Trick to grab round object in mill vise if their radius is more than the jaw height? - Page 2
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  1. #21
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    Bolt muffler clamps on the pipe and clamp in your vise

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    OP,
    And the holes have to all be parallel in two planes? Or not? How parallel? Sounds like the bars/tubes are quite long. How long? I know you work in less than optimal conditions with quite limited equipment. Depending on your answers there may be some simple solutions to the parallel issue. I like the flat barstock in the table slots idea posted above by ratbldr as a basic clamping solution.

    Denis

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    Quote Originally Posted by legoboy View Post
    ...he said to many machinists become vise dependent...
    That's just silly. A vise is often the fastest and most efficient way to hold a part and if that's the case it's
    the tool you should use.

    Anyone who has spent any time around a milling machine will tell you that there is no other machine in the
    shop that will challenge you as much when it comes to mounting odd ball parts--that's half the fun of using one...

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    Really

    Some sort of "fixture" that includes a vise, or just take the damn thing off the table. Two bolts, what could be easier?

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    Recently I had to bore holes in a 3-1/4" copper boiler for a 3/4 scale locomotive. I made two V blocks from plywood and bolted 1" square CRS to the ends of the V blocks. This gave me a place to clamp the boiler on the ends. I added a base the length of the boiler which was clamped to the table. I used C-clamps to hold the boiler to the CRS.

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    I don't know if you have access to a CNC mill but if you do something like these vise jaws are very easy to make. Local roofing company needed to be able to grab 20' long extrusions to do ops on them. I believe they were like 4.75" radius if remember right. They needed to be idiot proof for the guys using them and keep everything aligned. They used two vises in a line for better rigidity. Was a quick job for my CNC mill.

    20180517_200202.jpg

    20180521_230938.jpg

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    Honestly haveing a set of 3 or 4" high jaws for your mill vice is really useful, theres other ways of doing the same minus a vice, but tall jaws are pretty dang useful in the long term scheme of things.

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    Quote Originally Posted by EPAIII View Post
    You wanted a trick so here is one. It uses two pieces of uneven angle.



    I am sure it is for light duty only. And it may be more trouble than it is worth. Both angles need to be held down by the round so the two fill blocks should be the same thickness.

    Personally, I would just clamp it. But that would require removing the vise and putting it back again when this job is done.
    I doubt that would work. Self ejecting part jaws.

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  11. #29
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    I appreciate all of the advice!

    I wanted to make the thread about the general case so it's useful to more people in the future, but since questions are coming, let me explain my specific application.

    I'm building a trommel - which will use "drums" of woven stainless wire cloth to screen sawdust. The application is a point of use drinking water filter factory that I've been helping set up here in Guinea-Bissau for several years. The water filters are made of fired clay (kind of like a big flower pot), but the clay has sawdust mixed into it. We carefully control the particle size of the sawdust, and then when the filters are fired in the kiln, the sawdust burns out, leaving voids in the clay that are big enough for water molecules to pass through, but too small for bacteria to fit, so they stay inside the "pot" while the sterilized water flows through into what's basically a 5 gal paint bucket with a spigot. The filter is also treated with a colloidal silver that kills everything.

    The sawdust particles have to be just the right size. So, we screen them through a 30 mesh screen and throw out the coarse stuff. Then we run them through a 60 mesh screen and throw away the fines. What we're left with is the stuff that's the right size to use. However, the way we've been doing it is too slow, now that we're trying to ramp production up. (The facility should be able to do about 200 filters a month, and each one is enough for one family).

    So the trommel I'm building is actually a double trommel.

    one-shot.jpg

    The unsorted sawdust will get dumped into the innermost chamber which is the coarse mesh. The coarse stuff will stay in that chamber and fall out the other end. The fines+what we want will fall through the inner coarse mesh to the outer chamber, which is surrounded by the fine mesh. The fines fall out the bottom, and what comes out the other end of the outer chamber is the material we're looking for. The central shaft is 2.75m long, and the outer drum dia is 1.2m. It'll spin slowly, 20 rpm.

