Tuesday, November 17, 2015

Plate Crown Fork


This was a fun beginning to a much bigger project that came about when the man behind Dapper Dre Enterprises mentioned that he liked the look of bikes that were more classic and angular.  He mentioned  liking a bike I made some years ago, so after our conversation I revisited that bike and the blog entry I posted about it, HERE.  It was a traditional level top tube touring bike, but the plate crown fork stood out, so why not revisit that.  I re-read that post and at the time had concluded not to make one of those for a good long while, or until I have a mill.  Yeah, I remember now why, drilling out matching holes in plates with a drill press and then filing them to round sounds like a terrible idea.  At least I raked the blades to achieve offset rather than angling the holes at the crown...you can probably see where this is going.  Anyway, fork now complete, my favorite comment about it so far came in the form of "How the f^@k did you make that."  Well it took a while but here are the basic steps.


Lots of time went into the working drawing and pre-planning and angles were calculated rather than measured.  I periodically have to recall those high school trig classes out there in the shop and this fork required several of those old formulas...really practical math, folks.  As well I cut a new die for the crush bender to form the lower plate; the upper is the railroad track die used to bend the yoke on Joe's Murray in the last post. 


This thing came in handy for once.  The Palmgren 400 lathe milling attachment.  I picked it up at my local machine supply, Quality Tool, about a year ago in serviceable condition for $100 and haven't touched it other than to clean up and oil.  I bought it initially thinking it would be the tube mitering station, but quickly thought better of it, things just didn't quite compute.  And yes, Flagstaff has a machine tool store even though it doesn't really have too many machines, and I won't bother linking you to it because the guy that runs it is even more of a techno-luddite than I am, so you can find him in the yellow pages, or just drop by, he is there, tucked into the corner by the beauty college with barely even a sign.  Yesterday I picked up a Kennedy tool box loaded up to the gills for not too bad either.



Steerer hole cut into plates and tacked against the crown race seat.  The top plate will actually serve as the crown race seat the sleeve is just to give the proper O.D for the race's press fit.  This whole sub assembly is then sweated with brass and cleaned up. 


Time to make the holes for the legs.  Calculations for rake and crown to hub widening are programmed on the Palmgren and the compound slide respectively.  Then marks are centered before cutting.


 

Holes cut....I almost lost it here.  The expansive angle to the hub was set for the other side so my cut went the wrong way.  Luckily, the metal to the inside (steerer tube side) of the hole was all still there and the 1.625 degree angle of cut was not enough to drastically affect my canvas.  At this point I still didn't have much of an idea of how the fork was going to look in the end, but with the mis-cut I started getting the idea.  I would have to close that gap in at the outside, just like any old lug point.


The rounding cuts were added while in the lathe followed by much manual sculpting.  The closed holes were carved into lug points and made for some fun tight quarters brazing.  



Looking forward to seeing this with a layer of paint and then all done up on the bike which is in process as I type this.  Lots of work into this one!  



Tuesday, November 10, 2015

The Trade

Steel for Steel.  A nicely equipped, tough as nails, American made touring mountain bike frame built for long travel forks and plus sized tires....and in exchange....a nicely equipped, tough as nails, American made metal munching machine.  

I got wind last fall that in the garage of a notable Flagstaff mountain bike personality sat a Bridgeport mill, collecting dust, taking up space, no longer needed in shop operations, not even five miles from here.  I was immediately interested, but with winter approaching and side jobs waning for the season, had little money to afford such a hunk of metal.  I tracked down the owner of said machinery and arranged to head over for an inspection anyway thinking maybe an arrangement could be made.  Save for a little dust it seemed quite clean, minimally used, included a fair assemblage of attachments, an adjustable boring bar, a swivel vise, and perhaps most importantly a phase converter for the variable frequency drive.  You mean I don't have to climb a ladder to change speeds on the belt and pulley drive?!?....OK, I want!, but how?  Then out of the man's mouth whose name is worn on more bicycle frames than I can imagine...."I'd be willing to trade you the value of one of your frames toward it."  Joe Murray, you sir have a deal.  


