Bridgeport noise diagnosis

[SJorgensen]

I don't know what a new BP series 1 should sound like so I don't even know if I have a problem or not. I notice a sort of squeal during kerf cutting but not when cutting on only one side of the bit. It doesn't seem to be coming directly from the cut. I'm not sure if there is something loose in the Kwik Switch nut that is making the sound.

Should I be looking forward to replacing bearings? How do I check that the lubrication system is working properly. What does the surface finish tell me about the condition of my bearings?

What ABEC class of bearings came originally and what should I look for in a replacement?

How hard is it to replace these bearings?

Thanks in advance for your advice.

Spence

[Rustybolt]

Start simple and then move to more complex scenarios. Check to see if the belt is tight or needs replacement. Unless they've really been abused the bearings should last a long, long time.

[jdunmyer]

Spence,
Aren't there oil cups on the side of the head? One of those is for the spindle bearings.

<<Jim>>

[SJorgensen]

No, it has an oiling system with a spring-loaded plunger that I pull up before running the machine. little 1/8" lines run to all the critical areas. I can see a nice clean film of fresh oil on the ways and just a nice amount on the spindle and it does drip out everywhere but not too bad. I wipe it down every once in a while. However I can't directly see what is getting oiled inside the head.

I'll try to just not let the sound bother me, its just that it would be so much more enjoyable without the squeal. I'll check the belts. I know a machine repairman that usually works on the BIG stuff. I'll have to find a way to get him to visit my shop and see what he thinks about the sound.

Just like when riding a motorcycle; It's just that much better when the motor sounds just right.

I've been thinking about fabricating some kind of drip edge for the knee to keep the oil from dripping everywhere and running down the sides. Has anyone done that?

[lane]

The oiling system only oils the table saddle and knee along with ihe screws. The head is manualy oiled and greased. As far as bearing they are SPECIAL and can only be gotton from Bridgport.but not likely any thing wrong with them.

[MickeyD]

Mine used to randomly do that until I replaced the top bearing on the spindle side vari-disk. The bearing was a little dry and tight and would make an evil high pitched shriek every now and then. You might as well put in a top end kit if you think the noise is in the upper head. Replace the upper bearings, drive bushings, and belts and the machine will run like a new one. Costs about $250 for the kit and a good part of a Saturday to install it.

[pcarpenter]

I'm guessing that "new BP series 1" really means "new-to-you BP series 1" or you might not be asking this question. Do, by all means, let the sound bother your. Fixing the problem before spindle bearings are damaged may save you a bunch of money.

Get one of the downloadable copies of the manual and look at a head diagram. There are lots of bearings (moreso in the VS head), and you can use your knowledge of where they are located to listen while someone else makes the cut to see if the noise is likely bearing related and if so, which bearings. I have a cheapy HF "stethoscope" that has a solid rod for input. It is designed for listening to engine noises and comes in pretty handy for locating the source of bearing noise. You may want to pick one of these up if you don't have one.

The answer to your original question is that the quality of the bearings depends on their location. All of the head bearings except the spindle bearings are pretty typically a typical quality radial ball bearing and in my experience, were not proprietary. The spindle bearings are ABEC 7 from the factory and are a radial contact thrust bearing pair. They are proprietary and have a center race ground offset from the outer race such that a pair of differential inner and outer spacers define the preload.

You can do a search here on Bridgeport spindle (here) and find a post from a while back where this was hashed out. If you need spindle bearings, don't let someone sell you a standard bearing pair based on the first 5 or so numbers/letters in the part designation. The extra numbers/letters in their designation defines some pretty important specifics that make them cost a lot...and work correctly They define the proprietary differences (like differential race heights) etc.

Do read up on head lubrication. The spindle bearings do get oil in a cup on the head and *nothing* in the head is lubricated by your one-shot oiler. That handles oiling way surfaces and cross-feed nuts only.

Often, the original oil lubed spindle bearings have been replaced with sealed, grease packed bearings that not only do not need oil in the cup, but may have their grease washed out by thin spindle oil. The only way to know is to remove the quill "cap" and look to see if you see balls on the other side of the shield/washer. If you see a typical plastic bearing grease seal, they are newer, sealed bearings.

Ease of replacement depends entirely on which bearings you end up having to replace. The spindle bearing set itself can be removed without major head disassembly. These are the most expensive bearings, however. Great care needs to be exercised in bearing removal after you get the spindle out of the quill and you may want to read up on spindle repair. The spindle pair has to go back in correct back-to-back orientation, too.

The other bearings in the head require more disassembly, but are far less costly.

Paul

[SJorgensen]

Thanks for that advice Paul. I'll go over it and check my mill out carefully.

Thanks again,

Spence

[JPR]

I should be Barden 207HCDUM which is the ABEC 7 medium preload.

[SJorgensen]

Problem solved!

What a difference it makes when you get things dialed in right!

I was grabbing the earplugs and it was starting to get real scary, but now the noise is gone. Two factors seem to have been at work.

I was cutting a part out of 3/4" x 8" x 9" #6061 Aluminum stock. I was using a 4 flute carbide cutter 3/8" x 3" (not a rougher.) I was cutting in three passes of about 1/4" depth of cut at 1425 rpm.

Because I wanted to cut the entire periphery without bumping into hold-downs I drilled two 1/2" holes about 4" apart in the middle of the stock and bolted down the stock on a 3/4" thick x 5" diameter piece of sacrificial scrap material.

I was using a 4 flute carbide cutter, but I found that I had written my G-Code based on a two flute, so the load per tooth was too light by half.

But most importantly the problem turned out to be the way that I had mounted the material by bolting it down on a pedestal in the center of the stock. All the material outside of my kerfs was left out hanging in the air to ring like a tuning-fork. And boy did it sing.

After I switched to a two-flute and added some additional support and hold-downs on the outside of the kerfs the noise completely disappeared and the material was really hogging out super, with really nice sized chips and no smoke or steam coming from the coolant on the bit. Clean up was so much better because the chips are much bigger. Now I can have a conversation while machining or listen to some music or radio. Much much better.

I've learned something very useful and thanks for all the input.

Spence