Trimming around a design?

[myxpykalix]

Ok I have a problem. I carved a design for a chair back but the depth for the cutout wasn't deep enough. I took it off the table thinking i could just run it around on the router table. Its not an option to put it back on the table to reestablish 0,0. The cutting surface for the bit is smaller than the length of the side to be cut and if you can see the top is curved not allowing the bearing on the cutter to ride it corectly.

My thought was to try to get a longer cutter with a shank mounted bearing. I then would take the cutout sbp file and cut a masonite template and attach it to the bottom and then use the template to cut it better. Does that sound reasonable? Is there an easier/better way to do this? Thanks.

6613

6614

[dubliner]

Jack, how about a 1/4" ply cutout of the pattern on the bottom & use a bottom bearing bit instead? Can you tell I'm not a real "Botter" yet!

[beacon14]

any chance you can run the cutout file on the empty spoilboard then use the resulting outline in the spoilboard to position the part and then re-run the cutout file?

[fleinbach]

David,

Sounds like a totally a great solution! And if you didn't want to cut it into the spoil board you could cut it into a scrap piece instead. If you indexed the scrap piece so it can be removed and then replace you could attach the work piece from behind with screws to hold it down.

[beacon14]

Frank

Two heads are always better than one.

Way to go.

[paco]

Jack,

can't you just lower the trim bit? I often remove 0.03" tabs from 1/8" stock with flush trim...

[myxpykalix]

Maybe im missing something from you two guys who are smarter than me...BUT...
Cutting the "cutout" in the spoilboard or another larger piece is a good idea but the resulting "cutout" pattern will be smaller than the carving that needs to be trimmed so how would i be able to visually position the larger carving overtop a smaller pattern in the spoilboard correctly?

Taking your concept a step ahead here is my thoughts on how to do it.
Take the "cutout" pattern then offset the vectors by an inch or so and make some tabs cutting out the waste material (in pink). Then taking the carving laying it face down on table i could lay this template on the back, position it correctly then tape/glue/hold piece on template. Turn template over hold down to table cut it out.
This is all with the assumption that i previously registered the "square of the jig to the table and the "cutout" within the square so i can flip it back over after attaching the piece to it. Does this make sense? Thanks for your help, this stimulates my braincells with your help!

6615

[fleinbach]

Jack,

You wrote:

"I carved a design for a chair back but the depth for the cutout wasn't deep enough"

Unless I'm misinterpreting it sounds like you ran the bit around a profile but did not cut all the way through. If so then you are correct we missed a step above. Since this means you would have finished cutting out the profile by some manual method and would have excess material making accurate alignment difficult but not impossible. In this case you would need to carefully cut several notches manually around the machine cut profile stopping where it was acurately cut. Then you would be able to align the piece to the newly cut template for recutting.

[myxpykalix]

Yes the cutout toolpath wasn't deep enough. Leaving 3/4" material on the perimeter.


6616

I took it off the table thinking i could just bandsaw/jigsaw the excess off and just run it on the router table with a bearing bit. Well i've got the excess off but in this pic you see how lousey it looks. And as i described above that jig will go on the back with the open area (in pink) to line it up and attach it as close as possible. Is that doable?

6617

I need to learn patience also...

[fleinbach]

Yes, it is doable. I would make 4 relief cuts with the band saw as shown here.


6618

That should be sufficent to give you a good alignment with the template.

Also whenever I am recutting something like this and have some doubt whether I will have made an error and wind up cutting my finished piece I do some probing passes first. The first one would be to run the profile above the piece to see if it will follow through the way It's intended to. Then I might make a real cut about 1/4 " large to make sure I won't screw up and ruin the piece. Once you are satiafied you can make the final pass.

[rhfurniture]

Jack,
What I do with 3d chair backs is to have a 50mm (2") square tab above the middle top and below the middle bottom that I locate through with a central 8mm dowel. I also use the tab as a hold down point. I then clean them off by hand afterwards. You can also then flip it and carve dante's inferno on the back if you want.
R.

[myxpykalix]

I can always count on getting good advice here. I will try this and report my progress. Thanks again guys...

