Author Topic: Spindle problem with cincinnati tool and cutter grinder 2 spindle  (Read 2426 times)

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #25 on: September 14, 2017, 08:27:47 AM »
Yesh and sometimes a little of discretion can ruin the whole thing....you think you have the exactly right pressure plate and all and then something is skewed and then it's easily too much force on wrong place and when bearing just jerks, instead seating right....cold sweat breaks.

These are small and relatively cheap bearings and I have suspicion on all work I do. I don't think I will cause irreversible damage, just lost work/dignity, some lost time and cash. That's all.


Tried shortly to google good method and DIY-fixture or contraption to measure bearing inner clearance (radial/axial) and to measure "high spot" on IR/OR that is bearing inner/outer ring coaxiality in relation of raceway....my English her is pretty sketchy, because I find only chinese videos :lol:

This looks nice, but I don't get how that frictionless and differential measurement works:
http://www.prattandwhitney.com/Content/LabMaster_Universal_Bearing_Measurement_Instrument_.asp

Click those pictures bigger at the bottom of the page.

Thinking of using V-block and that sort of stuff at home and have bearing resting over a surface plate, but I'm probably going to measure more my weebly-woble than bearing on my first try.

Any advice?

Pekka


Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #26 on: September 14, 2017, 03:48:10 PM »
I soaked the bearings overnight on IPA and got all grease and most of gunk out.

Self-aligning ball bearing 2305 seem to clean up completely and is charming himself with clear iternal clearance as it should.

The ball bearings are bit more troublesome. The ball retaining ring (cage) seems to be shedding some stuff. Part of that is something like flakes or something, bit like grud you get when put wrong type of oil on sychro gear box....and when viewed 20x magnification shows some metallic grit on surface. The cage sheds that stuff in 2 minutes on ultrasound wash (heated, about 70W) that first I though I ruined it, balls would not turn easy, but when rinsed in IPA it pretty much comes out.

So, the plan is to find replacement.



« Last Edit: September 15, 2017, 03:59:29 AM by PekkaNF »

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #27 on: September 14, 2017, 03:54:05 PM »
Armed with 0,002 mm/div lever dial indicator and some hardware tried to measure concentricity of inner ring to ball races, barely could measure outer ring, inner ring was easier.

I need a fixture or setup, this size bearing is too small to measure on surfavce plate. Hard not to move the bearing while it is rotated.

Hopeless to measure internal clerance, indication is clear enough, but too many moving parts.


Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #28 on: September 16, 2017, 03:35:14 PM »
Did some cleaning, belt pulley had almost lost crown and had some wear. Quick mounting on lathe a bit spin restored it good enough, very little material was removed, more like smoothing than anything else.

Secon thing as to check all threads and clean them. All went well. i notices that fixed bearing end bearing outer ring retainer had some resin left in the thread, looks like it was glued with a thread locker, cleaned i up and planning to use weakest thread locker I have (blue in color).

Then I check the fit on shaft and shell. I used very little layer of micrometer blue to see if there are any problems, There were some little abrasion marks on the other end, i used plastic abrasive pad, just one quick round and they seem to disapear most of it. Shaft measured out 24,995 mm ant six places and on one 25,994 mm. Nominal is 25,000 mm and that size bearing should have inner ring about -10 m tolerance. Looks fine to me.

Shell to bearin outer ring was firm sliding fit...did not quite drop of it's own, but when straightened with a press  (by rotaing sheel/outer ring just when arbour kisses the outer ring seating bushing) it bottoms with "swoosh" with a slight manual effort.

Shaft to inner ring as an easy press fit, basically all has to be straight, can't push it manually, but press has no eferrot at all.

Both fits were that perfect that no dye was left on mating surfaces, pretty much all color was pushed ahead of the bearing.


Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #29 on: September 16, 2017, 03:46:24 PM »
Now the interesting part: Trying to figure out how to replace matched ball bearing set.

I tried to measure axial play of one bearing....not really a standard way because inner ring tilts too easy on this measurement, got about 0,14 mm axial play, think that axial play is average about 8,5-10,0 times of radial play....

6205 has a 25 mm bore the C3 has a radial clearance range of 13 28 microns (m).

