The Fan slides onto the collet nut, and is a friction fit.
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I love this locating solution. In practice though, threads and how they seat isn’t repeatable. Maybe on the order of a few thousandths, which might be ok for your application.
For better repeatability, put a small counter sink in the vice holes, so the sides of the bolt shaft contact against the side of the countersink. This should be just as accurate as a precision pin, which is about as good as you can get.
I may do this on my vice, but instead put two countersunk threaded holes on each of the two fastened end pieces, rather than the slider in the middle. Since the slider has some slop in it.
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I was actually surprised how well it worked, I am contacting the stock at the head of the bolt, so it solved my challenge of part retention . I’d love to see your approach.
The trick is to use over-long shoulder screws, and ream a short hole in the vise/toolplate with threads beneath it. The tip of the cylindrical body of the shoulder screw does the locating and the threads just hold it down.
There are also “hollow dowel pins” that you can use for the same purpose–matching reamed holes in the workpiece and tooling with concentric threads below the reamed hole. If I remember the hollow dowels we used (several employers ago…) were 1/4" diameter and the screws were 10-32. Here’s an example illustration from Driv-Lok
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Randy, thanks for clarifying. Very well said guys. Your saying create a precision pocket in addition to the threads to secure the shoulder bolt shaft in the case of lateral forces, as well as initial alignment. Which is much more accurate and proper than relying on the threads alone. In other words the shafts of the shoulder bolts should be longer than the height of the stock and seat into the vice jaws in this case. You guys are great.
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Hey, you’re great for doing this project, Apollo. I also think “retro rockets” are cool. And I see what you did there, tapped holes right into the vise jaws! Like a boss. 
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Hey, just curious - how accurate would the repeated seating be if you used used a chamfered hole and used the bevel from the head of a flat head screw to locate the stock? That seems like it would be pretty good, no?
The chamfered/tapered hole itself would be a pretty good locating feature, but the problem is the same.
If I’m thinking about what your suggesting right, you’d have a through hole on the workpiece with a chamfered feature and fasten a flat head screw into the threads on the base. The screw would be located relative to the workpiece, but not the base, as the threads are still not guaranteed to seat perfectly concentric.
Oh, I see - I feel dumb now; the problem is in the screw->base interface.
I’ve experienced this first-hand when bolting directly to the base. I thought it would be a lot more accurate than it was, (although I wasn’t using a straight bolt, not a flat head screw). You can see pictures at this thread.
I’m mentally designing a multi-screw flip base for this same ring project, with the hope that the multiple errors will cancel one another out.
With multiple screws, you’ll get a standard deviation effect. The more you add, the smaller the deviation. But, there are usually other factors that come into play with flipping a workpiece and perfectly aligning it. Namely, you have to ensure the top and bottom are perfectly parallel too. Otherwise, when you clamp it down, the second machined side will be a little skewed as it forces that bottom face flush against the table/base.
The Carbide flip-jig is great, because it takes care of all of the alignment issues for you with parallel machined surfaces on top and bottom and locating pin features that go right into the y-table. The workpiece can be any shape or size, just as long as it fits inside and doesn’t move.
@CookieMonster that collet fan looks awesome! Is it something you sell? Any info would be great. If you have a link, please post it, I’m sure there are several of us who might like to have such a thing…
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Agree, interested too in the fan 
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Hey, in this picture: http://community.carbide3d.com/uploads/default/original/1X/318f513af444ffd2dc10a85817d32820348d1fc4.jpg you slotted some blocks in the inner channel of the vise to locate your stock - do you have the dimension of those blocks (particularly the width)? I’m measuring about 28mm - just wondering if you had a more exact measurement to get those in super tight…
And I was curious - it looks like in that image the pins are being used to locate the stock in the Y axis in addition to providing the compression force to hole the stock steady (along the X axis) - that is, the vise jaws themselves don’t contact the stock - the jaws are pushing the plastic blocks together, and the pins on the blocks hold the stock. Is there a reason for that? I was considering using the plastic blocks solely to locate the stock in the Y axis, and then (by not having the blocks extend outwards so far in the X axis), simply holding the stock directly with jaw pressure… Would there be a good reason not to do this?
Thanks.
The Vise Channel Blocks -
In that picture I used HDPE that was 1/2" thick and 28.65mm wide to fit the Vise channel as tightly as possible.
The correct dimension for the blocks is “Snug”
The lower in the vise the better, so thinner material would be better, 3/8" is good.
Regarding the vise jaws pushing against the stock or the blocks-
Ive tried it both ways and it depends on the job; the thickness of the material; the amount of material being removed.
When you remove a lot of material, the stock will bend in between the jaws and the work can shift.
The reason why the flip frame works so well is because of its frame structure, so tryto keep a frame around your material, the hammer handle for example:
http://community.carbide3d.com/uploads/default/original/1X/fbb9c93f67713f8728eebd59f6f8f5fbac02455f.jpg
I would use the stock to clamp against to start and not the blocks.
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Thanks for the info!
For the finishing pass on brass could you use a #121 .0312" ball cutter?
so you get a really smooth finish?
Thanks
Tim
The Surface finish on that Brass Rocket was more a result of a 30% step-over not the diameter of the tool.
For a smooth finish I should have used a 10% (.006) step-over.
The problem with using smaller diameter cutter’s is the reduced flute length they offer.
Unless the part has very shallow elevation changes, the 1/32" wont have the ability to reach the necessary maximum depth.
Heres an example of a 3D sample part in 6061 with the 1/16th (#111) with a .004" stepover.
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Thanks Apollo I plan to make a 1/48 scale cannon the full depth would be 7mm. Machined both sides with a depth of 4mm probably.
Thanks Tim