[coolhammerman]

Friends:
It seems that you are making this way too hard. Just because you have a Bot doesn't mean it's always the right tool to do everything. If I were faced with this situation, I would:

1) Use a pencil to draw the edge right onto the work piece where I wanted the finished edge to be.
2) Band saw close to the line, but not actually remove the line.
3) Sand up to the line using either an oscillating drum sander, drum sanding attachment in a drill press, or tip of a portable belt sander.
4) finish up with hand work.

With such an irregular perimeter you will find it is very forgiving and doesn't have to be perfectly symmetrical. Turners make chair legs which are close, but not exactly the same shape. The human eye averages the shape (as long as they are reasonably close to the same) and we can't tell the difference.

Remember the old masters didn't have the luxury of a Bot. They did everything by hand and their work was often not all that perfect, still beautiful, but not perfect.

I would just break out some elbow grease and git-er-done!

Good luck.

[bcammack]

Jack,

Using a shank-mounted bearing bit and a masonite template is the first solution I thought of as well. The only other thing that comes to mind is using a pin in the router table near the bit and trimming it freehand.

[fleinbach]

Ron,

If we keep doing it the old way how will we justify all that money we spent on the Bot?

Anyway I have done exactly what you suggest several times since I've owned the shopbot mainly because I could do it manualy quicker then setting it back up in the bot. But if I have the time I prefer using the bot because I do get a more uniform outline. I have done lots of quality looking profiles by hand BS (Before Shopbot not the other meaning) but they require lots of patients and dexterity. Somewhere along the way I seem to have lost one of them so I let the machine do the work.

[myxpykalix]

Ron,
While you are correct that, that is probably the best non bot answer. Because of my horrible arthritis any repetitive movement (like hand sanding) makes my joints feel like they are on fire. So I take full advantage of that fact when justifying spending money on powertools.

I guess one of the reasons i want to make sure i get this right is that I want to impress my "peers" here.

[joe]

I'm with Ron on this process. A bandsaw would be the tool of choice here. I would then use shaping rasps to complete the contours. Those of us who started out with chisels and mallets enjoy, look forward to, using our honed techniques.

Like everyone here I enjoy using my CNC but, it's folly to use a router to do a job not it's not suited to do.

Jack, this looks like a fun project. Please post your results.

Joe
www.normansignco.com (http://www.normansignco.com)

[Brady Watson]

As with most boo-boos on the Bot, it's a good opportunity to learn from your mistakes. I think most of us have done something like this at one point in our Bot experience.

The thing to realize is that you NEVER pull a part off of the machine before checking to see if it cut all the way thru. If it didn't cut deep enough you can write another profile pass or just use the Nudge feature in SB3. Once you pull it off the machine it is difficult, but not impossible, to index the part back on the machine to finish out the cut. It's pain in the butt situations like this that will stop you in your tracks in the future...prompting you to check if the machine cut thru all the way or not.

-B

[myxpykalix]

Well Brady, once again you point out that i have yet to "snatch the pebble"...lol. One of my thoughts was that I could just turn it over and "surface" the waste off (see second pic above) taking the thickness down to where it removes the back/bottom of the material. But I like the thickness of the piece and additionally it acts as a support to the tenon in the seat not allowing the back to move in the mortise. I think my next project is a sign to hang on my wall to help me think it thru that says..."Now what would Brady do?" lol...thanks

[coolhammerman]

Jack:
Sorry to hear of your arthritis and its effects as you decide which path to pursue. That is why I used my own situation as the example. At 57, I'm strong and reasonable agile (arthritis free for now), but have way too much energy reserves stored at the belt line (read fat)


I purchased my Bot to aid me in and existing business and in the process discovered an interesting truth. I can and did all of the steps operations and techniques (except one) with other tools I already owned. The Bot just does them more easily, more accurately and is repeatable, but not necessarily faster. It also can't make the sharp inside corners due to the radius of the router bit. Still, it is worth using the Bot because it is much easier on me physically and eliminates several preparitory steps needed to do it the other way. A good parallel might be that the Bot is a multipurpose woodworking machine not unlike a ShopSmith is multipurpose machine so you get lots of capabilities rolled into one unit.

In my small manufacturing system the Bot replaced a table saw, a radial arm saw, a large band saw and a drill press. I eliminated templates, stacking 4 to 6 sheets of plywood (I used to cut smaller manageable rectangles out and stack them together so I could band saw multiple parts).

See www.wildandwoody.com (http://www.wildandwoody.com) to see what I make.