Shaft was measured 24,995 mm and 6205 has an inner ring diameter tolerance of -10 m, leaving the true average around 24.995 mm...and outer ring is not affected (could not measure any compression when mouned), therefore we have straight C3 tolerance to play with - I think.

So, that seems to confirm that C3/P5 ball bearings should be my starting point. What do you think?

If I get good quality C3/P5 I should be able to shim that set close to original set.

Pekka

Offline gerritv

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #30 on: September 16, 2017, 08:37:29 PM »
Very methodical and for me educational. I won't fear my eventual spindle bearing replacement as much as I did before.

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #31 on: September 17, 2017, 02:37:24 AM »
Thank you.

I am electrical engineer, but I have been tinkering with machines all my life. At one point I was involved in servohydraulics and mechanical maintenance. It is diffenet to follow guidelines and practices or design something new. This is something old and obiviously clearly successfull design that I can't rebuild (blueprit) with original parts, I have to get a little creativive with different rpalacement parts that went in originally.

I know a little of some things and when I try to do something rather new to me, I try to learn enough. But at the very begining of learning curve it is really hard to find out what is essential and what is not and some information you get it wrong or not really usefull on the application you have at hand.

Like lubricant and clenliness. Someday it is rally not that critical, and on some systems it is laa important.

I'm prepared to wash all parts, dewater, lightly oil, use lintfree cloth to clean all critical surfaces and use clean good quality grease fron new tube. But I'm not going all grazy about filtering all liquids, air and grease.

This assembly is a bit tricky: There is no provision for removal of the bearings from IR, therefore have to get them right first time. Both ends are removed by pulling the bearing from OR and that transmits the extraction force wrong way: OR->balls->IR and the IR is mounted with light press fit, this could mean brinneling the bearings.

So I have to mount bearings to shells, calmp OR very lightly to keep the bearings in place and then press bearing IR to shaft using a fitting bushing. Will need to "dry" run the thing without bearings, to make sure I have all bushings and pads ready before I start the work.

I have to measure the belt carefully. Looks like I can't order the te belt and bearings from one place, so postage will add up a little.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #32 on: September 17, 2017, 07:00:19 AM »
About belts, flat belts and their reliability I should know something.....

But I rather use calculators, because they tell me is something looks about right or misses the mark a mile or more.

So, I streched the original belt over two 25 mm OD electric conduits (sor of like pulleys) meassured the max. distance, streched hand force and youg tape manipulation and got result of 1083 mm, threfore the belt length is about 2195 mm, tried to cross reference that agains information on net.


Used this calculator:
http://best-drive-belt.co.uk//belt-calculator/flat-belt-calculation.html

Bit of monkeying arounnd with numbers to make them sit into actual physical parts and calculator looks like this:

So, I'm thinking of buyin this belt 25 mm wide. What do you think?
http://best-drive-belt.co.uk/flat-belt/flat-belt-det.251202200.html

Pekka


Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #33 on: September 18, 2017, 09:50:57 AM »
Could not buy the belt! I have been buying from them before, but this time I typed in all the info address and all and when I got to pay, I got blank page. Three tries with two different browsers.

I could not find right away anywhere shop that a) has web shop that sells to private customers b) has any technical data in it.

This looks iffy:
https://www.accu.co.uk/en/flat-belts/39064-B-F-25-2200

Any EU-area shop suggestions?

Got the bearings ordered, with plenty of shims.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #34 on: September 19, 2017, 10:46:02 AM »
That supplier never answered on my email. Ordered belts from Finnish company. All up cost about 95 for two belts delivered home (minimum order of 2 pcs. from Germany).

I don't have yet bomb proof way to measure axial/radial play and TIR on individual and mounted bearings....have to device something. Need first pretty close to 25,00 minus tolerance short shaft to stack the bearings and measure clearances.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #35 on: September 21, 2017, 04:06:29 PM »
I have tried to figure out how to measure bearings and proove shimmed bearings. I have odd ends of 25 mm linear rail rods. They are hardened 3 mm deep and pretty well ground. Shortest piece is as close as I measure same diameter than the grinding head spindle shaft.

Cleaned the ends, cooled down the shaft keeping it hour outside +10C and used hot air blower to heat up the bearing IR to about +50C, then parts fitted with finger pressure.

Tried to measure them on granite surface plate, but I don't have heavy enough prisms to make system rigid enough...I was measuring the flex of the system...

