IH Saga

[ksanalytical]

So I ran a series of parts on the mill, all the while wondering about the amount of heat and noise the head generated. I'd seen others with bearing failures and such so when I was finished, I set about tearing everything down. That was 6 months ago.

The geared head was my primary concern and it turns out it was well founded. The top bearing on the final gear shaft (which drives the spindle) was destroyed. It had actually been spinning in the head the whole time. At least the mystery of excessive heat was solved. On closer inspection I noticed that the inner race had split, which I assume was the cause of the failure. After buying a complete set of replacement bearings, I also found that the cause of this particular failure had been a poorly sized shaft which was oversize enough that the inner race of the original bearing had sheared off a thin ring of steel as it was installed in China.Some light trimming on the lathe smoothed things up and the new bearing (one size large OD) went on easily enough. The pocket in the top plate being destroyed left me with few options but to open it up to the next size. This left one wall too thin for my comfort so I filled in the recess with JB Weld in an attempt to bolster it. Thorough cleaning of the head got the iron fine and sand out.

In the middle of all this I decided to do something about the oil distribution block which was mounted directly to the front of the column where it would limit Y travel. Between moving it to the side and plugging the center port, travel was increase by more than 0.5". That required reworking the oil hoses some. AutomationDirect sells translucent nylon hoses which are great because they allow you to see the oil as it moves. I also added two check valves on the hoses which feed the Z carriage and Z ball screw nut as it became obvious that the oil was draining back out of them between uses.

The Y-travel was being limited toward the front of the machine by a gib which was longer than necessary and would interfere with the Y motor drive plate. Cutting the gib off gave another 0.5" of additional travel. This isn't as useful as it leaves the tool off the table at the rear, but I could see it being important to get the tool clear of the material to the back side in some instances so we'll call it a gain nonetheless. While experimenting with this, I drove Y onto the gib and left it sit. I didn't realize that it had pushed into a fault state. I also didn't think about the common practice of wiring the fault pins of the Geckos to a constant 5V source so that they reset perpetually. So the motor cooked itself in short order. The replacement was slow in coming, but did arrive without me having to come up with a way to retrofit different motors. Thanks to Tommy for that one... This also burnt up the drive apparently as I had to replace it as well. Luckily I had a spare on the shelf.

I'm actually working on a simple microcontroller program to reset the Geckos on startup, then fault them all in the event that one faulted. Anyone interested in such a device? The most expensive part will be the board and that will depend greatly on volume. Expect $50 or so with sufficient interest.

I was concerned about the bearings in the spindle as well as it seemed like a place where $60 for good bearings might make an appreciable difference in the performance of the machine. Disassembly of the quill required a press as the top bearing was TIGHT! While it was apart I also noticed a large amount of Al chips in the lower bearing. If you haven't followed Cruisers advice about that leather gasket, do so soon. As mine was all apart, I bored the threads out to the OD of a grease seal which matched the spindle nose. This should seal MUCH better. Reassembly was slow as my parts washer was a non-functional gift that required some work to get running. I found the Kluber spindle grease online in a 50g tube for $20 or so. I don't know that it's as critical as some say, but that's cheap insurance and enough for three complete packings by my estimation.

So we're back in business right? I tried to drive the 4th axis and got buzzing, no movement. Replaced the drive. Still no movement. Tore the motor down and found out the hard way that my practice of leaving it on the table constantly was a bad idea. The stepper is not sealed and coolant had pooled in the bottom. Cleaning with a wire brush seems to have correct this.

Now I turn on the spindle and it's definitely quieter and smoother than before. The head builds zero heat after a hour of running at 1000rpm. The bottom of the spindle is getting hotter than ever though. The quill is still fairly cool, but the spindle nose is not. I put about 30 degrees of preload on the spindle assembly nut beyond zero vertical play. Could that have been too much? Further, I have three thousandths of runout 1" below the taper. I don't remember seeing anything like that before. I actually measured it because it looked strange while spinning. Like it was vibrating. What kind of runout are you guys seeing?

