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uute
08-17-2001, 07:19 AM
Going back to the original senario, is there a plane bearing that would survive w/o pressurised oil? How hard would the shaft have to be?

1 5/8" at 2100 is under 900 fpm, fed with an oil cup, guess that doesn't leave much for cutting forces on 50-70kpv bronze.

just trying to think it through, maybe learn somthin

uute
03-03-2006, 04:29 AM
Been reading the recent bearing posts, seen what Evan posted for Snowman about the superfinised shafts for high speed.

Had planed a mill spindle w/ 1 5/8" shaft of 303 stainless in sintered bronze bearings. Top speed is 2100 RPM. Am I looking at trouble?

Shaft would be just filed & polised w/ 400/600 grt sandpaper. Not heat treated. At those speeds, shouldn't be running anything but a small endmill or drill.

Space constraints lead me away from tapered rollers.

uute

Millman
03-03-2006, 04:39 AM
4 Years on this forum and you haven't read the posts? Machinists Bible ring a bell? You just want to see your name in print?You mispelled Superfinished; Explain.

------------------
BFH

Forrest Addy
03-03-2006, 06:40 AM
"...shaft of 303 stainless in sintered bronze bearings. Top speed is 2100 RPM. Am I looking at trouble?"

Yup.

Spindles should be pretty hard for wear resistance in the spindle taper (above Rc 50 in most commercial machines. 303 stainless is quite soft and malleable and has an unfortunate tendancy to "fret weld." You'd be much better off using a pre-heat treated medium carbon or alloy steel (Rc 35) for this application. It's more difficult to machine but it gives excellent finishes and better wear in a plain bearing.

Sintered bronze bearings in this size and RPM are not reccommented without pressure lube to transfer heat away from the bearing. If you're going to do that you might as well use bearing bronze. In mill spindles of the past they used bronze bearings scraped to fit with tapered journals and adjusted the diametral clearance by machining off the thrust face of the bearing to loosen it or the spindle thrust face to tighten.

torker
03-03-2006, 07:27 AM
<font face="Verdana, Arial" size="2">Originally posted by Millman:
4 Years on this forum and you haven't read the posts? Machinists Bible ring a bell? You just want to see your name in print?You mispelled Superfinished; Explain.

</font>
Attaboy Millman! Nice answer to the guys question!
So who made you the "Grammar Nazi" around here? (You may want to check some of your own spelling in previous posts)
I see your giving others hell about using the search function also.
Is that because you don't know the answer...or you just want to see your name in print? http://bbs.homeshopmachinist.net//biggrin.gif
Russ

mochinist
03-03-2006, 08:45 AM
<font face="Verdana, Arial" size="2">Originally posted by Millman:
4 Years on this forum and you haven't read the posts? Machinists Bible ring a bell? You just want to see your name in print?You mispelled Superfinished; Explain.

</font>Seriously you have mental problems.




[This message has been edited by Neil (edited 03-03-2006).]

Forrest Addy
03-03-2006, 10:46 AM
Please. Lets stick to shop problems not personalities.

Evan
03-03-2006, 11:05 AM
Superfinished is the term South Bend used to describe the finish on the hardened and ground spindles they made for their lathes with plain bearings and the "high speed" option.

A highly polished spindle isn't a good idea. It needs a certain level of very fine roughness to hold an oil film on the surface. When you see specs for this kind of application they will usually specify a maximum and minimum surface finish roughness.

Millman,

I thought you were familiar with high precision machining. Superfinishing is a standard industry term, also called microfinishing. Try doing a Google on superfinishing.

Here, I'll save you the trouble:

Google superfinishing (http://www.google.ca/search?hl=en&safe=off&c2coff=1&q=superfinishing&btnG=Search&meta=)

Wirecutter
03-03-2006, 12:47 PM
<font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
Please. Lets stick to shop problems not personalities.</font>

Second that - thanks, Forrest

Carl
03-03-2006, 01:38 PM
<font face="Verdana, Arial" size="2">Originally posted by mochinist:

Originally posted by Millman:
4 Years on this forum and you haven't read the posts? Machinists Bible ring a bell? You just want to see your name in print?You mispelled Superfinished; Explain.

</font>Seriously you have mental problems.


http://img.photobucket.com/albums/v35/lathefan/6b1998bc.gif



[This message has been edited by Neil (edited 03-03-2006).]

kevin sr
03-03-2006, 02:18 PM
super finish
bronze bearing
2000 rpm
seazed in 10 minutes

uute
03-03-2006, 03:45 PM
Thank you for several serious replies.

