# Latest Project: A Universal Milling and Grinding Fixture (see pics)



## jgedde (Sep 6, 2012)

Here is my latest project.  This is a universal holding fixture which can be used to machine compound angles, sharpen drill bits (standard method, or multi faceted), grind lathe bits, and more...

First, here are some 3D models:







Now some exploded views:




And for the current progress (not including turret discs which are also done sans engraving)



Since I have created 3D models (in Alibre 2012), I will be creating drawings.  Of course I'll share these on this forum for those who want to make one too...  Of course, as progress continues, I'll add photos so you can all see how it gets made.

  I welcome all comments, suggestions, critiques!!!

John


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## Bill Gruby (Sep 6, 2012)

Looking good John. Will be watching this one close.

 "Billy G" :thumbsup:


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## ScrapMetal (Sep 6, 2012)

Looks like a slick project.  I'll be interested to see the plans.

Thanks,

-Ron


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## jgedde (Sep 7, 2012)

Shawn,

I'm using Ablibre 2012 Personal Edition.  I've been an Alibre customer for several years.  That being the case, I have a few extra features that I'm "grandfathered in for" that aren't part of regular PE.  

The one's that matter are a three seat license (rather than 1), and the advanced import/export toolset.  The latter allows me to import STEP files for piece parts (like hardware) from McMaster (this might be part of regular PE).  I can also output Parasolid files for CNC, Solidworks, IGES, STEP, etc for import into ProE or Altium.

Again, I'm not sure if the standard Alibre PE allows you to _import _step files.  Apart from that, there's nothing I did using my version you couldn't do with standard PE.

Now, I have just have to have Alibre make 2D dimensioned drawings for the parts and I'll have a complete set of paper plans (I'll post as PDFs).

The next step for me is to design some toolholders that fit the 2" bolt pattern on the fixture...   Then, make drawings.

John


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## Rbeckett (Sep 7, 2012)

John,

Looks like a great tool if you make one, it really would do quite a bit ot accurate grinding.   Thats an idea for sometime down the road fer sure.  Thanks for the heads-up for what is hopefully coming next.  Any ideas of the materials list and time frame for completing it yet?  All your stuff is so slick I gotta figure it out like you did. Great work as usual.
Bob

Bob


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## jgedde (Sep 7, 2012)

Thanks for the good words Bob!

As for timeframe, it'll take as long as it takes.  That wasn't meant to be snotty, but at the rate I'm currently going it may be a month or two to complete.  Too much stuff going on as of late.

Plans I can post should be forthcoming in about a week.  

Materials are from my scrap bin, but I did design it with plans for others in mind.  That said, it generally uses standard size materials machined slightly undersize for a nice finish.  For example, the graduated pucks are made from 2.75 round stock turned down to 2.70 to get rid of any scale, scratches, dings, etc thus allowing bottom of the bin materials to be used.

The base plate would likely be the only somewhat pricey piece being made from 1" thick stock.  Mine was made from an old cast steel microscope base I had in the junk bin.  Another option would be to use a 0.750 thick piece and weld on a 1.25" dia protrusion (which I did because the scope base was only .850 thick).  The protrusion is the center section in the chucked up piece in my photo above.  I simply drilled two holes in a disc, welded it on through the holes, then machined it to OD and faced of the weld beads.  You can't tell it is actually two pieces.

John


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## jgedde (Sep 8, 2012)

Here's the first drawing.  I'm not a guru when it comes to GD&T, but here is a drawing of the base that gives all pertirnent dimensions...  Please feel free to review and comment (especially those well versed in GD&T).

View attachment Base.pdf


John


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## Tony Wells (Sep 8, 2012)

Doesn't look too bad, John. I will make a couple of comments on your GT&D. A parallelism callout will not have a reference to a circular tolerance zone as you have drawn on the 3.750 OD ring. Same with the flatness callout on the bottom of the base, Datum A. The True Position on the 0.2490 reamed holes should be referenced to a diameter such as the 3.750 ring OD rather than a flt surface as you have drawn as Datum B. Depending on what you have fitting the reamed holes, I presume dowel pins, the mating part will have a feature that fits closely somewhere, and that's what you should look for to determine the reference datum for their True Position.

That's all I see at a glance. I'll study it a bit more and see what else I can find. I don't see any concentricity callouts, which I would expect to see, given all the parts that must rotate with some precision.


