Methods to squaring

deakin

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curious to see what different methods come up for this exercise.

you have a (rough) cast iron casting approx 6.5"x6.5"x3/8". (3/8 we'll call the edge). one side has a feature somewhere towards the center. - we'll call that the bottom - therefore we only need to square the perimeter of the bottom.

due to the thickness you need to take a minimum of material off. you only have a 6" vise.
what would your approach be.

pick your machine(s)
 

JimDawson

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First remove the vice from the table and put it on the shelf. Then secure the part to the table by whatever means that works. Supported on some kind of parallels or jacks if needed. Square the part to the machine using shims as needed and make chips.
 

Alexander McGilton

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Can't use my mag chucks? Placed in the mill or surface grinder?
This is a job well suited for the surface grinder, It may be known for it slow material removal rate by mass, though it is incredibly fast at traversing surface area. Just grind the surfaces enough to expose the high spots then you may bring it to the mill for those heavy cuts.

If that's not an option, as Jim said, clamp it to the table. These hold down clamps that bite the sides would be help full. They allow you to plain a surface without clamping on top. you may then machine off the bite marks in a second operation. Photo credit to CNCCookBook
1585415487941.png
 

deakin

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First remove the vice from the table and put it on the shelf. Then secure the part to the table by whatever means that works. Supported on some kind of parallels or jacks if needed. Square the part to the machine using shims as needed and make chips.
how would you clamp it without the clamps interfering? and if you moved the clamps during the cut would it not be possible that the rough surface on the parallels would change the the work side position some?
 

RJSakowski

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The method would be dependent on what precision you want. Probably the simplest way would be to clamp to the table using a sacrificial plate and side mill all four edges. This will give you accuracy in line with the squareness of your mill. You will have to move your clamps around to do all four edges and there is some danger of shifting the workpiece when doing that. For the sacrificial plate, I would use an incompressible material rather than wood or plastic. The sacrificial plate can be slightly smaller than the finished work to avoid cutting into it if you don't want to sacrifice it.

Facing the plate is a little more challenging as ideally you wouldn't want to clamp to the surface you're finishing. There are toe clamps like the Mitee Bite that can hold your work from the edges. https://www.miteebite.com/products/riser-clamp-kits/ Super glue and painter's tape can also be used.
i would clamp stops to the table to keep the work from shifting if I used that method (belt and suspenders). Alternatively, you can clamp one half and face and then clamp the other half and face.

Finally, most machinist's vises have the ability to move the jaws to different positions. My 4" vise will accommodate pieces up to 10". This will alow facing the work and cutting two sides, then flip and rotatye and face the second surface and the other two sides.
 

JimDawson

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how would you clamp it without the clamps interfering? and if you moved the clamps during the cut would it not be possible that the rough surface on the parallels would change the the work side position some?
When working with rough castings it is common to machine some locating bosses first, then clamp as needed to do the rest of the work. This is where you get creative with your work holding.

On the other hand, if you have a 6.5 inch part and a 6 inch vice, just remove hard jaws from the vice. Now you have a bigger vice. Or make some step soft jaws that do have a 6.5 inch opening. I do this all the time. I don't even have a set of hard jaws for my vices.
 

deakin

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remember the bottom is not flat. there is a feature on it. lets change the size to something too large to fit a vice with jaws removed - my mistake in presenting the exercise
and we want precision within a thou +-
 

JimDawson

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remember the bottom is not flat. there is a feature on it. lets change the size to something too large to fit a vice with jaws removed - my mistake in presenting the exercise
and we want precision within a thou +-
Ahhh, moving the goalposts. :grin:

Ok, then machine a fixture that supports the part but has clearance for the protrusion on the back side. Clamp as needed, but machine the surface except where the clamps are at. Move the clamps, but indicate the surface to make sure you maintain the same height. The toe clamps shown above do a fine job of workholding also and allow full access to the work surface.

Or,

Build a ''vice'' on the table to hold the part. A fixed end stop and a movable ''jaw'' consisting of an angle piece with a couple of set screws in it would normally suffice.
 

Mitch Alsup

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you have a (rough) cast iron casting approx 6.5"x6.5"x3/8". (3/8 we'll call the edge). one side has a feature somewhere towards the center. - we'll call that the bottom - therefore we only need to square the perimeter of the bottom.

due to the thickness you need to take a minimum of material off. you only have a 6" vise.
what would your approach be.
Remove the jaw faces from the inside of the vise and install on the outside of the vise.
Tram vise in new configuration.
Position part so both side edges are exposed and mill the exposed edges. This becomes reference surface #1 and #2
Position reference surface #1 on the back jaw of the vise.
Side Mill both side faces of the part. You now have 4 reference surfaces that should be very close to square.

Check that the part is approximately normal to the spindle.
Fly cut or shell mill the top of the part.
Flip part over and fly cut or shell mill the other surface.
 

deakin

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guilty of overlooking what i normally take for granted. - like not wanting to spend the day building a fixture for a one off part and not wanting to fiddle around shimming and fussing over getting dialed in after moving clamps - however that was the way i figured using what most people would have for equipment.

ii have another way that is relatively quick but uses automotive machine not generally found in gen mach shops - hence why i was curious
 

deakin

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Remove the jaw faces from the inside of the vise and install on the outside of the vise.
Tram vise in new configuration.
Position part so both side edges are exposed and mill the exposed edges. This becomes reference surface #1 and #2
Position reference surface #1 on the back jaw of the vise.
Side Mill both side faces of the part. You now have 4 reference surfaces that should be very close to square.

