Author Topic: Internal hole measurement - bearing seat - opinions?  (Read 9486 times)

Offline PekkaNF

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Internal hole measurement - bearing seat - opinions?
« on: June 18, 2011, 07:08:35 AM »
About internal measurement.

Fork from this thread:
http://madmodder.net/index.php?topic=5524.0
Internal micrometers opinions please?

I have slight problem producing correctly dimensioned bearing seats. Part of the problem is measuring the hole diameter and geometry right.

I realize threepoint is a way to go. But if I have no iclination to commit that hefty investment yet, the range of bearings I'm likely to encounter would require quite a few of those.

How do does this type bore gauge compare with telescopic bore gauge:
http://www.machine-dro.co.uk/35-to-50mm-internal-dial-bore-gauge.html

I have some acceptable micrometers, setting out or reading the diameter is not big deal.

That dial type gauge looks like it would come handy when boring the bearing seat and I'm gradually approaching right ID. Still two point, can't detect ovality, but least could see if it comes out barel or diameter is all wrong.

There is learning curve with any measurement instrument - I realize that - what I'm trying to find out that:
* How accomplished machinist measures a bearing seats for correct fit ?
* Is bore gauge/telescopic gauge way to go?

I have quite a many old books and there are may ways to measure internal diameters. However nowadays many measuring instruments seem to more affordable than back then. People have tendency to use available technology.

So:
* Mike the OD of the bearing (to check the mike)
* Set the bore gauge to the measurement +/- fit
* Check the bore and machine until happy

Or use slightly more expensive telescopic gauge and mike it after each measurement? Just more fiddly or potentially more accurate?

Or am I into wild goose chase and really should machine bores oversize instead, glue fixed bearing and aim to to have free bearing sliding fit?

Pekka

Offline Bogstandard

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #1 on: June 18, 2011, 07:46:21 AM »
Forget telescopic bore gauges, you are losing accuracy because you are trying to do two point measuring twice.

I have almost a full range of bore gauges, and that is what they are for, measuring bores that are normally deeper than bearing seats, and can be swept around until you get your max measurement.

I have my own two ways of measuring and making for close fitting bearing seats.

The first is an internal mic, and if you get your technique right, the hole will get very close to where you need to be. I can usually get within a couple of tenths (0.005mm). I would always try to go just under correct size, and gently scrape and use emery cloth/wet-dry to final size.

The other way is if you don't possess an internal mic.

Make a go gauge, about 1 thou (0.02mm) undersize. Very gently bring the bored hole until the go gauge only just enters the hole, then super fine cuts until the bearing just enters the seat, or as I do above, scrape and emery/wet-dry to size.

If you go just over size, no more than 0.002" (0.05mm) then a bearing lock adhesive (Loctite) can be used to good effect.

You can also use disruption methods to get a slack hole to tightly grip a bearing. By carefully centre popping around the internal bore you have made, that will raise metal edges which will grip a bearing very tightly, but you must make sure that you 'pop' equally around the internal hole, otherwise the bearing can be pushed off centre.

There are many ways to get a good fit, these are the ones I use.


Bogs
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Offline John Stevenson

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #2 on: June 18, 2011, 08:13:58 AM »
This is just my take on it and I do a lot of internal bores in my job, Friday alone I re-sleeved 9 motor housings from 40mm up to 110mm in diameter, so that's 18 boring operations, bore to fit the sleeve and one to finish to the bearing bore.

As you can understand being bearing fits they need to be good.

Now over the years because it's a paying job I have bought bore gauges, telescopic gauges, internal micrometers, pin micrometers [ like in the other thread ], all in imperial and metric. About the only thing I have not bought are the ring mic's and to be honest I'm glad I haven't

I have slowly used these as bought to try them but the honest truth is I have always dropped back onto the telescopic gauges and a cheap pair of digital verniers to rough out with external micrometers to finish off.

I find internal micrometers very hard to use to get an accurate reading, most times on smallish holes they are tool bulky to get a decent feel.
Bore gauges are good but require loads of room and often on smaller machines having to remove the tailstock to get square.

