Need ideas to mill a radius botom pocket, no cnc.....Help please - Page 2
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  1. #21
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    Oh and for all you guys wanting to put a bar between centers and do this on a lathe, not me. If I had to do it that way I'd rather bore the side holes first and use those to support the bar, basically line bore it with built-in bushings. Less setup time on the mill.

    But I'd still go with the back spotfacing tool from both ends as the most efficient manual method of all.

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    Thinking more about it, I belive your right. rough it out with aball end mill thn go to the bar through the hole. I'll have to make the bar.... Thanks

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    First thing I'd be doing is looking at a redesign. If that inside radius was flat instead that would be a dead easy
    part to make. While it's always good to have ideas and options I've never been afraid to challenge my customers
    to come up with better (meaning simpler) ways of doing things. We are all in this to make money (I'm assuming
    that) and keeping things simple is usually a better way to do so...

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    Hi LKeithR:
    I agree with you in principle, but the pushback I've received in the past has been:
    "Well if you had the right gear you should be able to do this...what's WRONG with you!!"
    Sometimes the complainer is a total fuckwit, other times they have a point.

    For this project, it's a fair challenge without a CNC mill and a sinker EDM... however, if you have that gear it's not an impossible design by any means.
    I suspect from the nature of the OP's question, that this may well be a personal project; he's trying to restore an irreplaceable thing or make something to match his existing part, and the time it takes is not important in the same way it is for those of us who do it for a living.
    The original looks like a diecast or maybe investment cast part...if he's trying to make a cosmetic match for that part he's going to have to get creative, and with only a Bridgeport and a lathe in his home shop (I'm speculating here) he'll be doing a bit of screwing around to get there but he may well not care so long as he gets to his goal.

    At least we've given him several workable ways to make his geometry...which one he picks and how good a job he makes of it is up to him.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    I don't know about everyone else, but I'm looking forward to the end of this story. Interested to know how he does it and how it turns out.

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    I have a quillmaster that could probably be angled to get at that inside corner. I might get lucky with the tooling, or have to grind a d-bit to hit the angle.
    One side at a time, pivoting the workpiece around the center hole axis.
    Tight quarters, though.

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    Default Old school

    Quote Originally Posted by k2steve View Post
    I will try to attach a pic of the part. I need to duplicate this mount for a new reshaped clamp. the part is only roughed out but square right now, thought I'd do the part I don't know how first while I can hold it easily.
    I cannot figure out a way to do the bottom of the pocket. It is 1" wide, 5/8" radius at the bottom and square to the sides.
    Is there a way of doing this, I never learned CNC nor have a machine to play with. just conventional machines and tooling. Thanks for looking, hope there is a way to do this.....Thanks Steve
    Just contour mill the radius. Rough it out like an upside down ziggurat and then contour mill it. Move in from edge to edge moving a few thou in with a ball end mill and down. Takes a little trig, (over and over and over -I program an old Radio Shack calculator or one could just use an Excell spread sheet) and will leave a small radius in the corner which can be taken out by hand filing. No big deal but time consuming and any misdial will be visible.

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    I think that part is cast. So I would figure out how to cast a rough part, then machine any details like the holes. Alternately re-design it to be made in multiple parts that are assembled and screwed / welded together.

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    As you may suspect, that part is undoubtedly a casting. Probably a one step manufacturing process with very little or no clean up after it comes out of the mold. Only the threads would need tapping. That way, and made in quantity, it can be dirt cheap. And it, along with any mating parts, were engineered/designed with that in mind. The molds for that casting process were probably expensive and difficult to make; another sign that it is designed for mass production. It is not well suited for manufacture in small quantities or with basic machine tools like a lathe or a milling machine.

    I am not sure how much leeway you may have in the design, but if you can re-engineer it with a larger radius between the half barrel shape and the two round, flat sides, it would be easier to make. Of course you would have to re-engineer the mating part(s) as well.

    OK, how can it be made? You do not say what the material is but it looks like metal. Since it is a casting and a complicated one at that, it probably does not need to be a very high strength alloy. What is referred to as pot metal or zink is likely what it is. So, perhaps a material with even less strength may suffice.

    One real possibility, especially if this is just for a prototype, may be 3D printing. 3D printers can make a wide variety of complicated shapes. Those inside corners are no problem. The open arch at the bottom would require supports (extra, thin columns of the plastic material that are broken off after printing) but that is a standard technique in 3D printing and you can just check a box while printing the design to include them. The threads would have to be tapped after it is 3D printed, but they would need to be cut in any event. And, depending on the actual material (plastic) used, the surface finish would not be as nice as your example part. But it would be perfectly functional. I know you said no CNC, but 3D printing is easy to learn and not all that expensive. You can get started for a few hundred dollars. There are 3D design programs like Fusion 360 that you can start off with for free. But they usually want you to pay for their use if you start making money with them.

    Also there are more expensive 3D printers and processes that can print metal parts. These metal parts often require baking in a high temperature oven as a finishing step. These 3D printed metal parts can rival metal castings and even parts cut from some solid metal alloy stock in strength.

    Another way would be actual casting with a plastic. You would need to make a pattern and then use any of many mold making compounds to make the mold. Then you choose a room temperature plastic that comes as two liquids that are mixed together and then poured into the mold. It hardens in minutes and you have your part. You can add things like fiberglass fibers to increase the strength of the stock plastic mixtures and even coat the mold with various powders to get a fast surface color/finish. Unless you want to make a complicated mold with movable parts, you would need to drill and tap the holes. Otherwise the process is fairly straight forward and easy.

    Injection molding is far more expensive but would allow a greater range of plastics.

