Philosofy
407 posts
Jan 15, 2012
4:22 PM
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I've always admired the brass combs made by people. Even though I never held one, I wanted to have a harp with the heft of brass, so my harp would feel less like a toy.
So, for Christmas, I asked for a brass bar, 1/4" thick, 4 feet long. Enough for about 12 combs. I had an idea percolating in my brain for a couple years now on how to make a comb on my drill press, using a variation on a pin router.. On my first attempt, I used a Dremel bit, but that flexed a little much. So I bought some end mill bits online.The result was unacceptable. the drill press table moved a very small amount, but enough to screw up my results.
So, I moved to the table saw, and a variation on a box joint jig. I was sooo close. But I found that if the dado blade or tooth spacing was off by less than 1/128" of an inch, the comb wouldn't fit the reed plate.
Hats off to you guys who can do it. I'm pretty good, but this may have whipped me. My next try is the router table, but I'll have to get a new router collate and different size end mill bit.
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Philosofy
408 posts
Jan 15, 2012
5:10 PM
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That's what I'm finding out. I see the one from Harbor Freight is crap. Any recommendations? What size do I need?
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STME58
62 posts
Jan 16, 2012
12:15 AM
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Philosofy,
Thanks for posting your experience. Things are seldom as easy as they seem, and it helps to learn from others experiences. I have been reverse engineering my Golden Melody and hope to make a brass comb. Most of the dimensions seem to be on whole or half millimeters so I think I am getting them right. 1/128" is about .2mm so, based on your expoerience, I need to be better than that.
If you have time and there is a community college nearby, you might enroll in a machine shop class and make the comb as your project. You will learn how to do things right and safely and will know much more about what kind of mill you want and if you still want one after you find out how much a good one costs.
I am fortunate to have access to a CNC mill where I work. It would be well worth it to buy a brass comb if that is all I wanted but I have learned quite a bit about the harminica just taking it apart and measureing it. I am sure I will learn more when I assemble the new comb and it dosen't work.
Last Edited by on Jan 16, 2012 12:17 AM
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Philosofy
409 posts
Jan 16, 2012
5:59 AM
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You might not need to be better than 0.2 mm. The method I tried on my table saw made one slot using the previous slot as the starting point. My tines ended up being 0.2 mm thicker than they should have been, so you get 9 tines X 0.2 mm = 1.8 mm. The width of the total comb slots were 1.8 mm wider than they should have been, which didn't line up with the base of the reeds.
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Greg Heumann
1428 posts
Jan 16, 2012
8:18 AM
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You can buy manual and CNC milling machines from all over. One of the best suppliers of imported machines is Grizzly.com - they have a wide range, good support, etc. Many CNC milling machines can only be operated by the computer. You should NOT start with one of those as the learning curve is very high. You should start with a machine where you can move the levers and handles yourself to get "the feel" until you learn about speeds, feeds, materials, when/why to use a 2-flute endmill vs a 3 flute endmill vs a 4-flute, etc.
Drill presses are not meant to handle side loads on the spindle. Milling machines are. With a little practice you can hold tolerances to .001" or less, even with one of the cheaper Chinese imports.
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/Greg
Last Edited by on Jan 16, 2012 8:19 AM
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oldwailer
1825 posts
Jan 16, 2012
8:21 AM
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@Philosophy--I have a pretty decent mill, and I find metal combs much more challenging than wood or plexiglass. For the softer ones, I just carefully cut the slots with an 11/64" end mill--one single pass for each slot. With metal, I need to increase the depth on each pass--as many as 6 passes per slot are needed to get it right--this increases the possibility of screwing it up 6x. What I mean to say here is that you might find it to be instructive to make a few wood or plexi combs first before tackling the metal ones.
When I had a Harbor Freight mill (that I started with), I was able to cut good combs out of plexi or wood--but it took a while to get the hang of getting the mill adjusted properly--you have to learn to adjust the gibs a lot to keep the side movement down to a very close tolerance. I never tried a metal comb with that mill.
CNC would be as great way to do it--but then you'd also need the software--and I don't want to have to start writing software for the damn thing--I'm already too far invested in this diabolical habit of making harps. . .
Greg was posting at the same time--I hadn't even realized that a CNC could just be hand operated--without software--gotta look into that possibility--I have a set of plans for building a CNC--that could be adapted with cranks instead of step motors--hmmm. . .
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Oldwailer's Web Site
Always be yourself--unless you suck. . .
-Joss Whedon
Last Edited by on Jan 16, 2012 8:26 AM
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billy_shines
24 posts
Jan 16, 2012
9:48 AM
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i used to cut small 2" brass letters on a delta scroll saw. if i di a brass comb now id just clamp it use a hand held hack saw and follow up with mill files.
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lor
73 posts
Jan 16, 2012
10:31 PM
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@oldwailer
You don't have to write software for the CNC, only instructions based on measurements of the object, which will be interpreted by the software in the CNC machine.
If you're contemplating making a CNC machine, you'd have to write software that will handle anybody's instructions - a huge undertaking if you're not already a computer/hardware interface programmer.
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STME58
63 posts
Jan 16, 2012
10:47 PM
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The shop where I work retrofited manual mills with computer controlled motors. THe controller came with the software. These can still be used manually. WHen under CNC control the moving handwheels become one more thing to watch out for in an already dangerous environment. I hope to be able to get the CAD model I made of a Golden Melody Comb into brass using one of these.
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