How do you do this?

[rjwz28]

I want to route a round hole with a step. I built a router lift and attached it directly to the table top. Now I need to install a round insert in the table. It has to have a lip or ledge to hold the insert and of course be flush to the top. Do I need to make a round hole jig to use as a pattern?

Thanks,
Rob

 

[Stone Message]

Hi Rob

I am sorry but I have no photographs to help you but...

To cut a circle accurately I would use a trammel - something that fixes to your router and has a peg or 'trammel point' which is like the sharp bit that you find on a compas for drawing circles.

The problem with trammels when routing is that if you use them to cut all of the way through then the pivot (trammel) point suddenly disappears as you complete the cut as the centre piece is no longer attached. It can cause problems in weaker materials just before the final cutoff. To overcome this do not cut all the way through the circle on the first pass. Make a channel that is deep enough to take a bit that has a ball bearing fixture. At the end of the first pass, make a plunging cut all the way through to allow room for the ball bearing cutter.

Now turn the piece over and use the ball bearing cutter (it might be a flush trim bit, a rebate bit or some shape that you need) following the clean circular edge that you created in the first pass. Once the hole is established you can then shape it further by using other cutters in your router.

I seem to remember answering something like this a couple of months ago but I can't remember where.

I hope that this helps.

Peter

 

[peter halle]

One way would be to use a smaller hole saw to cut the interior hole that goes all the way thru, and then use a rabbeting bit with a bottom bearing to route the step.  A little bit of math would ensure a great job.

Peter

 

[mastercabman]

One way would be to use a smaller hole saw to cut the interior hole that goes all the way thru, and then use a rabbeting bit with a bottom bearing to route the step.  A little bit of math would ensure a great job.

Peter

+1!

 

[GhostFist]

One way would be to use a smaller hole saw to cut the interior hole that goes all the way thru, and then use a rabbeting bit with a bottom bearing to route the step.  A little bit of math would ensure a great job.

Peter

BINGO!

 

[rjwz28]

Okay, 2 things I forgot to mention that is important. It already has a 1-1/2" hole.  And 2, the hole needs to be 3-1/2" in diameter.

Sorry, for not stating that earlier.

Rob

 

[Stone Message]

Get a scrap piece of MDF and make a template - I would use a trammel but others might do it another way. Then use the template to guide the router to make the desired hole.

Peter

 

[rjwz28]

Get a scrap piece of MDF and make a template - I would use a trammel but others might do it another way. Then use the template to guide the router to make the desired hole.

Peter

That's what I was thinking of doing, but how would you center the jig with the existing smaller hole?

Rob

 

[Stone Message]

I have just remembered...you are making a router table.

If you had a big enough cutter you could use your setup to create the hole from underneath (router side through to the top).

Alternatively...

Mount your router in your table. Put a (say 1/2 inch) flute in it. Take a second router and a scrap of MDF. Put a 1/2 inch hole in the MDF to act as the hole to take the 1/2 inch bit which is now the trammel point. Fix the second router to the MDF and make a perfectly centred cut.

Making the step is easy - use a ball bearing rebate bit.

Peter

 

[peter halle]

Peter's idea is good also.  Here is a way to do it with a hole saw also.  I have used this on doors where the bore for the lockset was somehow wrong.

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Peter

 

[Deansocial]

If you want to use a holesaw get you arborber and put the 3 1/2 saw on followed by a 1 1/2 saw to act as a guide.

Personally i would router it.

 

[sgryd]

Here is a great tool for routing round holes: Hole template
If you use it with two different size template guides attached on the router it would be easy to route the stepped hole.

Are you making the hole for custom inserts? In that case you might consider a square hole. It would be much easier to make new inserts when you need them. Here is what I did on my drill press table:

The round insert at the bottom belongs to the original table. It's simple to cut new 10x10cm inserts when I need them.
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//Michael

 

[mouppe]

Get a scrap piece of MDF and make a template - I would use a trammel but others might do it another way. Then use the template to guide the router to make the desired hole.

Peter

That's what I was thinking of doing, but how would you center the jig with the existing smaller hole?

Rob

Does it need to be exactly centred? Increase the diameter by 1/8" so you have sufficient clearance for a 3 1/2" bit and eyeball the centre.

 

[rjwz28]

Okay, here it is. Thanks to all of you for your input I did it. What I ended up doing since my router was already mounted was to insert a piece of brass tubing in the 1/4" collet as my center. Then I drilled 2 different holes in a circle jig I made a while ago and did it with a straight router bit. Came out fine.

Thanks to Mike in Tuscon for sending me the insert!

Rob