this thing is finally done...... i just have not had the time to devote to bow building this winter that i had hoped to have had..... these things should have been a two week max project including the prototyping of the riser..... at any rate, they are finished.
the video clips are active.... just click on them and they should play on their own.... unfortunately, photobucket only allows 100 meg files so some of the processes had to be done in multiple clips.
it makes it a little harder to follow but it sure as heck beats my pin-headed ability to explain things with regular pics and captions.
hope you enjoy it. starting with raw lumber
the small surface checks have all been filled in and now i am ready to cut some blocks from them..... the woods from left to right are zebrawood, cocobolo (this is a big chunk. as a reference, that edge sander is a 6x80... the other side is full of eyes and swirls), macassar ebony.
here are the first few pics
ok, finally got a little time to get back to this project and should have most of this week as well........ i am designing a new riser and just finished ripping a prototype out of ash to play with limb pad angles...... i should be done with that in a day or two and these risers will be of that design....... what i am wanting is a 3 piece that will look like a 1 piece when assembled and will not have the limb bolts protruding from the limbs......
i think bob morrison's shawnee riser is is by far the cleanest looking way that anyone mounts limbs on a 3 piece so i will be doing mine similar but the riser will be milled out so that the limbs are inset in the riser. i want the bow to have somewhat of a one piece look to it when bolted together. it is funny how my taste in bows changes all the time..... instead of doing all the "gawdy" spliced veneers and wild flares that i usually do, i just want a bow with nice simple clean lines..... i figure i'll let the wood give the bows their "sex appeal" so both bows will have figured veneers.
today i just cut the blocks and squared them up. i look at this process like the foundation of a house...... a good foundation to work from is very very important in creating perfect glue lines and a strong riser. so i take a while ensuring that the blocks of wood i start with are squared and perfectly flat. i do this on the mill because in one pass i can eliminate any cupping or bowing on a block and because i can control the depth down to .001".
another garage ninnie set up....... i mounted an 8" digital caliper to my downfeed as well as larger ones to my X and Y axis'
i rough saw the lumber to 3 3/4 X18" (these 60" recurves will have 16" risers)...... the lumber is sold as 8/4 but is usually 1 3/4"- 1 7/8"...... with some of the common exotics at over 50.00/board foot, i sure wish they sold it as 7/4
now for the milling...... i start with the flatest face down and lock it in the vice and then tap it down to insure that the face is flat against the bottom of the vice. from there i find "0" on the caliper by touching the cutter to the surface of the block and zero out the caliper. and using a 3" face mill, i start by removing .030..... that is usually enough to get the first face flat....... the shutter speed on the camera is a little fast in these pics but the mill is acutally cutting, if you look close you can see the chips flying.
now that the first face is flat, i flip the block on edge, put my 1 2 3 blocks behind the block against the stationary jaw of the vice to add support and mill the first edge....... it is really important that the milled face goes against the 1 2 3 blocks that are agains the non moving jaw of the vice because it is perfectly perpendicular to the table and will ensure that the edge being cut is square. this pic shows the chips in mid air a little better
the mill really makes a mess
from there, i flip the board over keeping the flat face against the 1 2 3 blocks and mill the other edge....... after that, i only have the other face to flatten/square but now i am going to get it to 1.70" thick. i mic the blocks and adust the downfeed to the desired depth and mill the other side flat....... now they are ready for cutting and shaping accents.
though i just milled the blocks to 1.70", my limbs are 1.5" wide but i will final demension it after the blocks are all glued up with the accents.... i can do this on the mill but i only like to take off .070 max in a pass...... without a powerfeed, this takes a while so i run it over to my performax with 36grit and shave it down to about 1.550"........ that only takes 4-5 passes/board....... from there it is back to the mill. i set the block milled face down, lock the vice and tap the block down to make sure it is flat against the base of the vice, find "0" and remove the last .050 with 1 pass...... we will get to this step later.
here is the result of this process...... though this process takes a while, it speeds things up later on that require the lumber to be square.
