First some praise, then a question.

[Hobgobbln]

First off, I would just like to say that this is the friendliest and most helpful machining site I have come across. I found this a few weeks ago and have been checking it daily and learning a ton. I had been reading a few other boards for the past year (which I won't name) and quite honestly was getting discouraged.

I bought a Grizzly mini mill (X2) about 3 years ago. I had never run a mill or lathe. I spent days trying to get it trammed but was not able to. I could get close, but Y axis was always .10+ off. I kept searching for tips but none worked. On most of the other sites, when some one asked for help with a bench top machine, they got flamed for not having "Old Iron". Needless to say, I got discoraged, put a plastic bag over it and ignored it until about 2 weeks ago. I came across black85vette's post about his tramming mod as well as rudydubya's, tried it and poof, problem solved.

Thank you all very much for posting your tips, tricks and mods so the new guys don't make a deposit to the scrap yard instead a withdrawl. ;D

Now the question (bear with me, I'm new to all this). I got the mill trammed to within .0005 in Y and dead on in X. I made a test cut in some 1/2" 6061 with a 1/2" HSS 2 flute endmill a few thousandths deep. Finish was terrible. Checked the tram again and that's when I noticed that I had an impossible tram. Test dial indicator showed

-X=0
+X=0
-Y=.001
+Y=.001

I don't know if that is the way to describe the axis so I'm describing it like a Cartesian graph from algebra.

How can I be getting those readings? I was using a piece of 1/2 glass as a flat surface (I'm a glazier by trade). I rotated the glass 90* and got the same readings. I'm guessing my spindle bearings are shot. Any thoughts?

 

[BigBore]

First of all, a friendly HMEM welcome (that's the good kind) Your reasons for being here are much the same as mine. Good, skilled, sincere people and opposing opinions are given in a mature, professional manner. (that's good too)

Again, welcome and enjoy. I'll bet your problem gets solved soon and I will take notice of it.

Ed

 

[rake60]

Welcome to HMEM Hobgobbln.

What is the sweep range of your test measurement?
A .002" variation over a 1 inch area means nothing when you are
making a part that is 1/4 of an inch wide.

Rick

 

[Tin Falcon]

welcome

Do not think that little bit of apparent spindle run out should be a problem. Normally tramming is only done in the x axis. the lousy finish is probably running the mill too slow and or feeding too fast.
The Cartesian plane is exactly the way one should describe the mill table the z axis is the vertical spindle movement.
Look up proper speeds and feeds . Then play a bit until you get a decent finish the beauty of the variable speed machines is you can adjust on the fly.
Sounds like you are on the right track and climbing the learning curve.
The folks at LMS wrote a manual for your mill lots of good info
http://littlemachineshop.com/info/MiniMillUsersGuide.pdf
Tin

 

[hobby]

Hi,

Welcome to the forum,
That was a very nice introduction, the people around here are very caring, I too was a member years ago 2 other machining forums, and they were more of flame wars going on, this forum is like a breath of fresh air, where everyone has good manners, and are willing to help out in any way they can.

I am only a hobbiest at this no expert, so please only take this for what it is,

About your tramming, In my opinion being .001" out probably isn't anything to be concerned about, However, I myself never trammed my micromill, I know it is off on the X axis, and propbably the Y axis, I bought the larger table and base so I just bolted the column on to the new base and began machining with it.

The tram is so bad on the x axis, that when I transverse my table from right to left,
I get a nice non vibrating cut, but if I go from left to right then the end mill deflects so much that at the end of the cut I get tremendous vibration as the column is returning bach to it's original setting.

Yet By taking my time with the cuts, working around the out of tram condition, I can get very acurate machined surfaces, as I take it to a few thou. on the last passes.

So what I am saying is even if your column is out a few thou. by working with feeds and speeds you can still get acurate enough machined surfaces, to make parts.

I'm only speaking from experiance of what I have found with my machine,

But to get the machine as close to tram as possible , is definately a GOOD practice, in learning the proper way for machining parts.

Some times you need to experiment with the feed rate and depth of cut, as well as speed of spindle, to get better finishes, and sometimes the cutter itself or the material just won't cooperate,

I suggest, that you take smaller widths of cuts, and experiment with different feeds and speeds and even cutters, and see if yoiu can attain a smoother machined surface.

