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StewMac 1933 Pre-war OM-28, Assembly Instructions Manual

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Binding the back: glue the thin ivoroid/black purfling first 
(ivoroid side in, black faces out) followed by the thick ivoroid 
binding . The binding joints at the neck block and tailblock 
must be trimmed for a close fit (pictured) . Bind-ALL is a 
solvent based glue, so it will melt the joints together . Allow 
6-8 hours drying time before removing the tape .

It’s best to wait at least two days before scraping the bindings 
flush to the wood, because the plastic will shrink slightly as 
the glue solvent evaporates . Use a scraper blade to smooth 
the bindings flush to the guitar’s sides, back and top . Scrape 
in the direction of the wood grain, and avoid digging into 
the wood . Practice on scrap if possible .

Opening the dovetail joint 

Now you can remove the side wood covering the neck joint 
opening in the neck block . With a sharp stiff knife or a saw, 
score through the sides until the waste wood can be snapped 
off up to the scored line (pictured) . A Dremel can also be 
used to remove this wood as shown . Follow with a sharp 
chisel and a file to smooth the sides flush to the inner walls 
of the dovetail (pictured) . 

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Summary of Contents for 1933 Pre-war OM-28

Page 1: ...1933 Pre war OM 28 Acoustic Guitar Kit WRM3H2 Assembly Instructions stewmac com tools ideas for guitarmaking StewMac ...

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Page 3: ... Installing the fretboard side dots 28 Installing the frets 28 Installing the fretboard 29 Neck shaping and fitting Shaping the neck 30 Installing the nut 30 Fitting the heel cap 31 Understanding the neck joint 31 The neck heel sets the neck angle 32 Fitting the neck to the body 32 Neck adjustment side to side 33 Neck adjustment tilt the neck back 33 Neck adjustment tilt the neck up 34 Tightening ...

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Page 5: ...e the greatest acoustic guitars ever built However theoriginalsareVERYexpensive andVERYhardto find Those two facts alone make these guitars inaccessible to most musicians However while you might not be able to BUY one you can BUILD one or at least a very accurate replica We ve meticu lously reproduced an original pre war 1933 OM 28 down to the smallest detail Not only does the StewMac Icon Guitar ...

Page 6: ...and rubber balloon or newspaper for soundhole The following tools and supplies are recommended to as semble your kit Though all of these tools aren t necessary to build your kit they make many assembly steps easier and more professional Where applicable item numbers for ordering from StewMac are included For binding installation you have a couple of different options to choose from depending on th...

Page 7: ... Herringbone purfling 2 19 Purfling strips 2 20 Binding 4 21 Bridge pins 6 and endpin 22 Strap button 23 White side dot material 24 Bone saddle 25 Bone nut 26 Rosewood peghead overlay veneer 27 Maple bridge plate stock 28 End trim heel cap 29 Reinforcing ribbon 30 Tail block strip 31 Cheesecloth 32 Kerfed lining 8 33 Cardboard body form 2 34 Building an Acoustic Guitar Kit DVD 35 Blueprint 36 Brac...

Page 8: ... neck block are flush where they meet the sides but the 5 side will be higher than the sides as it tapers up toward the interior of the guitar The side of the neck block that touches the guitar sides is curved A clamping caul with matching curvature illus trated should be prepared from scrap wood and placed against the outer side seam The same caul will fit both the neck block and tailblock areas ...

Page 9: ...for supporting the guitar sides MakeaU shapedwaistclampfrom3 4 thickplywood using the waist clamp measurements illustrated The purpose of the waist clamp is to hold the guitar s waist tight to the inner cardboard mold maintaining a constant shape until the back is glued on Use a file to round the two inner edges of the waist clamp to remove edges and protect the guitar sides To start out install t...

Page 10: ...re square to the plywood surface If either end is slightly out of square use a thin ta pered wedge pressed between the cardboard inner body mold and either the neck block or tailblock as needed to force the blocks and sides into square pictured Having the sides properly squared up at this stage is important The blueprint included with your kit illustrates the positions of vintage style cloth side ...

