Cove Cuts on a Radial Arm Saw

Intro: Cove Cuts on a Radial Arm Saw

This is a Google Sketchup drawing of picture frame stock made from cove molding that I have made on my radial arm saw.  No special cutters are required.

STEP 1: Basic Setup of the Saw

A cove cut pushes the work piece into the side of the blade rather than the front edge and reproduces the circular profile of the blade in the workpiece. 

Cove cuts can be made on a table saw.  Here you see the basic setup on a radial arm saw.  The workpiece is guided by two fences with one on each side of the workpiece.  The two fences blend into the background in the photo, so I outlined their working edges with red lines.  

In order to achieve a smaller radius cut, I used the 7 1/4 inch blade from my circular saw rather than the usual 10 inch blade normally used on my radial arm saw.  The motor is tilted to about 45 degrees so the teeth bite into the wood more easily as it is pushed toward the saw.   Notice that the motor has also been rotated clockwise a few degrees (as viewed from above the motor) so that the yoke is no longer fully in the crosscut position.  The spoon handle lever that locks the yoke (yellow arrow) was loosened to allow the motor to rotate and is again locked to hold the motor in position.

STEP 2: The Basic Cove Cut

A cove cut is made by a series of light cuts until the desired profile is achieved.  On a radial arm saw, lower the arm about 1/16 to 1/8 inch for each pass.  A lighter cut fed very slowly through the saw will give a smoother cut.  This is especially important at the end of the process.  Still, the saw tears at the grain and leaves fine saw marks.  Quite a bit of hand sanding is needed to make a nicely finished piece.

STEP 3: Remove Excess

To make picture frame stock from the cove cut piece, set your saw to remove the sections in red.

This is an acceptable way to make picture frame molding, but there are also many things that can go wrong.  Each cut requires a great deal of precision.  If the wood chatters or a tough section of grain makes the workpiece jump a little, a gouged out section can appear and damage your good efforts.  Still, there are times when such a piece of picture frame molding works just fine. 

STEP 4: Make a Bowl

A variation on a cove cut is cutting out a bowl recess in a piece of wood.  I used pusher sticks to keep my hands away from the spinning blade.  See the red arrow.  This pusher stick holds the workpiece down firmly against the work table.  See the green arrow.  This pusher stick is used to rotate the workpiece 360 degrees in steps.  If the position of the saw leaves a button of wood in the center, just remove it with a chisel at the end.  

What you cannot see in the photo is a pin under the workpiece about which the workpiece rotates.  (See the next step.)

I needed to make four of these.  They were to become the top layer in a stack of three pieces.  I needed to make supports that raise someone's bed a few more inches above the floor.  He has had two knee replacements and will have trouble getting in and out of a bed at the normal height.  The raised bed will make it easier for him.  The bowl-shaped indentations will provide a nesting place for the bed's casters.

STEP 5: The Pin

I clamped an old piece of particle board to the saw's work table.  In this particle board I drilled a hole for a 1/2 inch dowel pin that serves as the pin about which the workpiece rotates.  I drilled a corresponding hole in the bottom of the work piece.  Then I positioned the lowest portion of the saw blade over the center of the dowel pin as precisely as I could. 

STEP 6: What the Saw Manual Suggests

I bought an additional manual on using my radial arm saw.  It gave a procedure for making a bowl cut, but I saw some potential problems with it.  The first step was to lift the indexing pin and hold it lifted, which is not an easy task even when a sharp saw blade is not spinning at 3000 rpm a few inches below.  The second part of this suggested operation is to loosen the spoon handle lever (green arrow).  If it is loosened fully, the yoke and motor have some undesirable movement that will result in uneven cuts.  The spoon handle lever can be loosened just enough to allow the motor to swivel, but this is an uncertain process.  I would rather have things locked down so nothing is left to chance.  There is one more part of the suggested process.  See the next step.   

STEP 7: The Rest of the Suggested Process

With the yoke a bit loose and the saw running, the operator is to lower the arm so the blade begins to cut on the workpiece.  Then, while still holding the indexing pin high, he is to use his other hand to swing the motor 180 degrees by grasping the end of the anti-kickback paw rod.  (See the red arrow.)  There is still the problem of how to hold the workpiece down on the table.  Now you know why I used a dowel pin below the workpiece and pusher sticks to rotate the workpiece.

STEP 8: One More Cove Cut Project

This is a cross I sometimes wear when I am leading the worship service at the church where I am the pastor.  It was made with three cove cuts on each of the two pieces.   I made several of these at the same time.  The first step was to make a cove cut in a longer piece of wood, as in step 2.  Then I cut that piece crosswise into narrower pieces.  Finally I made a cove cut on the side edges of each of the narrower pieces.  The two pieces of each cross are joined with a lap joint.  The horseshoe nail heads are a decorative touch and have no particular meaning.  

Comments

[kransbox]

You have some skill that is for sure. I would have never thought using a radial saw for this.

[Phil B]

I cannot take credit. Craftsman published a guidebook for radial arm saws and a couple examples of cove cuts were shown in it. I made a couple of adaptations in the execution. Thank you for your comment and for looking at this.

