just go ahead and create a temple? Cause with the MFS and the right router bit, you should have a perfect template. I say the right bit...just match the diameter to d. of the item and the finished knock out will be perfect.
   By the way, don't set the MFS by measuring whether you measure twice or not. If you router bit has a flush bearing, simply but the MFS snuggly against the cooktop of whatever...and lock the pieces down. If you are using an up spiral bit and a collar, find out the offset and get spacers of the same width and use them when you snug the MFS rails against the spacers and cook top. For me, I go a long way before I trust myself to measure...imp or metric...I am an equal opportunity mistake maker.

I agree about not measuring, John, but you dont want to use the cooktop flange plus spacers, unless you want the cooktop to fall right through the countertop. There should be a rough opening specified by the manufacturer that has some wiggle room already spec'd in.

 

[greg mann]

Jerry,

You are right, of course, that the flange can be used to set the MFS, if the setter understands to use appropriate bushings to make a smaller pattern. I was just pointing out that to make mention of a flush trimming bit followed closely by remarks about setting the MFS to the outside of the stovetop could confuse someone into cutting too large a pattern. I knew that wasn't what John was implying, and I think he understood my comment in that context. It seems that calculating bushing offsets comes difficult to many people. In my work we use cutter radius compensation to control profiles in CNC machining. We program actual part dimensions and then invoke a radius compensation to offset the cutting tool by its radius. For all intents and purposes it is an electronic bushing. Some folks grasp the concept immediately while for others it can be a long time before the light bulb comes on.

 

[Dave Rudy]

Greg,

I'm one of the slow learners on this topic.  Jerry, how about giving us a more detailed explanation of how to calculate offsets using guide bushings (or do you know where there is some good material on that subject)?

THanks

Dave

 

[jonny round boy]

Dave, it's fairly easy to calculate offsets once you know how.

Offset = guide bush dia. - cutter dia.
                            2

So, with a 1/2" router bit and a 30mm guide bush, that would be:

30 - 12.7  =  17.3  =  8.65mm
    2              2

So the template needs offsetting by 8.65mm from the cut line.

Setting up the MFS for a hob cut-out - let's say the cut-out you need is 560x480mm. You need an offset of 8.65mm all round - so you add 2 lots of 8.65mm (17.3mm) to each dimension. This means that, to cut a hole 560x480mm, you'd set the jig to 577x497 (ignoring the 0.3mm!) and clamp it down. Then running around the inside with a 1/2" router bit & 30mm collar would give you a finished cut-out of 560x480, with a 1/4" radius in each corner.

Hope that makes sense.

PS - Sorry, I only work in mm, not feet & inches

PPS - Yes, I know I've used 1/2" for the router bit, but only 'cos it's a standard size!!!

 

[woodshopdemos]

Dave,
  I am a slow learner too and prefer to work in pencils and drawing.
Here is an example that I found on my site:

Measuring the actual offset:

a picture of the offsets:

Cutting (before Festool) the template to the line:

Routing to the template:

The hinge in place:

 

[Dave Rudy]

Thanks John and Johnny -- I plan to print this thread out and take with me to the shop when I return on Saturday -- seeing it in three dimensions will bring your good explanations to life.

Dave

 

[greg mann]

IIRC, I think Jerry has a couple pages on guide bushing calculations attached to his MFS tutorial. I believe his explanations are quite good.

 

[Jerry Work]

Hi Dave,

The other posters have covered this quite well.  The best thing to do is grab a few scrap pieces of plywood or mdf with one piece thinner than the rest.  Take any of the thicker pieces and a jig saw and make a random edge cut out so it has a hole of some shape in the middle.  That will be your template.  Now double sided sticky tape the thinner piece onto a sacraficial piece to hold the thinner piece in place.  Place the template on the thinner piece with double sided sticky tape and route its edges using whatever diameter pattern following (bearing on the shank end of the bit) straight bit you happen to have available.  Set the cut depth to just clear the tinner piece so you cut all the way through it.  Keep the router base flat on the template and follow all the way around with the bearing riding on the inside (cut out) edge of the template.  You now have a male piece that is the shape of the template but smaller by twice the diameter of the router bit since the inside edge of the router bit formed the shape of the male piece you just cut.  Now the chore is to take one of the other scrap pieces and cut a female recess in it into which your male piece will fit perfectly.  Very quickly you will visualize the size of router bushing required to do so since now it is the outside edge of the bit that will be cutting the walls of the recess.  Do this a few times and you will have no problem visualizing how to inlay any shape into any surface.  Hope this helps.

Jerry

Greg,

I'm one of the slow learners on this topic.  Jerry, how about giving us a more detailed explanation of how to calculate offsets using guide bushings (or do you know where there is some good material on that subject)?

THanks

Dave

 

[Dave Rudy]

Thanks Jerry.  Excellent advice.  There's talking about it and then there's doing it.  I'll let you know after some time in the shop on this one.

Dave

 

[lordinteriors]

i was bored and staring reading (researching) old threads about products i would like to purchase the mfs being one of the jrb if your about i have fitted a few of these type of hobes before and it was hard work i made a template out of mdf for mine but it took alot of time and effort as for granite the guys i use actually rebate it for me i would like the mfs for hob and sink cut outs but like you say it is expensive

lee

 

[woodwreck]

The alternative is the same thing ordering your own extrusion See "Affordable alternative..."""rr just below your entry