you can see by using a straight edge that the face is flat
they are so flat that that these two surfaces sit perfectly flat on eachother.... you cant see a joint.
all edges are perfectly square to the facesThe Risers
ok, got the geometry of the new riser worked out to maximize my limb performance on what will be a deflexed riser.............. so lets roll.
first, i had to get my templates made.... i always use plexiglass for my templates because it allows me to see my centerlines and allows me to place my accents where i want them depending on the grain of the wood.
grinding out a template.
once i have my blocks cut to dimension, i find the center and scribe a line all the way around the block.
once the line is scribed, i lay the first template on the riser block, make sure the edge of the template is flush with the edge of the block and line up the centerline on the template with the centerline on the block.
now i cut that section out of the block while being careful to "save the line."
from here, it is time to use the edge sander to grind to that line..... but first, it is important to make sure the tool is square.... i am probably a little anal about this stuff but i check my tools for square before each use.
now i just grind to the line...... i start with 36 grit to remove material fast, then switch to 60grit for final removal.
here is a piece that is done..... i love figured macassar!
the block that was just cut and ground will be part of the belly side of the riser...... now it is time to scribe the line on the block of wood that this piece will be glued to...... again, i line up the center lines of the two blocks and then clam them together making sure that the edges are flush with eachother.
now we have to scribe the line.............but.............. there will also be glass accents in between the two blocks and so we have to account for that or there will be a bunch of static stress build into the riser......... not good for glue lines..... this next step i picked up from bill howland.... i have done this tons of different ways but his is the easiest i have found (once i get the table and guide bearing done for the sander, everthing will be done with jigs so this step will be eliminated). i know that i will have three accents in these risers at this joint...... the total thickness of them will be .120....... so i took a piece of aluminum rod and turned it on my lathe to give me a wall thickness of .120"...... from there, i lay my pencil (not a pen here because you can't get the ball point right against the wall) on the inside of the wall and roll the guide on the outside of my freshly ground block...... the line will have the .120 built in and the parts will marry perfectly with no internal stress.
now it is time to cut that block and being careful to save the line again i'll rip it out on the band saw.
to do the inside radius, i need the idler wheel on the edge sander...... but first, i make sure it is square to the table.
now, i grind to the line, then take a piece of action boo that i have ground to .120 i put it inbetween the two blocks to simulate the accents and find the high spots...... this takes time and i forgot to snap a pic of it....... these two sections of the riser blocks are ready for glue up....... these risers will be glued up in two stages because the outer accent stripes will also act as the beds for the limb pads...... i want to make sure that they are perfect.
i should say that there are two bows going together in this build along (just so it doesn't get confusing..... one for scott nicholson as a small "thank you" for two alaskan hunts of a lifetime and one for me..... from the bows i have seen of scott's, he likes the red colored woods so his riser will be cocobolo/african blackwood/cocobolo with highly figured curly waterfall bubinga veneers. mine will be macassar/zebrawood/macassar with cathedral grain zebrawood veneers. both sets of limbs will have maple (old stock...... the good stuff!) actionwood cores..... though it is not the fastest, maple actionwood is my favorite for durablity and stability..... also, for some reason, maple cores seem to be slightly quieter in limbs but that is subjective since i have never actually measured the sound differences between cores.
a little technical difficulty...... i was getting ready to glue up the risers and checked for square just in case..... the outside radius' were perfect but the blocks that i cut the inside radius' were horrible and not consistent..... after checking the little end table on the idler wheel, i found that this table was FAR from flat.... i called bill howland and his was the same story..... called my buddy who had grizzly send him another table and both were no flat. i emailed ernie to see if his was but he said he hadn't checked it...... i freak'n hate chinese made machines
....... oh well, i just introduced it to the japanese made mill and fixed that little problem........ she's flat now!
