BanjoDaddy2000 - Posted - 12/18/2024:  12:21:14

Hi All,

I’m not much of a shimmer - I think it’s a temporary fix until a neck can be re-fit - but I’d like to try it to see if I can lower my way-too-high action until I can get it fixed by a professional.

My question is: what is the best placement for a shim in order to do this?

Would it be the area of the top circle in the photo below or the bottom circle?

If it’s the bottom circle, would it be ideal to drill a hole in the shim that the coordinator rod could go through?

Thanks for any help or advice!

— Jeff

 

pasdimo - Posted - 12/18/2024:  12:28:44

I often used shims to lower the action and it works fine, if they are not too thick, as a credit card for example. I always put them against the top circle. Maybe some people do differently.

BobbyE - Posted - 12/18/2024:  12:30:24

Upper circle to draw the neck down.

Bobby

KCJones - Posted - 12/18/2024:  12:33:17

Is the upper circle around the tension hoop/ flesh hoop? Is that a good place to shim against?

Owen - Posted - 12/18/2024:  12:36:06

I've never shimmed a banjo.  My efforts at cobbling/repairing stuff says that a shim at the top would lower action; a shim down below the flange would raise the action and a shim at your bottom circle would create a teeter-totter [depending on the precise location of the lag bolt???].  I trust that guys that have shimmed a banjo or three will provide further insights.

Edit: I see I'm too slow on the draw. 

Edited by - Owen on 12/18/2024 12:37:09

lightgauge - Posted - 12/18/2024:  12:48:15

Shim at the lower circle and yes to drill a hole for the lag. Shimming at the top circle will hold the neck away from solid contact at the ring where it is designed to sit. If you cannot remove the neck, slide them in each side against the lag.

banjukebox - Posted - 12/18/2024:  13:07:14

Definitely the bottom circle for the reasons lightgauge
mentioned. There should actually be a small gap between the neck and the tension hoop at the upper circle.

heavy5 - Posted - 12/18/2024:  14:41:38

Shimmed many , many banjos w/ brass shim stock , usually starting w/ no thicker .010 shim stock . If u slot the hole on the bottom end of the shim for the upper lag , u don't have to remove the neck but the strings need to be fastened to the fingerboard & by temporarily unfastening the tail piece . I Velcro down the strings to the FB first then remove & set aside the TP w/ strings attached & Velcroed to it just long enough to slide in the shim over the upper lag downward after loosening the con rods so the neck can be slid rearward . May sound complex but it's not . .010 shim stock after drilling the hole can be shaped & slotted w/ scissors . Shimming in this fashion usually takes about 30 min including making the shim .

BanjoDaddy2000 - Posted - 12/18/2024:  15:02:38

Really appreciate all the responses. Thank you!

zz4350 - Posted - 12/18/2024:  15:06:10

quote:

---

Originally posted by heavy5

Shimmed many , many banjos w/ brass shim stock , usually starting w/ no thicker .010 shim stock . If u slot the hole on the bottom end of the shim for the upper lag , u don't have to remove the neck but the strings need to be fastened to the fingerboard & by temporarily unfastening the tail piece . I Velcro down the strings to the FB first then remove & set aside the TP w/ strings attached & Velcroed to it just long enough to slide in the shim over the upper lag downward after loosening the con rods so the neck can be slid rearward . May sound complex but it's not . .010 shim stock after drilling the hole can be shaped & slotted w/ scissors . Shimming in this fashion usually takes about 30 min including making the shim .

 

---

Good advice.  Can pickup some K&E brass shim stock at a local hardware store. I use scissors to cut that .010shick stock or small tin snips if using .015 or .020 thick stock. Cut it so it doesn't show beyond the enges of theneck shape.  It allows for not hitting the tension hop sso the head can be tightened as needed. If your head it tightened to 89-90 on a drum dial gage and your action is still too high shorten the bridge a bit (assuming you are staring with at least a 5/8 bridge.

I've used this on at least 20 banjos over the course of the last ten years without any issues.  If the shim gets thicker than say .025 and bridge becomes shorter than .600 inches then a neck refit might be in order.

heavy5 - Posted - 12/19/2024:  02:56:21

Another good reason for shimming verses using the con rods is u are not putting your rim out of round w/ the rods putting unequal pressure against the ring as the rods should both be at neutral for the best sound . Also , I always make sure the upper con rod washer is not clamping against the ring even if it needs grinding to reduce one side of it .