[aeray]

As my father would say "...those things crippled more people than polio..."
I would recommend that the proposed guide have a thorough safety section.
They are useful though, and dirt cheap, used. I have to stay mobile, and so use a sliding compound miter saw which weighs a bit less, but it won't do this.
I use the tablesaw variation of this trick on an almost daily basis to cove out the back of door and window casings when the jambs aren't in the same plane as the wall. It lets both edges of the casing sit tight to the wall, rather than rocking on the high edge. When I have used it to mill replacement mouldings (for historic renovations), I find that taking a few minutes to make a profiled scraper is worthwhile. It produces a smoother, "crisper" result then sandpaper.

[Phil B]

Cove cuts are ideal for the backside of your door and window casings.  A table saw makes a good tool for cove cuts because the blade is covered by the work piece during the operation.  I have used my radial arm saw since 1972 heavily enough that I replaced the motor bearings once.  I use what guards i can, but depend heavily on pusher sticks to keep my hands away from sharp things that spin.  Nothing on that saw has ever drawn blood.

A custom scraper is a good idea, especially if your setup does not change.  The radial arm saw is my multi-purpose tool and I constantly change the setup for different jobs.  It would be very difficult to setup for the same profile I used to make the scraper.

Thanks for your comments.

[woodguy23701]

Nice write up and details. I have done this on table saws and radial arm saws for years. I have found that carbide tipped blades work best (over standard steel blades). I think this because the edge of the tooth can act as a cutting edge as well.

[Phil B]

Thanks for your comment.  I began using carbide tipped blades as soon as they were available for a reasonable price and have never regretted it.  Do you find you need to sand away saw marks on cove cuts?  How do you use cove cuts?

I posted a few things I have learned to do with a radial arm saw and got comments indicating many folks these days are not familiar with them.  I have been trying to demonstrate some information about a greatly overlooked tool.

I learned once the edges of carbide tips make a good knife sharpener.  Those things are tough. 

[rimar2000]

Good work, Phil.

I am doing housekeeping in my garage (after will be the turn of  the shed in the background, and after the attic) before starting to work on my construction projects. One of them is a "poor man's radial arm saw"

[Phil B]

Osvaldo,

I wish you well with your "poor man's radial arm saw."  If I can answer any questions about these saws to help your work, please ask.  I think I mentioned the Craig's List web pages.  I continue to see good used radial arm saws available for only $50 to $100 US.  One of those would save you so much effort.

[rimar2000]

Thanks, Phil, but I cringe to buy something from so far away. I bet the shipping to Argentina will cost more than the price of the tool.

Apart from that, I love designing, cutting, welding, to err and use bad language, cut back until the thing takes shape.

[Phil B]

Craig's List is present in Buenos Aires.

English: http://buenosaires.en.craigslist.org/

Spanish: http://buenosaires.es.craigslist.org/

I tried to check some of the listings.  It may be more difficult to find a radial arm saw there.  Check the "Free" listings, too.  Sometimes people give away amazing things.

All of the bad language you may use needs plenty of beer to go with it.

[rimar2000]

Thanks very much, Phil, I checked the list but in "herramientas" (tools) there is nothing.

[Phil B]

I made a guess that herramientas meant tools.  We have quite a few Mexicans living in Idaho, and many of our signs are now bilingual.  You can also post that you are looking for an item and someone may respond.  Craig's List may be something new in Buenos Aires.  It may take a year or two before people begin to use it much.  My son buys many things from Craig's List.  I think you have to check it regularly to see if it might have what you want to find.

[kelseymh]

Another very impressive writeup!  I think it's about time for you to put together an Instructables Guide to Radial Arm Saws :-)

[Phil B]

Thank you.  I had thought about doing just that.  There are one or two more things I want to do that are more specialized somewhat like this Instructable is specialized.  Then I would want to link all of them in the comprehensive Instructable, even though many of them already show up in the "Related Instructables" column.

[kelseymh]

It wouldn't have to be a new I'ble.  I was thinking of an I'bles Guide, such as the recent "DIY CNC Guide", or "Chocolate".

[Phil B]

I would be highly in favor of a guide to radial arm saws.  I know the person who submits the guide must be an editor, which I am not.  Still, I would like to prepare and publish a couple more things before a guide were produced.  Also, there are a couple of things I have submitted that should be included, but the one publishing the guide may not be aware of them because they do not have "radial arm saw" in the titles.   Thank you for your interest.

[kelseymh]

Hi, Phil.  You can create a Guide, you just can't "publish" it.  A PM to one of the Staff (Noah, Sarah, or Ed are your best bets) will get the ball rolling. 

If you recall the "Guide to Kiteman" that came out last December, although Sarah was the official Staff "publisher," it was myself and a small band of conspirators who gave her the list of I'bles to include.

[Phil B]

Thank you for the information.  I will give it some thought, although I am not certain how soon I will be ready.  I wanted to publish the Instructable on making A Precise Table Saw from an Electric Handsaw for at least a year before I had everything ready.  I have had a couple of message exchanges with both Sarah and Noah and always found them to be both cordial and helpful.  I have not communicated with Ed. 

[mikeasaurus]

The intro picture and description drew me in, the process was the hook, and the final product was unexpected-awesome!
A use for the radial that I had not considered before. 

[Phil B]

Thank you very much.  If you have a radial arm saw, I hope you find new enjoyment and productivity with it. 

When I was doing the cross shown in the last frame, I used pusher sticks to hold things down and keep my fingers far, far away from the blade.  I also clamped any kind of stop block to the table I could to assist in accurately and securely holding the pieces in place while I made the cove cuts.