dougharps
2336 posts
Dec 16, 2022
8:31 AM
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With winter approaching I expect to have time for doing some harmonica performance improvements. When mounting reed plates on custom or self-sanded flat combs, the process of flat sanding draw plates is often proposed.
I understand that when using self threading screws into the draw plate there is metal raised up around the hole that can affect the comb/read plate seal and cause leakage.
Why can't we touch a rotary tool with a mild bit specifically to level only the raised metal around each hole, as opposed to sanding the entire surface of the draw plate?
If it is the troublesome mound where the self threading screw enters the plate that causes the problem, why sand the entire plate?
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Doug S.
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Gnarly
Alternatetuning
3093 posts
Dec 16, 2022
8:49 AM
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I don’t flat sand draw plates much ( mostly use my slab o’ granite for chromatic work), but as I understand it, the intended result is to make the draw plate flatter and thus more airtight.
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nacoran
10414 posts
Dec 16, 2022
1:08 PM
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I think it's not just the screws, but the rivets. You probably could sand every rivet and screw, but flat sanding is a much less labor intensive way to do that, since you can get the whole side all at once.
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Nate
Facebook
Thread Organizer (A list of all sorts of useful threads)
First Post- May 8, 2009
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SuperBee
7083 posts
Dec 16, 2022
1:33 PM
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Agree, it’s not the screws at issue usually. There is generally enough space in the clearance hole. But when you are replacing say a marine band comb with an aftermarket comb there usually isn’t any relief for the rivets. The stock comb has a relief stamped in at the ends of the slots.
With a sp20 type harp, the stock comb also has plenty of space but aftermarket combs are usually solid and create the same problem
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Gnarly
Alternatetuning
3094 posts
Dec 16, 2022
9:02 PM
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No rivets on Suzuki plates, they still benefit from flat sanding.
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SuperBee
7084 posts
Dec 17, 2022
1:05 PM
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Maybe, but that’s a different issue.
You can still put those plates together with an aftermarket comb without flat sanding and the harp will be as good as it was before.
With a Hohner wood comb Harp, if you replace the comb with a solid aftermarket comb or flat sand the original comb, you need sand the draw plate to eliminate the rivet bumps in order to assemble the harp.
Same with a special 20 when replacing the original comb with a solid comb, because you lose the relief space.
In other cases, sanding the draw plate is optional and the degree to which it helps depends on how flat it was to start with. I’ve done a lot, used to do it as a matter of course when setting up a harp but the improvement is incremental, ie other things make a much bigger difference.
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dougharps
2337 posts
Dec 17, 2022
1:06 PM
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Thanks for the quick responses to my question!
I will have to look closely at the Suzuki harps I am considering improving. I am not seeking a level of perfection to build overbend harps, just reliable consistency in regular play with occasional 6OBs. I already routinely adjust the gaps and reset plates on all my new harps unless they seem perfect OOTB. (Maybe two or three out of all my harps in all brands)
I intend to check all my Manjis and Olives and start by working on any that seem uncooperative or reluctant to respond sufficiently to my technique.
Making certain that stock Manji or Olive combs are flat with light sanding using fine grit paper on a granite slab using a Manji specific sanding block I purchased from a forum member seems a lot easier than also sanding the brass draw plates on Manji or Olive harps.
I will have to check each less than satisfactory harp for raised metal at the screw holes or warped plates and address any obvious problems before reassembly. As Gnarly noted, the reeds are welded, so no rivet issues.
If any harps seem leaky after sanding the comb, eliminating screw "volcanoes" and carefully resetting the plates, I may have to try sanding the draw plates on those problem harps.
I would expect the rolled brass plates to be sufficiently flat when pulled into place by the machine screws to minimize leaking on a flat comb. If the plates seem too curved, I will straighten them. Sanding the metal to get a plate flat shouldn't be necessary, but if I am wrong in some instances, I will do what is needed to improve those harps including sanding draw plates.