Page 11: ...ock and the front shoulder area first Work around the sides to the tailblock moving the pivot point frequently until the sandpaper beginsgrazingthewhitepencilmarksonthetopedgeofthe sides It s easy to oversand the sides and the kerfed linings leaving the neck block or tailblock higher than the sides and causing a hump in that area later Keep this in mind and give the blocks a little extra sanding W...

Page 12: ...abletheremoval of the straightened ends on each ring left from the bend ing process Note the outer rings will be hidden but the smallest inner ring will be exposed Practice the trimming on the hidden ones first you want to get the exposed one perfect A few extra minutes of careful work here will make a big difference in the appearance of the final instrument Glue the purflings in place with Bind A...

Page 13: ... the braces lay the pattern on the soundboard transfer the hole positions in pencil and connect the dots on the soundboard when the pattern is lifted away The pattern MUST be correctly centered along the soundboard s center seam with the soundhole properly located Note that the soundboard and the back have been trimmed to allow about 1 8 overhang all around This offers a little freedom when assemb...

Page 14: ... tuck under Reclamp the X braces onto the soundboard and workboard Check the fit of the tone bars in the notches Disassemble apply Titebond to the braces and tone bars reclamp and let the glue dry overnight This work can be done in stages depending upon the number of available clamps Use two flat clamping cauls for each pair of tone bars with the soundboard resting on your workboard to keep it fla...

Page 15: ...ld not contact the braces This surface must be relieved to contact the maple bridge plate Shoulder brace caul 1 3 4 3 4 7 1 2 2 1 1 4 2 5 8 Bridge clamping caul These surfaces must contact the soundboard the notches should not contact the braces This surface must be relieved to contact the maple bridge plate Shoulder brace caul 1 3 4 3 4 7 1 2 2 1 1 4 2 5 8 Bridge clamping caul These surfaces must...

Page 16: ...tured Follow the pre machined taper of the braces as you chisel Fitting the soundboard to the sides To find the guitar s accurate length between neck and tailblocks first measure 4 from the top edge of the sound hole towards the neck block illustrated Make a pencil markonthecenterline ontheundersideofthesoundboard Measure 19 1 4 from this mark to the tailblock end and make a mark This is the body ...

Page 17: ...rdandtracethebracepositions onto the kerfed linings with a straightedge using the marks as reference points For the X braces be sure to hold a long straightedge between the reference points at the proper angle shown in the blueprint The positions of the tone bars shouldalsobemarkedifyouchoosetonotchthem Thetone bars don t notch in as deep as the other braces and only a slight filing will be needed...

Page 18: ...ymore The body won t rock on the waist clamp nor will it lose shape from the weight of the clamps or the clamping process PRACTICE gluing the top in place by dry clamping it in the order of the steps numbered below After doing a dry run for practice we suggest that you remove the clamps and do it again It pays to be able to move quickly and surely when glue is applied 1 After aligning the centerli...

Page 19: ...lace the four braces in position with their curved surfacescontactingtheback andnoticetheirmoreextreme curvature a 20 foot radius Unlike the top gluing setup a flat surface is not used as a gluing caul for the back braces Instead make a radiused outer gluing caul by tracing the outer curve of the longest back brace onto a 20 piece of scrap 2 x 4 wood illustrated Saw and sand it to shape You can ma...

Page 20: ...pencil mark on the back gently push the sides and tailblock slightly untilthe body length mark meetsthe sides and lightly dry clamp You may find it easier to have a friend help in case you need to manipulate the neck block and tailblock into shape Use a white pencil to mark the positions of the ends of the back braces on the sides File 100 deep notches in the kerfed linings and the sides to accept...

Page 21: ...t clamp fastened to your workbench for most of the routing and remove it to rout the waist of the body Wood tear out is always possible when routing but espe cially with long grain quartersawn tonewoods Therefore start with four climb cuts so called because the router is climbing or being pulled along as the bit grabs the wood Withasaw chiselandfile removethesectionofsoundboard that covers the top...

Page 22: ...t and swing out again as you approach the last brace This takes some practice With the router unplugged prac tice with the wedge and try to keep the router bit square to the sides It s virtually impossible to get it perfectly square everywhere at all times but with care and a little practice this method will also give you excellent results The first pass is for the interior strips and is made with...

