Spindle WOBBLE?

[sheepdog]

My new Mini Mill has 1/8" spindle wobble and at mid-range speeds it shakes the entire machine. At full speed it smooths out and the drill bit I placed in it seems to be true and not wobbling. The wobble is so ugly I have to put the plastic spindle cap on it so I don't look at it.

Is this what I can expect from a Little Machine Shop Product? I am really shocked that a precision machine would wobble this much. Maybe if I put ear plugs in (cause I can also hear the wobble) and the cap on the spindle I could live with it.

Please advise, Mark

[Bob La Londe]

Have you contacted LMS yet to ask them if this normal?

[sheepdog]

Originally Posted by Bob La Londe Have you contacted PMS yet to ask them if this normal?

don't know pms but if you mean little machine shop yes i have emailed them about this and one other small problem with an accessory. i am going to upload a video to see what you think. sorry i could not hold the camera more steady, but you can still see the wobble if focus on the spindle sides.

http://www.youtube.com/watch?v=Du4Qyyu_Gz4

http://www.youtube.com/watch?v=Du4Qyyu_Gz4

026 - YouTube

026 - YouTube

mark

[Bob La Londe]

LMS. Darn smart phone sometimes disagrees with me about what I am typing. LOL.

I'm not sure I am seeing runout in those videos, or floating end slap. I do see what looks like a non-perpendicular cut to the end of the spindle. If that is typical workmanship for your mill then what you are experiencing may be "normal." The noise does not seem overly onerous to me for a low end mill, but it is a little loud. Then I run mini mills with a wood router on the Z-slide so loud is of course relative. LOL.

From what I understand about spindle design the back side is stabilized with a lower tolerance bearing just to keep it from slapping around, and the tool end is where the better bearings usually are. Better is also relative of course. Based on the cost of the machine.

Optimimum (in general) is two back to back angular contact bearings at the tool end of the spindle, and a floating bearing at the other end to stabilize it over its length.

On a mill like yours it may have totally different bearings and setup.

Have you chucked up a tool or precision rod and indicated it to see how the nose of the spindle performs? I would turn it by hand to do this. My next thing would be to grab the spindle nose and shake it left to right and front to back gentley to see if there is any side play. Then push and pull on the end end the spindle to see how much end play you may have. Do not expect there to be zero unless you have a very expensive spindle. Your hands may be as good a measuring tool as your eyes. Also when playing with the tool end watch the floating end.

Overall this will give you a better feel for the condition and quality of your spindle and spindle bearings.

Which specific mill and its price might be helpful. Is this an X2 manual mill? I quick check shows a head assembly for this machine on the LMS website, but I do not see the mill offered for sale. Can you provide a link to your machine.

Sorry, I'm no expert on mills. Just another hobby hack with a couple mill in his home shop (OK, 5! LOL)

On second listen I do hear a little clicking in the background that could get worse at speed. Its hard to tell from the video sound track about the sound really. If you like I would be glad to post a couple video clips of my two manual mills (different class machines with multiple pulley belt drive) for comparison. Neither is particularly tight, but then I bought them both used.

[sheepdog]

Originally Posted by Bob La Londe LMS. Is this an X2 manual mill? Can you provide a link to your machine. Sorry, I'm no expert on mills. Just another hobby hack with a couple mill in his home shop (OK, 5! LOL) On second listen I do hear a little clicking in the background that could get worse at speed.

my machine is what i believe to be an X2 LittleMachineShop.com - HiTorque Mini Mill, Tilting Column with Tooling Package

i went down this morning and put a 3/16 collet and drill bit in upside down protruding about 1/2" out the bottom so i have a smooth shaft to look at.

the spindle does not seem to be lose at all anywhere in fact it is very tight. it looks like maybe the outer portion of the upper spindle is just out of round slightly and they machined the lower center as accurately as they could. because the bottom end of the spindle and the drill bit do not reflect the same type of eccentric movement that i see on top where the drawbar top is at. i wish i had a run out instrument to check it better.

however this thing is gear driven and so i have to wonder if the surging i hear in the gear noise is caused from the eccentric spindle top. there is at times a weird small clicking that seems totally unrelated and in different time with everything else that's going on so i'm not to excited about that right now.

i don't really care if the top wobbles as long as the bit doesn't wobble is what i'm getting at. but it seems other have asked the same questions and had concerns like i have had. i did a search on google and found this thread and a video showing a grizzly that a guy bought from little machine shop and he has even a little more wobble than i do. i just expect this mill to run it's bit as accurately as a 99.00 wood router you can buy at home depot you know.

milling head runout [Archive] - The Home Shop Machinist & Machinist's Workshop Magazine's BBS

grizzly milling head.AVI - YouTube

mark

[Bob La Londe]

