Bridgeport spindle warming up

What it the mills rated top speed? If you're exceeding the rating, you're pushing it too much. They aren't intended to be overspeeded with a VFD.

As for temps, shoot it with an IR thermometer and see what it really is, mechanical things do warm up with extended operation. Precision machining centers use coolant systems for spindles and often ball screws to stabilize the temperature to maximize accuracy. If you could hold your hand on it it was probably perhaps 120 degrees, the question is what temps were under the cover.

Pete C.

If it runs normally today, you got away with it. If not, you didn't.

GWE

At least it wasn't the main spindle bearings getting hot. As best as I can tell, on the 1J head, the bearings on the driven pulley are not sealed. So, I think you can drip some spindle oil into the gap between the rotating and non-rotating parts of this bearing, right on top of the head beside the drawbar nut, to get some oil in it. I do this a couple times a year. If these bearings are cooked, it is not terribly hard to get in there and replace them, and they are not exotic bearings. There is a procedure to follow, however, or all the springs fly out. The whole bearing carrier is on a vertical slide, to engage or disengage the direct-drive clutch with the cam ring. The pulley assembly contains the spindle brake, too.

Jon

Yes, I do that periodically.

Thanks, Jon, Pete, and Grant. It did not give off an impression that they were cooked, though, I think, I should back off on speed a little. I will try to carefully look at how mill works, tonight.

I also have a nice Last Word 0.0005" dial indicator now (came in that box of "inspection equipment) that is perfect for measuring spindle runout, which is what I will also try to do. This indicator is a little thing.

i

a lot of waste heat is generated by the belts. Check your tension and check belt temps next time.

Gunner

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Gunner, that makes quite perfect sense. I am not sure if you mean that my belts are undertensioned or overtensioned, but if I had to make a guess, they are under tensioned. (bringing up a question of how do you actually tension after changing).

i

Iggy, The Starrett Last Word indicator is not a great tool. I've owned one since

1957 and it gets used only very infrequently. They have a propensity for not reading when you get down to fine movement-so they won't display when an item is running out by a few tenths, leaving you thinking everything is fine. Not trying to discourage you, just to bring to your attention that things may not be as they appear. There are other mechanical indicators that are more reliable, although I'm not convinced any of them will approach the level of sensitivity of an electronic indicator.

Keep your eyes open for a B&S BesTest. They are amongst the very desirable indicators. Others will likely suggest some good names.

Harold

Lean on the motor while tightening the bolt. That should be more than adequate. Don't use any type of lever.

Harold

Harold, I know that you do not like Last Words, I have it since I brought it home last week. I would like to find a good digital model.

i

I think I posted it some time ago. I prefer the MarTest (AKA PupiTast) for such tasks:

With the classical indicator, the tip will move into the direction of rotation and give false readings. You can easily observe that when changing direction of rotation. Not so with these indicators. And if you don't buy cheap Chinese scrap, you'll find a nice test certificate with exact values. Only then you know what you can expect from your tools.

My 0.002mm mechanical MarTest has an overall error of 1.8µm. Including the reversal error of 1.2µm.

Nick

Swing the pulleys against the belts, apply slight..slight pressure and tighten down the clamp. Not rocket science. If the eelts are glazed..spritz some belt dressing or replace em. They seldom slip under even the toughest loads on a vert miller

I should mention Lagun has a vent at the front of the head to disappate belt heat. Blows right in your face if you are tall and is a bitch on hot days.

Gunner

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It felt hot, but I could hold my hand to it.

Gunner said that they were rated to up to 5k RPM.

I have a Craftsman reader, probably made at tha same factory in DungInBung, China.

i

How hot is "quite warm">

UL has (had?) a spec for the max, temp of surfaces that people could touch that was 137 degrees F. Although the tenderness of people's fingers varies, if you can't hold your hand on it for over a few seconds, it's probably hotter than 137. If it feels hot, but you can keep your hand in place, it's lower. This doesn't hold true if you are gripping the hot thing. So, if these bearing can stand a "50 degree C rise", like many electric motors have on their nameplate, it appears that the bearings could easily run at 192 degrees F in a 70 degree F shop. That would be 'way beyond "quite warm to the touch".

I just did a little googling on Bridgeport spindle speeds and it was a little confusing. +bridgeport +"spindle speeds" Sometimes they say 2700 rpm max, and sometimes more.

A friend bought a $9.95 IR reader at HF the other day. He swears by it, but I think it reads too low. Any other experience with it?

Pete Stanaitis

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Ignoramus8624 wrote:

The 1J head (4 step pulley, 1 Hp) goes to 2720 RPM. The 2J head uses essentially the same spindle (just a little longer) but has vari-speed and 2 Hp motor, and goes to 4300 RPM. The difference is mostly in the belt ratios available. So, with a VFD, you are not likely to harm the spindle bearings by running it up to 4300 RPM or so. The rest of the bearings in the J heads are nothing special, so I wouldn't get too worried about them.

Jon

0.0005 is a bit coarse for that. I love my Mitutoyo 0.0001 indicator with the second needle indicating how many turns the needle made. Unfortunately that is at work and my employer issued it to me. For my milling at home, I have a chiwan 0.0005 test indicator :(

Your Last Word is likely fine for all other milling tasks.

Be warned personal choices in test indicators can be as contentious as discussions about religion or war policy.

Wes

I'm an X- Bridgeport field engineer There is only one thing that will get a spindle top end really hot without making a racket or being obvious. The nose piece and spindle are ever so gently touching. Loosen the Nose piece ( loosen rear set screw first) Put about a .002" feeler to get clearance all around, Tightened nose piece till its snug ... not balls to the wall tight just snug... the tighten the set screw ... once again not tight because if you tighten the set screw too much the quill will stick and won't go completely up.

Tom, I am a little dense today, what do you mean by Nose piece?

Thanks

i

[ ... ] [ ... ]

With the minor distinction that it happens to be on topic here, unlike the other two. :-)

Enjoy, DoN.

According to spaco :

Well ... some have vari-speed pulleys, and some have step pulleys. You get a different range with the two different styles.

Some are running from 60 Hz, some from 50 Hz, with a resulting

20% lower speed range.

All of the IR readers are dependent on the emissivity of the object being measured. Flat blacks tend to have higher emissivities, shiny chrome much lower. Mine (from a hamfest, not from HF) says (in fine print at the top of the display) "Em=0.95, so it would be more accurate with a flat black surface than with a shiny metal one. (The shiny metal would read low.)

Some may have options to switch the expected emissivity, but you need to *know* that emissivity of what you are measuring to be able to do this in an informed way.

The best bet is to look for a black area to measure, and the flatter the black, the better.

Enjoy, DoN.