FD- thanks again for the RPM and feed rates....... you tip on using the file worked like a charm..... it is cast iron.
i'm going to spend the rest of the day finishing up the edge sander project since my parts FINALLY arrived.back to the risers
now that the edge sander's table is flat, i reground the inside arc to the line to match the outside.
i clamp the two halves together with a piece of maple that is the same thickness as the combined layers of accents to see where i have to remove material to get the surfaces to mate perfectly.... it takes a little time but if you hold the two risers up to a light you can see even the slightest imperfection.
in this pic, you can see the pencil marks on the african blackwood indicating where material needs to be removed.... i typically work off the inside arc because the outside arc is easier to get nice and smooth from working off the platen on the edge sander.... the inside arc requires using the idler wheel which is easier to leave "stall marks" that need to be removed.
now that the mating surfaces are perfect, this riser is ready for the first stage in this glue up.
prepping for riser glue-up.....
if you keep everything organized, glue-up is not all that messy.
the riser clamped and curing
i forgot to take a pic but when i start the clamping, i sit the riser blocks and accents on two aluminum rods that are layed flat on the table and oriented so that they are running from back to belly...... this allows the glue to squeeze out the bottom as well as the top and does not try to force the accents out of the stack due to all the hydraulic pressure created if you try to clamp them while laying on a flat surface....... it also nearly eliminates any slipping and sliding.
after the risers are cured, i clean the glue off them by running them through the mill again, and now it is time for the second phase of the glue-up.....
i use another template with a larger arc that is also flat..... the flat sections are 17 degrees and will actually be the limb pads for this particular riser.
cutting out the new line but saving the line.
grinding right to the line
ok, now is the important part...... in the prototype riser for this design, i determined that i wanted 17 degree limb pad angles but i didn't have a 17 degree block so it was time to quickly make one. this is what i will need to start..... precision angle, 1 2 3 blocks, my squared base that i use for just about everything and my small angle plate.
first, i flatten the base of the chunk of dymondwood as well as the sides and then using the 15 and 2 degree angles, draw the line and cut it out on the band saw.
next, i clamp the small angle plate to the mill table and using a dial test indicator, i adjust it so that it is perfectly parallel to the table.
from there, i set the 1 2 3 blocks agains the angle plate and put the 15 and 2 degree angles agains the angle plate and clamp the block of dymondwood to it ontop of the angles...... because the sides are milled flat as is the base, the top will come out square to the sides once milled.
time to mill
finished 17 degree block
now it is time to cut the riser's accents/limb pads so i have to remove the small angle plate and use the big one (it weighs 65lbs)...... i have to use the dial test indicator just like the last one to adjust it so it is parallel to the table...... this is where the mill is very slow because of all the set-up that has to be done.
milling what will be the limb pads with the new 17 degree block
now i go back to the edge sander and mary the arc into the flat sections that were just milled...... and it is now time to trace the arc onto the next section of wood..... again, this is done with a turned piece of metal that will be just as thick as the accents..... this one is thicker because on top of the accents that will match the other set, there will be a piece of phenolic that will be the actual limb pad.
back to the band saw to cut and save the line
now, i put the inside arc on the mill and flatten the mating surfaces to 17 degrees and make the line that i drew just disappear.....
from here, fit the two together just like i did the first set of accents and glue it up. after the blocks are cured, i put them back in the vice and clean up the faces of the glue queeze out........... again!
(these risers are becoming a pain in the butt lol)
cleaned up blocks and just about ready to become risers.
now i take the template that is the final shape of the riser and scribe it..... it is time to cut out the back of the riser and get it ready to cut limb pads and drill holes.
but first,off to the edge sander to grind to the line so i can glue on the riser's overlays that will match up with the lams in the limbs...... i know i could have done less glue ups on this but because the accents need to line up with the limbs and one of the accents will actually be the limb pads, i wanted to keep everything as accurate as i could.
ready to glue the overlays
clamped and curing....... you can see that i have a sort of jig clamped to the riser..... there is also a 1/4" piece of very hard rubber in there to apply even pressure.
