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    Default custom lathe tool

    I am looking at making some replacement phenolic pulleys for an antique piece of equipment. I have a blueprint from august of 1940 that gives the dimensions for the groove. Who could build me a tool that can cut the phenolic for the dimensions in the attached pic? I currently do not have the ability to grind my own tooling, I barely have a lathe that works.

    I will still have to find a way to cut the pulleys out of the flat sheet, I am thinking a large hole saw, bore the center hole, then turn the outer to the finished dimensions, then cut the groove.

    Any advice is appreciated. Tim
    Attached Thumbnails Attached Thumbnails b12-1080-.jpg  

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    Phenolic cuts like butter, do you not have a bench grinder? Are you over thinking this?

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    Quote Originally Posted by astjp2 View Post
    I am looking at making some replacement phenolic pulleys for an antique piece of equipment. I have a blueprint from august of 1940 that gives the dimensions for the groove. Who could build me a tool that can cut the phenolic for the dimensions in the attached pic? I currently do not have the ability to grind my own tooling, I barely have a lathe that works.

    I will still have to find a way to cut the pulleys out of the flat sheet, I am thinking a large hole saw, bore the center hole, then turn the outer to the finished dimensions, then cut the groove.

    Any advice is appreciated. Tim
    I have sheets of phenolic with canvas and linen cloth reinforcement. I make pulleys and drawbar knobs for my old watch lathes by cutting the blank with a hole saw. Then I chuck the blank in a lathe and bore the center hole and face to a thinner dimension if needed. With the blank mounted on the new drawbar or on a mandrel, I turn the outside. For 5 mm round belt grooves, I use a carbide tool that I ground for the purpose. I have made tools with a female radius for turning knobs. For any other odd shape, like that little 3/32" 15 degree groove, I use hand turning tools, same as for common watch repair jobs. I only make special tools if I will use them more than a couple times.

    A set like this is too big for watch parts, but the skew might be about right for your groove.

    https://www.amazon.com/Benjamins-Bes...gateway&sr=8-6

    Larry

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    Lets think now, custom tool sir ?'' thinks to self, 'this ones ripe for the picking - a bit of 3/16or 1/4 HSS and about 10 minutes on a bench grinder,' ………………... ''that'll be $150 + shipping sir.''

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    Quote Originally Posted by dalmatiangirl61 View Post
    Phenolic cuts like butter, do you not have a bench grinder? Are you over thinking this?
    I have to meet a spec/blueprint with this, tolerances need to be held or the cable slips. The cable is 1/16" 7x19 galvanized and/or stainless. It is real tight tolerances on these, not high quantity, just high quality.

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    Quote Originally Posted by Limy Sami View Post
    Lets think now, custom tool sir ?'' thinks to self, 'this ones ripe for the picking - a bit of 3/16or 1/4 HSS and about 10 minutes on a bench grinder,' ………………... ''that'll be $150 + shipping sir.''
    I can measure the radius accurately and the angle too, bench grinder is not the quality I am looking for. EDM machined carbide, yes, Tool steel yes, and I could probably build a jig to grind the radius then grind the angles or grind the angles then grind the radius, but I just picked up 2 bench grinders from the 50's, but I need to get some good abrasives for them before I use them.

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    Making a pulley groove from a single cut/tool works fine for most applications, but if it's dimensionally critical, I find it easier to break it up into the individual features.

    Use a radius'd grooving tool to make a slot to the depth you want, then cut the sides using a narrow tool and your compound set to the proper angle.

    The quality of the cut will mostly come from your set-up (speed, feed, cutter geometry, etc.), but the accuracy of your work, or how well it dimensionally matches your print, is mostly between your hands and the machine.

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    Default custom lathe tool

    Quote Originally Posted by M.B. Naegle View Post
    Use a radius'd grooving tool to make a slot to the depth you want, then cut the sides using a narrow tool and your compound set to the proper angle.
    Yup, that’s the way I’d do it too. Three cuts: straight in then with compound at +7.5 then -7.5 all with the same tool. And you probably won’t even need the straight cut, just the +/-7.5 degree cuts should do it.
    Last edited by Mal01; 05-17-2019 at 10:37 AM.