I mentioned that I would like to make the bike on the machine and arranged to pull it out of there as soon as possible.  The Viking crew was wrangled on a slushy Saturday last December.  One Kubota tractor with fork attachment, two three quarter ton Chevys, two two-axle trailers, the standard arrangement of carpentry tools and rigging, one hour of time at each shop, lunch at Satchmo's.  Done.  What would a guy do without the Neffs?  



I rounded up all the scrap metal I could and spent few months learning this machine.  Old metal was repurposed; fixtures made from scrap, bolt patterns, Tee-slots, Tee-nuts, tapped holes, boring!!!   So many possibilities.  I do love me some recycling!  Joe stopped by on a ride with a sweaty folded computer print out in hand.  A scale CAD drawing of the bike he wanted me to build.  It was time to pay the debt.


The bike to be wanted 29+ wheels and 150mm of Fox 36 fork.  We discussed some specifics which included a dropper post, a granny gear (YESSS!), thru axle rear with offset for good chain line, and rack mounts (YESSS!).  A properly sturdy bike with timeless accommodations.  I must say that of all the production bikes I ever owned, my favorite, and the only one that ever really fit me was the one of Joe's design.  I took the dimensions from his print out to full scale on my drawing board to double check clearances and setup the jig.  The seat tube would need to be bent and some serious tire/chainring clearances would need to be resolved as always.  It was time to make my own plate bender (see back a few posts: Yoked).  Commence mill work. Working with a 30.9 seat post and a bent seat tube required a call to Solid bikes for one of their seat tube plugs, a real nice piece of turned and internally relieved 4130.  This piece comes as a press fit to be stitch welded, but would be reduced to accommodate brass flow into the joint.  The seat tube is the pre-bent True Temper Chromag downtube with the lower (actually in this case the upper) butt cut completely off.


Now building offset rear end bikes for large tires presents a new set of problems to solve, especially when considering it is not likely a bike I will ever own myself.  Finding the center line on the jig is no problem but confirming the accuracy of your work without actually having a 142 thru axle wheel dished so the hub sits 6.5 mm to the drive side is a little bit more complicated.  I did however have a freshly laced 29er wheel with a 135mm XT threaded axle hub at my disposal, so I devised some concentric end caps and spacers to make up the offset dish.  


The cones fit thru the dropout and thread to the 10mm axle.  The one on the right is longer since it has to accommodate the additional 7mm of spacers making up the difference in outer locknut dimension.  Now this regular old school 135mm center dished wheel sits on the centerline of this offset bike allowing me to visually confirm that this monster truck won't have an unwanted rear wheel steering issue.  Thank goodness.


Onto final frame prep.  I went with an 83 mm bottom bracket shell to accommodate a granny gear without having to use some oddball crank like a Mr. Whirley.  The shells come .5 mm over width to allow for facing after getting distorted in the heat cycle....and they do.  


So now she waits in a high gloss orange waiting for some unmarked parts to be slung on and abused.  





Thanks for the project and the trade, Joe!  I hope you like your bike.

Sunday, October 25, 2015

Ponies


I've been balls deep into the wood pile this week trying to get the homestead ready for: 

El NiƱo.  


Then sometimes your old retro-grouch bike geek buddy rolls up to your wood pile with a van full of sweet new wonder bikes and offers you a private demo of the new Salsa Pony Rustler.  Pretty hard to pass that up.  There have been bike demos down the street all year, seemingly every weekend.  I didn't take out a single bike that wasn't my own all year, but after throwing a leg over the Bucksaw last November, I have been a good deal intrigued by Salsa's line-up.  They are one of very few (my opinion) companies really pushing the developmental envelope continually for the last five years, rising to the requests of some really top notch riders and characters, and in doing so have both opened up what were once nice markets to the masses, and outright creating others.   The Pony Rustler does just this: its a capable machine and I came away mostly impressed.  Being a nit picker and overly keen on my own steeds I had few complaints but most of them were fit related to a personal choice level.  