now that the overlays are on, it is time to clean off the glue again.................. this is the first time i had ever used the video function on this camera and had no idea it recorded sound..... turn your volume down as i have a tendancy to have the stereo cranked in the shop while i am working
now its time to cut some limb pads...... these risers are set up so that the glass and wood lams will line up with the coresponding accents in the riser..... the limpads will actually be the phenolic accent and i will need to remove .040 of the phenolic to line up with the .030 belly glass and .010 veneer ( i didn't put veneer accents in the riser). now i have the riser outline scribed on the riser block and so i rough cut the limb pads out on the bandsaw staying way off the line. from there, the riser is put on the mill using the 17 degree block and the limb pads are cut..... at first i am cutting wood but as i approach the phenolic, i take only .001 off at a time so i know when i hit it exactly so i can remove the needed .040.
scribing the lines of the riser profile
cutting limb pads....... now in the next video clip, don't get the wrong idea when you hear the gal at the end of the clip moaning....... again, i have the radio turned on and that is a little "white zombie" playing in the background..... not porn (sorry hank LOL).
finished limb pads...... i didn't show this in the video or pics but the corner of the limb pad and riser where the limbs will butt agains were cut out with a 1/8" dia. ball endmill since hard corners can be a weak spot.drilling the riser
since we have had a few threads on the subject, i figured i'd do this part as some video clips because i suck at explaining things...... my wife bought me this little camera for filming some of my hunts for this site and i figured it would work perfect here..... only problem is, the cam is on my head so i can't see what i am filming..... sorry but the video sucks but i think it will atleast give some idea as to how i do it on the mill and why i can get perfect alignment every time..... btw, the sound on this little cam is pretty poor as is the image (but i didn't expect much from a cam that is half the size of a hotdog). just turn the volume up so you can kind of hear what i am saying..... i sound like i am on helium with this cam LOL.
since photobucket only allows 100 meg files, i had to do the drilling section in multiple video clips..... sorry
after i had recorded all the clips, i realized that you really could not see much that i was talking about so i shot this short clip just to clear a few things up
now that the drilling is done, it is time to install the brass inserts in the belly of the riser that will provide a solid base for the limb bolts to snug up against..... but first, i need to make them. they started off as 5/8" brass round bar and i cut them into 1" lengths for turning the inside diameters. prior to cutting them, i used a 6" piece of the round bar and turned the outside diameter to be exactly the same as the endmill that i would use to drill the hole with.
brass is turned on the outside and cut into 1" pieces
now the inside diameter is turned and the hole for the limb bolt is drilled. i also durned them down to .75" in length.... they are ready to install.
the hole was drilled with an end mill...... i had not moved the mill's table since drilling on the top side of the limb pads so i knew it was still centered...... using a different edge finder to find the edge of the hole that i had previously drilled from the top side, i centered the endmill lengthwise and drilled the hole 1" deep for the brass .
brass is installed and curing
now it is time for the sight window...... i use a small template to scribe the line and then cut it out on the bandsaw while sabing the line...... this was the first time i had used the carbide tipped bandsaw blade..... it was awesome..... absolutely no dulling.
now that it is rough cut, i mill the strike plate so that it is 3/16" past center. i then go back and cut it at 5 degrees from back to belly so that a peak is formed on the strike plate that is inline with the peak of the shelf to maximize fletching clearance...... the shelf is then cut with a 3/16 dia. "box core" carbide router bit to made the junction between the strike plate and the shelf rounded.... it is also cut on the 5 degree angles to max fletching clearance........ in the pic, you can see the 5 degrees is done on my adjustable angle table instead of a milled block like i did the limb pads.
once the sight window and shelf are cut, the precision work on the riser is done and it is time to shape and contour the riser...... i have already scribed the profile of the riser from a template to the riser block so i rough cut it on the band saw.
then grind to the actual scribed line
now is where the fun begins...... within 45 minutes, this will go from a clunky looking block of wood to looking like a riser. in order to keep the contours symetrical, i scribe some reference lines on the riser's back and belly using a block that i made that has different holes in it..... they are 1/4, 3/8, 1/2, 5/8, 3/4" from the base of the table to the center of the hole and the same diameter as a bic pen.
