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Internal hole measurement - bearing seat - opinions?

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PekkaNF:
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

Bogstandard:
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

John Stevenson:
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.

Davo J:
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

PekkaNF:
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

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