I know it's not the most popular sentiment around here, and I make no excuses for Tommy in the situations others have described, but he's been especially helpful with regard to these problems when called. Most of my free time is on Saturday and Sunday and he's been completely willing to talk on those days.

Hoping to get back to work...
Ken

[jetflatline]

I'm guessing you bought a turnkey, right?

All of these head bearing issues make me think you or Cruiser should start a "rebuild your IH head" business.

[Cruiser]

Hi Guys,
Jet, I thought of making top cover replacements with some mod, But, I didn't think it would pan out, The cost would be the first thing to make it a slow mover, and the options would be the second, then a multitude of other things ......
Ken, Since you mentioned turning the threads in quil, I'm assuming you put in a rubber oil seal on the spindle end. If this is so, You might find that the spindle is a tad bit larger than the rated size for the seal and requires about ten or so thou turned and polished off of the end of spindle. If it is a rubber seal, it can and will get extremely hot if the spindle is too large ! Mine got too hot to touch at first, then I cut the spindle down and all is well.
As to the run out, My guess is that the Chinaman is running them on a worn out machine or his collets are out of whack. A few thou can get lost in the shuffle as it just makes the cutter in effect a bit larger and some loss to the finish.
It is possible to re-machine it in your machine with a small boring bar clamped in the chuck and some fancy locating & programming. But, its a deal that can make or break and must be done exactly correct from the get go !
If you try this, I'd measure everything very carefully and close, with utmost care. then black out the bore and taper of the spindle with a Black Flow Master. Then you can run your program, check with mirror, drop Z a Few thou, run again, check again till you get a clean up of taper. The taper can actually be moved up the throat of the spindle quite a ways, but, I'd be leary of going too far and keep it as close to where it is as possible.
As to the bearing preload, the type of bearing would dictate how much preload, and I always count the locking notches when I do mine with the AC's. I usually go two or three with new bearings and about 2 with used and find that they stay with the setting. I have found that sometimes I have to go back and tighten, if after a warm up I can then shake or rattle the bottom bearing. It should only be tight enough to keep it out of the getting loose and rattle stage which is quite detrimental.

[ksanalytical]

Yes, I bought a turnkey. Fabricating a new head would have been a slick solution, and not too complicated with good measurements from the old, but I'm the only person I know to have spun the bearing in the head. All others are modding for one reason or another.

The heat very well may be the rubber. I'm not running oil so there's no reason for me to worry about it too much, but that would explain a lot. If the heat was generated in the bearing, the quill would probably be as warm as the spindle, my spindle is the only part building heat and only at the nose. Thanks for that suggestion.

The runout is annoying, but I'm not going to recut the taper under any circumstances. The next step is to put a DTI on the taper itself rather than trying to measure on the tool (I'm using an empty face mill holder for the best precision I can muster).

UPDATE: The taper showed less runout than I can reliably measure so I removed the drive keys thinking they might be interfering with the tool holder. Now runout is less than I can measure with my cheap dial indicator 3" below the taper. I use the NT30 spindle with BT30 tooling (custom long/metric drawbar). I'm probably just going to leave them out as the biggest tool I use is a 2.5" face mill... I guess they'd be easy to grind for clearance though.

Ken

[ninefinger]

Ken,

How old is your machine? I bought my mill from Machine Tools Warehouse (its an exact copy of the IH mill) and it was received by me in February 2010 (fresh off the boat from China)

I found the same thing as you with respect to the bearings being tight on the shafts. I had to grind the old ones off and they popped / cracked when I broke through the inner race. You could see the ball impressions in the top seal of the bearings from where the assembler used a bigger hammer to get it to go together. I caught mine early enough to prevent spinning the bearing in the head. In my case its not really much quieter now but definitely less heat than before.

I also have the NT30 spindle and those drive dogs are funny. If I recall correctly the mounting hole is off center by just a tiny amount but it matters and will cause grief as you have found out.