using the 1/2" hole for these risers, i scribe the reference lines onto the belly of the riser and do the same thing on the back but with the 5/8" marking hole....... these lines will give me a reference point to grind to.
belly lines scribed
to illustrate what i am talking about, here is scott's riser roughed out next to mine that has the lines scribed.
here is scott's riser roughed out with 60 grit..... about 45 minutes prior, it was a block of wood
from here, i will remove the 60 grit belt and go to 120 and then 220 on the edgesander to minimize the hand sanding that needs to be done.
here are a few video clips of the shaping process...... they are not long or very complete, i just wanted to give a feel for the process and to show the guys who were intersted in the spindle attachments that i built for the edge sander how they worked.
TJ- these next few clips are for you buddy.
from here, the risers will sit until the limbs are done and everything will get hand sanded at one time and then sprayed.Limbs
from here i start the limbs (though the cores were cut and ground during some of the curing time for the risers)....... these particular limbs will be made from old stock maple actionwood cores...... highly figured curly waterfall bubinga veneers in scott's bow and figured zebrawood veneers for my bow.... .040 ULS glass on the back with .030 on the belly.
first i have to cut some blanks for the cores and veneers ...... on the .002 taper, i use a master taper against the rip fence to cut the material to save lumber.....
fresh cut core blanks..... the grey core is the master .002 taper
now it is time to cut the veneer blanks...... you can see in this piece of zebrawood that it is pretty bland but if you look at the end of the board you can see that there is some pretty grain to be found if you chase it....
after adjusting the table of the bandsaw inline with the grain, i was able to pull some nice veneers out of this board.
here are scott's veneers..... this pic does not do them justice.
after the blanks are cut, it is time to grind them. in this pic, i am grinding the parallels to a desired thickness of .050. on all my cores, i start with 40grit for fast removal and finish with 80 grit..... on my veneers, i take them very thin so i finsh them with 100 grit.
grinding the parallels
i also have mounted a 145lb magnet with a dial indicator on my drum sander.... this allows me to hit exact thicknesses with repeatablity.
here, the parallels are done
now for the veneers, i use MDF as my sleds because the stuff is so uniform in thickness...... the piece that i grind my veneers with varies .0015 from end to end. what i have done is recessed the forward 1" of the board by .020. i attach double sided carpet tape to it and then can stick the veneers to it and feed it tape end first..... this allows me to get the veneers extremely thin by pulling them through the sander instead of pushing them and possibly making them curl up into the drum
here i was grinding the maple accents that went into the risers..... it is the same for the veneers
typically, the prettiest veneers are flat sawn..... this is the weakest grain orientation that we can put into the limbs. the only two customs that i have personally seen delaminate from normal use were both flat grain veneers and they definately came apart in the veneer. what i do, is take the veneer down to .010 or less, this allows the glue to soak completely through the veneers and i have never had a limb fail that was done this way, even some really hot-rodded glass limbs.
veneer fresh out of the grinder
a piece of paper is about .007 thick.... the veneers are thin enough that light passes through them
now that the cores and veneers are ground, all that is needed is to grind some wedges..... in my recurves, i use a parallel wedge and in my hybrids, a tapered wedge. i start off with a 10" piece of lumber and grind it to .325. then, using a little wedge template, i scribe the line and grind.
it is very important that the ends of the wedges be paper thin to avoid thick gluelines that can be weak spots in the limbs...... the ends should look something like this (kind of like torn paper).
now it is time to cut the glass..... i just do it on my miter saw with a carbide blade.
there is a lot of debate on cleaning lams off with solvents and others do it with compressed air, i have done it with air for ever and never had a problem..... some of the solvents i have tried seem to start to disolve the composites which makes me nervous so i just stick with air.
now we are ready to glue up a limb. i lay everything out on freezer paper to keep the glue off the work bench. at this point, i have put a piece of plastic wrap that i have folded in half on the bottom half of the form.... the metal pressure strip as well as my heat tape are under the plastic. i have set another piece of plastic to the side ready to go on top of the lams..