I know this is contrary to what a lot of people use but it suits me and works for me an at the end of the day if it didn't work I'd starve  :lol:

John S.

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Offline Davo J

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #3 on: June 18, 2011, 08:30:41 AM »
I also like the telescopic gauges as I find I can get the same feel with the mic's between them and the bearing size. Also it doesn't matter if the mics are not calibrated perfect because I am using the same measuring tool to measure both the bore and the bearing, which cancels out any errors between between measuring instruments.
It will take a bit of practice to get used to the telescopic gauges to get a true reading, but they are not hard to use.

Dave

Offline PekkaNF

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #4 on: June 18, 2011, 09:02:50 AM »
Than you all,

You guys are extremely helpfull. this is exactly sort of answers I wanted. Good honest methods and opinions. This will help me in decsision making.

Very good info.

I thought that bore gauge would be ideal to me, reach in worst cause something like 120 mm deep at the other end of the bore and get there to verify sliding fit for free bearing and fight to get a larger diameter to correct fit for two angular contact ball bearings. I didn't think of tail stock pecking my elbow and wrist. All of them are unwieldly?

I have heard that you don't want slop on telescopic gauge, othervise measurement will be a chalenge. I'm starting to realize why I have seen use of internal calipers.

I have been checking Mitutoyo telescopic gauges, that is one barand never let me down. Then again, one friend bought one cheaper set and he has been happy with it. I probably should make a bit more than 100 km round trip and have a hands on try and hear first hand experience.

The plug gauge method definately has it's merit. I probably have to do the same spindle (and other contraptions) few times over before I'll get them sweet and being an engineer I see benefit of minimizing inventory on different bearing sizes:)

Pekka

Offline Dave G

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #5 on: June 18, 2011, 11:27:25 AM »
Hi Pekka, I used to do some jig grinding and very close tolerances can be held. These parts were normally hardened die plates and the holes had to be very close. We normally snuck up on the proper size by measuring with dial bore gauges or intramics but for final size we used plug gages. The only problem with plug gages is they are hardened and if they aren't they may gall when trying to insert in the hole. At home if I have a bearing seat to machine I bore with a precision boring head and before starting I will make a few plug gauges in .001 increments leading up to the finished size. Care must be taken when inserting the plug gauge and alot of feel is involved. Roundness of the hole should be alright if you do your boring last. By this I mean, don't bore a hole to size and then mill material off the part close to the hole as the part will move and the hole will no longer be round. One of the things I like to do when sneaking up on a size is if the finish dia is say .0005 over a nominal size I like to get the part .0005 over the desired size .005 to .010 before reaching size. I make my last few cuts the same amount to keep the tool flex consistant. I also try to design my engines with a thru hole if possible so I can size the holes with my Sunnen hone. You would be amazed at how round a hole that has been honed will be. I served my apprentiseship and was employed in a bearing factory for 30 yrs and we had all the neccessary equiptment to measure holes for size and roundness. I once worked with an old timer that ground all the ball races in gyro bearings that were used in missles for the government. The most precision bearings that we made. He related to me that they would get roundness within spec for the most part but every now and then the ball races would be out of spec. They fought this for months until someone had the notion to watch the local traffic pattern outside the plant. What they found was that every time a large semi truck would roll past the plant is when they would get a bad part. Their fix for this was to pour a separate pad of material to set the grinder on that was isolated from all the rest of the factory and the surrounding area. He told me it took 2 weeks for the grinder to settle down after the improvement and it solved all their problems. Sorry for length of this but I find it quite interesting and I hope you do also. Dave

Offline Pete.

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #6 on: June 18, 2011, 12:10:16 PM »
Quote
Make a go gauge, about 1 thou (0.02mm) undersize. Very gently bring the bored hole until the go gauge only just enters the hole, then super fine cuts until the bearing just enters the seat, or as I do above, scrape and emery/wet-dry to size.