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## jgedde (Sep 8, 2012)

Tony Wells said:


> Doesn't look too bad, John. I will make a couple of comments on your GT&D. A parallelism callout will not have a reference to a circular tolerance zone as you have drawn on the 3.750 OD ring. Same with the flatness callout on the bottom of the base, Datum A. The True Position on the 0.2490 reamed holes should be referenced to a diameter such as the 3.750 ring OD rather than a flt surface as you have drawn as Datum B. Depending on what you have fitting the reamed holes, I presume dowel pins, the mating part will have a feature that fits closely somewhere, and that's what you should look for to determine the reference datum for their True Position.
> 
> That's all I see at a glance. I'll study it a bit more and see what else I can find. I don't see any concentricity callouts, which I would expect to see, given all the parts that must rotate with some precision.



Thanks Tony, I was hoping you'd chime in!  )

1) What I was trying to indicate was that the plane on top of 3.750 dia boss should be parallel to the base's bottom.  How should that be done?

2) The center section (the 1.250 dia) is the pilot diameter for the base turret and nothing else, so concentricity is taken care of.  The 3.750 and 2.875 diameters don't need to be all that concentric to the 1.250 diameter apart from aesthetics.  See runout of the turret with respect to the pointer would just look bad.

3) As far as the dowel pins: they serve as an anti rotation device for the mating part (the base clamp).  The goal is to prevent the tightening of the center bolt from rotating the base turret.  The mating part needs to slide freely, but with no side play, over the dowel pins.  So, their location with respect to holes in the mating part is important.  I'm not sure how to go forward given this requirement.  Can you offer any advice?

I'm currently enamored with true position since we have a design (and print) at work for a near zero backlash planetary gearbox (for a satellite) that specifies TP to 0.0001" from multiple datums (we need the low friction of a planetary with the low backlash characteristics of a Harmonic drive).  

We've found only one guy in the country who can make these parts consistently!  He came to our shop and set up our wire EDM machine with fixtures that we're nothing short of amazing!  Now we can do it too!  The trick was to use this fixture to move the workpiece rather than move the wire.  He's relying on our wire EDM machines incremental rather than absolute accuracy.  The wire simply cuts a hole, but never moves more than 0.050 or so.

His fixture used ceramic dovetails, indexers with sub arc sec accuracy.  Even our master machinist said he "felt inadequate" in the presence of this guy!

Getting back to my design, ANSI 14.5m is a tough thing to get my mind around.  I know how it all should fit together in my mind, but getting it on paper is a horse of another color...  Makes me appreciate mechanical engineering more and more.  Maybe I should stick to high reliability electronics design and leave the precision to the pros?  Just kidding...

John


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## jgedde (Sep 9, 2012)

Tony Wells said:


> Doesn't look too bad, John. I will make a couple of comments on your GT&D. A parallelism callout will not have a reference to a circular tolerance zone as you have drawn on the 3.750 OD ring. Same with the flatness callout on the bottom of the base, Datum A. The True Position on the 0.2490 reamed holes should be referenced to a diameter such as the 3.750 ring OD rather than a flt surface as you have drawn as Datum B. Depending on what you have fitting the reamed holes, I presume dowel pins, the mating part will have a feature that fits closely somewhere, and that's what you should look for to determine the reference datum for their True Position.
> 
> That's all I see at a glance. I'll study it a bit more and see what else I can find. I don't see any concentricity callouts, which I would expect to see, given all the parts that must rotate with some precision.



Tony,  How about this one?  
	

		
			
		

		
	

View attachment Base.pdf


Thanks,
John


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## lockstocknbarrel (Sep 9, 2012)

Hi John,
What A great start, this is a project that is high on my priority list.
Looking forward to the next set of drawings to study.
Well done and thank you for taking time to share.
Kindest Regards
Beagles


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## Tony Wells (Sep 9, 2012)

John, I'll make some annotations on that one and shoot it to you. It appears that by default, all your tolerance zones are noted to be circular, but that is not the case when dealing with flat surfaces, as in flatness and parallelism specifications.


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## jgedde (Sep 11, 2012)

Tony Wells said:


> John, I'll make some annotations on that one and shoot it to you. It appears that by default, all your tolerance zones are noted to be circular, but that is not the case when dealing with flat surfaces, as in flatness and parallelism specifications.