Pick-A-Lick - Posted - 12/19/2024:  05:48:52

Shim the area in the bottom circle to maintain a space between neck and tone ring.

I have shimmed a couple of banjos using heavy weight rigid black card-stock similar to the paper used for a standard two pocket folder cover. I figure that banjo necks are made of wood and so is paper so the materials are compatible, not to mention that it only takes a couple of thicknesses to make a big difference. It’s very fast and easy to get the correct neck angle by adding or removing a thickness of the paper. Set the banjo on its tailpiece end with neck straight up. Loosen the strings and the neck bolts a bit and slide a small layer (or two) of paper in from each side until it touches the neck bolt. Snug up the neck bolts and check your action. Add or subtract a layer of paper as needed. Any paper that protrudes can be marked with a pencil, removed and trimmed, then reinserted. 

FWIW the paper shim does not affect the sonic qualities of the banjo. The neck bolts and bottom of the neck are still solidly attached to the banjos rim.

Edited by - Pick-A-Lick on 12/19/2024 06:02:39

lightgauge - Posted - 12/19/2024:  06:41:07

We all have different experiences and I have never used paper to shim, so I can't comment on it working. In my simple mind, neither sound or vibration are transmitted by paper, so how does it not dampen the neck to pot connection? We don't even want glue in a banjo that stays soft.

Oldtwanger - Posted - 12/19/2024:  06:44:42

For many years I have used the ubiquitous flat clear plastic packaging material for shim stock. It is readily available and comes in several different thicknesses. I cut suitable sheets, measure the thickness with a dial caliper, mark that thickness on each sheet and store them for future use. It cuts easily with scissors, is invisible, and it is hard providing excellent contact and vibration transfer - better than wood veneer. Always the lower locations to maintain the gap at the tension ring.

Shim stock

 

Old Hickory - Posted - 12/19/2024:  06:58:53

quote:

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Originally posted by KCJones

Is the upper circle around the tension hoop/ flesh hoop? 

---

Yes.

 Is that a good place to shim against?

---

No.

Edited by - Old Hickory on 12/19/2024 06:59:12

Old Hickory - Posted - 12/19/2024:  07:15:41

quote:

---

Originally posted by BanjoDaddy2000

If it’s the bottom circle, would it be ideal to drill a hole in the shim that the coordinator rod could go through?

---

Yes, it's the bottom circle. (As shown in the photo)

Yes, you drill a hole, but it's for the hanger bolt.

Cut the shim to the shape of the face of the heel at that point.

I have made shims from the wood fiber veneer that now-defunct LMI used to sell. And also from maple veneer cards that I bought on Etsy. I use a dab of glue stick to hold it in place. It's not permanent like other glue, so the  shim peels off if I want to remove it. Which I've done when experimenting with different rims that didn't produce the same action on the same neck.

The other shim materials recommended here are all good. Old credit cards are good when you need a thicker shim.

heavy5 - Posted - 12/19/2024:  07:25:15

I'm cornfused here ?

Lets not talk in "circles " but lag bolts .

If u shim around the upper lag , you are reducing string height

Around the lower lag u are raising string height

Right ?

Frank , the pic of your shim is just like what I do except the slot is at the bottom to slide in from the top .

Edited by - heavy5 on 12/19/2024 07:32:22

lightgauge - Posted - 12/19/2024:  07:52:32

Right

lazyarcher - Posted - 12/19/2024:  08:38:05

Ive always used maple veneer for shims. It can be sanded to exact thickness or stacked if needed. Def use the bottom location so the stretcher band can move when the head is adjusted.

latigo1 - Posted - 12/19/2024:  08:42:20

You would not shim at the top circle. There should be no contact between the neck and the tension hoop.

Old Hickory - Posted - 12/19/2024:  10:01:12

quote:

---

Originally posted by heavy5

Lets not talk in "circles " but lag bolts .

If u shim around the upper lag , you are reducing string height

Around the lower lag u are raising string height

Right ?

---

Right.

But the reason for talking in circles is that the circled locations in Jeff's photo were at and above the upper lag, both for lowering action. His "lower" circle did not refer to the lower lag, which may have caused confusion for some. His upper circle indicated the tension hoop, which is not a good place to shim.