Check that the part is approximately normal to the spindle.
Fly cut or shell mill the top of the part.
Flip part over and fly cut or shell mill the other surface.
except we clarified the parameters in post 7 - part too big for any vise (in theory)
 

JimDawson

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guilty of overlooking what i normally take for granted. - like not wanting to spend the day building a fixture for a one off part and not wanting to fiddle around shimming and fussing over getting dialed in after moving clamps - however that was the way i figured using what most people would have for equipment.

ii have another way that is relatively quick but uses automotive machine not generally found in gen mach shops - hence why i was curious
Van Norman to the rescue :) I have done that.
 

deakin

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Ahhh, moving the goalposts. :grin:

Ok, then machine a fixture that supports the part but has clearance for the protrusion on the back side. Clamp as needed, but machine the surface except where the clamps are at. Move the clamps, but indicate the surface to make sure you maintain the same height. The toe clamps shown above do a fine job of workholding also and allow full access to the work surface.

Or,

Build a ''vice'' on the table to hold the part. A fixed end stop and a movable ''jaw'' consisting of an angle piece with a couple of set screws in it would normally suffice.
if i were doing a bunch then a fixture would be in order!
 

RJSakowski

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To be fair, you need to give a better description of the problem. There are many ways to skin a cat, some better than others for a particular situation. What is meant by a "a feature somewhere towards the center"? No mention of tolerances required.

In machining, setup is usually the most difficult part of the work. Many times, the time spent making a tool, fixture, or jig greatly exceeds the time in making the part.
 

deakin

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To be fair, you need to give a better description of the problem.

i can never figure what someone else is thinking. i had intended the part to be too big for whoever's avail vise but didn't make the dimensions large enough for missing jaws

No mention of tolerances required.

above - 1 thou +- (and that's just arbitrary)

In machining, setup is usually the most difficult part of the work. Many times, the time spent making a tool, fixture, or jig greatly exceeds the time in making the part.

above - not mentioned in first post but taken for granted by the lazy author
 

Mitch Alsup

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except we clarified the parameters in post 7 - part too big for any vise (in theory)
OK,
a) Take part and raise it off the table (after removing vise) with something (or several identical) 1/4"-ish so the cutter does not hit the table.
b) Clamp the part to the table with at least 5 clamps (so we can maneuver several clamps while we mill without losing its position) and make it as square as feasible.
c) mill all 4 edges trying to keep at least 4 clamps holding the part to the table.
d) flycut or shell mill the top while carefully moving the clamps.
e) flip over and flycut or shell mill the bottom as in (d).
 

deakin

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OK,
a) Take part and raise it off the table (after removing vise) with something (or several identical) 1/4"-ish so the cutter does not hit the table.
b) Clamp the part to the table with at least 5 clamps (so we can maneuver several clamps while we mill without losing its position) and make it as square as feasible.
c) mill all 4 edges trying to keep at least 4 clamps holding the part to the table.
d) flycut or shell mill the top while carefully moving the clamps.
e) flip over and flycut or shell mill the bottom as in (d).
except, in my mind, moving the clamps that rest on uneven surfaces can change the angles to the...
would have to move it more that 1/4" of the table because my imaginary feature on the bottom could be...
 

Shootymacshootface

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I think that a lathe would be just as accurate as a mill, if not more so, but not as accurate as a surface grinder.
The very nature of a lathe will eliminate many possible variables that a mill would have.
 

projectnut

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To be fair, you need to give a better description of the problem. There are many ways to skin a cat, some better than others for a particular situation. What is meant by a "a feature somewhere towards the center"? No mention of tolerances required.

In machining, setup is usually the most difficult part of the work. Many times, the time spent making a tool, fixture, or jig greatly exceeds the time in making the part.
Been there done that. I have several shelves full of fixtures that took longer to make than the part they supported. Some of them are so old I can't remember the part they were built for. I always keep them thinking some day I'll either make more of the same parts, or repurpose them for something else. So far about 10% have been modified for other uses. The others just set there collecting dust.
 

RJSakowski

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Been there done that. I have several shelves full of fixtures that took longer to make than the part they supported. Some of them are so old I can't remember the part they were built for. I always keep them thinking some day I'll either make more of the same parts, or repurpose them for something else. So far about 10% have been modified for other uses. The others just set there collecting dust.
I once made an extractor for push broken wheel studs from a hub on my FWD vehicle. It took me the best part of a day to find it in a chunk of steel. It took me less than a minute to press out two broken studs. The alternative would have been to disassemble the front wheel drive. Driving the studs out with a drift was not an option because of the likelihood of damaging the wheel bearings. I have never used it again although my neighbor borrowed it to remove some broken studs from his vehicle.
Stud Puller.JPG
 

Mitch Alsup

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except, in my mind, moving the clamps that rest on uneven surfaces can change the angles to the...
would have to move it more that 1/4" of the table because my imaginary feature on the bottom could be...
The clamps have to be arranged around the part being held such that you can remove 1 clamp and move it while 4 others remain holding the part firmly in place.

{theoretically only 3 clamps are needed to old down a part without machined surfaces, 3 with machined back side.}
 
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