How much clearance for 4th indexer trunnion table outboard bushing?
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  1. #1
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    Default How much clearance for 4th indexer trunnion table outboard bushing?

    I'm building something similar to this stallion thing and wondering what folks have run for clearance in the outboard support bushing? I don't want it to bind up and overload the indexer, but I don't want sloppy either. I was thinking .002" to .003" for a 2" ID in aluminum bronze. Bushing will be 1.5 or 2" long.
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    Use a split clamp around the bushing. Tighten it as much or little as you want. Works good for mine.

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    I would look into a sealed needle bearing.

    Ed.

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    Quote Originally Posted by atex57 View Post
    I would look into a sealed needle bearing.

    Ed.
    If truly sealed, and running line-to-line on a hardened journal (at least Rc58), I'd go this route. But if you can't seal it properly then a plain bearing with a running slip fit (~.0002" - .0005" clearance) would be my choice. Again, hardened shaft in the bearing, I'd even try setting up an air purge line to that side, since you'll have one for the RT anyway.

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    Shaft is soft. I'm good with a bushing and grease. Probably be fine with no bushing and grease, but might as well. If it wears out before I die I will consider seals.

    .0002" sounds crazy tight to me. This is something you did and it worked?

    This is essentially a 200 lb weldment with ends trued up between centers. The parts are not ground, the subplate is not ground. We're spanning 40" and cantilevering 12" off the side of a VMC table in a shop that has a temperature somewhere between 40 and 95 degrees. Normal indexer on a VMC type scenario you know? I'd love to think that a tenth per side would slip right in there, but I wouldn't bet on it.

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    Could you use a set of opposed roller bearings? I think I saw some guy on YouTube do that.

    Do you care to show any photos of what you built I’m interested in building something like that.

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    Quote Originally Posted by Garwood View Post
    Shaft is soft. I'm good with a bushing and grease. Probably be fine with no bushing and grease, but might as well. If it wears out before I die I will consider seals.

    .0002" sounds crazy tight to me. This is something you did and it worked?

    This is essentially a 200 lb weldment with ends trued up between centers. The parts are not ground, the subplate is not ground. We're spanning 40" and cantilevering 12" off the side of a VMC table in a shop that has a temperature somewhere between 40 and 95 degrees. Normal indexer on a VMC type scenario you know? I'd love to think that a tenth per side would slip right in there, but I wouldn't bet on it.
    If you put the a frame on before you set it down with the forklift or whatever you can have it a few tenths no problem. use lots of heavy grease. I wouldnt use alum bronze with will wear out the shaft,

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    Quote Originally Posted by Garwood View Post
    Shaft is soft. I'm good with a bushing and grease. Probably be fine with no bushing and grease, but might as well. If it wears out before I die I will consider seals.

    .0002" sounds crazy tight to me. This is something you did and it worked?

    This is essentially a 200 lb weldment with ends trued up between centers. The parts are not ground, the subplate is not ground. We're spanning 40" and cantilevering 12" off the side of a VMC table in a shop that has a temperature somewhere between 40 and 95 degrees. Normal indexer on a VMC type scenario you know? I'd love to think that a tenth per side would slip right in there, but I wouldn't bet on it.
    It is tight, or stated better, close. I've done such things, but not with a soft shaft, just with a ground/polished/hard shaft for longevity and accuracy. I wouldn't want to use a soft shaft with a metal bushing, would be OK with it if polymer but can't be sure of reasonable life.

    And sure, if it's a weldment where you don't have confidence in the concentricity of the shaft relative to the bushing then you have to open things up to suit. But if I had my druthers I'd go for best accuracy and fit I could to stabilize that end of the fixture.

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    I did about the same thing with a 6" square 40" long block and the end support is just a block of 2" aluminum with a 2.001 hole bored in it ,,, I run it about about every day and and its been aluminum on aluminum with just coolant for lube going on 5 years ,,, for a plain bearing that size and the low RPM it spins its over kill ...

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    Quote Originally Posted by D.D.Machine View Post
    I did about the same thing with a 6" square 40" long block and the end support is just a block of 2" aluminum with a 2.001 hole bored in it ,,, I run it about about every day and and its been aluminum on aluminum with just coolant for lube going on 5 years ,,, for a plain bearing that size and the low RPM it spins its over kill ...
    Thank you! Sounds good to me.

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    IIRC I put a 2" self aligning pillow block there.

    The whole "shaft" can flex and change the alignment.