I'd like to add that in some instances -- but not this one as shown in the photo -- shimming behind the tone ring skirt can also tilt the neck back and lower action. This is only the case with a very loose fitting ring that be pushed back so the skirt is set back from the wood band between flange and tone ring. I have one banjo like. I shimmed with two thin strips of wood veneer on the rim on either side of the hole for the upper bolt. This pushed the skirt flush with the wood band and lowered the action a little. Photos attached. I may have done this with another banjo. I forget.

Jeff's banjo should not be shimmed behind the tone ring because the skirt is already flush with the exposed wood band of the rim.

Shims behind tone ring

Heel fit after ring shimming-1

Bruce Berry Banjos - Posted - 12/19/2024:  13:23:56

I know the experts have spoken and reinforced each other's opinions. But I'll say shimming is never a good idea for a banjo.
It's kind of like building up the brake pedal in your car so you can push the pedal further.
It's a *fix...
But a "way too high action" is an indicator of a bigger problem than setup.
Your banjo wasn't designed to be that way, and it shouldn't need shims.
I personally would not waste a set of strings on a setup which needed shims.
Just my $0.02

lightgauge - Posted - 12/19/2024:  14:14:01

On a new neck or build, I agree. On a used neck, with not enough wood beyond the last fret, it beats throwing a neck away. Sometimes, it is just to try a neck to see how it sounds and feels.
Clearly, some of us tinker too much!

Old Hickory - Posted - 12/19/2024:  16:03:28

What Bobby said. Necks that are swapped won't always work. And maybe you don't want to permanently alter the neck in case you ever use it in yet another banjo.

I have a parts banjo made with a 70s Gibson neck that a previous owner modified to work with 1-piece flange by gluing an approximate quarter-inch extension onto the lower lag area of the heel. Sized it produce good action with the 3-ply rim he used. So far, so good.

In my further modifications, I acquired a 1999 RB-250 rim. This rim was turned for a different size flange than the unknown rim in the banjo when it came to me. So the action with co-rods neutral was higher than I like. I forget how high. I shimmed the top lag area with maple veneer about .025 thick. Affixed with a dab of glue stick as I said above.

So my question would be: What is the significant structural difference between gluing on an extension of the upper lag (my shim) or carving away a bit of the lower lag area? Permance is all I see.  And if chose instead to affix my maple shim with wood glue, that would be as permanent a refitting of the neck as carving the lowe lag or extending it the way the previous owner did.

One thing about this approach is it doesn't remove and reinstall the hanger bolts to keep them at the correct angle. Instead, it lets the co-rods slightly bend them. I'm fine with that. I think that's preferable to deforming the rim with the co-rods.

heavy5 - Posted - 12/20/2024:  06:59:15

Ken , IMO , your fix is fine . If it plays well , sounds good , what's wrong w/ it ---- nothing .
One of the down sides of posting here is some people tend to nit pick things apart when there is no need .
But that's how folks are .
It's still an interesting good site requiring sometimes reading between the lines .

Old Hickory - Posted - 12/20/2024:  09:48:29

quote:

---

Originally posted by heavy5

Ken , IMO , your fix is fine . If it plays well , sounds good , what's wrong w/ it ---- nothing .

One of the down sides of posting here is some people tend to nit pick things apart when there is no need .

---

One of my good Hangout and real-world friends is a builder who not only believes in shimming (I think his preference was aluminum flashing) but who also did the unorthodox action of shaving the rim at the lower lag area when the desired change was lowering action. If that neck and rim are meant to be together, why not?

I also have done the baking soda + super glue trick to "temporarily" adjust the slots in a couple of nuts until I could get around to replacing them. Like my shims, these temporary fixes have become permanent. The same banjo with shims behind the tone ring was my first with with baking soda super glue nut slots: Early 2015, in time for the Joe Val festival.

J.Albert - Posted - 12/20/2024:  10:51:27

How high is the action?

Instead of a shim, have you considered a slightly lower bridge?

BanjoDaddy2000 - Posted - 12/20/2024:  11:31:56

Hi John,

That’s a good question. I have two banjos that have 5/8” bridges on them that I just can’t quite get the action I’m looking for on without cranking the truss rod or messing with the coordinator rod nut — both of which I don’t like doing at all.

I also really prefer an 11/16 bridge for the bit of extra room it gives my right hand for picking closer to the neck.

I’m not sure if I’d really want to use a shorter bridge than 5/8”.

Thanks!

RDP - Posted - 01/02/2025:  22:05:14

Try a different bridge or adjustment of coordinating rods slightly.