The B plus platform is here to stay and the potential here for cool fun bikes is off the charts.  I can't say I'm a big fan of spec'ing the boost though, or really why the industry decided to side step what people really want in these future bikes.  ("Boost" is what the industry is calling the widening of the drive line to accommodate the space required from 3" wide tires) From Salsa's point of view I get that its what's available in the form of OEM parts that work; its more that I don't understand the move from the industry.  The boost front hub gets a wider 110 mm OLD (outer locknut dimension) spacing.  Downhill bikes have run this since the original Boxxer fork I believe if not sooner, AND you get a 20mm thru axle that greatly improves performance.  Why make a silly and inferior hybrid axle system for a bike that's clearly meant to rip up downhills when better options have existed for years? And the same goes for the drive line.   The argument here is that going to the 83mm downhill spec bottom Bracket will move your pedals outboard, and it will....a whole 5 millimeters per shoe, I think cleats have more adjustment than that. 

But going here will allow you to run something really novel in the world of future bikes....a granny gear.  With more people heading out with loaded rigs for overnighters and more, all those gears we used to take for granted ten years ago are actually still quite useful.  Less so for big rings, but those 2x setups are pretty attractive.  Think Colorado Trail, y'all.  I believe we referred to it as the granny gear 500 back in 2012, and even in the world of carbon wonder bikes I just don't see the topographical facts of mountains changing.  Really though, its four days after Marty McFly and Doc Brown flew into 2015 in a retrofitted nuclear powered DeLorean.  And just where are those hover boards, anyway? Can't we have these new wonder bikes without the influence from the road bike weight weenie market?  Don't be a sissy.  Its just a couple grams.

Those guys back in 1985 were proud to be making cutting edge 30 pound rigid bikes and you would have been proud when it got you to the top of the mountain and bugs in your teeth the whole way down.   I propose we re-appropriate "boost" as a fitness term for the added effort of having to heave that extra 10mm of crank spindle and 5mm of thru axle to the top of the mountain.



Ok, rant over.  Back to the matter at hand.  I don't really pay much attention to the mainstream bike market, save for what parts and "standards" are doing.  I, for one, am not the type of person in the market for a new carbon squish.  The whole point of posting this tonight is to give nod to those pushing technology in our sport, and to those truly talented beings of our biking world, one who just rolled up in an orange van and will offer much in the push into the future.  But today the notes were taken, and one of the most compelling notes was just how stoked the rest of the public was to ride this bike at the official demo yesterday.  So I do say Mr. Spielburg: Here's your future.

Sunday, September 13, 2015

Yoked!

So here we are into September and I think my bicycle output up until now would qualify as a personal "least productive" year to date.  That said I'm still here making stuff and plenty of that work is still bike oriented.  A lot of those efforts have been going across city limits to the other custom bike shop.  This year has been a year more consumed by tool building, and the payoff will be worth the effort both in the time saved over the long haul and more so in the overall quality of the finished frames.  There's only so much you can do with hand files, folks, and the argument here is not man vs. machine: which method is better.  The hand files still get touched to every piece of metal that makes its way onto the bike, but you just can't manipulate metal with files.

I've resorted to various forms of plate yokes on at least a few different bikes now, and with the dawn of the plus platforms becoming increasingly bright, the need to accommodate sound structure in an area with minimal space is ever present.  I needed a way to accurately persuade plate metal in a symmetrical fashion that would allow for maximal tire and drivetrain clearance.  I kept looking at this piece of railroad track we had sliced off its base a few months ago out at the Viking Ranch.  When it comes to industrial scale metal work the Viking Ranch is way more capable than the Moustache Shop.  His drop saw accurately sliced the mushroom top of the track off effortlessly.  Now to put it to use.  The first step in manipulating metal is work holding.  The track was drilled and tapped on the face and on the side and a clamp was made to hold a 3/16" plate at tight clearance so minimal flex is transmitted through the clamp.  The face clamp is used for the primary bends that need to be symmetrical and the side clamp will be for the secondary bends farther back toward the rear axle.  


