Machining WIP

[CUTS LIKE A KRIS]

I don't understand a damn thing said here but I appreciate it! Actually I think that I know what threads are....

 

[Nathan the Machinist]

Nathan, That looks like a Mori mill except for the tool changer. Is it a Mori? Thread mills are the way to go. We use them mostly for oddball metric stuff, but I'm trying to convince the shop owner to use them for everything. Cool WIP :thumbup::thumbup:

Nah, I wish it were a Mori. It is a "Bridgeport". Good Americian iron. Except it is imported from Britain. I think Hardinge bought the name. It has a pretty raw Fanuc controller, nothing near as user friendly as something like a Haas mill. But it has more balls than a Haas and has served me very well.


So, anyway, the rest of the steel arrived. While the steel I started with was precision ground, I ordered hot rolled annealed for the rest of the project. It is oversized, has mill scale on it, and the rough grinding on it appears to have been machined by vandals...

So I'm going to have to mill it down to size (nobody wants a 2 1/8" wide platen) and remove the raw edge. So I'm adding a 3" 6 flute face mill

and I sawed it up and stuck in the vice, 10 at a time.

look at it. nasty huh?

I took a picture of the cut, but it looks like, uh, a big face mill with coolant spraying on it (a fine mist). So I took a picture of the load meter instead. That was about a 5HP cut.

pretty though huh

So I got all my blanks to size and then finished roughing out the 36" plattens

So - uh - pretty much nothing very interesting. Being a machining WIP, I do have something else intertesting on another machine.

milling some scales in cocobolo and african blackwood.

I got the wood from "The exotic wood group". :thumbup: The blackwood is premo, and that cocobolo is sick. (it will turn red after a day or so).

The next installment will be more interesting....

 

[Bailey Knives]

Hurry up!!! I love milling stuff, even though I dont understand it...Take lots of pics for those of us who are learn visually.

 

[blgoode]

Brain skills Nathan!!! Brain Skills

 

[fitzo]

Neat thread, Nathan, and nice work. I guess I'm going to keep having to check in to see how those turn out in use.
CNC'ing scales is just too slick, too!

Regards,
mike

 

[Nathan the Machinist]

It's great to see you around here Mike. :thumbup:

 

[Stuart Willis]

Thanks for posting Nathan. Very interesting stuff. Now post some machining. I love it.

 

[Nathan the Machinist]

Thanks for posting Nathan. Very interesting stuff. Now post some machining. I love it.

Ah... right... too many picts of things machined, not enough of the actual machining... The trouble is, during machining there is usually a lot of coolant everywhere. But I tried to get some picts this morning.

So, while that machine was chewing on A2 all morning I needed to make a fixture to hold the part on its side for finishing the radius. So I'm going to do something I've never done before. I'm going to post about manual machining. Bleh. (manual machines don't have cup holders or nothing, how am I supposed to drink my beer)

But first I have to show the wonkey setup that was on that mill. (I'm going to hell) I was useing it to slit scales. Never do this.

I zeroed on the vice with an old school edge finder

I sawed off an 8" piece of 1X4 CRS, filed smooth any uglys and stuck it in the vice. I'm not sure if I'm the last person to put this vice on (my evil minion has been using this mill) so I swept it with an indicator to be sure it was square. It was.

And milled the end square

Look Stuart , I'm cutting chips in this pict too. In fact, I'm actually takeing the picture in one hand while turning the crank with the other. You'll notice I ran the cutter down so a sharp area of the cutter was making the cut. I'm also climb milling to get a good finish. That is usually a no-no on an old clapped out mill because the backlash can run away on you, but there are exceptions to the rule. This is a light cut and the lock for the way was dragging (okay, there is no lock - the wood chips in the ways were dragging)

A band of rabid beavers couldn't have gnawed that off any cleaner.

So, with a piece of stock ready, now to make a fixture out of it...

 

[Nathan the Machinist]

So, I need a fixture design. My intent is to put the bottom 2" into the machine vice and screw the platen to the top two inches. The fact that the vice jaws are only 1 3/4" tall means I have clearance. So all I have to do is accurately place two simple holes into this plate.

Here is my highly technical engineering drawing of the design.

I had zeroed off the jaw of the vice and I had milled the end of the work piece so I know where zero, zero is. So I zero out the read out and move go over to my first hole

I want the hole locations to be accurate, so I'm spotting the hole.

I'm using a center drill for this, which is a no-no. It is stiff and will accurately locate the hole, but the 60 deg included angle will have the drill starting the cut with the corners. Starting with the web (or actually just outside of the web) will reduce the tendency to walk. So I'm following it with a 118 deg countersink.

Which leaves me with an accurately placed 118 deg hole with the added bonus of clearance for my drill web to start.

It takes more time to describe this than it does to do it. A regular spotting drill works fine too.

Now I drill it out to about .220 with a random undersized drill I pulled out of my random drill bit box.

There is a special point I would like to make here. You will notice there is no coolant. There is no oil. I didn't run the drill really slow. I drilled through one inch of 1018 CRS in a few pecks with a firm steady feed. Took about two minutes total to do both holes. All the fiddling around people around here do to drill a simple hole just makes me shake my head. I want to grab my monitor and yell "just drill the freakin hole already!". I did let up upon exit, that is when your corners get wiped out. You'll notice the bit is just fine and it has untold amount of miles on it. The key is to feed it properly.