Jack, just as you will use other tools to complete your beautiful chairs (lathe, hollow chisel mortiser, drill press and various sanders), different tools do different tasks better than others.

Not to be long winded (too late?), I have discovered that very often I rushed to get something done and need to recut something or make some other adjustment. So, I:
1) Always use the C3 Prox switch command to establish a repeatable 0,0 point.
2) If I need an offset point I do it in whole numbers and write it down. (Example: Jog 2, 2,4. Zero 2) So I have a reliable repeatable reference point.
3) I normally cut whole sheets of 4x8 plywood. It is not practical to use a vacuum hold down system on BC material since I do so many one-off cuts and the material is rough and porous. I use screws. Those represent fixed points I can reattach If/when I have to. I build in the anchor points to the tool path so I don't inadvertently run into a screw and break a bit.
4) Since I'm not the perfect programmer and have a propensity toward hurry-up, (LOP Syndrome - lack of patience) I often stop the machine in mid cut to correct some programming error. That can result in losing my 0,0 depending on how I do it. Easily corrected because of the first two steps.
5) Because my material is not a consistent thickness (3/4" plywood is not .75" but everything from .69 to .73) I set my depth of cut to .70, put the dial calipers on my sheet and change the Z proportion to get the depth I need for that sheet.

Example:
Cut depth set at .700. Material is .720. I would set the Z proportion at 102.9% Before I ran those parts.

Sorry to ramble, but I don't write often. I use my Bot every day and wouldn't want to do without it, but it is not the best tool for every job I have discovered.

Respectfully,
Ron

PS: The one thing a Bot does better than any other tool I have so far...




. . V carve lettering.

[myxpykalix]

Ron,
You do some nice stuff on your site although it looks very painting labor intensive. I wouldn't have the patience to do that and i have no artistic painting ability.
One of the things i learned the hard way was to start out and C3 prox switch then write down that number where i set my 0,0. So you're preaching to the choir on that one brother!

Another thing I have encountered that hasn't caused a problem yet is when i'm cutting a thick piece of wood (2") and am hogging out as much as an inch at its deepest depth i have found that when it gets about 3/4 done it tends to want to curl up because of the excavation of lots of material. I have to then try to cinch it down.

[coolhammerman]

Jack:
I have two different product lines, one at http://www.wildandwoody.com and another at http://www.coolhammers.com. The high volume one is Wild and Woody, also far and away the hardest. I manufacture the signs to a complete "Raw" stage - i.e. ready for paint. My customer has a paint department luckily. This was an ongoing business when I purchased the Bot and this is why I bought it.

The other line is brand new (http://coolhammers.com) and my wife and I do all of the painting there and also do our own marketing. Mostly religious for now, but secular stuff is in the works. This painting is fun and relaxing for now. Kind of like paint by numbers for adults. What I enjoy most is the design work. Still lots of handwork, but due to my 5 years making the other signs, I'm as fast as lightning on this type of work. I average less than 3 minutes per sign for handwork. I did 14 signs last Sat in about 40 minutes. Still having fun with this line because it is new and fresh. This product came about as a result of having a Bot, getting pretty good at design and programing with the other line and our desire to donate something cool and different to our church. Since we are all byproducts of your experiences, I combined all of that to come up with these signs. Then we learned to paint in our "Folk Art Style" and viola! A new Marketable product.

Wishing you good luck and good health,
Ron

PS If you are interested in my woodworking background and credentials, go here: http://coolhammers.com/ron_brown_biography.htm

[myxpykalix]

I went to your site and read with interest. I saw a link for your dvd's and sent it on to the president of our woodworking club to see if they want to add it to our library. Keep up the good work.

[bill_moore]

Jack If you have not solved your problem I would like to present another option.
Put a smaller bearing on the bit pictured, drop the bit untill it will follow your contour. Then after that put a bottom mounted bearing in and ride it on your first cut. Depending on how much you want to remove it may take several passes.

[myxpykalix]

The problem i was having was the area to cut was taller than the bit. So i had to try to go over an area, raise bit go over same area. I'm looking for a taller bit. We are going to have a camp shopbot here locally with a bit mfg coming so i'm saving up to get a good assortment.

I have taken a jig saw and cut off much of the waste and so its more of cleanup at this point. Then i have to clean up the endgrain so its gonna be a while till i finish. thanks