lams ready for glue up
mix the glue in a disposable plastic bowl and using a digital scale, i mix 30g of resin to 20g of hardner.... i know this may be anal to some, but after hot-rodding so many sets of limbs, i always like to know for sure that it was not the glue that failed because i didn't mix the proper amounts...... it was just one less thing to rule out. once the glue is mixed, i use an adhesive applicator to spread the glue.... i forgot to take a pic but it looks like a miniature paint roller.
i don't do this anymore but did it for this particular limb just to illustrate how i used to keep my wedge from sliding around when i first started building bows...... what i do is leave the outer 1/4" of both sides of the wedge as well as the mating srurface of the core lams dry of glue.... on the wedge, i would apply just a drop of medium CA. once everything is together, i would press that section of the lams together and let them sit for a minute or so.... the wedge would stay put during the intial squeeze out....... a word of caution..... you absolutely can't get any CA on your lams or near the epoxy.... if the two make contact they will cure within seconds...... the reaction is so violent, that it will actually smoke...... don't ask me how i know this LOL
here i am applying the CA to the wedge
from here, i pick up what will be the belly side of the limb half and stand it on end being careful not to get glue on the glass. i lay the half on the other half and carefully stand up the entire limb on the butt end and align all the lams. i then place it into the form and lay the other piece of plastic on top of it... the pressure strip, heat tape, and hose follow in that order and i bolt on the top half of the form..... if you hold onto the hose while placing the top of the form on, none of the lams will move if the hose stays still. once bolted together, i adjust all my stop blocks and make sure all the lams, preasure strips and heat tapes are in line and hit the hose with 20 PSI........ i wait for one minute and then take it to 40PSI..... wait another 30 sec and go to 60PSI....... 30 sec and full pressure (for me that is 90 PSI). what this does, is slowly squeezes out the glue without forcing the lams to go sliding out due to the hydraulic pressure...... also, because i use such thin veneers, too much air pressure to fast will split them due the hydraulic pressure.
here the lams have just been set into the form and is ready for the top half of the form
now the limb is at full pressure and cooking on the heat tapes at 160 degrees. from start to the end of cool down, the heat tapes allow me to be grinding on a limb within 2 hours of it being glued up.
you can see that the wedge went nowhere during glue up.
you can see that my form is marked with lines to determine where i will cut the end of the butt off the wedge (1 3/4") and center lines on the form to allow accurate centerlines to be scribed onto the limb.
here is the line to mark for the butt cut-off
here i am marking the centerline on the limb...... since i take a lot of time when building my forms to ensure they are flat, i can use the centerline marks to give me an accurate centerline on the limb (one at each end). the glass can slide around in the form a little and in my opinion, premarking a limb before curing is not an accurate way to do it since this could cause the cord length to actually be scribed diaginal on the limb resulting in building twist into the limb.
here is a limb fresh out of the form.
now using the scribed centerlines, i scribe lines close to the outer edges of the limb and clamp a piece of .050 glass to the limb to use as a straight edge to scribe a line.
from here, i put a 40 grit zirconia belt on the edge sander and use the wheel to remove stock fast going close to the line.... once close, i move to the platen on the edge sander and remove material until the line just disappears. it is important to clean up the edges first of all the glue.... if you don't the clumps won't allow you to sit the limb flat against the table resulting in a grind that isn't square.
now i have a nice straight edge. it is time to clamp the limb blanks into the limb squaring sled and take them down to the width of the risers..... i use 40 grit to take them close to the final dimension and take the last few passes off both sides with 220 grit to minimise hand sanding later.
this nest step may be going a little far in some people's opionion but i think its important.... during glue up, we know that the base of the form (back side of the limb) is prefectly flat.... but due to the air pressure and the way that the hose induces the force against the lams, the base of the limb pad will be very slightly convex..... maybe only a .005 crown but put that limb on a hard flat table and watch how much it will rock back and forth. typically, i put overlays on the limb pads but because the way this riser is set up, i couldn't here but the process is still the same. i put the limb in the vise and because i have a .002 taper in the limb, i have to counter it with a .002 taper to make sure the limb is flat.....
