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Brad Dorsey

Fitting Bass Bar With Graphite

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We have discussed fitting bass bars many times before here.  I bring it up again because a viol maker just told me his method that I had never heard of before:

After final scraping of the inside of the top he figures out where he wants the bar and marks it location with pencil marks.  Then he brushes on a swath of hot glue about two inches wide centered where the bar will go and glues on temporary bar locating studs.  He lets the glue dry overnight.  The next day he fits the bar.  He applies graphite from a soft pencil lead to the top to mark the bar in the same way that chalk is commonly used.  After the bar is fit he wipes off the glue and graphite with a damp paper towel and glues the bar.  The purpose of the initial glue application is to allow the graphite to be removed and prevent it from permanently darkening the inside of the top.

I'm tempted to try this graphite method the next time a fit a bar, because it seems that it could solve some frustrations that I commonly encounter:

1.  I think the graphite would give good coverage in a layer of uniform thickness.  My chalk appears to not spread in a uniformly thin layer on the top, and some places don't seem to take any chalk at all.

2.  I think the graphite would transfer readily to the bar and be very easily visible on the bar.  I'm not happy with the way my chalk does either of these.

3.  He says no graphite remains on the top because it's applied on top of the glue layer that is later washed away.  Traces of my chalk remain.

Lest you think I'm not using the right type of chalk, I'll add that I have used several different types, including brands that have been recommended on this forum, with the same results.

The only potential problem to this graphite method that I can think of is that washing off the graphite and glue could impair the fit of the bar by raising the top grain or even warping the top a little.  Otherwise, the graphite seems to offer several advantages over chalk.

What do the rest of you think about this?

I'd rather keep focused on the graphite here and not have everyone tell us their own bar fitting tips, because we've been through that before.  Just tell me what you think about the graphite.

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it sounds like a massive PITA and, as you say, I'd be concerned about the washing off process affecting the fit. I've never had any problems using chalk, but we can't really go there without contravening your "fitting tips embargo"...:P

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Brad, interesting.  The proof will be in the pudding.  I do quite a few BB's and I don't really trust the chalk in the final fitting either.  I finish with carbon paper (carefully!) and that last 5% I get a perfect fit.  If the graphite method works, there will be no staining on the top (would imagine that in the cleanoff, you could stain the top if not careful....?) and the fit will be perfect.  Only way is to try it.  It will either be clean and fit, or not.  We can theorize all day long (as we often do here)as to it not working.  Maybe a try of the staining issue would be to take a dustbin top and try it, sans the fitting.  I would say, if applying the glue, graphite it, then wiping it off works, it's worth a trying.  

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Don's method of applying a more colored marking material over a thin layer of tape sounds no less viable, and wouldn't have the downside of re-wetting and distorting the plate.

I have also used fluorescent chalk for fitting various things on occasion, which appeared like ordinary white chalk under regular light, but bright orange under a near-ultraviolet "party lamp".

________________________________________

Brad wrote:

" I'd rather keep focused on the graphite here and not have everyone tell us their own bar fitting tips, because we've been through that before.  Just tell me what you think about the graphite."

I will presume that refers to the graphite -over-glue combination. While I have never tried it,  I have enough experience with all sorts of things to anticipate a problem or two.

Apologies for not conforming to your response specifications. :)

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2 minutes ago, JohnCockburn said:

it sounds like a massive PITA and, as you say, I'd be concerned about the washing off process affecting the fit. I've never had any problems using chalk, but we can't really go there without contravening your "fitting tips embargo"...:P

Really? I would think the only extra work would be washing off the glue.  Doesn't sound like too much to me.  Maybe I haven't thought of something.  I'm only concerned about washing the gluey/graphite onto unprotected wood

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1 minute ago, David Burgess said:

Don's method of applying a more colored marking material over a thin layer of tape sounds no less viable, and wouldn't have the downside of re-wetting and distorting the plate.

 

I remember this, but the tape barrier makes me nervous about getting that final perfect fit.  I should really just walk away from the computer and try both before commenting..........

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It sounds  horrible  to  me.  Graphite is so dirty  and  fine grained - it would  be  all over the place. 

I hate the idea of having  to clean a violin before varnish. It should be spotless. So I wash my hands regularly, and smudging graphite about would  do my head in. 

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This is a valid point for making new instruments.  But all I do is regraduate old ones that are already varnished.  I don't have to worry about making a mess on the outside, but I'd rather not leave a mess on the inside.  This could be a deal breaker for me.

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1 hour ago, Jeff White said:

I remember this, but the tape barrier makes me nervous about getting that final perfect fit.  I should really just walk away from the computer and try both before commenting..........

What is your definition of "perfection" ?

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In principle a bass bar can be fitted  cleanly without any chalk or other 'helpers' especially on new instruments. 