This is what I just did to fit a bearing into a sprocket carrier. I actually wanted a shrink fit so I made a gauge 2 thou smaller than the bearing then machined the carrier until I could just get this in. Then I heated the carrier and dropped the bearing in. When it cooled off it was held tight and the bearing is as smooth as silk.

Offline bry1975

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #7 on: June 18, 2011, 02:44:10 PM »
Oops wrong post.

Offline dickda1

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #8 on: June 18, 2011, 04:33:11 PM »
I agree with Bogs' assessment of telescopic gauges.  Measuring twice (bore to gauge then gauge to micrometer) has always been a source of frustration for me.  The slightly under plug gauge is the way I use.
-Dick
« Last Edit: June 18, 2011, 07:35:00 PM by dickda1 »
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Offline John Stevenson

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #9 on: June 18, 2011, 04:39:32 PM »
You still have to set a bore gauge with a micrometer.
Plug gauges are OK if you are working to just a few sizes and even then you have to be able to use another measuring method to get close to finished size before you can use the plug gauges.

Years ago our predecessors used  firm joint calipers for most work and made bigger and better things than we do today.

John S.
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Offline dickda1

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #10 on: June 18, 2011, 07:36:58 PM »
"Years ago our predecessors used  firm joint calipers for most work and made bigger and better things than we do today."

When I read about how craftsmen used to chase threads on a lathe in a distant but still memorable age, I am humbled.

-Dick
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Offline Bogstandard

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #11 on: June 18, 2011, 09:23:42 PM »
John S,

The reason I always put in my posts 'this is the way I do it'.

Everyone has their own way of achieving things, and no two people will do it EXACTLY the same way, even though they think they do. If you end up with a good result, then the way you are doing it must be correct, for yourself.

What would the world be like if there was no diversification, everyone doing things the same way?


John

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Offline Anzaniste

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #12 on: June 19, 2011, 06:41:14 AM »
I feel much better having read this thread. I just thought that it was me who was a bit useless at measuring internal bores. I now wont feel so inadequate when it takes me so long to be confident about a bore measurement.  :thumbup:
Scrooby, 1 mile south of Gods own County.

Offline loply

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #13 on: September 30, 2011, 09:54:52 AM »
Hi folks,

I know this thread is slightly old but I thought I would chip in.

Just received a set of internal telescopic bore gauges, a cheap set made in China.

On receipt I noted that the finish on the ball ends was a bit crude, shiny but faceted, and that the motion of the telescopes was "stictiony" and scratchy.

I buffed the ball ends on a soft cotton mop on my bench polisher until mirror like and not faceted, and I dribbled some engine oil into the telescopic parts and blew air in to spread around.

I then spent 10-15 minutes practicing on a range of bearings I had handy from 10mm ID up to 40mm ID.

To my surprise I was able to get results to within 0.01mm with ease, if I measured the same bearing three times I would get the exact same result twice and maybe 0.01mm off on the third attempt.

My technique was to put the gauge in at an angle of about 15 degrees, expand it, lock the screw pretty tight and then slowly rotate it up to vertical and then a bit beyond whilst simultaneously wiggling it back and forth by 5 degrees or so in a direction perpendiclar to the main movement.

I then mic'ed the gauge using the ratchet on my mic.

Really pleased with the results, didn't expect such accuracy with such ease.

I suspect results will be less predictable on turned bores, but that's a function of the uneven surface finish, not of the tools or methods, I guess.

Offline Joules

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #14 on: September 30, 2011, 11:15:41 AM »
 My prefered method is a guage a few thou under size (.010) then use feeler guage strip to creep up on that final diameter.  Ok for 20mm+ sized holes, and saves getting the gauge stuck.

