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Stuff-Maker
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Discussion Starter · #1 ·
Hello,

I'm making small hardwood bobbins for knitters. This is a Photoshop illustration, but it demonstrates what I'm looking to do.



We built Matthias Wandel's 3D Router Pantograph which cuts the raw shape from 3/16" hardwood of various species. Shaping the contours at the edges has proven a lot more difficult.

I built a tumbler from a salvaged furnace blower unit, a couple of threaded rods, hockey pucks, bearings, a large tire inner tube, and a dry wall compound bucket. The mechanical aspects of the tumbler are working well, but I haven't found a medium that abrades the corners in the way I wanted to yet I've tried construction sand, play sand, Black Diamond blasting media, red garnet, crushed walnut shells, oyster shell, torn up sand paper, and small scraps of the hardwoods to which I glued sand with TiteBond woodworker's glue.

The blasting media, garnet, and sand all had some effect, although it was very slow, and in some species, the sap wood part of the grain wore faster, and a driftwood-like texture resulted. The walnut shells had virtually no effect. The oyster shell, and sand papers both show promise, as does the hardwood/sand, but TiteBond isn't the right glue, as it doesn't hold the sand for long.

We've also looked at router bits. We've tried a 3/32" straight bit, a 1/4" straight bit, a 3/16" radius round nose bit, a 3/8" radius round nose bit. I see on eBay listings for CNC toolpaths with contours like I want, and these seem to call for 1/8" / 3mm ball nosed bits.

We have our Pantograph set so that when I trace around the 2X master, it makes the right size objects. The master is made of 3/8" Baltic birch plywood, so as I rasped, filed, and sanded the contours of the edges, I could visually follow the receding plies to make it taper evenly.



I'm open to try anything. If you have an idea, I hope you'll suggest it. Thanks for reading.
 

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Old School
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That's quite a project for sanding. Most blasting media will wear away the softer parts of the grain. If you're using CNC an edge forming bit may come close. But, I'm guessing nothing can beat the personal touch by hand sanding. That sanding should be done with the grain direction. With that said, in doing numbers of these could be overwhelming. At the moment, I can't come up with a bulk method that would satisfy all aspects. Maybe after I have breakfast.:smile:









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I would imagine on a large scale it would be necessary to have a machinist make some custom tooling to sand in specific shapes like that. I would picture a bit almost like a router bit with a radius but instead of a cutting edge have abrasives adhered to it. It would still be a lot of labor. More than likely the best solution would be work on tooling sharp enough it could cut the shapes smooth enough sanding wasn't necessary.
 

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Stuff-Maker
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Discussion Starter · #4 ·
Thanks for your responses. Heh, when this was all still in my brain, and before I started actually making them, the sanding was not high on my concerns list. Yeah, a lot of labor could be involved. I do not have a CNC yet, but I'm headed in that direction just as quickly as I can get there. Our Router Pantograph used a Bosch Colt, and as I intend to construct my own CNC, it will be used there, too. Steve, you mention custom tooling.Before I go that route, and it is on my radar, I wonder if something like this already exists.



This wouldn't eliminate the need for sanding, but it might prepare the bobbins for tumbling, and then only a light hand sanding to follow. I'd like the little nib at the tip of this to cut both at the tip so I can plunge with it, and also along the shaft with either a single, or double flute. Any ideas where I might start, or do you think an abrasive might be better?
 

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I doubt if there is any equipment that already exists to sand the pieces. You might talk to a machinist and see if they can come up with an abrasive disc to do that. The biggest problem is the small diameter. An abrasive would build up heat and lose the grit sanding something that small. It's like a spindle sander. They make them oscillate so it doesn't stay in one place and build up heat.

On a afterthought I see embossed molding in the stores. I'm not sure how they are made but it looks to me like the design is pressed into the wood. If that is really how they are made perhaps your parts could first be pressed to get the design and then cut out.

 

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Stuff-Maker
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Discussion Starter · #6 ·
Steve, my son and I have been trying to source some kind of image, or other illustration to show to a machinist as a means of getting started in a discussion. We live in a town of about 30,000, and there are a number of machine shops here, and in Pittsburgh 45 minutes away, but I'm not even sure what to look for when searching for a machinist. Yes, these are small tools; 2.75" x 2.25" x 3/16". They are not easy to hold to hand sand, and once cut out, are fiddly to clamp down to the t-slots in the table that holds the router pantograph. I'd like to pursue your idea. Do you know of anyone who does the kind of machine work you recommend with whom I could speak?
 