Now to apply the force.  Keeping the pressure as close to the bend radius as possible will assure the metal being bent follows true to the form, but I did want the ability to change to 1/4" plate if the need presented itself and allowing for a little leverage off the track sides seemed like it would save my vise, so I kept the rollers a bit outside the width of the track.  The single leg attachment on the bottom of the female "crush lever" assembly is to orient the clamped work piece.  Above the primary bends have already been applied to the machined raw plate.  Below the secondary bends have been added with a more basic lever assembly and a reposition of my work piece clamped in the form.


Before being bent the flat 3/16" plate is cut to something of a diamond shape and the center is relieved to a thickness of .100" on the inside where it will be attached to an extension from the bottom bracket shell.


The yoke and extension are then brazed together and proper inside penetration of the brass is ensured.


The sub assembly is then mitered to the correct length for tire and chainring clearance and tacked to the BB/seat tube sub assembly.  


Stays are now ready to be mitered and attached.  I picked up some slotting saws at a machine shop closing in Phoenix and got the slotting arbor on the Barker PMO mill attached and running for the first time.  Makes a crisp cut.  


For such a small mill I have been really impressed with what it can do as a versatile bike machine.  So far I've done just about every miter on a frame and fork with the exception of seat stays, and all with a very basic swivel vise and a cabinet full of Paragon tubing blocks.  Clearance is tight, and setup is probably not the fastest out there, but the miters are accurate and its been a fun transition.



Stays are mitered and tacked first at the dropouts then at the yoke.  Now awaiting the rest of the bike.  It'll be a sweet one, I promise!

Wednesday, June 17, 2015

...In Dealing with Arizona Mud

Growing up in the Dirty South, mud, rather, "muddin'" was looked at as sport rather than obstacle.  There were bike rides through my teenage years that were purposed with finding the largest puddles we could and riding through them.  That was what big rings were for: full speed charges through puddles after rainstorms, pulling up that front wheel at top speed until it came down through the pooled water to stamp into the sticky ooze below and relieve the rear wheel of all traction duties ejecting the rider over the bars.  That was how I learned to wrench bikes in more ways than one.  The Georgia/Alabama red clay that provides the namesake of the dirty south was a source of pride amongst those who ventured outside.  I remember entering a race where lawnmower goggles were the preferred attire over sunglasses of any sort and the first downhill quickly turned into a run to the creek at the bottom for an impromptu bike wash to get things rolling again.  That clay turned into a slick peanut buttery grease that would stop tires from rolling and kill all fun in any direction.  Racers would routinely apply cooking spray to frames and tires and I even remember one spray on product ("Mudd-off" I think) that was dedicated to the task of shedding mud from bicycles.  Oh where we would be if it actually worked!  I guess I would have nothing to type about today.


Flash forward twenty years to life in the other dirty south...the southwest...home of the Basalt lava flows of the San Francisco volcanic field.  Producer of a mud far more unforgiving than anything ever witnessed in the east.  Yeah, I know, you think the southwest is a desert of endless sunny days with ridiculously warm temperatures making it uninhabitable to normal humans.  Well the third part may be true, but this year has brought about an above average rainfall for the spring leaving areas open for daytime bike adventure long into a season that most years would have left forgotten in the heat by April 1.  I was fortunate enough to receive a phone call from Will over at WTB who was en-route to a five day Coconino 250 attempt over memorial day weekend.  In that moment the wheels were set in motion for a long weekend adventure.  I wouldn't be able to make the whole 250 with the group that identified themselves as the California Camels, but it did allow for a multi day adventure ride through some new country to meet up with another steller adventure that you can read about HERE.