Page 23: ...ing Cut a 6 piece off of each of the two supplied 040 ivoroid black purfling strips Check the fit of the end trim with the purfling on each side the black line should be on the inside in the channel slide until the wedge tightens the pieces Whenthefitisperfect gluethepurflingandendtriminplace with Bind ALL Clamping should not be necessary After 24 hoursdryingtime trimtheendstomatchtheroutedbinding...

Page 24: ...plastic will shrink slightly as the glue solvent evaporates Use a scraper blade to smooth the bindings flush to the guitar s sides back and top Scrape in the direction of the wood grain and avoid digging into the wood Practice on scrap if possible Opening the dovetail joint Now you can remove the side wood covering the neck joint opening in the neck block With a sharp stiff knife or a saw scorethr...

Page 25: ...uss rod s adjustment nut Mark the position of the ad justment nut on the face of the tenon nut side down Mark the length of the adjustment nut on a 17 64 drill bit with masking tape to act as a depth stop Run the bit in reverse to start the hole and then drill open the truss rod channel to accept the nut Now slide the Hot Rod Truss Rod into the neck channel from the heel end with the adjustment nu...

Page 26: ...nut end of the fretboard with the break angle where the peghead begins Pencil a mark on the peghead face 3 16 from the nut line Align the peghead overlay with this mark This will leave some extra overlay wood to be trimmed away when the nut is fitted later Using Titebond glue and clamp the rosewood overlay ve neer grain running lengthwise to the face of the peghead aligning it with the pencil mark...

Page 27: ...hooting block is a long square edged sanding block for creating smooth straight surfaces We usedacarpenter slevelandfastenedthesandpaper to it with double stick tape pictured Making a fretboard Trimming the fretboard Mark the location of the fret markers on the fretboard using the centerline that you made earlier The large diamonds will be inlaid at the 5th fret and 9th fret thesmallersquareswillb...

Page 28: ...fret Since the fretwire is more curved than the fretboard the fret straightens as it s hammered in This causes the barbs on the fret tang to move sideways in the slot tighteningthefit Avoidtippingthehammerfacesothat its edge hits the fret or you ll dent the wire Hammer from your wrist in short crisp blows pictured A scrap piece of fretboard has been included with your kit as well as enough fretwir...

Page 29: ... the slot Let it run through the slot and out the other side Loose frets can be clamped using a 16 radius sanding block as a caul before running the super glue into the slot Use wax paper between the caul and the fretboard With flush ground fret cutters nip the fret ends close to the edge of the fretboard don t dig into the wood Use a smooth mill file or sandpaper on the carpenter s level to bring...

Page 30: ...le along the length of the neck pictured When the pencil marks were re moved orleftevenlyandslightlybelowthegrainof themahogany weswitchedtofinergritsandpaper Using a rasp followed by a half round bastard file shape the neck s heel When the heel is close to the final shape stop Finalize the shape later when you add the heel cap Neck shaping and fitting Shaping the neck The guitar peghead tilts bac...

Page 31: ...unt of wood to remove from the heel to change the neck angle so that a straightedge laid on the frets will be flush with the top of the bridge A How far the straightedge falls below the top of the bridge In this example 1 8 125 B The heel length from the fretboard bottom to the heel cap In this example 3 5 32 3 156 C The distance from the neck body joint to the saddle In this example that s at the...

Page 32: ...remain ing inner area up to the tenon pictured After under cutting the cheeks this way you should have a neck fit that is very close Still you may need to remove a little wood from the outer contact edges to adjust the neck alignment Removing wood from the upper part of the neck cheek edges will raise the neck decrease the angle remov ing from the bottom will lower it increase the angle Taking woo...

Page 33: ...ment is removing wood from the bottomoftheheelcheeks Removingwoodfromthebottom of the heel on both the treble and bass sides equally will tip the neck back illustrated Remove the wood in a wedge shape which tapers to zero at the top edge of the cheeks Usetheformulain Understandingneckanglegeometry to determine how much wood to remove With a sharp pencil and a straightedge mark the area to be chise...