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Doug S.
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florida-trader
1576 posts
Dec 17, 2022
2:41 PM
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Here are a few thoughts/comments regarding flat sanding draw plates. I will cut to the chase first because when all is said and done, this might be the most pertinent piece of information. It takes less than a minute to flat sand a draw plate and it is very simple to do. I have never heard anyone claim that flat sanding the draw plate will do harm to a harmonica or decrease the level of performance. So, even if the improvement is somewhat debatable, if it only takes a minute, why not do it?
OK – with that said, here is some minutia for you to sort through.
First, if you are going to flat sand draw plates, it is important that you have a surface that is actually flat. A lot of people mention using glass or a piece of Corian or a cutting board from the Dollar Store. None of those surfaces are flat, so flat sanding on one of those surfaces is kinda pointless. Get yourself a Granite Surface Plate. It is a two-inch-thick piece of granite that is 9 inches by 12 inches and is guaranteed accurate (flat) up to 1/10,000 of an inch. They cost about $40. You can find them at Woodcraft in the U.S. of probably at any store that caters to woodworkers. I use 320 or 400 grit sandpaper and I always wet sand.
There are indeed little volcanos that emerge from screw holes on reed plates. These can cause a leak, but I do not believe that they are the main issue. Yes, there can be high spots where the reed rivets protrude through the back of the plate. But that is not the biggest reason. The reason I flat sand the draw plates is because they are almost always warped. In most cases, it is not easily visible to the naked eye, but all it takes is a few seconds of sanding on a flat surface and you will instantly be able to see high and low spots on the reed plates – even Suzuki plates with spot welded reeds. A draw plate that is flat sanded married to a flat comb makes for an airtight seal and it most definitely improves the responsiveness of a harmonica. If a reed plate happened to already be flat (rare), well, I didn’t do it any harm by making it flatter. In the overwhelming majority of cases, the reed plate is not flat. Some minor warping might not make too much difference, but I often see reed plates that are bowed and/or warps to the extent that the harp has major leaks which are robbing the harp of responsiveness. It is hard to tell until you hit it with the sandpaper, and going back to my original point, if it only takes a minute, why not do it? You have nothing to lose and everything to gain.
Custom work is about paying attention to details. It is not like there are one or two things that you can do to a harp to make it play up to its potential. It is about a hundred tiny little details that collectively result in dramatic improvement. Flat sanding the draw plate is one of them.
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Tom Halchak
Blue Moon Harmonicas
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Sloppy1
60 posts
Dec 17, 2022
6:16 PM
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Tom,How do you hold the plate when you sand it so it puts even pressure when sanding? Seeing if you have any tricks.
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florida-trader
1577 posts
Dec 18, 2022
8:26 AM
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Here's a great trick for you. Get yourself a Suzuki HarpMaster comb. It has a recessed cavity for the reed plates - like a Special 20 comb. All of the Suzuki and Hohner reed plates fit into the cavity. You can partially sand off the lip on one side of the comb so that there is still a small lip to hold the reed plates in place but not so big as to prevent the reed plate from coming into contact with the sandpaper.
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Tom Halchak
Blue Moon Harmonicas
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dougharps
2338 posts
Dec 18, 2022
9:47 AM
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Tom, thanks for your explanation.
I previously purchased (but never used) a Manji specific tool I bought from forum member dchurch on his dBomb Shop website.
dBomb Harp Plane
The tool is called the Harp Plane and I bought the version made to fit Manji and Olive combs. To my surprise I learned today when looking it up that in addition to sanding combs it is also made to hold reed plates for sanding.
I had envisioned a long slow process sanding brass and was avoiding it, but following your post indicating that it was a short process, I plan to do it correctly and in addition to the combs I will sand the draw reed plate of each Manji/Olive I work on.
Thanks to all!
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Doug S.
Last Edited by dougharps on Dec 18, 2022 9:48 AM
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