The Shop > Tools

Internal hole measurement - bearing seat - opinions?

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bp:
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

John Stevenson:
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.

bp:
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 

Doc:
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.

PekkaNF:
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.

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