[ksanalytical]

I think I got mine in 2010... At least that's the year I wrote it off my taxes. : ) As far as the quality goes, I guess we get what we pay for with Chinese machines. God help us if they ever figure out how to make a quality product over there.

Ken

[jetflatline]

Have any of you "I took it all apart and fixed it types" written a consolidated FAQ or HOWTO on this? I'm upgrading the motor on mine and trying to put together a checklist of "all the crap I need to do while it's apart" and starting to dig through everyone's posts.

[IH CNC]

Yes the industrial hobbies head has had a few issues many of which I think we have addressed. Some being bearings detonating in the head. What I believe it is is some casting slag but also poor assembly in China. What we have been currently doing on our CNC is to run the head for a couple minutes and while its running drain the oil and then shut it off. This will remove most if not all slag. We have been talking to China about these issues and hopefully they will be resolved. We too have been contemplating a new head but I do not think it is the best solution just yet. You cannot beat the amount of torque you get from the gears. Yes your RPMs are limited but I doubt that you can cut at 6000 rpm what I can at 3600. A new head design is very simple but It would mainly be used by the CNC guys. If you guys have any questions give me a call 860-538-4397 available til 1 am EST. Tommy

[ksanalytical]

Jet,

I did basically the same thing, but kept finding that everyone seems to do something different. For me it's pretty much summed up below. I'd replace all the bearings whether they were bad or not. Pull the head and clean thoroughly with a parts washer or whatever you can come up with. I used carb cleaner and it worked real well. Replace the oil. I can't recommend Mobil DTE light (iso 32) as it foams up pretty bad, but definitely replace the oil. It's cheap.

I replaced the bearings in the spindle with Timken. That makes a noticeable difference but ran me more than $60. I used the welder trick to remove the larger race as it's hard to get to. Worked great, but be careful with that one. Packed the bearings with Kluber spindle grease, but the stuff that was in the spindle seemed to be working great. I don't know what it was though. I ground down the inside of the quill as it had lots of "slag" iron grit and a wire brush just wouldn't do it.

I used a friends large lathe to cut out the threads in the bottom of the quill to fit a metal/rubber oil seal. I can't remember the size, but I just took the whole spindle/quill to the bearing shop and they put it on the counter.

Cruisers posts on his quill mods were helpful even if you don't go for tapered roller bearings. At the 3400max RPM I run, there's really not much benefit to them.

Post any questions and I'm sure people will chime in. Wish I'd taken a few pictures. Evey shop should have a dedicated digital camera.

Tommy,

Coming back to the forums was the right thing to do and I think your current and prospective customers will appreciate it. Thanks for your help with the problems (even the user induced failures) I've been dealing with. I'm almost back to making chips.


Ken

[brt]

Jet,
Tommy,

Coming back to the forums was the right thing to do and I think your current and prospective customers will appreciate it. Thanks for your help with the problems (even the user induced failures) I've been dealing with. I'm almost back to making chips.
Ken

As a current "prospective", and soon to be "current", customer, I couldn't agree more.

[scudzuki]

Spindle bearings are not meant to be "packed" with grease. There is an appropriate amount of grease for a given bearing size and exceeding that amount will create excessive heat.

Joe

[Cruiser]

Spindle bearings are not meant to be "packed" with grease. There is an appropriate amount of grease for a given bearing size and exceeding that amount will create excessive heat.

Joe

This notion with respect to the design of the IH spindle is not correct !
there is a lot of open space for the grease to migrate to and it is common for these bearings, stock especially to vaporize the grease ! If an insufficient amount is packed into the bearing then it will most assuredly burn out quickly ! That is one of the problems with the factory job is that they do not put in enough grease and it is not a clean cavity !
The rule you are referring to is for the application of a greased bearing in a tight confine where there is no room for expansion, or circulation.
Use plenty of the proper grease and don't be shy, worse case scenario is that it might make a mess !