Then I got the idea of nipping the bearings together on press using bushings over the shaft. Worked well.

Now I only have to find out a way to lapp the shaft slightly down.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #36 on: September 23, 2017, 04:36:33 AM »
The bearings and belt did not arrive for this weekend, leaving me time to make some gauging and fitting utsensils.

1: made small about 25 mm long hole axially at the tight end of the arbor to ease extraction of the bearings - allows cold spray spout where needed.

2: Made M6 internal thread at the other end to lock bearing axially during the measurement.

3: Lapped the other end about 0,002 mm smaller, achieving easy sliding fit, when all parts are at same temperature. This was fun part. Could not really gauge it on cool garage, beacause part was warm.

Lap was not best possible, rather hard structural steel, but cast iron would have been much more work.

Checked the ends this morning against gauge blocks and readings are:

Gauge blocks 25,001 mm

Tight end: 24,990 mm

Sliding fit end: 24,988 mm

Finish loks awfull on the picture, it is rather difficult to see on normal light. I was affraid it would not show.




Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #37 on: September 27, 2017, 01:21:41 AM »
I got bearings Yesterday, rushed to test them.

2305 is "tight" must wash it and fill partially with other grease.

6205 were SKF Explorer" series and seem to rotate very true, hard to measure radial excentricity. Better than speck. Axial play is hard to measure without good rig, it wobbles 0,15 mm axially, pretty close the same than original ones.

Stack them on very close fitting shaft with a 0,2 mm ground washer DIN 988 between outer rings. Almost all axial and radial play disappears, radial exxcentricity statys very close to zero, but there is some axial excentricity (maybe 0,002 mm) and some "mushiness" of 0,005 m with manual force.

I think that anomality I noticed is largely due to ring sides not ground to straightness for pairing these bearings.

I'm going to play a little bit more to see if mutual placement of the rings will mach these bearings better, but it looks nearly good enough.

I have only one try when these bearings are pressed on spindle. They have no provision on exterting the pulling force to inner ring.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #38 on: September 29, 2017, 12:25:54 PM »
Unbelievable week at the work.

Tried shims:
0,1 mm axial wobble 0,16 mm
0,2 mm hardly any detectable axial clearance, no detectable preload either
0,3 mm, clearly preload

Looks like 0,2 mm shim is a charm.

Pekka

Offline gerritv

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #39 on: September 29, 2017, 01:30:44 PM »
Wow, just wow.
A very educational thread. I don't have tools that measure to that level so not sure what will happen when it is my turn to do this.

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #40 on: September 30, 2017, 07:44:04 AM »
Thank you. I'm trying to educate myself as well :wave:

I could not sleep, and tried to "pair" the bearings better.

Put 0,3 mm shin between outer races and just nipped the clearing out, but that way it will not show on rotationalin sensitivity. The idea was to measure radial and axial play/movement.

I used 0,002 mm/div indicator and could not get play, some movement with finger pressure, but really next to nothing.

The interesting part that when I measure very carefully radial centricity I really can't detect any real movement on the needle, I can see it moving, but on the same place. If I coax some force I can read deflection on the measuremet system (fine adjustment of the normal magnetic stand is not up to task on micrometer scale), but hardly much TIR.

Axial TIR is differen and that I'm trying to establish..Needle moves on markings, tried to "ride" them with shim, but shim rides the markings.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #41 on: October 01, 2017, 06:48:33 AM »
Got message that the belt will be on it's last leg in Finland. Should get it at the begining of the week. pressure is mounting.

Played a little more with the bearings, a little gentle swipe on best diamond lap I had and burr on markings is now nearly non detectable.

Checked the straighness of the bearing rings. They look pretty straight even wth a dial indicatot that has resolution of 1 m. I can see 1-2 m high/low difference, not yet sure how does that realtes to ball races. Have to figure how to stablize measuremet the way that it produces meanigfull results - to align inner/outer rings to mimize excentricity.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #42 on: October 02, 2017, 07:05:26 AM »
Got some time to do bit more testing with the bearings and with/no preload. Turns out that the required shim thickness depends how you stack the bearings. Although bearing inner and outer races are pretty good and coaxial with ball raceways, they are not the same axially. Simply they are not optimized to work as matched pair.

