I have read articles in FWW about cutting cove molding by passing the stock at an angle over a TS blade little-by-little. I have never tried this before but I am thinking about whipping out a couple of Lonnie Bird Philadelphia secretaries this weekend. Does anybody have experience or comment on this technique, particularly from a safety point of view? Also, I only have a 3/4 hp contractor TS.
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Replies
jackhall ,
Plowing a cove on the TS can produce a wide range of different size cove details . I have done this many times . Safety is a major concern , you are pushing the stock at an angle across the blade . I have clamped a guide board down to the saw table top and by keeping one edge against the guide board you progress slowly increasing the depth of cut ever so slightly on each subsequent pass . The rule of thumb was never cut more then the height of the teeth on the saw . Depending on what type of wood , how hard along with the power or lack of power of your TS a minute bite at a time may produce a better result and be safer . I have made some beautiful base moldings for dressers and made various things with this method . You will need to scrape or sand or both to clean the cuts up before finishing .I think the danger is if the board you are pushing moves away from the guide board or when you get to the end of the cut you are looking right at the whirling blade while perhaps bent over and pushing forward and off balance , it can be disastrous . Not for folks who are not extremely comfortable with the TS .I have seen the set up made with 2 guide boards utilizing 1 on each side of the work piece also.
So you are thinking of whipping out a couple of Lonnie Bird secretaries this weekend , hmmmm , I think your pulling our chain , or have no clue what it is you are about to embark on .
best of luck to you dusty
"Safety is a major concern , you are pushing the stock at an angle across the blade."
If I use two parallel fences to guide the stock and only take small bites on each pass, is the likelihood of the board kicking back any greater than with just ordinary rip cuts?
jackhall ,
Kickback IMO is not the problem as far as safety is concerned . More the fact that you are making many passes to get the desired profile or cove . When you are near completion depending on the size of the cove , the blade may be up an inch or more and when you get to the end of the board , whammo your hands or pushstick are right there feeding into the direction of the blade . I have always only used one guide board and pushed down , forward and against the guide board .If using two guide boards and depending on the lengths of stock you will be running , anything but a real straight board may have a tendency to get caught between the guide boards and I suppose a kickback could occur .In general I feel the risk increases with this type of cut , whether you use a molding head cutter or a saw blade . Just my take on this . There are many ways of doing things , you need to find where your safety and comfort level are, and trust your gut feeling . I have heard it said that just before many mishaps on the TS , folks often get the feeling that this is not good .That IMO is the time to STOP , and re-evaluate the way you are going about that particular task . You will never be sorry you stopped to be safe , other scenarios may prevail by not stopping .
be safe dusty
we want a finger count , before and after !
Thanks dusty. Lots of good stuff for me to think about.
I've done a few of these over the years, on 3 or 4 different saws, and don't recall ever having any problems.
As said above, the greatest risk is at the end of the cut as the unguarded blade emerges, and when the cove is almost complete and there's lots of blade visible.
I nearly always stop the cut just before the blade emerges, leaving a few inches of solid wood between the blade and the push stick. I push forward over the blade, until the coved section is long enough for the job, then stop and either lift off or pull back. If the blade is always fully covered, and you take small bites, you'll be safe enough.
Malcolm New Zealand | New Thinking
There are two main factors that determine the shape of your cove: the angle you use relative to the saw blade, and the bevel setting of the blade itself (can be anywhere from 90 to 45 degrees). You can make the cove more elaborate (eliptical) by introducing a sled that you work piece rests on as it goes over the blade.
Your jig can be as elaborate as you want to make it. The simplest would be two boards set at the desired angle across the blade, pushing your work piece between them. Feather boards on one side of this fence work even better.
Do you need some sort of feather board to hold the work piece down? It is nice to have, but not essential. Push blocks (the kind you use for jointing a board) work nicely. For safety sake, in the beginning, it would be prudent to attach some sort of board that overhangs the fence board by a half inch of so -- not so much to hold the work piece down, but more to keep it from flying upward.