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    Quote Originally Posted by digger doug View Post
    IIRC I put a 2" self aligning pillow block there.

    The whole "shaft" can flex and change the alignment.
    I've seen it done that way, but this is on a 50 taper machine so the toolholder bodies are extra big. This trunnion is a fixture for a family of parts, but I also need it to hold a 6" double vise in case I need it to pull overflow duty for my HMC. The self aligning bearings stick up pretty high. they will probably get in the way at some point. With a bushing (or just a through hole) I can keep things as low as possible.

    To run the vise the way I want it to, the table height has to be 1.8" below center so the wrench can grab the hex to open the vise through a 1.2" hole. Because I have a 1.2" hole in it I'm going to a 2" diameter. If I didn't have the through hole I'd be fine with a smaller shaft and could probably use a pillow block bearing.

    I want to do up a tombstone like what DD made that I can swap out for this trunnion. That will be the next project.

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    Quote Originally Posted by Garwood View Post
    I've seen it done that way, but this is on a 50 taper machine so the toolholder bodies are extra big. This trunnion is a fixture for a family of parts, but I also need it to hold a 6" double vise in case I need it to pull overflow duty for my HMC. The self aligning bearings stick up pretty high. they will probably get in the way at some point. With a bushing (or just a through hole) I can keep things as low as possible.

    To run the vise the way I want it to, the table height has to be 1.8" below center so the wrench can grab the hex to open the vise through a 1.2" hole. Because I have a 1.2" hole in it I'm going to a 2" diameter. If I didn't have the through hole I'd be fine with a smaller shaft and could probably use a pillow block bearing.

    I want to do up a tombstone like what DD made that I can swap out for this trunnion. That will be the next project.
    I made this one 42" long for a VF-6.

    Underslung was maybe 3" so the fixture presented the part at about centerline.

    The centerline was about 12" above the table, 42" long piece is a welded box section that holds the hydraulic pull down cylinders, and the changeable fixture on top. The welded box is bent 1/2" plate forming a "U" 12" wide x 6" high (and 42" long), removable lid dowelled and machined (for torsion resistance).

    Ask Zahnrad Kopf how his version is coming, I sent him some screen shots and ideas (that I can't discuss here)

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    Ends are 6" 1045. Bottom is 1.25 A36.

    I turned the ends to 6.050" to set the plate at the correct height and put centers in them. Milled all sides of the plate square. I ground a little weld prep V at the very bottom so the weld wouldn't protrude too much.

    I welded the sides first and then checked square. They were still good. I finished welding the bottom then I flipped and welded the top. I'm hoping I don't have to skim more than .030 or so off the top. We'll see. That plate had about .015" of twist to it to start with.

    When it cools it will go in the Pacemaker to finish up both ends. I'm bolting this direct to my indexer spindle since mine doesn't have a T-slot plate. I'll put the hole pattern in with the boring mill.
    Attached Thumbnails Attached Thumbnails tacky.jpg   easybake-trunnion.jpg   trunnion-weld.jpg  

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    Quote Originally Posted by Garwood View Post
    Ends are 6" 1045. Bottom is 1.25 A36.

    I turned the ends to 6.050" to set the plate at the correct height and put centers in them. Milled all sides of the plate square. I ground a little weld prep V at the very bottom so the weld wouldn't protrude too much.

    I welded the sides first and then checked square. They were still good. I finished welding the bottom then I flipped and welded the top. I'm hoping I don't have to skim more than .030 or so off the top. We'll see. That plate had about .015" of twist to it to start with.

    When it cools it will go in the Pacemaker to finish up both ends. I'm bolting this direct to my indexer spindle since mine doesn't have a T-slot plate. I'll put the hole pattern in with the boring mill.
    I'm not seeing how a pillow block (2" shaft) would extend above that 6" dia end plate.

    Also, I would look up Lincoln electric design of weldments book "elastic matching" problem.

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    Quote Originally Posted by digger doug View Post
    I'm not seeing how a pillow block (2" shaft) would extend above that 6" dia end plate.
    There's a whole bunch of machine work left to do. That 6" diameter will be flush with the top of the 2" shaft that is 2.5" in the pictures. I left it full diameter so I can use a steady rest in the lathe. Everything is oversize now.

    I will look at elastic matching.

    This is a build it with shit I have laying around in as short a time as possible. Probably how this stuff normally gets done. I thought about just hogging out the 6" bar, but the only 6" LOC tool I have is a 3" indexable. I didn't want to listen to "the sledgehammer" running for that long.


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