I then chase the hole with a 1/4" four flute endmill that measures a couple thou under. There is a reason for this.

This should be done with about 2-4X the feed you used on the drill, in one smooth motion - no pecking. But I lost my nerve and pecked halfway down. I didn't want to risk the chip getting stuck on a flute and galling. I used a few drops of oil here.

I want this hole straight, round, accurately placed, and undersized. The approach I took got me that.

Screws are almost always under nominal. If you'll recall, my threads are thread milled, so they are accurately placed. Even if my drill bit walked, the milled pitch diameter will be accurate. So, I can use these accurate holes and accurate threads to accurately fixture my parts...

 

[Stuart Willis]

Thanks Nathan. I thought you had forgot how turn cranks. I like the old school stuff and then the last pic....A mic that was not digital

 

[Nathan the Machinist]

Okay, the next thing to do is to stick the new fixture in the vice and finish the radius.

I removed the bulk of the material before with it held solid in the vice, so those two little 1/4" screws will hold it fine for these last little cuts.

Roughing with a 1" 5 flt rougher

This is what that cut looks like

I had to stick the camera behind the vice to take that pict. I put the fixture in this way because I had already zeroed on that jaw, so making that my working surface prevented me from having to zero out the fixture again.



And now the finish cut. This was done with a 3/4" five flute finisher.

I left .010 stock allowance from the cob mill. So I decided to shave off five and then finish the last five at low speed and feed to try to prevent any vibration, full DOC to prevent any step lines.

And that is that. Right? The finish could be shinier, but it is smooth and chatter free so it's good right?

One of the most humbling things a machinist can do is stick their work under a tenths indicator. Nothing is ever perfect.

The variations in finish you see are actually very minor and don't represent a problem. There is a problem, but it isn't the wonky finish.

The two edges are over a thou higher than the center. It is probably workable - but I'm going to try a different finishing cutter before settling on this. Might be a few days...

 

[butcher_block]

nice work
so far as the high edges i think most of us will be knocking the corners off anyway

least i know i will be

 

[A C Richards]

Very nice Nathan. Love the process. I am feeling a little sd I no longer have a nice CNC, or any CNC for that matter. Been thinkin real hard about getting one but just can't justify it right now. If I do It is not going to be a very large machine due to space restrictions. Oh well just have to live vicariously through you I guess. You just need to do more WIP's.

 

[Nathan the Machinist]

nice work
so far as the high edges i think most of us will be knocking the corners off anyway

least i know i will be

I don't think I explained the problem very well. The part is a little bit saddle shaped in the direction it should be straight. Knocking the corners off won't really fix that. It would probably work okay, but I'd rather not risk it. Lapping all these out on a plate would be a drag. (I made a pun)

This part isn't scrap. I'll put it back on, tweak an offset, and dust off a couple thou with a different finisher. If that works I'll run the hell out of then. I just ran out of time...

 

[drewfacehotm]

I don't think I explained the problem very well. The part is a little bit saddle shaped in the direction it should be straight. Knocking the corners off won't really fix that. It would probably work okay, but I'd rather not risk it. Lapping all these out on a plate would be a drag. (I made a pun)

This part isn't scrap. I'll put it back on, tweak an offset, and dust off a couple thou with a different finisher. If that works I'll run the hell out of then. I just ran out of time...

you don't think that might be a little pushoff from the extra matrial on the corner from the big fly cuttler. a free pass might be all you need, or a ball mill with a .006 step over

 

[butcher_block]

ooo ok
your right it might be fine but i understand not wanting to chance it

keep up the great work

 

[Justin.Mercier]

This part isn't scrap.

I certainly hope not! That's flatter than the platen on my KMG right now lol. I'd be happy to buy your 'scraps' Sometimes machinist mentality is more perfectionist than the applications they will be used for =D

 

[Frank Barron]

So I should be sending you my cheque soon?

Send address for mailing.

 

[fitzo]

Very nice, Nathan. I'll be interested to see how these work out. The difficulty in the past with radiused platens has always been the belt drag over the concave surface. The tendency towards more powerful motors driving the grinders may overcome this. I look forward to the reports from the field.

 

[Nathan the Machinist]

Y'all think I'm nuts sweating a couple thou irregularity...

There is a lot that you can do with grinding technique to eliminate the dreaded 2" divot and other surface imperfections in the grind. But having a truly flat (or even slightly convex) surface to grind against helps. When I was learning to grind, my grinding wheel was concave a few thou. That doesn't sound like much - but a few thou show up in your grind unless your technique prevents it. We don't all have your grinding skill Butch.

Frank! I was wondering if you were going to drop by. This is just a machining WIP, for fun. When these are are done I'll start a thread in the appropriate area and bump the "is there interest" thread with a link. I don't want to spam this forum, this is just because it is fun.

Drew, my earlier roughing from the top did leave a scalloped surface, but I left a .020 skin in the minimum material areas for finishing. I reroughed it from the side, then semi finished, and then took a dust pass. I'm confident any remanent from the first roughing operation is long gone. It is probably the cutter. The gold standard for cutting a straight side wall is a straight flute cutter, but they tend to leave a choppy surface...

Mike, I think they will work best if you only stick it out far enough to create a few inches of contact and grind in that area. I'm not sure full contact is necessary. I don't know... Perhaps I should look into low friction coatings, like Teflon impregnated hard chrome used on certain molds etc. Though that ain't cheap. If only there were an industrial chemist around with some suggestions...