If I recall a belt drive conversion is pretty common on a lot of small gear head mills. Belts are pretty forgiving. Both of my manual mills are belt drive, and my Taig CNC mill came with a belt drive spindle... although admittedly a quite good one. (The Taig)

I would be concerned with putting the cutting flutes of a drill bit inside my tool holder or collet. Its an uneven clamping surface which could distort a collet, and you never know with an inexpensive tool if the drill bit or the tool holder is harder. Still for a one time test its probably ok. If your machine just came with a drill chuck then who cares. Drill chucks are notoriously sloppy anyway. I would suggest getting some collets or a collet chuck for end mills. I happen to like collet chucks myself because of the easier collet changes, but many people have pointed out that you have to add the runout of your collet chuck to the runout of your spindle. It also reduces your available Z clearance by the amount of the chuck sticking out of the spindle.

[Bob La Londe]

Originally Posted by sheepdog my machine is what i believe to be an X2 LittleMachineShop.com - HiTorque Mini Mill, Tilting Column with Tooling Package however this thing is gear driven and so i have to wonder if the surging i hear in the gear noise is caused from the eccentric spindle top. there is at times a weird small clicking that seems totally unrelated and in different time with everything else that's going on so i'm not to excited about that right now. mark

I went to that link and the third bullet point is:
"No gears in spindle drive"

Most powerful mill in its class with most low-speed torque in its class
Includes tooling package
No gears in spindle drive
Largest table and X-Y travel in its class
R8 spindle (Includes 1/2" drill chuck and arbor)

That is certainly an odd twist if yours is gear driven.

Anyway, at $795 its not an expesnive machine by any means. I would confer where possible with other owners and see if your performance is normal. (Which sounds like what you were tring to do here before I jumped in. LOL)

[sheepdog]

Originally Posted by Bob La Londe I would be concerned with putting the cutting flutes of a drill bit inside my tool holder or collet. Its an uneven clamping surface which could distort a collet, and you never know with an inexpensive tool if the drill bit or the tool holder is harder. Still for a one time test its probably ok.

you make a really good point about the drill and the collet cause i was also concerned about that so i just slightly tightened it and the bit is very long with a good deal of flat shaft on it. i think it will be ok.

the machine came with 7 collets and one drill but the drill collect was double threaded and is useless cause it would strip the threads of the drawbar if i forced it. i have written them and gave them photos to show the extra threads.

here is the picture mini mill

and a picture of the machine mini mill

i think i have a good looking machine that probably looks better than i can expect it to work considering the money i spent for it i guess is what the conclusion is. im still just shocked there is any warble at all on this or any other mini mill machine no matter who makes it.

mark

[Bob La Londe]

I'm not.

I've spent some time over the last several months looking at spindle design and studying on making my own spindle for a high rpm application. I've got a Hurco I bought used (at a stupidly good price) that I am retrofitting over to a newer Mach 3 controlled CNC system. The guys at Hurco recommended I NEVER run it over 3500 RPM, and that I probably ought to stay under 3200 given the age of the machine. Most of the milling I do requires high RPM spindles to get decent production rate so I have been studying making my own high speed spindles. Making spindle speeders. Finding speeders that might work, etc. To get the durability and speed I want the only reasonable price option is one of the Chinese VFD spindle motors, and then the quality is suspect until its actually seen a few thousand hours of run time. Most of the other options cost more than your whole machine. A couple of them 3-4 times more than your whole machine. That is just for a spindle. Even using the Chinese spindle costs more if you count time, and extra fabrication hardware to mount it, etc.

Again. I'm no expert. Not even a really knowledgeable hack. My conclusion based on the little bit I have managed to learn is that you can buy a cheaper machine and get good work out of it, but if you want it to be like a more expensive machine you will have to spend some time working on it.

Now admittedly I am looking at high speed were tolerances are much more critical, but still. Quality costs time or money and sometimes both.

Do not be discouraged though. I make usable parts all the time on my little chinese no-name (literally) manual mill/drill, and I keep a large drill bit chucked up in it for a particular job I do routinely. My next larger manual machine is an old Harbor Freight RF-30 (says RF-30 right on it). I keep one of my better swivel base machinist vises on that table because it gets used routinely for one off manual jobs.

One of the hardest things I had to learn about machining is that the machines are not perfect, but the parts you make on them can be better than the machine itself if you learn how. The next thing I struggled to learn was no matter how good the machine and no matter how careful the planning the parts will never be "perfect" either, but with care they can get pretty darn close. Even in aerospace (which actually isn't the most precise machining field in many regards) they include a tolerance or allowable margin of error that is often much larger than you might think.

And of course there is always the possibility that your machine really is made below the acceptable standard for that machine and you may be able to get a replacement or replacement parts. Certainly follow through with LMS.