Advice of Shaping an oval mirror

[john lawson]

I am helping my son make a 6' oval mirror frame that will be fabric covered. We need to shape the frame into an oval cross section. He has already made a pass using a roundover bit with the router but it does not come close to taking the amount of material needed. I am also concerned with keeping it consistent.

There is a plywood template glued to the bottom so we have a good bearing surface both outside and inside. I was thinking of using a straight cutter on the shaper with a rub collar and then "stepping up" so that the bearing rides on the previous cut. I am researching cutters and bearing options now to see if I can find the right one(s) to make the cuts. My thinking was to create a series of steps, none of which would be too deep, and then follow the deeper parts of each "step" as my guide to keep from going too deep. I would use and electric planer for this, then follow with a spoke shave, card scraper etc until we get to sanding.

I am looking for any other ideas, either different from what we are thinking or add to the direction we are already heading.

Thanks in advance.

[Mel Fulks]

As small as that is I would not use a shaper unless you have one of the rare hold down springs. I would whittle and then use some coarse sand paper glued to a block,with the cloth covering you don't need to worry about scratches,only shape.

[john lawson]

As small as that is I would not use a shaper unless you have one of the rare hold down springs. I would whittle and then use some coarse sand paper glued to a block,with the cloth covering you don't need to worry about scratches,only shape.

"As small as that is"? That is 6' not 6", so that is a lot of whittling, LOL.

[Mel Fulks]

Oh,for goodness sakes! But it's YOUR fault for not putting a Coke can next to it....THAT is the international Internet indicator of relative size!!. Could be done on edge or flat down on a shaper with custom tooling. But whittling ,draw knife,block plane, and the sandpaper will work. Not a big job ,he will be happy with his expanding capability when it's done. Like the fabric idea.

[john lawson]

Yes, could run it either upside down or right side up depending on bearing and tooling. And your right, he can do it by hand, but I am trying to get him to use a shaper to save time and put more precision into the job, and if it saves enough time it will save him some money. The customer is paying him for two days of labor so I am trying to get it down to a one day job and make more money with same or better quality, plus he will learn how to use a shaper for template/pattern work.

[Mel Fulks]

The oval cross section is a nice refinement but obviously more dificult than than just a round over. I doubt you will find any appropriate tooling at a justifiable price. I do think it could be done by hand pretty quickly,having done a lot of shaper work in commercial shops I might STILL do it by hand rather than make or buy tooling. With fine grained white pine I think I could do it by hand in 90 minutes or less. Good luck.

[Jerry Miner]

you don't specify the width, but would something like a "thumbnail" cutter work? (with the right bearing, of course)

MLCS Thumbnail (http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/shaper_join.html)

[Mike Berrevoets]

Just an idea....

Make some kind of router carriage? I am thinking two rails. One of the inside diameter and one of the outside diameter. A frame to hold those consistent and the rails on the frame that are the shape of the profile plus an inch or two. The router sits on the rails and could be rocked over the profile with a straight bit to create the profile. Move it along the length and do it again, and again, and again.... (Boring router screaming work)

id do something like this but then after I was all done making the jig I would have wasted so much time tweaking the thing I would have been better off just hogging off the material by hand. But, I like making jigs and that is part of the fun of woodworking for me. And I don't do it for money so wasted time is just fun time in the shop for me.

I searched for a picture but came up empty. Maybe because my idea stinks.... But it's an idea and maybe it will spur some other better idea.

[Lee Schierer]

What about modifying a scraper steel to the profile you want and sharpen it like a scraper. It might not be as fast as a router, but it should produce a pretty consistent profile and leave a smooth surface as well. I did something similar to add a double bead detail in the middle of a fairly wide board. I was amazed at how quickly it worked and the beading came out looking like it had been machined.

[john lawson]

This is a great idea, not sure how to do it, but a great idea, it would allow the use of either a straight or angled bit to hog of material in successive passes. Have to give this some thought. Thanks

By the way, it's 6 inches wide and 1 5/8 high or tall for the cross section.

I am now looking at using a straight cutter on the shaper with different sized rub collars or bearing to created different sized "steps" that would waste the excess material and create "depth guides" that would be used to cut away the rest of the excess using an electric plane and spoke shave.

[john lawson]

I have given this one some thought and here is a cross section of the template we are using for sizing the cross section. As you can see there is a lot of material to remove. While using a card scraper would work it would take a long time and result in sore and burned fingers.

If possible I want to use a machine just to emphasize to Matt how you have to think and plan for a job, including coming to a place like Sawmill Creek to ask for help and ideas.

