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sansbury
02-03-2009, 12:00 AM
I am working on a chess set that is going to require me to make a lot of blocks out of brass and aluminum. Pieces will be made from 1" bar stock, squared up and either 1", 2", or 3" tall depending on the piece. The sizes are all nominal, but I'd like the pieces to match each other by a few thous, or better. Partly for aesthetics, partly as a challenge for me to improve my technique.

For equipment, I have an X2 that has been converted to CNC, and a 7x lathe. My first thought was to take sections of bar 6-7" long and machine them square on the, and then cut smaller chunks off them which only need squaring on the ends. The length limit is so that I can machine the full length in one pass with a fly cutter or shell mill without making any turns near the ends, so I get a consistent finish.

Any tips, techniques, fixturing approaches greatly appreciated. I imagine if I wanted to make more than a couple of these I'd look for a larger mill, at least for preparing the stock on.

tattoomike68
02-03-2009, 12:02 AM
Start with square stock.

Carld
02-03-2009, 12:04 AM
Sounds like a good plan to me. Tattoomike seems to have the right answer.

3t-
02-03-2009, 12:10 AM
sansbury,

Take a look at the videos on this link. Great stuff here. I think it is "Machine Shop #6" that details stock squaring on a mill. If not #6 it is in one of the videos listed.

http://techtv.mit.edu/collections/ehs-videos/videos

I use the process described in "Machine Shop Trade Secrets" by James Harvey, get a copy you won't be disappointed.

Ken_Shea
02-03-2009, 12:23 AM
Start with square stock.
While the simplicity of that gave me a chuckle in the real world that often is not possible.

My approach if I wanted them all equal as possible would be to machine each separate side as a lot before machining the next side. Same for the ends after you cut then to length, machine the separate ends as a lot before doing the other end. Also use a positive stop in the vise so each piece has the same starting position.
EDIT:
Once you get one end of each cleaned up you could also stack them vertically in the vice and face off groups of them, but always in lots.

This is a simple but very effective stop similar to what I use only I paid $19 for a pair :(
http://www.cdcotools.com/index.php
Do a search for Work Stop on their site.

Ken

Carld
02-03-2009, 12:29 AM
Ken, the irony of the question is "how to square up stock". Now, if he is a machinist he would know such a simple thing as that. Even with a little imagination he should come up with a way using just a lathe. The problem to me is not many think before asking.

On the other hand I may be a little short with my answer because of the weather we have had.

To be fair, he didn't give any info about what size he is starting with to make it square. If I give him a fish he learns nothing, but if he has to fish he learns.

Ken_Shea
02-03-2009, 12:41 AM
No argument there Carl, although, from his question I presumed he was just beginning, and having been in the same boat with many efforts I know that what seems so obvious to the experienced is not to those new at it. When new you want to do everything just perfect and it is a tendency to over think what needs to be done, resulting in even more confusion, with experience, perfect results rarely just happen but good work often does.


Ken

isaac338
02-03-2009, 01:05 AM
To be fair, he didn't give any info about what size he is starting with to make it square. If I give him a fish he learns nothing, but if he has to fish he learns.

no no.. it's "give a man a fish, he eats for a day; teach a man to fish, and you give up your monopoly on fisheries"

Your Old Dog
02-03-2009, 07:49 AM
...........Pieces will be made from 1" bar stock, squared up and either 1", 2", or 3" tall depending on the piece..........

That's a good stock to use for chess pieces. It allows you to bore out the bottom to 1/2" and press in some rare earth magnets. Sure would create some excitement on the board if you only did a few pieces and started with them on opposite ends of the board :D

derekm
02-03-2009, 09:07 AM
Using sq stock is good because its considerably cheaper. Think about the volume of brass that you are going to make into swarf ...

thats money

because you pay for stock by weight (essentially). Brass maybe cheaper but its still a lot money for a six foot length of 1" bar (which is what will take if you add up 32 pieces av 2" allowing for cutting etc..).

To square it off will waste 36%. (math for max size sq inside a circle)

Circlip
02-03-2009, 09:12 AM
But 36c is a lot less than 36p

sansbury
02-03-2009, 10:06 AM
Start with square stock.

Look, when it comes to me, out of "fat, dumb, and happy" you can pick any two :D

OK, maybe the part I wasn't specific enough on was that this is for a fancy-schmancy decorative application, so I want the pieces to have a good degree of finish on them. I don't need a mirror-polish, a machined look is fine so long as it is clean and consistent.

The stock I buy locally is 1"x1" square, which are sold as offcuts $2.75/lb for 6061, $4 I think for 360. It is square but just the basic mill finish. I don't care if the pieces come out to .923" square so long as they're the same. I've found I need to take up to .05" off each side to be sure of getting out all the corner rounding, dings, etc.

Newbie? Guilty. I've done maybe a hundred or two one-off parts, but this is the first project that calls for a bunch of the same thing and where I'm trying to hit tighter tolerances. Sometimes when you are doing a hundred of something it makes sense to optimize the process in a way you don't do when doing one or a dozen.

Ken- thanks for the suggestion on doing each side as a lot. I can see where that could lead to more consistency.