    You could even combine these two methods and make the pattern with a 3D printer. Then sand and perhaps use solvents to clean up and smooth the surface before making a mold from it. 3D printed plastic parts are not as strong as solid plastic parts made with the same plastic. This would allow you to use a stronger plastic, one with a fill material like the fiberglass fibers. But making the pattern will be easier with CAD and a 3D printer.

    If it must be metal, perhaps you can use a small diameter, ball cutter with a long shank to form that corner radius and use a larger ball cutter for the remainder of the internal, barrel shape. Your rotary table would be used here. I am not sure about the rest of the external curves, but perhaps they can be approximated with a number of flat surfaces that are easier to mill. This will take time and patience.

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    Hi k2Steve,
    Could you mount it on a fixture plate & put it in a tilting vise that rotates keeping the centre line the same, lock the "X" axis & move the "Y" axis back & forth as you tilt the vise a little at a time taking small bites with a ball end mill. Finishing off the corner with a small square end mill or fix square piece of HSS or carbide in the quill, lock the spindle & ways & using the tilting vise scrape away bringing down the quill a little at a time until you have the finished corner. Bit unorthodox but it might work ��
    tilting-vise.jpg

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    Default Did it

    Got the parts roughed out, I will try to attach a pic, I tried the other day and it wouldn't go?
    I set up the part on the rotary table and used a right angle attachment. This is the first time I have used one, it worked well. Anyway the setup worked good enough. The bottom of the pocket has carved lines from the end mill arced across. Thank you all for the ideas and help. At first I had no idea how to do it. The rotary table is starting to free up now with use. Steve
    [/ATTACH]20200502_182759-1-.jpg20200502_191813-1-.jpg

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    Quote Originally Posted by k2steve View Post
    Got the parts roughed out, I will try to attach a pic, I tried the other day and it wouldn't go?
    I set up the part on the rotary table and used a right angle attachment. This is the first time I have used one, it worked well. Anyway the setup worked good enough. The bottom of the pocket has carved lines from the end mill arced across. Thank you all for the ideas and help. At first I had no idea how to do it. The rotary table is starting to free up now with use. Steve
    [/ATTACH]20200502_182759-1-.jpg20200502_191813-1-.jpg
    You might show the cutter, Just a flat bottom end mill?
    Buck

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    Quote Originally Posted by Terry Keeley View Post
    Thinking out loud here.

    Rough the bulk of it out square.

    To do the bottom radius could it be mounted to a rotary table on it's side then mount the rotab vertically and using a long cutter end mill the bottom?

    The part would be like a pendulum, would that work?
    Yes that would work, I set the table flat, thinking that way would be easier to center the spindle to the table, then center the pivot point of the part to the rotary table.

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    Quote Originally Posted by michiganbuck View Post
    You might show the cutter, Just a flat bottom end mill?
    Buck
    Yes, the pocket was 1" wide, I used a 3/8" four flute extra long center cutting end mill.

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    Quote Originally Posted by implmex View Post
    Hi LKeithR:
    I agree with you in principle, but the pushback I've received in the past has been:
    "Well if you had the right gear you should be able to do this...what's WRONG with you!!"
    Sometimes the complainer is a total fuckwit, other times they have a point.

    For this project, it's a fair challenge without a CNC mill and a sinker EDM... however, if you have that gear it's not an impossible design by any means.
    I suspect from the nature of the OP's question, that this may well be a personal project; he's trying to restore an irreplaceable thing or make something to match his existing part, and the time it takes is not important in the same way it is for those of us who do it for a living.
    The original looks like a diecast or maybe investment cast part...if he's trying to make a cosmetic match for that part he's going to have to get creative, and with only a Bridgeport and a lathe in his home shop (I'm speculating here) he'll be doing a bit of screwing around to get there but he may well not care so long as he gets to his goal.

    At least we've given him several workable ways to make his geometry...which one he picks and how good a job he makes of it is up to him.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    You are correct, I am paying back a favor and making four of these modified clamps in the garage. They have been time consuming, just a couple more comer radius and corner rounding and splitting and and and

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    That will do the trick. As long as the bottom is just clearance it doesn't really matter if it's geometrically perfect. At least, as long as you don't have an obsessive compulsive customer...

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    Alright, I know the original post said this was a "reshaped" clamp, so I hope this is how it's supposed to be, but the radius in question and the holes in the ears are parallel to the countersunk holes in the clamp in the original picture. On this new part they are perpendicular. I just know from experience it sure does suck to do a bunch of work on something only to realize you goofed on some step way back in the set-up, like holding the part the wrong way . . . please say it's supposed to be this way.

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    Quote Originally Posted by Zach201 View Post
    Alright, I know the original post said this was a "reshaped" clamp, so I hope this is how it's supposed to be, but the radius in question and the holes in the ears are parallel to the countersunk holes in the clamp in the original picture. On this new part they are perpendicular. I just know from experience it sure does suck to do a bunch of work on something only to realize you goofed on some step way back in the set-up, like holding the part the wrong way . . . please say it's supposed to be this way.

    The change is deliberate, that mount holds a speaker (two mounts per speaker) onto a oblong sail panel(I think that's what it's called on a boat)so that the speaker could be adjusted up and down.

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    Quote Originally Posted by k2steve View Post
    The change is deliberate, that mount holds a speaker (two mounts per speaker) onto a oblong sail panel(I think that's what it's called on a boat)so that the speaker could be adjusted up and down.
    Boat speaker clamps! Of course.
    HaHa. Well done, nice piece of work.

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    494686330_img_3773_277627.jpg If anybody want to see the finished product here's a
    pic of them in action, two sets, pic only shows one side.


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