However when a fitting helper is used: in comparison to chalk the use of graphite doesn't add anything to the fitting precision. The surface of spruce is by its nature so rough that chalk adheres well enough. (It seems to me that you must over sandpaper the interior, or not?) And removing the remains of graphite before glueing is just the most disgusting work I could imagine. :blink:

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I don’t see any reason to add steps to the process to get the same result. Also, I would be concerned about the washing, in terms of the graphite mess and in terms of the way it might affect the fit of the bar. Adding moisture to the wood opens a can of worms. 

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38 minutes ago, David Burgess said:

What is your definition of "perfection" ?

Fair enough.  I don't want to see any gaps at all. Like bridge feet to a top.  Overkill? I guess a bass bar could function just as well if not fit "that" cleanly to the top, but I have trouble imagining someone opening up my job and thinking that I can't fit a bb properly.  In my  upwards learning curve (hopefully), I frequently say to myself when making a judgement call.....Is that what it would look like if J.H. did it? (WWJH doB)).  At which time I get that wry smirk from him.  

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10 minutes ago, The Violin Beautiful said:

I don’t see any reason to add steps to the process to get the same result. Also, I would be concerned about the washing, in terms of the graphite mess and in terms of the way it might affect the fit of the bar. Adding moisture to the wood opens a can of worms. 

Hence my point of trying it.  Would take minutes of work (overall) to apply glue, dry, add graphite, clean, and see if a mess occurs.  Checking fit after washing is a different sort of possible waste of time (if it doesn't work).

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3 hours ago, David Burgess said:

Don's method of applying a more colored marking material over a thin layer of tape sounds no less viable, and wouldn't have the downside of re-wetting and distorting the plate.

3 hours ago, Jeff White said:

I remember this, but the tape barrier makes me nervous about getting that final perfect fit.  I should really just walk away from the computer and try both before commenting..........

The tape essentially gives a few thousandths of an inch spacing between the bar and the inside of the top, which is mostly parallel.  At the tips, you might get a few ten-thousandths extra due to the slope... so I guess my bars might have a "spring" of a few ten-thousandths of an inch.  Absolutely nothing to obsess about.

The only "downside" of the tape method is that some fibers of spruce can be pulled off if you have low-density spruce or strong tape, which is easily  solved by a very light casein/ammonia coating... which I would do anyway.  And use "delicate surface" tape.

I have used artist's charcoal sticks (is that what you mean by "graphite"?), which work OK... but my bass bars are processed and quite dark, so I use white chalk, which shows up better.  It's not as fine-grained and intense as I would prefer, but it works just fine.

 

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I find that  upside-down carbon paper works great.  Before gluing,  I clean off any black stuff that might have waxes etc in it.  (I use xylene which I know many are afraid to use.  Perhaps acetone would be fine.)

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19 hours ago, Jeff White said:

Fair enough.  I don't want to see any gaps at all. Like bridge feet to a top.  Overkill? I guess a bass bar could function just as well if not fit "that" cleanly to the top, but I have trouble imagining someone opening up my job and thinking that I can't fit a bb properly.  In my  upwards learning curve (hopefully), I frequently say to myself when making a judgement call.....Is that what it would look like if J.H. did it? (WWJH doB)).  At which time I get that wry smirk from him.  

I would talk of overkill only if it takes a hole day to fit a bar. If you can do your 'overkill' in a reasonable time frame you have mastered the bass bar fitting task. 

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Based on the OP’s description, this method requires at least two days set aside just to fit a bar. To me, that’s a lot of lost time.

My other concern is that there is an assumption that graphite lends greater accuracy to the fitting process. I don’t believe that to be true. I can imagine that it works as an aid to fitting, but the issue is more with the cleanup, the impact of the washing on fit, and the unnecessary loss of time. 

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Apologies if this has been mentioned and I missed it. . . 

I know that a lot of people don't know that when fitting bars the best way to see the chalk on the bar is to bring in a light right next to your eye as close as possible as if the light were coming from your eye, pointing the light and the bar down into the darkness under your bench, looking at the bar surface from a very low angle. The chalk catches this low light differently from the wood and it's not too hard to see.

I like David's idea of day-glow chalk and UV. Maybe we should commission a special batch of ochre-colored (wood color)  chalk with something that would glow in UV in it. I'd go in on a buy like that.

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2 hours ago, Bill Yacey said:

Using graphite sounds like a recipe for permanent dirty smudges and fingerprints on the plate.

 

18 hours ago, Michael Darnton said:

I know that a lot of people don't know that when fitting bars the best way to see the chalk on the bar is to bring in a light right next to your eye as close as possible as if the light were coming from your eye, pointing the light and the bar down into the darkness under your bench, looking at the bar surface from a very low angle. The chalk catches this low light differently from the wood and it's not too hard to see.

I fully agree,  white chalk work fine for me, you just have to learn to see it.

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On 12/30/2019 at 8:57 AM, Andreas Preuss said:

I would talk of overkill only if it takes a hole day to fit a bar. If you can do your 'overkill' in a reasonable time frame you have mastered the bass bar fitting task. 

Right, I'm looking for a solution to a problem that doesn't exist.  No problem in doing it in a reasonable amount of time, just always looking for a better way to skin a cat.   

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