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Discussion Starter · #1 ·
Good morning!

I'm planning my first project with my new Bosch router. I'm making a pair of Lazy Susan shelf units for canned goods. I need to cut 8 15" circles out of some old high grade 3/4" plywood I got at the local Habitat store. I have a 3/8" Freud spiral upcut bit coming soon, and I plan to use it with the Bosch edge guide circle attachment.

I searched this forum, and I did find advice that this is a successive pass proposition, but that's all. As I'm making eight of these, I don't want to be at it all day. I'm thinking three passes per circle, but I'd like to avoid too much split out of the plywood.
I plan to plunge this, but if it's easier, I could use the other base and twist the motor into the cut.

Thoughts? Thank you in advance. Hope your day goes well!
 

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Discussion Starter · #3 ·
do you have a bandsaw or jig saw ?
with a plexi faceplate on the router, you can make them consitently the same size.
View attachment 403860
I could make one of 1/4" plywood easily enough, and I could then use a screw for the center, rather than that tape business. Would that be easier to use than the RA1054 circle attachment?
 

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The straight guide assembled upside down can already be used to cut circles. Makita & B&D have a hole for circle cutting predrilled. You can drill one hole yourself if there is no hole in your straight guide. Extend with a bar or 2 longer rods for bigger circles.


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I have a 3/8" Freud spiral upcut bit coming soon
A 3/8" will work, I'd use a 1/4" up cut spiral. My reasons: less work for the router. Put the wear on a less expensive bit. Less saw dust.
I plan to plunge this, but if it's easier, I could use the other base and twist the motor into the cut.
I vote for the plunge. I would never adjust the height of a fixed base while the router is running.
 

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The Bosch edge guide works fine as a circle jig. Cut from the underside, and I'd make one more pass.. Later on, you can do an edge treatment to remove any chip out on the good side. A roundover edge is OK on ply, unless you plan on some sort of banding on the edge.

By cutting from the back side, you can use a short screw and not penetrate through to the good side. I keep a sheet of foam insulation around to cut on. It holds things steady and is sacrificial and pretty cheap

I had a sheet of 3/4 ply from hd that had a layer of bamboo, which splintered so badly it was useless. They have some OK ply, but it's not cheap. I suggest you consider finding a source of Baltic Birch ply, which has many layers and no gaps that appear if you happen to cut into one. I've found that a 5x5 Baltic birch sheet isn't a whole lot more expensive than the best ply, and at 60x60, by reducing the size to 14 3/4, you can get get all eight out of one sheet.

The edge will look great as well, especially after you finish it. I love the look of Baltic Birch edges.. Compare the edges between BBply and most regular ply, showing voids. Since you already have some ply, try a sample and if you encounter voids, you can fill them, or switch to Baltic Birch.
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Good morning!

I'm planning my first project with my new Bosch router. I'm making a pair of Lazy Susan shelf units for canned goods. I need to cut 8 15" circles out of some old high grade 3/4" plywood I got at the local Habitat store. I have a 3/8" Freud spiral upcut bit coming soon, and I plan to use it with the Bosch edge guide circle attachment.

I searched this forum, and I did find advice that this is a successive pass proposition, but that's all. As I'm making eight of these, I don't want to be at it all day. I'm thinking three passes per circle, but I'd like to avoid too much split out of the plywood.
I plan to plunge this, but if it's easier, I could use the other base and twist the motor into the cut.

Thoughts? Thank you in advance. Hope your day goes well!
I cut 2 small table tops (21") out of 3/4 ply and it does take some time to do as you make multiple passes. You will likely need more than 3 passes when using a router.

Since you are making 8 of them I would plunge my way through the first one. Then use the first one as a pattern to mark the final seven including the pivot hole. Use a jig saw or band saw and cut an 1/8" outside the traced line. Using the pivot hole attach the jig saw cut circle on top of your pattern. With the 2 firmly attached use a flush trim bit to smooth the top circle. There is a possibility the jig saw can cut through 2 pieces of ply at the same time which would speed up the process.

All of the suggestions are good. Pick one and be safe!
 

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A spiral upcut bit lifts all of the swarf and dust created out of the cut toward the router base, but in the process is also prone to lift and chip the upper surface of the material. Depending on what you want best protected, and whether you have both faces of the ply visible, you might want to work from the back of the sheet to get the best finish on the face. A spiral down works opposite, pushes swarf and dust down into to cut, leaves a good surface at the router base side, but can chip out on the underside as the spiral is pushing down. The absolute best solution is a compression bit, which is upcut at the tip and downcut for the rest of the length. Used with a sacrificial board under the work material, it can give perfect faces on both sides, but generally need to do the cut in a maximum of 2 passes, so needs a powerful machine. The 2 cut issue arises because the initial depth of cut has to place the point where the bit changes from upcut to downcut at least 1 ply layer below the surface so that the upper layer is being cut with the downcut section of the bit. If cut with the upcut section, the top layer is as prone to chipout etc as it would be with a spiral upcut bit.
 

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I posted this in an earlier discussion on router circle jigs so I will not go into the details to far. I build a 48" table top for a friend out of 1/4" plywood. Here is the router jig I built to do the job and the completed plywood top.
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I would just go to the big box stores and buy a circle cutting jig. They are not very expensive and work great. Lot less hassle than making your own and they are accurately adjustable right out of the box and fit most common router bases too. Cutting circles is fast and easy so the number of passes isn't that important to your time. Making your own jig would take a LOT more time than a couple extra passes on the stock.........
 

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Discussion Starter · #12 ·
So I did two passes with a 1/4" spiral downcut on all thirteen circles, with a thin plywood homemade circle gauge I got for a dollar at the local Habitat ReStore, with a cabinet screw in the center of each circle, then went back and finished each one with an upcut bit. I can tell that twenty-six passes of about 50" (16" circles) did dull the bit just a bit, but it is still useable. Combining the two was a great idea! Thank you for giving me this solution! There are two lazy Susans, one has two taller levels for juice bottles and such.
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You can find rolls of pre-glued edge banding at big box stores. The glue is heat activated using an iron or hot air gun. Lots of uTube videos on the subject. It will give the project a nice finished edge that you can then paint.
 

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So I did two passes with a 1/4" spiral downcut on all thirteen circles, with a thin plywood homemade circle gauge I got for a dollar at the local Habitat ReStore, with a cabinet screw in the center of each circle, then went back and finished each one with an upcut bit. I can tell that twenty-six passes of about 50" (16" circles) did dull the bit just a bit, but it is still useable. Combining the two was a great idea! Thank you for giving me this solution! There are two lazy Susans, one has two taller levels for juice bottles and such.
View attachment 404121
View attachment 404119
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View attachment 404120
It came out good... glad you only had to make two passes per circle!
 

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Great result.
 
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