I finally figured out what you were talking about...  It seems Alibre, by default, inserts the diameter symbol in front of feature control box tolerances.  I simply didn't notice them!

So, here are the current drawings so far for everyone's review...  I'll post them all as a complete set when they're oll korrect.  When a drawing is "Rev A", that will be a "released" version.

View attachment Axis 1 turret clamp.pdf

View attachment Axis 1 Turret.pdf

View attachment Base.pdf


John


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## Tony Wells (Sep 11, 2012)

John,
 I apologize for not getting your redline drawings back to you yet. Been pretty busy the last few days, but I am working on it.


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## jgedde (Sep 25, 2012)

Progress...  About 50% of the drawings are now completed.  

Here it is with a square workholder installed:



Here are pics of the machining and progress so far...












The base rotates freely and smoothly with zero side play.  The turret lock device using the two dowel pins and the center clamp worked even better than I hoped.  The idea was to prevent bolt tightening from moving the turret.  Close tolerances were required, so as to have no play, but it all worked out on the first try with careful mill table positioning using a dial indicator.  This thing rotates smooth as a baby's you know what with the bolt loose and locks tight with minimal torque.  See the exploded view in the first post for details of how it goes together. 

 A few drops of way oil makes it roate real nice, but it's a bear to get apart with the oil in there!  I have to use compressed air between the turret and the base to get the two parts to separate!

John


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## gmoushon (Oct 4, 2012)

Beautiful work John....definately on my bucket list.  Wish it was in native Solidworks; I've heard that it is difficult to convert files from Alibre.
gm.


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## jgedde (Oct 4, 2012)

I have the "advanced import/export" module for Alibre.  I can't export Solidworks native files.  I can, however, do STEP, IGES, Parasolid and a few others...

John


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## gmoushon (Oct 5, 2012)

STEP/IGES would work.  Is that something you would be willing to share?  
Thanks
Gaylan.


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## bvd1940 (Oct 6, 2012)

I will be watching with great interest in this build.
Real nice job.:man:


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## easymike29 (Oct 6, 2012)

John

Your design has one axis too many.

The base is needlessly weakened with the excessively elongated slots and the track for the t-slot key.

Gene


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## jgedde (Oct 6, 2012)

Yes, I'd be happy to share them when they're done.  I'll have to chat with Nelson/Tony to get them all up on the site at once.  The STEP files could end up being 30-40 MB all said and done.

On the other hand, I'd hate to see an exact copy of my design for sale at some import tool house CNCed from my files selling for less than the cost of the raw materials bought domestically, so I may just provide them upon request.

John


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## jgedde (Oct 6, 2012)

easymike29 said:


> John
> 
> Your design has one axis too many.
> 
> ...



Gene,

As far as the axis count, I thought long and hard on that, but I maintain that the axis count is correct.  If there were only three axes, you'd have to compute a compound angle at the toolholder...  The fourth axis takes care of that.  Remember, this isn't a CNC machine where the three axes would be sufficient.  It's meant for ease of manual use.

The slots are longer than I wanted them to be, but at that length they handle the T-slot spacing on Bridgeports as well as import mill/drills.  In reality though, the slots aren't too long, the base is too big.  I did this to gain additional surface area when using a magnetic chuck and to allow the edge to come all the way to the edge of the chuck for the alignment plate.

 I belabored the T-slot keyway depth and length as well as the thickness and size of the base.  A coworker ran it through FEA on Pro-E.  It made almost no difference whether the T-slot keyway was there or not.  Agreed it doesn't need to be all the way across.

John


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## easymike29 (Oct 6, 2012)

jgedde said:


> Gene,
> 
> As far as the axis count, I thought long and hard on that, but I maintain that the axis count is correct.  If there were only three axes, you'd have to compute a compound angle at the toolholder...  The fourth axis takes care of that.  Remember, this isn't a CNC machine where the three axes would be sufficient.  It's meant for ease of manual use.
> 
> John



You are sacrificing rigidity for the convenience of the extra axis. 

Gene


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## jgedde (Oct 6, 2012)

easymike29 said:


> You are sacrificing rigidity for the convenience of the extra axis.
> 
> Gene



Without a doubt.  Convenience is what this thing is all about.  There's no question a different fixture would do better for heavy milling: Like two angle plates bolted together with a calculated compound angle.  

