IH Mill Accuracy

[BobWarfield]

There has been a lot of discussion about how well made the IH mills are, and particularly about the quill runout. I thought I would take a couple of measurements on my machine (received at the beginning of the year) and share the results. YMMV.

Over the entire travel of the quill, 5", I measured a maximum deflection of 0.0075" on my Interapid indicator, which is much less than the 0.020" in 1" some others have experienced with early versions of the mill. Quality controls must have improved with time.

A couple of other important things to note. A huge amount of that deflection was in the last bit of maximum travel, backing off just 1/2" and using 4.5" of travel, the max deflection falls to 0.005". Over the course of an inch, it is slightly over 0.001", which ought to be fine for most HSM boring operations, but is still not great. For comparison, I found a copy of the Wilton B'port style mill manual somewhere on line and it lists the equivalent spec for that knee mill as being 0.000984", which is less, but not hugely so.

I was also curious how the Z-Axis was behaving, and so took the same measurements moving the Z-Axis with the quill retracted. The results are dramatically better. With my setup, I was only able to measure over about 1/2 the travel, or 10" (need to find a nice big cylindrical square to do better). Over that distance I got a maximum deflection of 0.00075", which I though was quite good. Note that I have not squared the machine (i.e. shimmed the column mounting bolts for squareness), but I had just trammed the machine in very carefully. The equivalent spec for the Wilton is not nearly so good, as they are quoting 0.002362". Another comparison is Tormach, which lists a figure of 0.001378" for 5.9" of travel in their QA spec document, so the IH would have qualified well within that spec.

I took all of the measurements a half dozen times, and found them to be completely repeatable as well.

It seems to me that quill operations can be handled just fine on the IH Mill, but if an extra measure of accuracy is desired, use the Z-axis and these mills are pretty darned good. I suspect an enterprising HSM might find some ways to tune up the quill so it performs better. My mill's future lies with a CNC conversion, and I will definitely look to drive the z-axis off the column rather than the quill for best performance.

I hope this helps those who are interested in understanding this mill's capabilities. I am pleased thus far with the mill's performance, and looking forward to continue to test its limits.

Best,

BW

[bill south]

Bob;
Have you decided how your going to power the zaxis??? My lathemaster is killing a 3/4" ballscrew due the weight of the head. I used a Warner precision screw rated at 750# but the weight of the head and the connector used to connect the ball nut to the zcarriage (stock connector modified to accept the ball nut) is causing a lot of friction and torque on the ball screw. The initial very low backlash increaseing almost daily and is up to about .050". This weekend I'm planning on dissassembly, rebuilding the ball nut and adding gas springs to help matters out (wish I had done that initially!).
Anyway, if this doesn't work, I was thinking of converting to a powered quill design. Now my question for you, have you seen a design for a powered quill????

Thanks.

Bill

[BobWarfield]

That's an interesting problem you've got there Bill. Are you sure the ballscrew is at fault and not your angular contact bearing mounting arrangement? I would check your gib adjustment carefully as well. Also note the couple of mods Aaron makes to these mills around the Z-Axis to tighten them up. They're documented on his site. Check out the CNC conversion kit's installation instructions, which are on the site, for more details.

Sure seems like something is loose to get that kind of play!

In my case, I ordered Aaron's kit rather than engineer my own. It hasn't arrived yet, which is fine, I want to be very familiar with this machine on a manual basis before converting.

Best,

BW

[Randall]

Bob
your deflection mirrors mine. In fact My deflection didnt increase till around 3 inchs of extension on the quill. I put the 3hp 3phase motor on mine with a VFD and I am really happy with it.
Randy

[BobWarfield]

Good to hear from you Randall. I'd like to try the bigger motor as well. I was just buzzing through 6061 aluminum with a 1/2" roughing EM the other night and could tell the thing wanted more rpm. It was very smooth and you could turn the handwheel just about as fast as you'd like.

Best,

BW

[Ron111]

Bob,

Good piece of work. Have you started lapping the ways and have you been able to check your table for flatness.

I'm sorry, Bob. I know it seems like I'm trying to give an extremely busy man, more tasks.

I'm also courious as to where Bill's backlash is growing. With Aaron's Zaxis Mod, I believe he stated the the attachment piece that goes through the plate, that supports the head, can pull all the way through (I can't think of the correct name for this Z axis ball nut mount). If that is the case (assuming that I understand correctly what he said) then without that mod it could be dangerous, if this piece pulled all the way through and it could allow the head to drop.