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Steve, my son and I have been trying to source some kind of image, or other illustration to show to a machinist as a means of getting started in a discussion. We live in a town of about 30,000, and there are a number of machine shops here, and in Pittsburgh 45 minutes away, but I'm not even sure what to look for when searching for a machinist. Yes, these are small tools; 2.75" x 2.25" x 3/16". They are not easy to hold to hand sand, and once cut out, are fiddly to clamp down to the t-slots in the table that holds the router pantograph. I'd like to pursue your idea. Do you know of anyone who does the kind of machine work you recommend with whom I could speak?
I did have a guy here in the Dallas area but the last time I needed something made he was no longer in business. I don't know if the economy got him or he retired. I entered "Custom Machine Shop in the Pittsburgh area" in google and came up quite a few places.

It might be better to pursue having the router bits better sharpened. I used to work for a man that sent his router bits off to Germany to have them sharpened. It's been too long ago to know where he sent them. When they came back they were literally razor sharp. More often then not when you buy a new router bit it feels dull when you get it and often one blade is much shorter than the one on the opposing side so only one blade does the cutting. When the router bits were really sharp you could route across end grain and it was like it was finely sanded so perhaps you could eliminate the sanding altogether or perhaps just the face.

 

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Stuff-Maker
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Discussion Starter · #8 ·
I did have a guy here in the Dallas area but the last time I needed something made he was no longer in business. I don't know if the economy got him or he retired. I entered "Custom Machine Shop in the Pittsburgh area" in google and came up quite a few places.
There are quite a few places like that around here. If approaching someone is to lead to a successful outcome, I find preparation has a lot to do with it. Of course, we could just take a bunch of bobbins with us, show them a finished one, and ask them if they know a way to get from here to there.

It might be better to pursue having the router bits better sharpened. I used to work for a man that sent his router bits off to Germany to have them sharpened. It's been too long ago to know where he sent them. When they came back they were literally razor sharp. More often then not when you buy a new router bit it feels dull when you get it and often one blade is much shorter than the one on the opposing side so only one blade does the cutting. When the router bits were really sharp you could route across end grain and it was like it was finely sanded so perhaps you could eliminate the sanding altogether or perhaps just the face.
Craftsmen of all kinds appreciate the value of sharp tools. Chefs; their knives, seamstresses & tailors; their scissors, woodworkers; blades, and bits, and on and on. What they have that I lack, I think, is a tool that would do the job better if it were sharper. I have not found the tool I need for routing the edges on these yet, sharp or otherwise. There are people who specialize in custom router bits, but they aren't cheap.

I guess what I was asking, though, is to know a little more about your thinking when you mention abrasive discs, and machine shops. That wouldn't be too hard to do if I had a better idea of your thinking.
 

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What I had in mind for sanding I'm having more and more concerns that it wouldn't work good for you. It would work however I think you would have difficulty keeping the abrasive on it because of the small diameter. I think it would get hot quick and the abrasives would come off. Perhaps a machinist can come up with something better.

Anyway this is kind of what I was thinking for sanding. It would be shaped like a router bit but solid all around and ran on something with a slower rpm like a drill press.
 

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Stuff-Maker
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Discussion Starter · #11 ·
That's a great idea! I'm thinking something like that with rasp teeth might do very well for quick removal of a lot of material. It won't produce a finished surface, but it's a big step closer.

What I had in mind for sanding I'm having more and more concerns that it wouldn't work good for you. It would work however I think you would have difficulty keeping the abrasive on it because of the small diameter. I think it would get hot quick and the abrasives would come off. Perhaps a machinist can come up with something better.

Anyway this is kind of what I was thinking for sanding. It would be shaped like a router bit but solid all around and ran on something with a slower rpm like a drill press.
 

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Stuff-Maker
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Discussion Starter · #12 ·
Those are closer to what I was picturing than I've been able to find. That tool company is new to me, too. The tips on the smallest of them is still 1/4", though, and that's too wide to fit in the little slot at the top. The slot is 3/32". Thank you, though, for the tip; I'm going to have fun in that catalog.

 
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