Face frame question + Sketchup question

[Greg Guarino]

If you wanted to build a face frame whose top member was arched, like this:

... how would you form the tops of the stiles? My sense of geometry tells me that over a 2.5" width, an arc with a radius of 36 feet would deviate from a straight line by a very small amount. (the height of the deviation in the middle of the arch is 1") So would you simply cut the tops of the stiles at the proper angles, leaving the cut straight, or would you somehow form a very slight curve to mate with the arched rail?

Now the Sketchup question:

I drew the bottom and top rails first, including the arch. Then I drew the stiles in place, butting up to the bottom rail properly, but with excess length at the top. I opened a stile for editing, selected the front face and tried to "intersect faces with model". Sketchup told me there was no intersection. I think I've had this happen before. If two surfaces are in the same plane, even if they obviously overlap, Sketchup does not consider that "intersection".

As a workaround, I moved the top rail forward by half the thickness of the "wood" and then did the "Intersect Faces" procedure on the front face of the stile. This time it drew the line I was looking for on the front face of the stile. I used the "pull" tool to "trim" the stile to mate with the arch. Then I moved the top rail back to its intended position.

Is this simply how Sketchup works? Or is there some other way to make parts whose faces are in the same plane "mate"?

[Leon]

You might rethink how your rails and stiles intersect. Look at this. Typically rails, outer rails fit between stiles. This does not address the inner stiles but I think you cab rethink a bit and come up with a simpler solution.

Anyway if you stay with this design exactly, cut the top rail first. Cut the stiles next and long. Clamp stiles precisely where you want them, under the top rail. With a top bearing flush cut bit in your router use the clamped top rail as the guide to cut a groove on the face of the stile. Once you have all stiles grooved, remove and cut off the excess, close to the line you want to keep. Now use that edge again to guide the bit to remove the remainder. Make several passes.

[Leon]

Now how to draw. Draw flat and everything. Do not make any of this as component yet. Make a complete copy and move to the side. Erase every thing in the first drawing that is not the rails. Go to the second complete drawing and erase everything that are not stiles. The ark on the stiles should remain. Now make everything into components and put the pieces together.

[Leon]

Just a hint here, non component lines in a drawing do not move well, they stick to other lines. BUT those lines copy perfectly..

[Sonny]

With a 36' (432") radius, and the chord is 2.5", the angle would be .331 degrees and the distance from the chord to the top of the arc is .00181".

Might as well cut the tops of the stiles straight across.

Sonny

[Leon]

While this will work but will leave a gap, small one, it will not be a strong joint, touching in only two points. Additionally at precisely what angle will you cut?

It is probably going to be just as easy to cut the matching ark on the stiles using a flush trim router bit and using the ark on the rail as the guide.

Something to also consider with a 36' radius I doubt he is going to get a perfect ark unless he uses his router on the end of a 36' long string, and then placement of the rail will be critical. ;~)

Better to print the pattern, glue to the rail, cut close to the drawing ark, and then sand smooth to the line. Remove the paper pattern. The ark will not be perfect but if you use the ark on the rail to guide the flush cut bit it will be a perfect match.

[John McCoy]

Greg Guarino wrote in news:mp66tv$qsi$ [e-mail]:

I'd probably dry fit it and see how tight the joint looked, and then take a pass or two with a block plane to make the stile fit if it needed it.

Now, if you wanted to get fancy, instead of tenoning the stiles into the rails, you could rabbet the rails and fit the stiles with a bridle joint, making it a decorative element. Perhaps make the stiles thicker than the rails so they stood a little proud or maybe routing a bead or something along the edges. That would hide the lower joint, and making the top flush would be easy.

(I saw pictures of a piece done that way somewhere, thought it was a neat technique)

John

[Leon]

Ok, one more example of using the top arc on the rail as a template to guide the top bearing flush cut router bit. I had a variable arc curve MDF template that I clamped to the cutting boards and cut a 1/4" deep grove in the cutting board. Then band sawed down the middle of the grove to separate the halves. Then removed the remainder using the existing original grove to guide the bit to remove the remaining waste. The strips you see go all the way through the boards and for each group of strips I cut the cutting board again.

So...... this method does work if you want a perfect fit. ;~)

[Greg Guarino]

Perhaps I misunderstand, but this sounds like a recipe for a stile that is too short; too short by the diameter of the router bit. Further, suppose I were to shift the stile 1/2" (my bit diameter) with respect to the rail "template", it still won't trace the same curve, not quite anyway. Now in this case it would probably work as the "curve" is extremely close to being a straight line. But with a tighter curve, I don't think the parts would mate properly.

Have I misconstrued what you meant somehow?

[Leon]

OK! Nevermind. My suggestion will NOT work well.

The arc on the stile will end up with a radius that is 1/2" shorter than the 36' radius on the rail/pattern. Assuming you use a 1/2" flush cut bit.

There will be a gap unless you put a 1/2" strip between the rail and the stile, again assuming you use a 1/2" bit.

Hope this was not too late.

[Leon]

OK, you left out the part where I said to cut the stiles long. Cut those to the correct length after tweaking the fit at the top rail joint.

Further,

Yes! you are right and I just a moment ago and addressed this. The radius on the stile will be 35'-11.5" instead of 36'.

On my cutting boards this work great because I fill the 1/2" removed material with 4, 1/8" thick strips.