The really essential thing to remember is take very, very small cuts. At the beginning of your learning curve, I would set the blade so it is just kissing the work piece, then raise the blade ever so slightly for each additional pass. If you go very gradually in this fashion, you won't have any problems with kick back, or the blade grabbing your work piece.
I would suggest using a stack of sample pieces -- either pine or even MDF will work), and change the various angles for each. Make a note on each board and save them for future reference. Somewhere along this experimental line, you will find the combo that will suit your present project.
Good luck, and remember to take small cuts.
I go with the 3-wing cutter also. The only thing that I do differently is that i will tilt the cutterhead and feed from the side that it is tilted to so-as to use the top of the cutter head instead of the side. I also use a thumbnail shape on the cutterhead.
Your comment about tilting the arbor brought up another item I remember reading about concering when cutting coves on the TS. If I tilt my sawblade to the left, which side of the saw should I feed the stock from? From left to right or rght to left?
Jack, the cutter I have is 1" wide across the top. I use it on a right tilt, so I feed from the right. This allows for larger / deeper cuts per pass.
The top most portion of the cutter needs to have a nice round over rather than a sharp corner. This will make for easier clean-up in the end.
So tilt right, feed from right. Tilt left, feed from left. Feeding against the tilt. You said it allows for a deeper cut, but is one direction any safer than the other?
Jack the cutter head that I use is an old molding head that I bought from Sears back in the early seventies. It has 3 inerchangable knives. they were sharpened to feed the stock straight into it like sawblades, there is not much of a sharpness angle on the side of each blade. By tilting the head, I am presenting the sharper top bevel into the feed direction.If you don't have a cutter head of this type, but have a dado set, you might try tilting it. You should be able to get a faster cut than a single saw-blade.
I do not mean to be picky, but all cove cuts on a table saw are elliptical. It apparently has to do with the fact that every projection of a circle is an ellipse or (the extreme case) a straight segment.
Metod
Almost but not quite, a cove made with the fence at 90 degrees to the plane of the blade will be a true circle.
John W.
John,
let me "win" at least one argument (I graciously conceeded the one about exhaling...): circles are just special cases of ellipses - when their two focal points collapse into one. Besides, my high school math teacher would be proud of me. For extra points: conic sections.
Metod
Edited 2/3/2005 6:50 pm ET by Metod
You do win this one and your math teacher should be proud of you.
John W.
Metod, you are correct that the cove cut on a table saw is an ellipse, with the closer you are to the stock being perpendicular to the blade the closer you get to a true circle/radius. Besides there is nothing that said a cove molding has to be a true radius, a cove molding is only defined as being concave.We are the people our parents warned us about. J. Buffett
Mike,
I was just trying to sound smart. :>)
Has a convex cove been invented yet?
Metod
jack,
I like using a molding cutterhead (three knife) with round nose cutters to do this. I think it makes a smoother cut, since the cutters are designed to cut from the side, and I feel better about the stoutness of the cutterhead.
The angle of attack determines the size of the arc cut into the stock. Nearer to parallel to the rip fence yields a narrow deeper cove; approaching towards a 45* angle will make a larger radius molding. Use long pieces of clear, straight grained stock- that is, cut 1 piece 30" long instead of two 15" sticks. Clamp the guide board (fence) on the infeed side of the cutter, so the force is pushing the stock against the fence. I draw the desired shape on the end of the stock, then raise the cutterhead to the maximum depth needed to make the cut. Play with the angle of the fence to get the cutter to follow the arc of that I've drawn on the stock. Then, LOWER THE CUTTER all the way down. Raise the cutter a little at a time (1/16" or so), making the molding in several passes, to minimise the sideways thrust against the cutter/arbor. Make two passes at the last height setting, the 2d pass will clean up some of the rags left by the first one.
Clean up with a gooseneck scraper, and/or some 80 grit paper wrapped around something near the right size to fit the cove, like a soda bottle.
Regards,
Ray
Hey Jack,
Ray is absolutely right in using the three wing radius molding cutter for the table saw to cut coves. The surface it leaves is far superior to using a standard saw blade, the scraping/sanding phase is dramatically shorter. The only draw back by using one is that they are typically a smaller diameter so you are not able to make as large of a radius cut as you would with 10" saw blade. All the other tips given have been right on and I will add my plead to take it SLOW.