Redesign w/ plan C v797.06 http://bbs.homeshopmachinist.net//biggrin.gif

And If i'd read none of the posts, I wouldn't have known to ask!

uute

Rigger
03-03-2006, 04:05 PM
You know Millman it's twonks like you that are forcing good people to stop posting on this board and we are all the worse off for it.

Your help and advice in no way makes up for what is being lost since you joined.

Rigger

[This message has been edited by Rigger (edited 03-03-2006).]

uute
03-03-2006, 05:50 PM
Amen Rigger!

Just ordered some rollers, found a cheap source, prabably surplus, limited selection:

http://www.vxb.com/

usually disclaimers

uute

CCWKen
03-03-2006, 08:14 PM
I've ordered from VBX. They are pretty good bearings even though the ones I got came from China and Russia. The Russian bearings had less than .001 freeplay--Probably .0005 or less. It bearly moved the needle on my indicator (.001).

abn
03-03-2006, 08:19 PM
Second the recommend for VXB...the ones I got were US made, good quality.

Evan
03-06-2006, 12:04 PM
bump

uute
03-07-2006, 02:28 AM
still trying to get a handle on the hierarchy fo plain bearings are. What's the order up from oilite (that's about the bottom isn't it? Or are some poly's below that?)

Cast bronze is next?? then what?

gmatov
03-07-2006, 04:02 AM
SB calls their spindle "superfinished", the bearing race it runs in is fine cast iron. Something I think does not exist anymore. Everything is rough grey iron, coarse grained. Worthless for a bearing surface.

The headstock ran for many thousands of hours with minimal lube. No babbit that required good scrapers to fit. More contact than antifriction bearings, the whole hole is the bearing.

It does not require a "rough" inner "race" to have oil cling to it for lube. It clings to the "rough" outer "race" for carrying the film. "Rough" on both parts would likely result in shear of the oil molecules, breakdown.

I've replaced more spindles and "antifriction" rolling member bearings than I have of the cast iron with superfinished spindles.

Some of the larger lathes, 60, 80 100 inch swing, a large roller, and I emphasize large, can be a blessing. Actually largest was 180, but it was only about 20 foot between centers. None of these carried the load on the headstock, all were on steady rests and dog driven, but still the headstock spindle alone was a couple tons.

Wow, that might be off topic.

Cheers,

George

Bump
03-07-2006, 05:49 AM
bump

uute
03-07-2006, 02:14 PM
Always amazed me that cast iron could be used as a bearing at all. As you say, properly made & maintained it performs very well.

The large bearing surface is one reason I was leaning toward plain bearings at the start. Lots of support. Always thought more surface was better, but looking at PV calc, it becmes a trade off doesn't it. Larger shaft, more support, but higher surface speed = lower load capacity. Hmm.

Motors run at 1700, 2100 didn't seem so much more. But double + shaft size & things look different.

Kind of had to chuckle at kevin sr, 10 minutes seems like a long time to drill a 1/16" hole. http://bbs.homeshopmachinist.net//biggrin.gif (I know that's not what he meant) Next speed down is 1400.

Allan Waterfall
03-07-2006, 02:32 PM
<font face="Verdana, Arial" size="2">Originally posted by uute:
Always amazed me that cast iron could be used as a bearing at all. As you say, properly made & maintained it performs very well.

</font>

There's a manufacturer of model aircraft engines in the UK that used cast iron main bearings at one time and those engines would run in the 10,000/13,000 rpm range.Phosphor bronze is used now,but I know some people prefered the older style plain bearings.

Allan



[This message has been edited by Allan Waterfall (edited 03-07-2006).]

uute
03-07-2006, 02:57 PM
Wow Allan, 13,000 in cast iron! That's pretty wild.

Makes 2100 in bronze look easy! http://bbs.homeshopmachinist.net//biggrin.gif

Must have somethin to do w/ shaft size. That always seems to be my personal problem! http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

Evan
03-07-2006, 03:59 PM
Ever tried calculating an approximate value for total "shaft" inches of "wear"? (in my case since married, + a year or two http://bbs.homeshopmachinist.net//biggrin.gif )?

It's sorta like piston feet per mile...

Strokes per "job" (average) x stroke length x average "job" frequency x years= ?

It adds up after a while http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

Good lubricant is essential.

uute
03-07-2006, 05:00 PM
Evan wrote:

"It adds up after a while "

Thought that was - it stops addin up after a while!! http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif