[SRT Mike]

We have a bridgeport series 1 that came with a Boss 8 control. We retrofitted the control with Geckos and EMC and its successfully machining parts.

The problem is that we have been unable to do climb milling - we always get a bad finish with gummed up material around the cut. We've tried playing with feeds and speeds until the cows come home to no avail. I dont have coolant on the machine but even when I use a spray bottle with kerosene or WD40 it really doesnt solve the problem. I am thinking maybe the spindle bearings are worn out. The machine came from a shop that left it around as a parts machine, so it's definitely possible its worn pretty well. When we got it, one of the boards in the Boss 8 was cooked, so it could also just be the machine sat due to that, not due to wear.

So anyway, is there an easy test I can run to check whether its the bearings? It does make a fair bit of noise when it's really cranked up to max speed (4k rpm). And if it is the spindle bearings, is it easy to get new ones or are they a specialized part? Is it something I could get from McMaster? How much $$$ to replace assuming I do the work myself (I've had the head apart before, no big deal).

[Jim Bass]

Hi Mike,

Try a good quility cutting fluid designed for the metal you are cutting. And use a lot of it, you need to keed the material and cutter lubed and cool, when the cutter and material gets dry and hot your poor finish will return. Heat is your enemy when machining.

I used wood, then kerosene and now natural gas to heat my shop. Keep up with technology, it will save you money in the long run.

Yours, Jim

[Daninwyoming]

I'm going back to wood to heat my shop. Can't afford natural gas.

[mxtras]

The first thing that comes to mind when someone says they are having problems climb milling is backlash or loose gibs. Check the table, knee and saddle for play. Evaluate the lead screws for backlash.

Scott

[Jim Bass]

Hi Mike,

Your comment "we always get a bad finish with gummed up material around the cut" tells me it is not bearings, it is not gibb adjustment. Those may be problems down the road, but if the chip is not coming off the material cleanly, you have heat and lube problems.

Jim

[NC Cams]

The "makes a fair bit of noise" is hard to use as an indicator to what the root cause of the problem is.

Splines will tend to chuckle if they are worn. Variable pitch drives do as well. And, yes bearings too will make noise if they are worn/damaged.

Try to pinpoint the source of the "noise" with a stethoscope. Or you can put a solid rod up against the machine and hold it against your ear. The source of the noise/vibration will more easily be pinpointed via this method.

Typically, spindle bearings are special versions of standard size bearings. The OEM's (from oem grade drawings I have) were specially matched and qualified for runout and accuracy. These were then selectively fit and assembled.

How? By properly integrating the high point of bearing and spindle eccentricities. Thus, simply R&R'ing the bearings is NOT going to fix things unless you properly re-orient the eccentricities.

Generic bearings that are the same size will "roll" but should not be expected to perform as well. Reason: the spindle bearings were typically precision preloaded for stiffness and running accuracy. THis is not something you do by feel or guesstimate, you need dial indicators that measure in 0.0001's and some know how.

The cost you will have to pay for replacement bearings depends on your accuracy and finish requirements and your budget.

If you spend the cash for ABEC 5's or 7's and have the spindle ID ground after re-assembly, you'll have a very smooth running, great cutting and highly accurate machine. THis is how Hardinge reportedly does the current BPT spindle assemblies/rebuilds

You could save some $$$'s by using ABEC 1's or 3's but you'd still have to regrind the spindle ID and you would still have more runout potential than with 5's or 7's.

If you have sloppy ways, loose ball screws and worn screw support bearings, the table can/will shake rattle and roll which will cause all kinds of finish/accuray problems.

If the machine has this many ills, perhaps that is way the shop you got it from used it as a parts machine. This doesn't mean it is junk, it just means it needs some care/service....

[machintek]

Simple:
Need a good cutting fluid.
Spindle bearings when going bad will exhibit:
Elevated temperature.
Excessive noise.
Bad finish in any direction.
Excessive play.

George

[gguidi]

Simple:
Need a good cutting fluid.
Spindle bearings when going bad will exhibit:
Elevated temperature.
Excessive noise.
Bad finish in any direction.
Excessive play.

George

I have a R2E3 with a boss 8 control. The spindle makes a lot of noise is this normal. It gets warm but not hot.

[machintek]

Are you in high or low gear? If in high, make sure the clutches are fully engaged, otherwise they rattle and do make noise.

George

[machintek]

Additional question. Is it the spindle or the drive in the head?

George