Hope this helps somehow.

Have a great day...

 

[vascon2196]

Welcome!

You will get all the answers you will ever need here....these guys really know their stuff.

Chris

 

[Maryak]

Hobgobbln,

Welcome to our forum. wEc1

Like others have already said, I think your finish problem is related to speed and feed. It may also pay you to look at the leading edge of each flute and make sure Aluminium has not built up, ( a PITA trait of this material), on the cutting edge/face.

Hope this helps.

Best Regards
Bob

 

[Stan]

It is easy to get a bad finish on aluminum without lubrication. If you are cutting dry, try some WD40 or kerosene along the cut path.

 

[ksouers]

Welcome to HMEM, hobgobbln.

I, too, have an X2 mill. And yeah, they are a bugger to tram. Basically, you won't be able to tram Y axis very well. It takes some shims and a lot of trial and error to get it close. Then a week later it'll all be wrecked again.

The column is quite flimsy. You'll notice that just a little finger pressure on the mill head will cause your indicator to deflect. And just raising and lowering the head then checking again can get a different result.

So, for the time being, I would recommend just ignoring Y axis tram. Keep playing with the tram on X, you'll need the experience. And just play with the machine working on feeds and speeds. Make some chips, get used to using the machine. In a couple weeks you'll be familiar with it's little habits. Make a couple things, something with non-critical dimensions like a couple T-nuts. They'll come in handy for clamping things down. You'll get lots of practice for hitting your dimension, finding an edge and drilling a hole on target.

Do you have a vise yet?

 

[Hobgobbln]

Thanks for the fast replies.

Stan- I was cutting dry. I do have some of the Kool Mist fluid from LMS. I'll try it next time.

hobby and Tin Falcon- Speeds and feeds are something I need to learn. I'm going to order The Machinists Handbook next week now that I am actually using the mill. I have tried different feed rates and cutters at a several different RPMs with similar results.

rake60- I was sweeping a roughly 6" circle. The glass is to rigid to bend under the pressure of the DTI spring and it was not rocking at all.

I guess I need to clarify my original readings. I'm not getting .002 of change in the Y axis. When I zero out the DTI I get the following

-X = 0
X = 0
-Y = +.001
Y = +.001

Imagine running the DTI over a potato chip or the rim of a cowboy hat. That's why I called it an impossible tram. If the Y axis were +.001 and -.001, that would make sense to me. How can I be getting +.001 both sides of the Y if I am rotating in a circle. Being a few thousandths off is fine with me. Its how I'm off that is making me question the bearings.

I really want to try making one of the air engines I have seen here but I want to get the machine working right first.

 

[Hobgobbln]

ksouers- We were typing at the same time. I do have a 3" swivel base vise from LMS and well as some other tooling that I read were basic requirements. IE..... parallels, clamp kit, 123 blocks, edge finders etc.

 

[joeby]

If I understand, the front and back of your table reads .001 higher than left to right.

The readings, if they had been taken on the table itself, would show a cupping or concavity of the table's surface. This doesn't seem to be unusual, especially on a table with a ground surface. The casting is not nearly as thick in the center as it is over the ways which are further out. When grinding, they heat up faster along the center and "hump" up. This hump gets ground off, and once cooled, sinks below where it should be.

The little bit that it is off probably will not be much of a concern, as has been stated in several other replies. Depending on what you are doing, you may be machining parts that fit into the low spot, or bigger parts that straddle it.

I wouldn't spend much time worrying about it. The tram you have now with the left and right being equal and the front to back equal, is about as good as you can get it.

Kevin

 

[black85vette]

Finish could also be the end mill. Try another one at .003 and check the finish. Lock down the head and the axis you are not using. Try it in X and Y. Could be a gib adjustment.

I may get corrected but I don't do my final tram with the DI. I get as close as possible and then start making very shallow cuts and watching the pattern to see if the lead edge or trailing edge is cutting more. Then I make very slight adjustments until my cuts are even and I get a nice cross hatch pattern in both X & Y. Then I have no ridges and get a nice flat finish. I check it periodically the same way. Saves time to not have to stop and get the DI set up.