Thanks

[Bill Orbine]

I see you have pretty much all the tools on your bench to do the job. Drawknife, power planer, spoke shave. Make sure they're sharp. On the other hand, the frame appears to be pressure treated lumber with some knots. Pressure treated lumber is still fairly green wood that's tough to tackle with sharp tools because it tears/catches so easy. Dried lumber is much easier and more forgiven. Google up you tubes videos on how to use these tools for shaping and sharpening. Outside edge is easy. Inside....well "GRUNT". You might be able to skew the power planer to minimize the planer bed surface in contact with the wood. along with drawknife follow by spoke shave to smooth out the rough and checking back with the cross section template you made. Card scraper is very slow for a frame the size you're making.... but it fine for final touch-up along with some sanding.

[Cary Falk]

What about having a custom knife ground to do half of the profile. Use a rub collar on the shaper. Run the profile around the outside and then around the inside? I'm not sure what the max amount of the knife can be hanging out without support. I would think there would be some sort of corrugated head that is used for raised panels that would handle it.

[Brian Tymchak]

you don't specify the width, but would something like a "thumbnail" cutter work? (with the right bearing, of course)

MLCS Thumbnail (http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/shaper_join.html)

+1. That's what I was thinking.

[roger wiegand]

I'd rough it to shape with a spokeshave, refine with a sander and be done before I could possibly set up a machine to do it. Perhaps do some of the heavier stock removal with a oval roundover bit in a router, but a spokeshave is pretty fast and you can make whatever profile appeals to you.

[Peter Quinn]

They don't make a corrugated back cutter head that even comes close to those two variables....3" projection, 1 5/8" cutting depth. Probably could get a custom 3 wing made up for $1k-$1500. But then you have to make 3000-4000 mirrors to make sense of the cost! I'm thinking router with a bowl mortising bit, like a big core box bit, on an elliptical jig, if that's how you made the original template, might be able to keep stepping down and ease the hand work burden. I have a variable angle shaper head that does 90-90 degrees, so vertices to horizontal, 50mm cutters, it's around a 7" head, I'm guessing with bearings that could be made to take out most of the waste in a segmented way, but those heads are again rather expensive for a one off, real nice to have it odd angles are part of your regular work. A CNC is really the modern efficient way to do this, but it seems you are past initiating that sort of thing. My thinking is if work is scarce than great, get out the hand tools and have at it. If work is steady.....sell the job, draw the job, make the blanks, farm out the heavy lifting. It's done a lot these days. I work in a shop with a cnc, we make stuff for some other local guys fairly regularly, stuff that could be done manually and previously was, but the router does it way way faster. I get all my templates and form pieces made that I previously made with trammel, bandsaw, flush trim, etc. pretty sure it's no more accurate, but way faster. I'd use a job like that to develops a relationship with the 21 century.

[john lawson]

I have decided go with a platform jig and rabbeting bit with bearing. The bearing size will control the depth of cut and the plunge will control the height giving me xy control. As I move across the frame I will change bearing size to give me more reach for the depth of cut horizontally. Each successive pass will create a new vertical wall that the bearing will ride on for the next cut. I have drawn up a jig and the biggest concern I have is controlling the height of the cut, so I am going to use a secondary 1/4"x 3'x3' table top out of plastic sheet that will go on the table. This will raise the mirror frame slightly and then I will clamp it lightly. This should prevent any gaps due to warped wood or uneven table top. Then I will rout about 2'-3 foot one each side and then move it 3' and rout again, so it should take about 6 moves to do one "pass" around the frame. It will take 4 or 5 passes to get the max movement toward the center of the oval and according to my math and the bearing I have I can get to the center. I hope to create a series of step cuts, the bottom of which will create the depth guide for the later cuts with the electric plane. I hope to get at least within 1/16" of the final dimension. If I'm successful on the router then the shape should be apparent to the eye and fairly easy to get to the final shape with a minimum of hand work. We shall see.

I am guessing this will take a maximum of 6 to 8 hours to complete if it works as planned, which is less than half of what was costed into the job.

I plan on taking pictures and will update tonight or tomorrow.

I'll post some pictures later tonight or tomorrow on the progress

I

[john lawson]

Well, here is and update. First math is your friend. I was able to graph out the height and depth of cut and transfer that to the router to keep track of where the curve would wind up. Second, as everyone knows, the set-up takes most of the time. It took me a couple of hours to make the router jig and get the hold downs correct. I wound up using cabinet screws rather than clamps as I could still pass over them with the router. Last, wish we had made it out of poplar rather that pine, would have been a better wood to work with. But overall, it went well. My son is finishing the inside of the mirror as I write this and the total labor of the job is about what was quoted. I hate to think what it would have been without the router.

Dang, no pictures, I took plenty but with the limit to upload it's too much hassle to edit, edit, edit. I'll try to get at least one.

[john lawson]

So here is my sketch showing stecps, but I had to modify this because the bearing and height were different. The first cut was about 9/16" height and 1/8" deep. The second cut was almost 1" high and 5/16" deep.

[john lawson]

So this is what the final shape looks like. I had to use a draw knife, micro plane rasp, and a spokeshave before sanding. Overall we learned a lot and it turned out well.

[roger wiegand]

Nicely done!