Knowing all that I know now, I may have tried matched pair angular contact bearings. What I don't know if buying C3/P6 bearing would have changed things. I'm playing here with standard (CN) SKF Explorer 6305 bearing.

I found combination that exact bearing faces are shimmed next to each others and IR/OR are turned in relation to produce almost no preload, almost no play and only 2 m axial throw on outer ring. On most "uneconomical" orientation the error is nearly 20 m....interestingly both configurations produce very little of radial throw. That probably means that fitting them into spindle tube will not change things.

Next decision is what bearing grease I should use.

1: I have standard new grease SKF:n LGMT 2
http://www.skf.com/group/products/lubrication-solutions/lubricants/general-purpose-industrial-and-automotive-nlgi-2-grease/index.html

NLGI 2, oil viscosity is  40 C, 110  mm/s


2: I have least five years old Klber spindle grease, two diifferent varities, They are kept cool storage, packed well, plastic bag wrapped around them....But open tub and most used.

3: Order 50g tube of Kluber ISOFLEX NBU 15? That would be right stuff, bit overkill for this one.

Pekka

Offline gerritv

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #43 on: October 02, 2017, 08:29:14 AM »
I would guess that matched sets are put together by doing what you are: measuring each one and marking perhaps the high spot. On the visible bearings on my spindle there is a vague circular spot marked on each outer race.

Gerrit

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #44 on: October 03, 2017, 04:04:17 AM »
Matched  bearing sets I have seen have markings IR/OR to show orientation.

I am not sure if modern bearings are matched only by selection of components or there is some grinding involved. I got once 15 years ago bearing that had inner race sides ground, and max/min marked with permanent marker on rings and handwriten note in the package.

Did not do anything Yesterday on this one, had plenty of other activity.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #45 on: October 12, 2017, 03:01:43 PM »
Found out that shim discs were not very straight either, two beaings each two rings and one shim all has to fit together.

I put all the stuff together, but did not mount it into grinder yet. Eager to test it. I think I got it, but will see when it runs some time.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #46 on: October 14, 2017, 02:23:06 PM »
Today was the big day to put it all together....and circumstances conspired against me.

Anyway, I used one hour to contemplate which way to assemble the spindle. It is mechanically symmetrical but bearings are quite different. Also the wheel head does not rotate 350 degrees, maybe 270 degrees.

It was easy to mount the spindle cartridge back in it's place and tighten the bearing nuts. I did not yet assemble the dust shields, I want to run it hour or so, before assembling all the rest.

It does run quiet, initila impression is positive. It does not warm perceptibly, but something happens because even when it runs easy, play of 0,005 reduces to 0,002 mm or smaller (finger load). Have to run it longer to see if it starts heating up or getting tighter.

Pekka

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #47 on: October 17, 2017, 02:49:46 PM »
Today I had extra hour, went to garage and tun the spindle empty for 40 mins. No load but the flat belt drive.

Starting temperature of the grage and spindle was was about 14C.

2305 lbearing temp increased to 16C in about 5 mins and stabilized there for the rest of time. Imeasured the sppindle temperature inside the shaft thread hole. Outside of the spindle warmed up in 30 mins to 16 degrees C. This is the free end of the spindle, really expected no problem there.

The fixed end with two 6305 bearings produced more heat and cased me to stop the spindle every 5-10 minutes and check how it feels. I also changed the rotation direction on every stop and once tightened the shaft/housing nuts.

Spindle "intenal" temp raised in 15 minutes to 22C and then stablilized to 21C after spindle housing reached 16C and stabilized there.

Thik it is behaving well, next step is to mount rest of the parts there (dust shields and such) and then to test magnetic table.

Pekka

Offline gerritv

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #48 on: November 09, 2017, 07:13:22 AM »
I know your spindle is together now, here is a fascinating series of articles on the topic of spindle rebuilds.
https://highspeedtechnologies.com/category/how-to-replace-cnc-spindle-bearings/

Lots of your analysis is confirmed in the articles.

Gerrit

Offline PekkaNF

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Re: Spindle problem with cincinnati tool and cutter grinder 2 spindle
« Reply #49 on: November 09, 2017, 11:05:44 AM »
Thank you very much. That makes very interesting reading!

P.S. so far this grinder spindle has been fine, has to to but real work soon.

Pekka