My ride over the weekend would be from Flagstaff to Mingus Mountain and back around Sycamore Canyon, but the early start to monsoon season left the route selection to be a touchy detail.  Rim country (referring to the Mogollon Rim of the Colorado plateau extending from central Arizona to southwest New Mexico) is a likely place to encounter the Basalt flows and the mud that they can produce, so any chance of rain when riding in this area, especially on unfamiliar roads and trails should not be taken lightly.  Descending the rim with a loaded bike is often a granny gear affair for 2000 or so vertical feet (that's right, granny gear downhill), but add some rain into the equation and prepare for a long and slippery walk for miles if you're lucky.  Choose wisely.

My route was looking good as the threatening skies kept temperatures down but never unleashed on day one.  The power line descent known locally as the Casner Route appeared from the top to be dry enough, and it held through to the bottom.  It wasn't until the next day that the signs of what could be started to appear.

This bear track on Mingus Mountain shows the grease that had since dried.  The pebbles that comprise the rest of the trail are nowhere to be seen within the track meaning they were carried off or pressed in.  The mud crack evident in the heel pad is a sure sign that life would have been miserable here under rear wheel power when the track was laid.  Other than this bit of evidence our day was again uneventful and filled with spectacular weather for late May in the high desert grasslands.  An overnight drizzle along the Verde River in Perkinsville would be cause for concern though. 

My route for day three was home following the Pines to Mines route.  If all went well it would be 70-75 miles of dirt road, mostly uphill with ~2500 feet of vertical.  No downhill fun, but a nice pedal and none too steep climbing.  I was out of camp early, bidding the sleepy Camels farewell as they dozed.  The overcast morning showed on and off drizzle.  As I steered toward the rocky climb up the western edge of the Rim, my eyes lay on the ground before me and the residual dampness of the soil below.  A freshly graded road leading toward a mining claim showed evidence of troublesome travel, but the moisture was still too low and the surface remained good.  About halfway up the rim the sandstone rocks that make the Pines to Mines downhill an abusive challenge turn to basalt, the soil to a rich rust red of decomposing iron, and though it wasn't raining presently the overnight drizzle had left its mark.  Tires start to clog, and tiny pebbles are released into chains and derailleurs.  The release of those pebbles was indicative of a mud solution still on the dry side. 


Add a bit more water and those pebbles serve as a binding agent for more mud.  Below the mud is showing enough moisture to stick to itself, but has somehow released from the tire (not common).  It was enough to stop movement and force a get-off, thus clogging my shoes with the same sticky clod.  At its worst imagine your wheels becoming a cinnamon roll of mud and rock.  Conditions here change literally by the minute, but if this area had seen real precipition, I would have no doubt been pushing a very slow and heavy bike, or maybe a sled (pushing the sled is what happens when both wheels lock up and the bike+mud must be pushed along on the skids).  Out here mud clearance is only a matter of the recipe.  No matter how much is built into a bike frame or fork it will be thwarted by the right conditions.  The only measure that can be taken is knowing when to stop before the mess takes hold.  Walking can sometimes save your drivetrain, especially if grass grows off to the side, but the best plan is avoidance entirely.


Memorial Day for me did not present this option; I was to be back on the job on Tuesday.  Fortunately the mud up the rim was short lived and rapid travel resumed atop the plateau.  Ominous clouds loomed around the San Francisco peaks obscuring them from sight, though it was sunny west of Sycamore Canyon.  I never got rained on, save for a drizzle coming around Sycamore Rim trail.  The mud started here, but by the end of the four mile stretch of singletrack, the sun had come out and the trail was rideable again.  I found myself under a power line that runs directly east/west along the southern boundary of the Navajo Army Depot, and here began the mud.  I fell immediately into the commitment trap as skiers call it.  The intended route of unimproved dirt roads proved immediately impassible.  The mud was in full slick status in lanes of travel, unrideable, and sticky at the edges collecting all vegetation and debris surrounding a tire track.  The two track following the power line was muddy but passable, and the decision to keep moving along this route seemed obvious in rising panic of dwindling daylight.  Walking the power line hills would be slow, but the urgency of the situation forced movement.  In retrospect a route north around the Depot would have been the wise choice, utilizing improved roads, but I had not been stopped along the power lines.  Three hours of daylight, twenty miles to good dirt. There was no option for rescue; no one could get there.