here is the taper that will be in the vise sitting on top of the parallels that will elevate the base of the limb pad above the top of the vise..
here is a little proof for ya..... the first pass of.001 has been removed (with overlays, i could take all the material off on one pass but if you try it with glass, you will pull strands of glass off the limb..... it has to go slow). you can see that there are high spots.
here is what it looks like after the limb pad is flat
now that the limb pads are flat, it is time to cut the limbs to length..... using the 1 3/4" mark on one of the limbs in the pair, i align the limbs on a flat table using the back of the limb as the base.....
i position them so that the curves of the limbs match perfectly and scribe the 1 3/4" mark onto the other limb.....
now i cut the butt of the limb off being careful to save the line. from there, i take the limbs over to the disk sander and grind them so that the line just disappears.... the disk sander also squares the limb butt.
now, i measure from the butt to the center of where my nock will be and scribe a line..... then move 5/8" further and scribe the line for the end of the limb. i cut the limb saving the outer line and then back to the disk sander to grind to the line and square the end of the limb.
now i am ready to drill the limbs. i put them into the vise and find the edge....... awh heck, i think video clips will explain it better than i can type it.
just a little info first.... instead of just drilling holes in the limbs to accept the steel pins, i like to use brass roundbar as the mating surface..... i turn out the brass so that it is .25: O.D. then drill a hole in the limb where the pin will mate with the limb that is large enough for the brass roundbar, glue it in and then drill the hole later.... it takes some extra time because of having to wait for the epoxy to cure but i like the idea of having a steel pin rubbing brass more than having it rub the finish out of the inside of the hole.
(on a side note....... i had just competed the entire build along right here and as i was typing the last sentence, all of the work from this saved point disappeared........ lets just say that a few choice words were yelled
here is a pic of the brass curing in the limb
now it is time to drill the hole in the brass as well as the hole for the T nut
here is where i am drilling for the brass roundbar.... because of the repeatability of the mill, i can remove the limbs from the vise, glue in the brass and then come back at a later time and drill the hole in the brass for the index pin as well as the hole for the T-nut.
and finally, here is the accuracy i get with the mill..... the limbs are completely interchangable between risers with no slop at all and the sides are flush with the risers
a pic of scott's limb on his riser and also his limb on my riser
now it is time to chop some materials into 2" strips for limb tips.... for mine, i used phenolic, brown glass, black glass..... scotts is phenolic, zebrawood, black glass. after the materials are cut and cleaned, it is time for glue up
after all the materials are cut and cleaned it is time to get ready for another glue up. i sand the limb tips as well as the butts so that the epoxy will adhere to the glass.
.... while the tips are curing i will also glue in the T nuts to save time. in the pic below, you will see some dymondwood jigs..... the two smaller ones are for the limb tips..... they are ground in the same shapes as the back and belly of my limbs...... this allows for even pressure on the materials to ensure good adheasion as well as reducing/eliminating any slipping during glue up. the other jig was made for these limbs.... the limb bolt hole is large enough for the T nut and there is an index pin installed..... this will allow me to use a limb bolt to keep tension on the T nut dring curing so i can work on the risers during this glue up. btw, there is a .020 piece of phenolic glued between the T nut and the glass.... it is probably not neccesary but i just didn't like the idea of having a metal to glass connection under the flange on the T nut .
here is a pic of everything clamped up and curing.
once the tips are cured, it is time to square them up. this is really important that they are square if you are using tiller blocks otherwise you can get a false twist reading.
now that the tips are square, i take the limbs to the edge sander and put the initial grind on the tips.... it is easier to get a straight line now than when the limbs are cut out. once i establish the center of the limbs and mark where my nocks will be, i'll come back and take the grind higher..... i just do this now to releave some of the stress on all the material for when they get put on the blocks.
now the bow is ready for the tiller blocks..... i just bolt it together, get the appropriate string and take it over to one of my work benches that i welded some padded bars to that allows me to string bows with tiller blocks on them since a stringer won't work yet.