Hope this helps and good luck
Robby Phelps RP Custom Woodworks
Edited 2/2/2005 9:48 pm ET by Robby
Jackall,
I have nightmares just thinking about it.
the three wing radius molding cutter...........
I have one from my really old RAS..
I used it ONCE.. Never again! Scared the c... out of me..
Using a cutter like that on a radial arm saw is very dangerous as you trap the material between the cutter and the table.For additional excitment try using a single tooth moulding head! <g>
Thanks.. Like I said.. I tried it ONCE! Never again...
Convex cove- if it's convex, it can't be a cove, can it? However, Grizzly has an attachment for cutting narrow pieces to varying radii. It was made for radiusing guitar fingerboards and things like that. If you want to build up a moulding with what amounts to very large beads combined with whatever other type of cove, ogee, 1/4 round, etc, this would work.I have been thinking about making a jig for cutting coves on my saw, in a way that I can do it faster and, more importantly, safer. The fence will be fairly high with a T slot in it for an adjustable wide featherboard that will hold the stock down, centered over the blade. This way, I can get it started and when it gets through far enough, I can pull the piece the rest of the way. No hands over the blade for any reason. Also, not likely to have kickback since the pressure will be over the blade and the fingers will be angled toward the blade. I may use the green board buddies that don't roll backward, instead. I'll try it with the featherboard first.If anyone wants to sand odd shapes, take a plastic bag and fill it with Bondo, pressing it down to take on the shape of the profile. Once it has hardened, remove it from the bag and wipe it with solvent to remove the sticky residue. Lay a piece of sandpaper on the piece and sand away. This works best with fine paper.
"I cut this piece four times and it's still too short."
Edited 2/4/2005 10:44 am ET by highfigh
Jack, yesterday I listed a post in the gallery that had a large cove on it that I cut in this fashion. Here is the link that to the post where I described how I did it,
http://forums.taunton.com/tp-knots/messages?msg=21575.12
The jig that I used is in the picture below. Just make sure that the two long pieces and and two short pieces are the same length and the hole center are also the same.
If you want to get into coves (and other shapes) in a big way, here is a set of cutters Lonnie Bird has put together for CMT:http://tinyurl.com/5cqwaThe cost is about $340.
Greetings,
I have cut crown moulding for a pair of Lonnie Bird Penn Secretaries that I have been building (on and off). I must confess, that I used the CMT Lonnie Bird crown mouldings set of router bits and table saw 'blade'. The set worked great, needing a little clean-up with a gooseneck scraper. I took VERY shallow passes on my 3hp Unisaw, used 2 2x4's as Bird did in the article for fences trapping the stock between them. Must say the CMT tablesaw 'blade' took the weirdest look shaving I ever saw.
Those Lonnie Bird secretaries might take a wee longer than a weekend to complete :-)
Best of Luck
Wow, I never would have anticipated that a simple question re: coves would degenerate to a math discussion on coverging focal points et. al.
Here's my two cents:
1) Go for it it's not that hard -- I'm by no means an 'advanced' woodworder and I have done it with good results. It's pretty hard to screw up.
2) Clamp a couple of peces of scrap (one on each side of the workpiece) to your saw as a guide. If they are thick enough, you've baically eliminated the major risk. Also, watch out for the belt of your contractor saw. When I do this operation I am working from the back of the table.
3) Go slow. Two reasons: a) you're only working with a 3/4 hp saw -- I'd think 1/16 cuts at the absolute max, probably less. b) This operation can really heat up a blade, and I have trashed one or two by being too aggressive on a larger saw.
4) Yes, there are better blades to use than a standard WW blade (e.g. cove cutters etc). If you can pick up one for less than the price of a good carbide blade, that's a better option. However the $300+ for the Lonnie Byrde cove set would be better spent, in my opinion, on upgrading your TS
5) Count on a lot of sanding and then a lot of scraping. I use 3M #77 (?I think)) spray on adhesive, to stick 60-80 grit around a short piece of PVC pipe. It works well. I've also had luck using bondo to make a cusome sanding jig, but I don't htink that will be necessary for a large cove. You will be surprised how long it takes to get the macine marks out. Clean it up from there with ~120-200g and go with a goose kneck scaper after that.