The hikes up reminded me of my fire line days; power line cuts make good fire breaks.  The downhills were rideable, speeding travel.  The hills increased in length and steepness as I came up to Volunteer Canyon.  Cresting the last hill before the canyon left a dismal sight of the next power pole over half a mile away.  The bottom of Volunteer canyon was several hundred cliffed out feet below; the sun in the tree tops to the west.  I decided to backtrack.  I needed to get to a known spot on the map before darkness set in.  A singletrack heading directly south was indicated on the map near my position.  I found it with a little searching around, the stacked ancient and rotting timber over the rolling topography revealed the rail grade heading south.  Though not rideable, the travel would be the best of the troublesome situation.  Unimpeded walking would lead me back to the impassible roads of my intended route initially.  The gain in eastward mileage through my detour offered no improvement in road condition.  It was dusk.  I knew what I had to do.  Fifteen more miles of hiking and riding, all of it adjacent to the road.  The amount of moisture fallen that day was one for the records.  The roads were left as a slick that would remain overnight leaving the grass and needle cast to the side as the only means of travel.  Water puddled into a shallow lake between patches of grass in the open meadow offering the bike a short reprieve from some of the mud.  Travel would continue in this manner for the next two hours until the improved gravel of Woody Mountain Road was under rubber.  I pulled the plug a little before 10:00 pm, calling for a ride when I reached pavement.  15 hours of travel time.  Over 80 miles covered.  Worst day ever in the saddle in over 21 years of doing this.  Saved by a rail grade.




The detriment of a day like this to a multi-day route is fairly obvious.  A drivetrain that emerges from a day looking like this takes hours to revive, requiring a full disassembly, and tools that are rarely available in the field.  While waiting out the mud may not always be the best option I would believe the time component to be nearly equal to that of the required bike service.  Of course that excludes weathering a multi-day storm.  The best option in dealing with a situation is careful route planning when travels show signs of turning.  Carry a map and understand the road travel grades in selecting a route.  Improved dirt roads offer a graveled surface that will likely rise above troublesome mud.  Unimproved roads may be smooth but will travel whatever geology the earth's surface may offer.  Avoid the basalt layers in the rain.  Beware aware of Juniper areas when storm clouds are present in Northern Arizona.  Choose wisely.  Walking in the grass before your bike clogs up with mud can save a major headache down the road.  Recognize the situation; pressing on will not change the weather, but traveling cautiously with regards to road surface when mud gets bad could ensure speedier travel later on because you saved your bike.  Clean out your tires before they clog up your frame and drivetrain.  A piece of stiff fencing wire does wonders at this.  Clogged pedal cleats are way more favorable than clogged chain and derailleurs, just as a 60 pound bike is better than a 100 pounder.  It will be slow; it will be miserable; it will come to a memorable end.



Saturday, May 09, 2015

Thru Axle Unicrown Fork, Vise Pedestal

This fork is on its way to Alaska after getting a coat of black powder to fit up onto a bike I did up a couple years back.  It is a long time in the works, mainly because for the longest time I didn't have a dummy thru axle, but then because the machine tooling obsession took over and I really didn't want to hand miter another unicrown fork.  It has the original Paragon thru axle dropouts that I ordered when they first came available, so that should put a bit of a timeline to the project to those of you who want to really pick this apart.  So now its done and its about the most badass rigid fork I can imagine.  Raked tapered blades, externally butted steerer, tabs for a truss rack, clearance for 29+or-"er.







Oh yeah, I welded up a sweet new rocket ship vise pedestal.  The angle of the photograph makes it look small and top heavy.  It isn't.  Its 36" high bringing the jaws up to about 42" from the floor in hopes of getting better posture when polishing brass.  Thanks to the viking for the time on the mig welder to make this happen.  Its super sturdy and I haven't even bolted it to the floor yet.  