    The "drums" will be made of flat bar hoops and traversing pieces of angle iron, covered in the wire cloth. So what I'm working on now is the way to drill the holes in the central tube (5" OD by 1/4" wall) from which spars will come to support the hoops. The spars are 20mm solid round, and my current plan, after abandoning another, is to turn the ends of the spars down to about 16mm and then drill/ream mating holes into the central tube. That, if done properly, should mean they all stand perpendicular to the tube on 2 axes. They'll be backed up by a couple of threaded holes on either side and tabs welded to the spares to make sure they can't come loose. I finished the split collar this morning, which will give me a way of making sure the four sets of reamed holes are 90 degrees apart on the tube face. I made stub shafts that are pressed into either end of the tube, where the mounted bearings hold the whole thing and the pulley or hand crank will attach on the back side (foreground of the drawing). Those are done and on, and that's what my split collar is grabbing.

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    img_20190509_113140.jpg img_20190509_113148.jpg img_20190508_111414.jpg

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    Quote Originally Posted by Jaxian View Post
    I don't know if you have access to a CNC mill but if you do something like these vise jaws are very easy to make. Local roofing company needed to be able to grab 20' long extrusions to do ops on them. I believe they were like 4.75" radius if remember right. They needed to be idiot proof for the guys using them and keep everything aligned. They used two vises in a line for better rigidity. Was a quick job for my CNC mill.

    20180517_200202.jpg

    20180521_230938.jpg
    Interesting! The only CNC in my shop is the 5x10' plasma table I built. I do have a Tree Journeyman 425 that I bought a few years ago, which is in Michigan waiting for a ride in the next shipping container that I get to send over - but the expense and work of sending containers over and importing them means it doesn't happen very often. I do dream of getting it over there though, as I think there would be a lot of tasks like this popping up where doing radiused stuff would be a LOT easier than manual!

    I didn't say in the other post, but the machine I'm using is a Cincinnati Toolmaster MT (heavier, fancier Bridgeport - but similar travels).

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    Quote Originally Posted by redlee View Post
    V Blocks and a stop.
    In fact you'd only need one V block.

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    JPA, The low tech method you are using to combine the most basic of components to make a high tech (and life saving!) ceramic filter is just plain elegant. You deserve a round of applause for that. Is that your invention or known and somewhat common methodology?

    Probably not needed, but I f you would like the hole sets to clock with each other, a similarly low-tech but adequate method to maintain angular alignment would be to temporarily attach a 1 meter (obviously arbitrary but “big enough”) piece of plywood to the end of the pipe and at right angles to it. Find its rotational center and scribe lines at 45, 60, or 90 degrees to it. Use a plumb bob or level to index the pipe.

    Denis

    Edit: I did a bit of Googling and see that clay / sawdust filters are fairly widely used for water purification.

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    Quote Originally Posted by dgfoster View Post
    JPA, The low tech method you are using to combine the most basic of components to make a high tech (and life saving!) ceramic filter is just plain elegant. You deserve a round of applause for that. Is that your invention or known and somewhat common methodology?

    Probably not needed, but I f you would like the hole sets to clock with each other, a similarly low-tech but adequate method to maintain angular alignment would be to temporarily attach a 1 meter (obviously arbitrary but “big enough”) piece of plywood to the end of the pipe and at right angles to it. Find its rotational center and scribe lines at 45, 60, or 90 degrees to it. Use a plumb bob or level to index the pipe.

    Denis

    Edit: I did a bit of Googling and see that clay / sawdust filters are fairly widely used for water purification.
    Yep, the filter technology is being used by about 30 factories around the world. They cooperate with each other loosely on advances in production technology, but are independent - some run as for profit businesses, others as aid projects, etc. They range from three women in a dirt floored room to a giant factory in Cambodia that makes thousands of filters a month. I'm just helping get the project going here in Guinea-Bissau.

    The trommel, however, is my design. I haven't seen a dual-drum design like this before, and am hopeful that it'll end up being an elegant solution to a currently-labor-intensive problem.