3t- I've seen that book a number of times in Google searches and found it interesting reading--I suppose it's time to buy a copy and be done with it.

tony ennis
02-03-2009, 10:13 AM
Sounds like the pieces are going to be mainly rectangular in cross-section then. How do you intend to break all 384 edges once you've machined all 6 faces?

Tinkerer
02-03-2009, 10:30 AM
Place the piece in the vice and mill the first side... then take and place that side against the fixed jaw. Then mill next face and repeat till all sides are done. Also if your moveable jaw wants to lift when you tighten it place a piece of drill rod between the the work and the jaw. To keep from marring the finish you can place a piece of note paper between all the contact surfaces. And as Ken already stated do each face in lots

I hope this helps.

Carld
02-03-2009, 10:34 AM
Ok, start with a 4 jaw chuck and reverse two jaws. Put the square stock on the flat of the two reversed jaws and snug them up. Then move the other two jaws to clamp the side of the stock. Does the stock clear the top of the jaws? If not then you will have to space the stock off the jaws.

Mark the stock with a pencil so it has a mark centered from the ends and the sides. Put a dead center in the tailstock. Align the center of the stock on the point of the dead center. Tighten the jaws and return the tailstock to the far end of the lathe. Turn the compound so it is parallel to the axis of the lathe. Put a cutting tool of choice in the tool post and align it on the work so that it will cut at center line.

Move the cutter using the carriage hand wheel, crossfeed wheel and compound wheel to contact the face of one end of the stock. Now the cutter is positioned to start. back the cutter away from the stock with the crossfeed handwheel. Start the lathe motor and select 300 rpm for starters.

Now advance the compound feed in .025" and start the chuck turning. Now manually crank the crossfeed in and make the first cut and stop when the cutter is just past the center of the work. Back the compound off so the tool clears the work. Back the crossfeed crank to the starting point and stop the chuck and look at the work. Is the surface free of blemishes? If not make another cut untill it is the way you want it.

Remove the work and turn it 90 deg to begin cutting a new side. Repeat the above steps untill the four sides are clean to your satisfaction.

After you have done the sides of all the pieces you can do the ends. For that you will have to reverse the two jaws you switched at the start. Now align the stock in the four jaws so it is centered somewhat, it don't have to be perfect. Now move the cutter to contact the end and retract the crossfeed, move the compound in maybe .40" to clean the end and if not clean take another cut. Do the ends of all the pieces this way.

Now your ready to make the Chess men.

EDIT: I left out some detail assuming that you could figure it out. Since you did not say if your using a lathe or mill to square the parts I assumed your using a lathe. If your using a mill I can detail the process out for the mill as well. If you have trouble figuring out any of the details I can go into extreme detail of each move to make and how many ways you may be able to do it.

As far as doing the CNC part of the work I don't know anything at all about that and your on your own as to programing and tooling for the CNC.

hornluv
02-03-2009, 10:39 AM
Take a look at the videos on this link. Great stuff here. I think it is "Machine Shop #6" that details stock squaring on a mill. If not #6 it is in one of the videos listed.

http://techtv.mit.edu/collections/ehs-videos/videos

You know, I have to take some issues with that video. First of all, why isn't he using a parallel under the part? He takes all that time to "align" the part with a parallel on the fixed jaw of the vice when he should have just had one under the part in the first place.

Second, he brings the quill down to the work instead of raising the knee. Sure it gets you there faster, but it isn't going to be as rigid. To paraphrase Mr. T, "I pity the fool who don't realize the quill is for drillin', not millin'!"

Third, he keeps putting his damn finger right next to a spinning fly cutter to point out the surface finish. He even wipes his finger towards the cutter while it is still on the part. Unless you like seeing your own bones, that's really not good practice. Keep your body parts one foot away from the action and you'll keep your body parts.

Lastly, files only cut one way. Sawing back and forth with a file is only going to speed up the wear on the file, not your cut. I also think it's an absolutely smashing idea to run a file across that nice, freshly milled surface to take off all those nasty burrs (there's unfortunately, no sarcastic smiley).

At this point (about 8 minutes into a 46 minute video) I stopped watching it.

sansbury
02-03-2009, 10:40 AM
Sounds like the pieces are going to be mainly rectangular in cross-section then. How do you intend to break all 384 edges once you've machined all 6 faces?

I've toyed with chamfering or corner-rounding, but for the first batch I'm OK with a plain old deburring tool.

Carld
02-03-2009, 10:52 AM
Sansbury, to read my post #15 for a method to do it.

sansbury
02-03-2009, 12:10 PM
Sansbury, to read my post #15 for a method to do it.

Thanks for the detailed suggestion! I have both lathe and mill, but the mill could be kept busy working on the details of the pieces while I square stock on the lathe. Since the lathe is manual, it would also be easier for me to walk each piece onto the final dimensions.

Having never really tried to survive with only a lathe, I always forget it can do square work as well as round.