Page 34: ... left by the chisel to side If you need to remove a lot of wood make two or three passes before changing to the other cheek The fit will change rapidly so check your progress frequently A small ledge of unsanded wood will remain on the bottom of the heel between the sanded cheeks Either pull sand it with the strip or use a sharp chisel to remove it Wood is seldom removed from the top of the heel b...

Page 35: ...rections If you decide to use spray equipment always thin nitrocellulose lacquers with nitrocellulose thinner only KIT TIP Aerosol Lacquers Aerosol lacquers have a tendency to spit if the spray tip gets clogged Wipe the tip clean often Also youcancleanthetipbyturningthecanupside downandsprayinguntilthespraystreamstops We recommended doing this each time you are done spraying to keep the tip clean ...

Page 36: ...iled the small mounds of glue flush before sanding the neck pictured If you don t fill the ends of the fretslots holeswillremainwhichthelacquerfinishwon tfill Filling the fret ends The neck needs extra sanding and grain raising in the end grain areas of the heel and the ears and the end of the peghead Sand up to 320 grit dampening to raise the grain Do this several times so the endgrain pores will...

Page 37: ...t of clear lacquer on the neck Applying a washcoat to seal the wood Werecommendusingagrainfillerforlevelingtherosewood andmahoganygrainpores Letthefilledwooddryovernight after application Light sanding with 320 grit Fre Cut will removeanyremainingbuildupoffilleronthesealedsurface Try to avoid sanding through the washcoat into the stained mahogany If a sand through does occur touch up the area with...

Page 38: ...um and fine polishing compounds Use a separate pad for each compound You can follow this withswirlremoverifdesired Cleanofftheresidueleftbythe polishes removetheremainingmaskingtapefromtheneck andremovethesoundholemaskingmaterialsfromthebody Dry sand the neck and body to a flat dull sheen with 800 grit Fre Cut paper Clean the residue from the paper often by wiping on a scrap of carpet or a brush O...

Page 39: ...ion the two sides of the dovetail and if you wish add a small amount on the interior walls of the neck block dovetail mortise Be sure glue contacts both sides of the shim too Slide the dovetail neck and the shim in place and apply your Install the neck accidental splashing Use low tack drafting tape to fasten clean paper on the soundboard around the area Keep the tape away from the line by 1 16 so...

Page 40: ...ter the bridge pin holes between the straightedge positions and mark the bridge s side locations on the soundboard with masking tape To square up the final location be sure both sides of the bridge s front edge are equidistant from the last fret Prepare three small wooden clamping cauls to fit over the Apply Titebond to the bridge and reclamp the bridge in place on the soundboard Use at least thre...

Page 41: ...l feel the saddle click into the slot when it reaches the bottom Remember the taller side of the saddle radius is for the bass strings Now it s time to trim the saddle to length and shape the ends Fit the saddle into slot Lightly mark the curve of the bridge onto the protruding saddle with a pencil and cut it 1 32 oversize to the line Then using a round file or a dowel wrapped in sandpaper shape t...

Page 42: ...the neck and reduces the relief Turning it counterclockwise bows the neck upward adding relief Always adjust the truss rod with care a little bit goes a long way The first stage of setup will produce a medium high action this may be suitable for bluegrass players but can be low ered for other playing styles The heights of the nut and the saddle should be adjusted together changes in one will affec...

Page 43: ...l fit without binding Whentheslotsarecorrect removethenutbygentlytapping it from the front and back sides to unseat it and then pry Reinstallthenut withoutglue andplaytheguitar Checkfor false notes or string buzzes caused by uneven frets Buzzing is corrected by leveling the frets Remove the strings and the nut mask the soundboard around the fretboard and the fretboard between the frets Adjust the ...

Page 44: ...enjoyplaying it for many years Protect it with a quality case keep it away fromextremesintemperatureandhumidity andinstallonly medium or lighter gauge strings And start building another guitar You can t stop now can you CONGRATULATIONS Place the pickguard in position on the soundboard Be sure it fits and looks correct and trim it with scissors if necessary You must warm the material with a hair dr...

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Page 46: ...21 N Shafer St Athens Ohio 45701 USA USA Canada call toll free 800 848 2273 9am 5pm weekdays Eastern time stewmac com i WRM3H2 12 19 tools ideas for guitarmaking StewMac ...

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