Just my 0.01p worth

          Joules
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Offline bp

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #15 on: November 04, 2011, 04:58:30 PM »
I know this is a bit late, but I've only just picked it up.
In his post Dave G recounts a tale of heavy traffic affecting the job.  Where I did my apprenticeship the machine shop was right alongside the sea wall.  They had a very long and narrow mill, about 60' long bed possibly more, maybe 3' wide, it was used for machining wing spars for aircraft.  I was told that the mill was built to machine the spars of the Saro Princess flying boat, the worlds biggest all metal flying boat.  Anyway, on the wall by the machine were tide tables.  I assumed that was for fishing or boating reference, but no, the state of the tide affected the mill, either made it sag or hog I can't remember now.  Apparently the operator was brought out of retirement when the company got a project that required the use of this "Spar Mill".
Imagine an accountant trying to work that out!!
cheers
Bill Pudney

Offline John Stevenson

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #16 on: November 04, 2011, 05:45:53 PM »
I'll bet it was a bastard when the tide was out, the moon was full and the wind was from the north.

Even worse if someone left the canteen door open.  :bugeye:

John S.
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Offline bp

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #17 on: November 05, 2011, 10:21:48 PM »
John S wrote ..."I'll bet it was a bastard when the tide was out, the moon was full and the wind was from the north.  Even worse if someone left the canteen door open."
Yes, Yes and Yes, and YES when all three coincided.  The Canteen was in a separate building, some way away, and even in the early '60's had self closing doors!!
cheers
Bill Pudney 

Offline Doc

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #18 on: November 05, 2011, 10:48:48 PM »
I just have to say that telescopic gauges take a getting the feel but once you do you will use them. I also agree you can get more info on bore size, out of roundness and taper with a dial bore. But in the 38+ years I've worked in a tooling shop I would say about 95% of the time I used telescopic gauges only when I have to hold a hole size to a +or- .0002inch if I have +or- .0005inch or more I use telescopic and I really don't remember having to much trouble hitting the bore size I needed. That's not to say that is the way you should do it it is just how I do things, as Bog said one way to do thing may not be the right way for some one else.

Offline PekkaNF

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Re: Internal hole measurement - bearing seat - opinions?
« Reply #19 on: September 01, 2019, 06:31:22 AM »
Now I have a little more experience and I generally get the fit I am after. Still not easy, still not routine, but still most advice is good.

My experience is mostly between 20 - 50 mm holes and bearing seats.

Bore gauge - I have bought bearing inner rings to set the bore gauge. Also have gauge block vice.
* Good only for final sizes and beeds smooth cut.
* Also need usually more swing place I have in the lathe. AND I need to remove boring bar to use it. Therefore I generally use it just verify before assembly.
* Takes some time to set all extensions etc. if the setup is different than previous. Without setting ring, takes even longer. There is a micrometer, but I don't have three hands and that adds one error source more.
* some modes have an indicator that indicates "wrong way". Pretty unintuitive, I know it, but always need to get my head around that the max. reading is minimum....

Telescopic gauge:
* My set is chinese. No amout of polishing will improve reliabilility. It was useless out of the box. First thing was to remove rust and polish the ends of the push-rod that is inside. The ends of the push rods were probably cut with wire cutter.
* One of them is semi decent, I get the idea how it suposed to work. Much "feel".
* Really think that shoud get better set, but they ruined my day.

Internal micrometer:
* I have one and luckily it covers much what I need. Most accurate tool I can use and swing in the lathe - while machining
* Also needs a lot more feel and getting to know than you might think.
* Also the scale is unintuitive, needs care when reading.
* Only need to wind the boring bar out of the bore, clean and measure. Fast and pretty reliable, when getting close to right size.
* Measurement depth is limited, but often enough with care

Digital caliber:
* Versatile, relatively easy to use, needs some practice
* Great range
* Accuracy needs verifying. Only Mitutoyo gets pretty close. Two cheaper ones needs searate calbration for ID jaws and you just can't trust the reading if zeroed normally jaws closed. Luckily digital ones zeroed into IR work fine, but really can't zero on bearing OD or with jaws closed. One of the cheap caliper has jaw shape that causes erroneus reading  when hole size is less than 15 mm.
* Great gettig to final phase, I often only use them.
* Very limited depth.

No matter which is used: Cleanliness is important, deburring is must and all will take some practice.