here is scott's bow being tensioned for the first time.
now it is time to find the true center of the limbs. while doing this build along, i had a break through (atleast for me lol) and have found a way to work the twist out of limbs without tiller blocks..... for this thread, i will show how i have done it for years and will do another thread on the way i will do it from now on.
the last time i used my little wood tillering jig, it made some funny creaking noises..... not wanting to risk anything, i figured i'd make a new one but out of metal this time.... i made the old one 8-9 years ago and didn't have a welder at the time. this little jig was just made out of some scrap, 2x2 square tube, 1" angle iron and some flat bar that i had laying around the shop. if you have a welder and some scrap, this little thing can be built and painted in about 30 minutes.
laying the first bead
cleaning up any sharp edges
cutting the string groove
just about ready for paint
time to find the true center of the limb...... now that the bow has the tiller blocks on it, it is placed on the jig..... the idea is similar to a tiller stick but by using the stick, you can induce torque on the string and riser giving a false twist reading..... by finishing out the riser and using a rope, the bow kind of free floats like it would in your hand if you had an open grip.
here is the rope on the jig
in this pic, the bow is on the jig.... you can see that the string is just off the belly of the limbs.... i like the string to be just barely off the belly because as the limbs "open up" the are less likely to show twist.... right here, they are at their least stable point and will be more likely to show twist here.....
to be able to easily see the twist in a limb, i just use arrows clamped to the back of the limbs.... the reason i use the back is the same reason i milled the limb pads flat.... the back is pressed flat against the form during glue up.... but the belly can have a little crown to it so i use the flat side to help with the accuracy of seeing twist. i use a square to set the arrows on the limb.... if the arrows are not parallel with eachother, you will get a false reading.
when i strung the bow, i just eyeballed where i thought center was..... you can see that it is off a little...... i think i have only hit center on a bow once on the first try in the entire time i have been building bows LOL.
from here, i start with the limb that indicates the most twist..... it involves moving the tiller blocks toward the "strong" side of the limb in very small increments..... since moving the blocks on one limb can cause the other limb to have a new reading, it is a balancing act that can sometimes be pretty time consuming.
here is what the arrows should look like on a limb with no twist
you can see that the true center was not the mathmatical center..... it was about 1/16 out.
now it is time to mark the true center..... i mark the edges of the tiller blocks and then mark the center of the two marks on the limb..... i'll make the mark 5/8" down from the end of the limb for the nock.
now i use my template to scribe the profile of my limbs.
from here, the limbs go to the edge sander and get the final grind put on the limb tip as well as the profile ground out. i start with 40 grit on the profile and then end with 220gr to minimize the hand sanding that will need to be done.
now that the limbs are cut out, it is time to cut the nocks...... i think this process is what set me over the edge to buy the mill (lol) when i saw bill howland doing it this way. it gives me a very accurately cut nock with identical angles and depths.
now that the nocks are cut, i use an abrasive string to start the string groove on top of the tip overlay..... the string allows the groove to be cut in the same attitude that a string loop would sit on it.
here it is after the abrasive cord has started the grove.
i almost always use 2 different color materials for tip overlays.... not only does it look nice, it also allows me to see a reference point to keep the nocks symetrical. when i am using the file, i make sure not to remove materail from the insides of the nocks since they were very accurately cut on the mill.
now i go to the belly side of the limb and using the square, i scribe a 45 degree angle to use as a reference to remove materail..... this opens up the area and allows me more room to work the file to round over the nock.
nock is round over and finished. while working back here, i can use the lams as reference for symetry . i'll finish the nocks with 220 sand paper to ensure they are smooth inside.
now that the nocks are done, the bow goes back on the tiller jig to double check that there is no twist in the limbs.... if there was, i would have removed material from the nock to bring it in line. i also shoot the bows repeatedly without string grooves to make sure that the string settles in the center of the limb after each shot.
now that the nocks are done and there is no indication of limb twist, it is time to scribe the line using the string for the string groove and then cut it.
after it is cut, i use the file wrapped in 220 grit to smooth it out.