The CNC detailing on the parts I'm not worried about--I'm a software guy by trade so that stuff comes to me pretty naturally. I've been fiddling with that stuff for about a year, and am starting to get my CAD->CAM->mill workflow somewhat figured out. It's the manual techniques, fixturing, and helpful tricks passed down through the years that I don't have.

steverice
02-03-2009, 12:50 PM
At some point I am sure that he is going to be demonstrating the emergency first aid kit and how to stop excessive bleeding from missing appendages.

vincemulhollon
02-03-2009, 12:59 PM
Pieces will be made from 1" bar stock, squared up and either 1", 2", or 3" tall depending on the piece.

I spent some time last Saturday morning making one cubic inch aluminum cubes, mostly just for fun. I am also a newbie, which might be why I am pleased with merely making a little perfect cube of metal. One hard learned lesson is that overall you'll save a lot of time by getting the saw perfectly parallel and perpendicular and set up a stop to get the length pretty close before you start. Machining is much slower than adjusting the saw, especially for a couple cubes.

As for the machining it was clearly a CNC flycutting job, so I wrote a program to take off 10 thousandths each time I pressed go, and at the end of the program get the spindle all the way out the way (and shut off) so as to measure the length with a caliper. That last move wasted enough time every cut that I modified it not to get out of the way,at the end and when I want to make a measurement I have the CNC manually jog the table.

Oh yeah, setting up the vise to make it easy to measure the length without removing the work seems to be a good idea, so mount the cube slightly hanging over the edge of the vise. Which means you could cut two at once except the "back cut" of the flycutter might mess up the finish on half the cubes. And also if you try to clamp three at once I suspect one of the three would fly away so I didn't try it. So I was stuck doing one at a time with a one inch spacer made of scrap on the other corner of the vise.

Liger Zero
02-03-2009, 01:01 PM
It's the manual techniques, fixturing, and helpful tricks passed down through the years that I don't have.

Indeed. I've puzzled out quite a bit, this site is great for getting tips to fill in the void though.

As for deburing, if you are brave enough you can whip up a tumbler using an appropriate sized can, tumbling stones and a shank to insert into your lathe chuck. VERY NOISY though and you'll have to figure out the "ideal" method of securing the lid to the can, it WILL pop open during operation.

I use big giant single-use tie-wraps myself...

This method works GREAT for deburring plastic parts at low speeds... I imagine it would work for metal as well with different media and speeds.

Al Messer
02-03-2009, 01:27 PM
Turn them Square on the Lathe---use a 4 jaw chuck. Too bad you don't had a Shaper--perfect for a job like this.

Carld
02-03-2009, 01:44 PM
Sansbury, I sometimes spend hours sitting and dreaming up ways to make a part. It's not something that is passed down, in most cases, it's something that a machinist devises in his mind. It's much better to spend hours working out a problem than spending time making mistakes on the machine.

When you operate a lathe or mill for few years and learn the can's and can'ts of the machine then it is easy to do the job in your mind and that eliminates a lot of scrap parts.

The most important aspect of being a machinist is working out a problem in your mind BEFORE doing any machining. It is easy to machine yourself into a situation where the part can't be finished because you have put one step ahead of another and you can't do the next step.

Always do the whole job in your mind and determine the flow of the work. It's the same with doing a CNC program so I don't think you would have a problem doing that at all.

Doing machine work is a lot like playing a chess game. One wrong move and you can lose.

Scishopguy
02-03-2009, 02:26 PM
As was suggested, fly cutting all the parts together is a good way to get them all to come out the same but one sugestion I will make is to use a piece of hard wood or sheet rubber against the moveable jaw of the vise. Bar stock tends to come slightly oversized and not consistent in size. It will only be a few thousandths but it is enough to let some parts be loose. By using a crushable material between the moveable jaw and the parts you will keep a loose part from jumping up into the fly cutter and messing up your laundry. Been there and done that.;)

Liger Zero
02-03-2009, 02:38 PM
Sitting and pondering is great but sometimes it helps to have an experienced hand to bounce an idea off of...

Take Scishopguy's suggestion for example.

dp
02-03-2009, 02:41 PM
Don't know if it's been mentioned, but when truing a side opposite a machined side you should also be dimensioning it. That's not the case when truing a side adjacent.

Evan
02-03-2009, 04:16 PM
Remove the work and turn it 90 deg to begin cutting a new side. Repeat the above steps untill the four sides are clean to your satisfaction.


I also have squared many a part in the lathe using a four jaw. I would make only one small change to Carl's procedure and that is to turn the work 180 in the chuck for the second pass. That will put the first trued side against the chuck face which is as good a reference as you will find and make the second side parallel to the first. You will then have two good sides to grip in the jaws when you do the remaining sides.

To avoid marking up the work I either put electrical tape on the chuck jaws or shim the jaws with aluminum flashing.

winchman
02-04-2009, 05:07 AM
How do you use these work stops?

http://www.cdcotools.com/picture/271

Roger

Ken_Shea
02-04-2009, 07:55 AM
Roger,
They come with a Allen wrench, you slip them over the raised portion of the back vice jaw, position and then tighten.

They are very handy, have used them a lot where machining is needed on multiple sides or where the X positioning needs to remain fixed for a particular repeatable machining operation.

Ken

winchman
02-04-2009, 10:41 AM
Got it.
Thanks,
Roger