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    In elevator applications it is essential to prevent rope slipping on the sheave. It is common to use an undercut below the rope seat. As I recall a 105* undercut was normal. That means the width of the undercut subtended 105* on the circumference of the rope.

    With a round bottom groove a little wear will cause a big loss in traction. With an undercut groove the traction will remain constant until the rope wears to the bottom of the undercut.

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    As posted in OP drawing ".025 r."

    So the cable is .050 " dia ?

    smallest aircraft control cable I have seen is 1/16".

    So what exactly are you making ?

    How do you think it was done originally ?

    a template was made of sheet metal, the lathe work continued
    until the template fit.

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    I agree c with the overthinking diagnosis.

    Bench grinder technology had not changed since the '50's, so that's not an issue. Neither have HSS or cemented carbide tool bits.

    You can get perfectly adequate abrasives for a bench grinder at any hardware or big box home supply store. (You need the green ones for carbide, they may not be at Home Despot.)

    I use hole saws to rough out disks too. I also think a round nose tool for the bottom of the groove and the compound for the sides is the way to go. A wedge shaped form tool seems like a good way to just push the sides of the groove open rather than cut a precise angle.

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    Quote Originally Posted by fciron View Post
    I agree c with the overthinking diagnosis.

    Bench grinder technology had not changed since the '50's, so that's not an issue. Neither have HSS or cemented carbide tool bits.

    You can get perfectly adequate abrasives for a bench grinder at any hardware or big box home supply store. (You need the green ones for carbide, they may not be at Home Despot.)

    I use hole saws to rough out disks too. I also think a round nose tool for the bottom of the groove and the compound for the sides is the way to go. A wedge shaped form tool seems like a good way to just push the sides of the groove open rather than cut a precise angle.
    My bold italics

    Not IME if the tool is sharp, a tufnol / phenolic tool needs no top rake, therefore is very easy to keep sharp with an oil stone, and with the cut taken carefully (along of course with a SHARP tool) the groove should be a mirror image of the tool.


    BOTOH, over the years, at a rough guess I've only machined 5 or so tons of Tufnol (phenolic) (much of it with much finer detail etc etc than that pulley), so what the 4X do I know.

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    I was specifically commenting on this case. Given the other questions here, I would not assume a sharp tool or that it stays sharp. (As a relative newcomer myself, I'm putting myself in the position of the OP and trying to imagine how I'd screw it up.)

    And if we're encouraging someone to grind their first tool, might as well make it easy on them. Symmetry isn't easy, grinding the arc on the end of the tool should provide plenty of challenge without trying to get the two sides tangent and at a precise angle.

    Since it's for one piece of antique equipment I'm not sure there's enough parts that the time saving of a form tool makes up for the learning curve.

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    Quote Originally Posted by fciron View Post
    I was specifically commenting on this case. Given the other questions here, I would not assume a sharp tool or that it stays sharp. (As a relative newcomer myself, I'm putting myself in the position of the OP and trying to imagine how I'd screw it up.)

    And if we're encouraging someone to grind their first tool, might as well make it easy on them. Symmetry isn't easy, grinding the arc on the end of the tool should provide plenty of challenge without trying to get the two sides tangent and at a precise angle.

    Since it's for one piece of antique equipment I'm not sure there's enough parts that the time saving of a form tool makes up for the learning curve.
    My bold italics, using an 8 or 10x eyeglass, oilstone and radius gauge makes that part quite easy.


    Serious Q, ..if the OP orders and receives a custom made CNC ground / wirecut / whatever hocus pocus come flavour of the week tool, how is he going to establish the tool is correct for his needs?

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    Quote Originally Posted by Limy Sami View Post
    ...
    Serious Q, ..if the OP orders and receives a custom made CNC ground / wirecut / whatever hocus pocus come flavour of the week tool, how is he going to establish the tool is correct for his needs?
    Not sure I understand the serious question.
    Fairly wide open tolerances although I do hate one sided rad callouts as you don't know where the best zero really is.
    With it so open here I'd make halfway inside which might not be the best choice. (Actually I'd usually contact the customer and ask)
    The part cut could be checked over two sets pins to verify dia. and angle.
    Are you saying the print may be wrong or that the tool may not be comped for top rakes?

