Dave's Woodworks
Holly Michigan
Updated on: 9/7/2011
Sheet 7 of 10
Notes From Dave's Shop
Large Cove Moldings
No Scale
Tablesaw Cove...
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Philippians 4:8-9 (NIV)
CAUTION..!
If the stock you are cutting the cove in is long.. you should use an out-feed support to support your stock.. an in-feed support may also be a good idea.. you will be concentrating on holding your stock tight to the table as it passes over the cutter and won't need the added distraction of your stock tipping coming in or going out..
Remember...!
When the cove is to be cut into stock that has not been assembled.. "Great Care" should be used when passing this stock over the blade.. the use of those rubber padded pushers (the kind used on a jointer.. and.. for the very same reason) should be employed.. this will keep your hands out of the blade and hold the stock firmly to the table top..
The use of in-feed and/or out-feed support may also be prudent..
Above all.. "Great Caution" should be used in doing this technique.. only removing 1/16" (or less) per pass.. paying close attention to what you are doing.. thinking about where the cutter is and where your hands are.. and in that way this can be done in safety..
A brief overview....
I use the table saw technique for cutting a cove.. I build a fixture that entraps both edges of the stock to guide it across the cutter.. for my "Music boxes" I set the fixture to a 45º angle to the cutter.. I angle (tilt/bevel) the cutter at a 45º angle into the stock.. this will give a little hook on the edge toward the back of the saw.. or at a 90º just a cove.. the diameter of the blade (of course) will have an effect on the size of the cove.. sooo.. different diameters for different applications.. therefore.. many different profiles can be achieved by varying these three factors...
1- the diameter of the cutter/blade... 2- the angle the stock crosses the cutter/blade.. 3- the angle (tilt/bevel) of the cutter/blade... This works great on hard woods.. and.. I've seen no damage to any of my cutters and/or saw blades as a result of this.. it does however.. leave a rough surface.. a curved cabinet scraper works great and quickly to smooth the resulting cove.. then sanding of course..
Cutting coves on the table saw..? you got to be kidding..! who would've thought..?
well.. read on..... And remember to.....
The profile...
Many different profiles can be achieved by varying three factors...
1-The diameter of the cutter/blade... I use a molding head cutter (with the cove cutters installed) and carbide tipped blades (it is important to use only carbide tipped blades).. with an array of different diameters of blades and cutters you can vary the cove profile.. of course.. the smaller the diameter the smaller the cove.. the larger the cutter the larger the cove.. I have cutters from 5" to 10".. molding head is 5" diameter.. the side cutter from the 6" dado set.. the side cutter from the 8" dado set.. also 7", 7½", 9" & 10" carbide tipped saw blades.. I usually select a diameter to fit the width of the stock..
2-The angle the stock crosses the cutter/blade... If the stock is passed directly across the blade at 90º.. the resulting cove would be a radius equal to the radius of the blade.. however.. as the angle decreases from 90º.. the cove becomes an increasingly narrow parabolic shape.. the blade height controls the depth of cut.. click this link to See chart
3-The angle of the cutter/blade... If we now introduce some degree of inclination (tilt/bevel) to the blade.. and set the fence ("jig"/fence) to any angle.. except 90º.. we will produce a curve with one end deeper than the other (the end toward the back of the saw will be deeper.. or hooked.. similar to one-half of a teardrop).. as the angle of the blade decreases from a 90º the deeper the "hook" (45º would produce your deepest hook)..
click this link to See chart
To position the cove on your material.. raise the blade to its final height.. then position the fence to its final location by measuring from the back of the blade to your fence (the number you use for this measurement is the distance from the planned edge of the cove to the edge of the material).. now lower the blade back down to about 1/16" for the first and each successive pass.. another trick.. would be to cut your profile in wider stock and then rip it to the desired width with the proper placement of the profile..
It is always prudent to make practice cuts to insure your profile is placed where you want it in your stock and that the profile is what you want before committing your good material to the operation..
The cove should be cut on the box after assembly if at all possible (with a box it is nearly always possible).. and yes.. it can be done before mitering and assembly.. however.. with the sides coved you run the risk of not getting an accurate miter.. also good square clamping is difficult.. as well as aligning the cove around the box...
The cutter I use for my music boxes (pictured here) is the molding head cutter (5" diameter) with the cove blades installed.. care must be taken to take only a shallow cut with each pass (1/16" or less).. a good technique is to cove a project after assembly of that part if at all possible.. often it is not.. then use hold-down pushers (the kind often used with a jointer) to pass the stock over the cutter..
CAUTION..!
Only remove a little stock (1/16" or less) with each pass.. a light final pass will clean up the cut a little.. I use a curved cabinet scraper to remove the saw marks (of which there will be many) before sanding (your favorite thing.. right..?)..
"Right tilt" saw set up
Ahhhh yes....
Sounds like a beach somewhere on a tropical island.. covered with sawdust instead of sand.. where you sit on your "mission" style chair in the shade of the "spreading chestnut tree".. reading your favorite wood publications and tool catalogs.. the surf coming onto the beach sounding like a "Unisaw".. in the distance you can hear the cry of the "PC 7518" shaping a profile in the edge of some QS white oak.. and all around you are stickerd stacks of every kind of wood.. kiln dried and waiting for your creative hand.. with not one piece of MDF of OSB on the island.......ahhhhh...
"WRONG..!"
NOTE..!
The advantages to cutting the cove on an assembled box are..
1. it keeps "your" body parts farther from the cutter.. "And that's a good thing..!" 2. it gives you something easier to hold on too.. 3. it is much easier to clamp your glue up with straight sides.. 4. the miters are made easier and more accurate.. 5. the coves align around the box perfectly..Now... onto the real thing....
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The jig... or fence.. is just 2 straight boards attached together (parallel) by a couple of cross pieces.. the space between is such that your stock (or box) will pass between them with little effort.. at the same time capturing that stock and preventing movement from side to side.. I have one "jig" for the music boxes.. cuz I make them often.. it also has a block attached at a 45º angle and a line scratched into the top of my table saw to indicate the set up line.. this makes the set up the same each time.. however.. when I need other sizes I just make up a temporary "jig" (fence).. I have no "one jig" (fence) that is adjustable for all sizes.. although.. one could be built very easily..
This "jig" (fence) is then clamped to the table saw top aligned across the blade at the desired angle.. another thing I have is a "zero" clearance insert cut to accept the molding head cutter I use on the music boxes.. although with a carbide blade any insert that will allow you to tilt (bevel) the blade will work.. with a "jig" (fence) dedicated to a certain box and size.. I've written on it certain table saw settings and other notes.. such as.. what side to place the top of the box as it passes over the blade.. and the maximum depth of cut..
If you are tilting the blade to make your cove.. it is very important to feed the stock into the tilt of the blade.. that is: if you have a right tilt saw.. feed the stock from the right to the left into the cutter.. if you have a left tilt saw.. feed the stock from the left to the right into the cutter..
CAUTION..!
If you don't know if your saw is a right or left tilt.. you shouldn't be doing this.....
Standing at the front of the saw.. with the fence in place (for this project it's set at 45º) and the box between the rails..
Standing to the right front of the saw.. the cove operation complete...
With the box secured in the vise I use a curved cabinet scraper and sand paper.. to smooth the saw marks from the coved area..
This box jointed base was run through this cove process after assembly. I had this brain storm while mowing my grass, a 3+ hour ride each week. The base was built one whole year before I built the chest (just to see if I could do it) .
(see the chest on my Case work page).
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