Have fun. It's not really that hard. We'll expect some picks on Monday.
Cheers,
Eric
It's not that hard, just do it safely. Feed the stock in so the blade won't make it rise on the way through and that it pushes into the guide. Also, make sure that your footing remains stable.
"I cut this piece four times and it's still too short."
"When I do this operation I am working from the back of the table."
Eric- Thanks for the tips. One question. Why would you be working from the rear of the table saw? Seems like you would be pulling the stock toward you.
I would add one more safety caveat, in addition to the one about avoiding the blade at the end of the cut.When cutting the cove you are, in a sense, creating an arched bridge over the saw. There is a danger in trying to get too much from too little, in that if the bridge gets too thin, the piece will collapse onto the blade. If you are applying pressure with your hands near that point, you have a disaster.In my experience with cutting coves this way, the most difficult thing is securing and guiding the stock. There are only a relatively few spots where you can safely contact it. Take the time to make a proper paralellagram jig, you will find future uses for it. Also take the time to make a long, over hanging push block, you will be safer, and feel better about the whole experience.BTW- You can make a very interesting variation of the elipse by tilting your saw's arbor before cutting the cove. This gives you a section of the elipse that is off center and asymetrical, sort of a "skewed" effect. I used it to make the sides of a jewelry box one time, and it turned out beautiful.Tom
Thanks for the tip. I had read about creating off-set coves by tilting the blade. That is certainly something I want to try.
Jack,
It really took me some time to think though why I do it this way. I've always fed the stock from behind the table and I thought that's just how "it was done". I'm definitely not pulling the stock. If you were to face my saw, the stock feeds from close left to far right, but the coves I have cut are fairly wide, so I'm often running the stock 60-90 degrees to the blade.
On my saw it is a lot further from the front of the table to the blade than from the back to the blade, so to keep downward pressure on the workpiece without having to lean over the saw, I walk around the left (as you normally feed it) side of the saw and feed it from around where the rar left courner would be if you were feeding stock normally.
Call me insane, but I use a couple of those orange handle push pads you get from Rockler and press downward about 4-5" from blade (I can feel the cringes). It's far easier to do this from the rear of the saw (again, the distance from front to mid-blade is much shorter than rear to mid-blade) than from the front. While the whole operation would be safer with some cleverly mounted featherboards, I think the pads and a push stick keep me plenty far from the blade, as it is covered by the workpiece for most of the operation. I feel far more at risk ripping stock (because of kick-back) than cutting coves.
So, pictures next Monday, right?
Best of luck,
Eric (aka nine-fingers)
Isn't the shaper a more natural choice for this task?
Can I borrow yours, I ain't got one or the space to put it.
Cheers,
Eric
Eric,
I don't have one either.
<Isn't the shaper a more natural choice for this task?>Actually, I don't think so.I have a 3Hp shaper, and if I needed to make a large cove, I would definitely use the table saw. A shaper head large enough to make the cove of a crown molding, or the coved side of a jewelry box, would cost a bundle, but I already have a saw blade that would do the job.Using a shaper for that type of job would also require a sled or carriage. If you took the same precautions on the table saw, you could expect the same degree of safety. The one advantage of using the shaper is that you would have less scraping to do to clean it up.Tom
Jack, there is a parallelogram jig that you can make that will help you to get the cove that you want. I don't think I can describe it effectively, but you can find it an most books on jigs. You set this thing for the width of cove that you want to cut (it's adjustable) and you set the sawblade to the depth you want your cove to be. Then you place the jig over the sawblade touching a leading and a trailing tooth, at an angle. This will give you the angle that you should set your fence to. Look in a book or two and you'll see it.
RCB. I think I know what you're referring to. I'Ve seen pictures. I've also seen the parallelogram jig used as a router guide. Thanks for the reminder.
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