    Most certainly this is doable on a bench grinder or belt sander if you are used to making your own cutting tools.
    Many here are used to this so it seems simple.... but do you remember your first attempts at hand grinding tool bits?

    Yes, a one off out of a tool shop will be stupid expensive so learning to do such is a needed skill.
    Bob

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    Quote Originally Posted by CarbideBob View Post
    Not sure I understand the serious question.
    Fairly wide open tolerances although I do hate one sided rad callouts as you don't know where the best zero really is.
    With it so open here I'd make halfway inside which might not be the best choice. (Actually I'd usually contact the customer and ask)
    The part cut could be checked over two sets pins to verify dia. and angle.
    Are you saying the print may be wrong or that the tool may not be comped for top rakes?
    Bob
    What I mean is how is the OP going to inspect the tool supplied? I agree with what you say about impliedtolerances etc etc, ………..but to me ( and maybe it was just me) the OP made a fair mount of play about how accurate the tool needed to be and how off hand grinding etc etc etc, wasn't good enough, ……..which when the tolerance on the radius alone, amounted to the difference between a 0.030'' & 0.050'' diameter hole - or a mere 40%

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    machinist are weird. The difference between galv and stainless cable diameter, the surface finish, the difference between stretched and unstretched cable are bigger than a good eyeball (layout with compass on sharpie dychem) radius sanded/filed/ground on a piece of stock. The centering of bearing/shaft and groove is a far more critical than radius at bottom of groove, the slip critical comes from side/wedging forces of taper. If the cable is riding on the radius then pulley or cable is tired out.
    of course, laser ultrasonic edm'ed with seismic compensation at 1 g datum cut on powdered diamond nano structure tooling with rake of .02 milli arc seconds is the only tool to use on a part with center found by hole saw with a Milwaukee general purpose twist bit.

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    Sheaves like this one are nowadays cut with form tools, which are out of HSS and profiled with wire EDM. Typically it needs
    to have a fourth axis so front relief can be put on the cutting edge. Typically the form tools are flat on top, zero rake.

    Doing this right means finding a wire EDM shop and suppling them with the drawing. They would be able to take it from there.

    I spent years of my life, nights, making sheaves of all shapes and sizes, mostly out of nylon. Sizes six inch diameter to over
    15 inches in diameter. The final grooving cuts were invariably done with a HSS form tool.

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    Quote Originally Posted by Limy Sami View Post
    What I mean is how is the OP going to inspect the tool supplied? I agree with what you say about impliedtolerances etc etc, ………..but to me ( and maybe it was just me) the OP made a fair mount of play about how accurate the tool needed to be and how off hand grinding etc etc etc, wasn't good enough, ……..which when the tolerance on the radius alone, amounted to the difference between a 0.030'' & 0.050'' diameter hole - or a mere 40%
    I do have radius gauges and precision protractors, I was just trying to make this a simple process to build several pulleys at a time, there are 2 pulleys in the system. The other pulley has a broach cut out of the center hole also. I am trying to sustain a fleet that is on average of 78 years old. The cable is 1/16, if the radius is too small, it will split the pulley, if it is too large, it will slip. I have a bunch of tooling and fixtures I need to make over the next few years. It is a frustrating process, having to learn as I go. I do appreciate everyone's comments, I am still hoping that someone can tell me who can grind me a tool that can make the groove in this pulley. I am thinking that I may have to make a .050 wide square tool for the first cut, then one that meets the above profile for the second one. Would that work? Regards, Tim

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    If there is more work like this requiring profile tool grinding and the need for inspecting said tooling and parts, the OP might consider getting a optical comparator. They are often available for little but can be quite useful for this sort of job and other instances requiring fairly accurate measurement of small parts. I turn mine on only a few times a year, but at those times I am thankful for it.

    Denis


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