    Ok, here's what I've got for setup. Tell me where I'm messing this up or what I'm not seeing.

    image2219011341177294429.jpg

    My plan:
    1) I have a pair of matched pairs of V blocks. The top ones that'll hold the tube have a 3" opening, which seems adequate to locate against. The bottom pair are just to raise the arrangement up enough to get over my vise so I don't have to remove it, because I'm lazy.
    2) Put the pipe centered in the V-blocks, which will align them with each other, at least however straight the pipe is.
    3) Indicate the back side of the two V blocks, adjusting until they're the same, guaranteeing that they are aligned to the mill X. Clamp the v-block stacks to the table.
    4) Indicate off the front and back (mill front and back) sides of the v-blocks to give me a Y zero.
    5) The location of the holes along the length of the tube isn't critical, so I'll use a tape measure to get close enough. (Successive sets of holes are further from each other than the mill travel, so no indexing.) I'll square the bored split block against some rectangular (and long) profile also clamped to the table. This will give me the angular alignment. Clamp the tube against the v-blocks and pop the first hole.
    6) I do want the four holes that are at 90's to each other to be the same location on the tube length-wise though, so I'll use a paper strip wrapped around the tube, located against the face of the v-block, to make sure the tube doesn't slide while rotating. Rotate 90 degrees, again squaring the split block against the rectangular profile, clamp, drill, ream. Repeat for the other two holes.
    7) Loosen tube hold-downs, slide tube forward to next set of holes, repeat steps 6 and 7.

    I don't know exactly what to use for the profile to square against - may be a 20' long I beam. I may have to move the vise anyway because of this. Arg.

    Anyone see an easier way to get this done?

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    Denis, I like your idea about the plumb bob. Rather than screwing with a long profile to square against, I may do something like that, if I use a clamp that clamps perfectly perpendicular to the bored split block and is adequately long enough, it should work fine.

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    To roughly locate the center of a round you can pinch a scale or other straight piece of metal between the tool tip and the round surface and adjust until the scale is horizontal. It is the same idea used to get a lathe tool roughly on center. You may already know this but it seems easier than "eye-balling" with a tape measure.

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    Quote Originally Posted by kenton View Post
    To roughly locate the center of a round you can pinch a scale or other straight piece of metal between the tool tip and the round surface and adjust until the scale is horizontal. It is the same idea used to get a lathe tool roughly on center. You may already know this but it seems easier than "eye-balling" with a tape measure.
    I may not have described what I meant properly, but the tape measure was for locating the holes along the length of the tube (aka first set of holes is 10cm from the end of the tube, second set is 112cm, etc).

    That is a good trick, but in this case I think I can edge-find against the two outer edges of the v-block for a more certain center.

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    Nope I just miss read.

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    Quote Originally Posted by LKeithR View Post
    That's just silly. A vise is often the fastest and most efficient way to hold a part and if that's the case it's
    the tool you should use.

    Anyone who has spent any time around a milling machine will tell you that there is no other machine in the
    shop that will challenge you as much when it comes to mounting odd ball parts--that's half the fun of using one...
    The point is that a vise is only one of many ways to fixture a part, many guys become so reliant on there vises that they cant think outside the box. So as an apprentice working in a Agricultural shop doing mainly repairs and one offs the objective was to figure out the best way to fixture a part not the quickest. In the case in hand the vise would be the last thing I would use to fixture a 5" dia tube.
    Last edited by legoboy; 05-09-2019 at 02:45 PM.

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    Is there a reason not to drill right through the pipe and then ream?
    That way you can just slip a round bar into the holes then rotate the tube until the bar is parallel with the table.
    Your machine is just a hand crank or powered at 20 rpm?
    You may have solved all these issues already but it is not clear how you will mount the screens on one set of spokes. In other words if your spokes are long enough for the outer screen how do you install the inner screen?
    It seems like you may need two part spokes, drill and tap one end so the second shorter spoke extension can be added after the inner screen is in place.
    Like I said you may have already solved these problems.

    With such a low speed you are going to a lot of trouble when eyeball accuracy would work just fine.
    Mark the pipe where the spokes need to be and make a jig to weld them in place. Is there a reason to have them removable?

    If you are going to incline the machine so the sawdust will tumble out the end then you need to direct it away from each filter size, one longer filter and one shorter filter screen would make it easier to funnel the chips away.

    Looking forward to seeing your finished separator.

    Michael


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