Others have mentioned cutting a straight line and what is going to leave you with some kind of gap. BUT John mentioned tweaking with a block plane, so that would work too. Regardless of which method you use cut your stiles several inches too long and after you have it good enough cut the stiles to the correct length.

No you understood me correctly, I made the mistake. I was just remembering how I did this 7 months ago with the cutting boards. It would still work for you but you would have to put a 1/2" filler strip in the middle of the joint and that in this case would look wonky.

Alternatively clamp the stiles in the correct position, trace the curve with a pencil, and use a disk sander to remove the material to the curved line.

Keep in mind that your arc is probably not going to be perfect so unless you use the exact position of placement as a reference the fit may be inconsistent on all of the stiles.

Just something to think about and it may not fit into your plans but build it like my cabinet doors in the link I supplied, Top rail between stiles. Then cut another rail to put over the front of the top rail to hide the joints. That top rail doing the hiding could be most any thickness.

[Leon]

OK, you left out the part where I said to cut the stiles long. Cut those to the correct length after tweaking the fit at the top rail joint.

Further,

Yes! you are right and I just a moment ago and addressed this. The radius on the stile will be 35'-11.5" instead of 36'.

On my cutting boards this work great because I fill the 1/2" removed material with 4, 1/8" thick strips.

Others have mentioned cutting a straight line and what is going to leave you with some kind of gap. BUT John mentioned tweaking with a block plane, so that would work too. Regardless of which method you use cut your stiles several inches too long and after you have it good enough cut the stiles to the correct length.

No you understood me correctly, I made the mistake. I was just remembering how I did this 7 months ago with the cutting boards. It would still work for you but you would have to put a 1/2" filler strip in the middle of the joint and that in this case would look wonky.

Alternatively clamp the stiles in the correct position, trace the curve with a pencil, and use a disk sander to remove the material to the curved line.

Keep in mind that your arc is probably not going to be perfect so unless you use the exact position of placement as a reference the fit may be inconsistent on all of the stiles.

Just something to think about and it may not fit into your plans but build it like my cabinet doors in the link I supplied, Top rail between stiles. Then cut another rail to put over the front of the top rail to hide the joints. That top rail doing the hiding could be most any thickness.

[Sonny]

My block planes are not sharp enough to trim end grain, properly.

I think I'd have better control using a sanding block to form the arc on th e stiles. It's not a lot to sand off, even for 4 stiles. I'd try to cut the stiles' ends with less than 1/4 degree of bevel, *straight across. M ost of the sanding would be along the point of the beveled edge/face and it would be sanded as far as, at least, 3/4 of the face. If 3/4 of the face fits flush, that should be good enough.

I'd set the saw blade to perpendicular and prop up the other end of the sti le about 1/16" ( < 1/8"), to cut that small an angle of bevel.

*Straight across cut: If you want the best angle (not exactly straight acr oss) brace end of the stile away from the (miter/chop) saw's fence by a tad . That angle is nominal, but at least you can easily adjust that "eyeball ed" cut, also.

Do a test cut and sand/plane on some scrap.

Sonny

[Greg Guarino]

Sounds like a good idea.

It had to happen sometime. :) Consider me the stopped clock.

I was just

No disc sander here. But we are talking about less than 2 thousandths. That shouldn't be difficult by hand. What I'm still trying to visualize is whether or not that .0018" "rise" that represents the difference between the curve and a straight line would be visible. Is there a rule of thumb?

That's something I'm reminded of all too often.

so unless

I may draw that to see if I like the look. This is all pretty far off - time-wise - by the way. It's just a twinkle in my eye. My wife and I were just discussing the possibility and I whipped up a sketch.

[Greg Guarino]

I've done that with doors. But in this case the entire unit will be above head height:

[this drawing didn't have the arch]

I figured it would look better without the end grain showing.

[Leon]

Yes, any time you get into something other than a straight cut on a joint it is a good idea to cut a little long so that you have some wiggle room while you sneak up on the fit.

LOL, I make plenty of mistakes but then that is how you learn and see why that idea or method will not work.

Test on a scrap. BUT .002 would probably not be viable especially on a coarse grain wood. BUT there is going to be less glue contact area, 2 points that actually touch and regular wood glues need to have a tight a fit. NOW if you dado the backs of the face frame, to receive the carcass of the cab, that would probably reinforce the joint and you could putty the gap if it is visible. OR pocket hole the joint from the back side of the joint and you would probably be good to go although dadoing the back of the face frame could be touchy to miss the pocket holes.

And or build it like in the drawing in the previous post and add a curved piece on top of the face frame.

Well unless anyone has a CNC it is not going to happen.

[Leon]

Yes and you could always cover the bottom of the entire face frame with a 1/4" strip of wood to cover the entire bottom, joints and all.

[Swingman]

Not difficult at all to make a jig to route the exact arch in the top of the stile.

You still want the joinery to fit perfectly, both for aesthetics, strength, and peace of mind.

Think JIG ... and use SU to your advantage:

Print, to scale, a template of the top curve of the part, which you can then use to both paste on the top of the stiles for the rough cut, and for making a simple router jig(s) to make the precision fit.

Since you are working on end grain of the stile, build a backup piece into the jig to mitigate tear out.

Just one, of many ways, to skin that cat. But doing it in such a manner that is is both pleasing and structurally sound makes you feel better in the long run.

[dadiOH]

Yes, absolutely!! A RCH MAY make a difference (sometimes) but

[Greg Guarino]