For grinding tools and cutters, it doesn't matter nearly as much since the forces are MUCH lower.  The extra axis also allows for sweep grinding.  Like standard ground drill bits.  I don't plan on doing this since the design lends itself to 4 or six facet drill grinds.

For the hobbyist, making more light cuts and taking longer isn't nearly the issue it would be in a production shop.  But, for onesies and twosies, convenience trumps.  Who wants to spend two hours fixturing something for a 5 or 10 minute operation?  Spending two hours fixturing something you'll use to hog metal all week?  That's a different story.

If you want a brick &^%&house with one less axis, buy a Rockwell Univise (if you can find one for a good price - a tough proposition).  

I believe the 3D models don't do the item justice as they don't show the welds.  In real-life the thing will look much beefier.

John


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## gmoushon (Oct 7, 2012)

jgedde said:


> Yes, I'd be happy to share them when they're done.  I'll have to chat with Nelson/Tony to get them all up on the site at once.  The STEP files could end up being 30-40 MB all said and done.
> 
> On the other hand, I'd hate to see an exact copy of my design for sale at some import tool house CNCed from my files selling for less than the cost of the raw materials bought domestically, so I may just provide them upon request.
> 
> John



Certainly understand your concerns...and don't blame you.  I'm a hobby guy and have this propensity for starting projects and not finishing them.  The design caught my attention and this project would be way down on my list of things to finish.  Heck, I don't even have a surface grinder yet!  (lol)   

Keep the photo's coming...definitely enjoy watching the progression.

gm


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## Hawkeye (Oct 7, 2012)

I think you're right, John. On-request is the better way to go. That will also let you know who and how many are planning to build your design. Always a nice thing to know when you've come up with something original.


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## bvd1940 (Oct 7, 2012)

jgedde said:


> Yes, I'd be happy to share them when they're done.  I'll have to chat with Nelson/Tony to get them all up on the site at once.  The STEP files could end up being 30-40 MB all said and done.
> 
> On the other hand, I'd hate to see an exact copy of my design for sale at some import tool house CNCed from my files selling for less than the cost of the raw materials bought domestically, so I may just provide them upon request.
> 
> John



I would greatly appreciate your consideration of my name on that request for a copy of the prints. 
What are STEP files??? I am not real PC savvy.:thinking:
I sure would like to incorporate your universal holder in my dedicated tool grinder)


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## easymike29 (Oct 7, 2012)

John

With your fourth axis can you grind the "flat" along the sharp edge of a threading tool bit without first computing the angle?

Gene


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## jgedde (Oct 7, 2012)

Gene,

Yes, the thread angle and relief angle can be ground simultaneously.  The pointers are adjustable so the unit can be calibrated using squares.

John


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## easymike29 (Oct 7, 2012)

John

I was not referring to the thread and the relief angle. I was referring to the (.25P) flat at the apex of the 60 degree angle.

Gene


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## jgedde (Oct 7, 2012)

If I were to make dozens of threading tools with the tip dressed as you ask, I'd probably just dress a wheel with the correct profile and go to it.  I could use this fixture to hold the bit for that...  Yes, one would not need to compute the angle...

But that would be overkill for just one or two. 

 I usually just grind that end dress by hand or leave it sharp...

John


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## jgedde (Oct 12, 2012)

Here's the latest progress...  

Safety First...  Lathe needs to be unplugged for what's next...




The graduating setup...  Rotary table laying on a block of wood on the lathe bed.  It's bolted to a faceplate to square it up.  A sharp 60 degree bit is laying sideways in the toolholder.  Numbering was done using an empty toolholder as a guide for the stamps:




Engraving underway:



The second axis support being made:




Finished support:




Assembled, welded and ground square.  The weld quality could be better but I was fighting with a helmet that kept flashing me and was too lazy to change out the 0.023 wire for 0.035.  Fill and paint will cover up the ugliness.  Axis supports and gussets made up and welded.  Base turret graduated and numbered...  Like that crooked Harbor Freight 3 and weak 4?.  I won't be using those stamps again for the other axes...  Plus the numbers are a bit large aesthetically speaking.




John


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## jgedde (Oct 13, 2012)

More progress...  Filling, priming and painting:

John


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