These little machines take some tweaking but can do some really nice work. Just not very fast.

 

[kd7fhg]

My two cents worth. I honestly can not remember the last time I clamped something to my mill table to machine it. the parts usually get stuck in the vice, on a jig built for the Job (so I don't ding up the mill table) or the rotary table. All of these will effect the tram of the mill head. The final step of the setup process prior to machining the part (or some times scrap) is to check the tram in relation to the material to be machined.

I hope everyone has a great day!
Rex

 

[rudydubya]

Welcome aboard Hobgobbln. I'm no expert, quite the opposite, but all the advice given above is well worth considering. Lots of knowledgeable folks here willing to help.

Rudy

 

[Blogwitch]

H,

I can't understand your reckoning on the Y tram. One of your figures should always be zero, that is your start point, then 180* turn gives the amount it is out, which is what you adjust to.

But looking at the figures you have already achieved, you have no need to worry about your tram, the machine will most probably flex more than that in general use. All you will achieve if you attempt to get perfection, is chasing your own tail, and never getting anything made. Be happy with what you have already done.

I personally wouldn't worry about buying feed and speed cutting charts either. You can get them free from all sorts of places on the net, but they mean nothing to the laymen machinists, which most of us are. Charts like that are made up for giving professional machinists a starting point to work from when cutting unfamiliar materials.

A different style or type of cutting tool, type of lubricant, type and size of machine and rigidity of the job can throw all those facts and figures out of the window. There are just too many variables to produce 'carved in stone' charts. Use them as a guide by all means, but don't think they will solve your cutting problems, it is a fact of life that the only way to cure those is experience. So relish the fact, that one day, you WILL be able to do perfect cuts, most of the time.

Charting your progress by trial and error is more important than attempting to follow charts religiously.

Get a lump of metal, and spend a few hours playing at cutting it up into bits, but do your playing logically, say play with the cutter speeds first, then your feeds, you will soon find that doing certain things gets the desired results. Don't forget to listen to your machine, more often than not, it will tell you when you are reaching it's limits, so back your settings away quickly.

Even the most experienced of us learn new things all the time, so you are not alone.


Blogs

 

[Mainer]

To expand a little on Blogwitch: Are you saying that from +X to +Y you get a change of 0.001" and from +X to =Y you also get a change of +1? If so, though I don't understand just how it's happening, you should be in pretty good shape.

 

[Hobgobbln]

Mainer- That's correct and I cant figure it out either.

Picture this, you have a 6" diameter navigation compass that is perfectly flat laying on your table with North pointing at the column. North and South and reading .001 higher than East and West. I have the Swarfrat series for my mill. In the tramming section he says to disengage the drive gears before tramming which I did. Maybe that is why I am reading play in the spindle.

I guess I am just being to fussy. I will spend some time cutting and see if things improve/get worse. I only have about 3 hours of use on this machine so maybe it needs to wear in more.

Thanks to all of you for the replies and advice.

Jeremy

 

[Omnimill]

Welcome Jeremy, I can't imagine the tram is causing your problem given how small it is. Can you post a picture of the poor finish so we can have a look? As already stated, some form of lubricant is often required on aluminium alloys. Nothing fancy needed Paraffin (Kerosene) is fine. Hope you sort the problem.

Vic.

 

[Ed T]

I am not familiar with your machine, but the tram of the machine has little if anything to do with the quality of the cut. So, like others have already said, it's probably something to do with the speed, feed, or depth of the cut or all three. Without revealing how I know, you can get a REALLY rotten cut if the spindle is running backwards. Your machine may not have reverse (mine does), but, since its new to you and has not produced a good cut, it might be something to check out. Since it is a variable speed drive it is not inconcieveable that something is wired backwards and, if its a dc drive, reversing the rotation is as simple as reversing the wires to the motor. Either in the motor or inside the control box (one may be easier than the other). If its a VFD converting single phase to three phase swapping any two of the three wires going to the motor will generally reverse the direction. This is probably easiest to do in the control box. There will (probably) be a terminal strip where the motor wires connect. UNPLUG the machine BEFORE you mess with the wires!!! It would only take a second to determine if this is the problem and it's fairly obvious once you consider it, but not so obvious otherwise.