Here's a better picture:



Thursday, April 02, 2015

Turning 4130


A while back after purchasing that lathe I got the idea of turning some tapered non-tapered steerer tubes that would better match up with the offering of 1 1/4" diameter unicrown blades and give a nice and thick attachment point for the fork "crown."  Prior efforts at achieving this effect were accomplished by brazing a sleeve onto the bottom of the crown to increase the diameter of a steerer tube where the fork blades attach.  Machining this piece takes one of the heat cycles out of the equation and ultimately yields what I believe is a better product as the reduction from 1 1/4" at the bottom to 1 1/8" at the stem clamp is carried inside the head tube by very gradual 0.75 degree taper rather than abruptly at the crown race seat.  This design utilizes the tried and true straight 1 1/8" headsets of any configuration (internal/external) rather than the 1 1/8" to inch and whatever taper cups that more and more bikes are going to, suspension forks or otherwise.  It should be noted that these designs do certainly have their place, particularly in the suspension world, but the reason for doing this is to create the best brazed bike I can, in this case a dedicated rigid.  This piece gives the blade's crown miter a full wrap of the steerer tube while simultaneously beefing up a part of the bike that sees more and more force applied to it with disc brakes and increasingly fatter tires.   Fat tires SUBSTANTIALLY amplify braking forces and chattery rigid forks are discouraging at best.


Starting with some 1.25" x .125 wall 4130 cromoly, I set about designing the steerer tube from the bottom up, giving ample room for blade and crown race seat attachment.  I carried the taper 80mm into the steerer and some trig starting with the O.D. of the crown race seat area and subtracting the stem clamp diameter gave me a change in radius of 1.1mm and a taper angle of around 0.75 degrees.  Click to photos to full screen.  Calculations at this point are more accurate than my tooling can read so I rounded up the math (I'm talking math into minutes and seconds here versus a machinist's protractor that reads 5 minute intervals).

With the design laid out onto the tube I setup the lathe.  Now I have not spent much time with 4130 on the lathe.  My first cuts were looking pretty terrible with lots of galling and I was getting discouraged when the phone rang with a call from my buddy Evan at Idyllic Cycleworks.  Evan owns Moustache number 4 and has since found himself getting increasingly involved in a bicycle oriented machine shop in Fort Collins, CO.  He was able to give me some pointers that started with some new indexible tooling and inserts that allowed for deeper cuts at a higher speed.  4130 is rather counterintuitive when machining.  All the metals have their quirks though as I'm finding out.  With these pointers and a new bit I started making some practice cuts.  Turn it UP!


The roughing cut above already improved upon my initial efforts by leaps and bounds.


Messing around with tip angle for finishing cuts.  Above are samples trying out different feeds rates and RPMs 


The results were immediately better, but presented me with the learning machiner's problem of needing to take a thick cut for a finishing pass to get an accurate diameter of 28.6 mm for the stem clamp.  I went about the process in a more planned manner than I have to date:  Two roughing passes of 0.028", then a finishing pass to take off the measured remainder accounting for tool deflection.


Now with a plan on paper, the next hurdle was the taper transition.  My lathe does not have a taper attachment allowing the turning of a taper under power feed, so the taper would have to be done using the compound slide under manual feed.  This meant a smooth transition from power feed to manual feed would be imperative.  This lathe will stop itself with the power feed on if an obstruction is met, so I made up a carriage stop.  By placing this in front of the carriage where the tool bit met the start of the taper I could manually engage the compound feed without stopping.  Stopping even for a second would produce a groove in the work piece that would be a direct trip to the recycling bin.  There is certainly room for improvement on this method by milling out a taper template for the cross slide to follow under power, but that's another project for another day.  In the meantime I managed to produce three usable steerers and one decorative piece of practice metal, and also some seriously long pieces of blued out phone cord lathe chip.  The blued out coil was a happy cut in chromoly, and you still can't fake a chip.


Thanks for following along in the geek text!