I hope that I stated my concern that correctly.

I was just giving Z axis backlash some thought and I would think that with the Z Axis, and the weight of the head, that you would have a minimal backlash, where the weight of the head would essentially preload the ball screw and on the angular bearings. I could see having backlash when using a single ball nut with a Gas spring, but am having problems visualizing backlash with 200lbs riding on the ball nut and the angular bearings.

Feel free to straighten out my thinking process!!

Ron

[BobWarfield]

Originally Posted by Ron111 Bob, Good piece of work. Have you started lapping the ways and have you been able to check your table for flatness. Ron

Ron, I haven't started lapping ways and won't until I'm about ready to perform the CNC conversion. I would like to take some more measurements on the machine, and will try to get around to it as I find time from my other projects. Perhaps I can just add them to this thread. I hope others like Randall will feel free to add their experiences as well.

I think there is a lot of interest in the IH mill, and this is so far the only forum for it that I am aware of, although the Lathemaster mill is similar. I think it's kind of up to us IH owners to keep the flow of information going so others can evaluate whether to join the ranks or try another solution. I must say the little Sieg mills are extremely cool as well and we've been seeing a lot of good posts around those machines.

Best,

BW

[Randall]

I did lap my ways and it was fun to do. By taking it a part I learned alot.
The lapping made a huge difference in feel when cranking the handles.
qwhenever I do the cnc conversion i amy do it again, I went light on the first round.
Randy

[Ron111]

Bob,
It's that's massive work area that keeps me coming back. I can just envision loading the table with multiple vises, and using the fixture offset tables in MACH 2 (or Mach 3) and sitting back for an hour or so and watching it work. But like I say, I keep coming back and reconsidering the IH.

Ron

[Ron111]

Randal,

"I put the 3hp 3phase motor on mine with a VFD and I am really happy with it."

What all did that take, how big of a project was it, and when you plan to cnc your mill, have you figured out how to control the spindle speed with Mach3.

What is your high end on spindle speed? Where did you get your VFD and your motor.

If you have time maybe you could give some us info on what it takes to do this modification and maybe a pic or two.

Thanks,

Ron

[BobWarfield]

Originally Posted by Ron111 Bob, It's that's massive work area that keeps me coming back. I can just envision loading the table with multiple vises, and using the fixture offset tables in MACH 2 (or Mach 3) and sitting back for an hour or so and watching it work. But like I say, I keep coming back and reconsidering the IH. Ron

I agree Ron, and think that sort of stuff is very cool. I always read everything I can find on fixturing and other production work. Not sure I'll ever need to make a bunch of anything, but it's quite fascinating. I've been tempted to just leave my 4" vise and 8" rotab all set up on the mill as well. There is certainly plenty of room for that.

RE your thought of loading a bunch of vises and sitting back, I have sure seen this done in a lot of the production-related articles I've read. I've seen Kurt vises (the 4 inchers would be nice and smaller for this, I think 4 would fit on the IH table), grinding vises (even smaller and hence more parts fit), but how about these collet indexers:



That's a setup that HuFlungDung did for some sort of a job he was doing. I've done a little bit of work with collets on the mill, just with simple collet blocks in the vise, and I have to say I love them. Seems like you could really bang out some parts using a setup like Hu's. It's tempting to consider that even if your part isn't round, a round boss plus a CNC program to deal with what's above the collet might not be a bad way to go for small parts. The boss could be cut off later, and "round" indexes so nicely!

Best,

BW

[Ron111]

Bob,
I've seen those collet fixtures in the JTS catalog, don't have an idea what their used for. So, what are they used for?

Is that the hand of HuFlungDung, my boys get a kick out of his cartoon charactor.

I currently use a 4inch vise from JTS that I have been pleased with for $58 & shipping. Same vise that enco sells for $90 or so with the rotory base, I removed the base. They also sell a 3 inch that I've considered. You could really load up a table with those (they must weigh about 15 lbs to 20 lbs each)

Also I've looked at the 4 inch double vises for $157 & shipping. But have never seen one in use here on the cnczone.

Have you ever looked at using fixture offset to do repeat milling at different locations. I played with it and it works welL

Take care

Ron