Hole diameter and tolerance for introduce a shaft

[jor1492]

Hello All,

Basically I want to specify the size of a hole and tolerance in a plate to introduce a shaft and then weld the shaft to the plate. See attached image.

Thanks in advance.

 

[CheckerHater]

To center your parts before welding fit like H11/h11 should be enough.

That will make hole 200 +0.250/-0.000, shaft 200 +0.000/-0.250

Don't take my word for it, wait for more responses

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[keyen]

jor1492, be aware your weld symbol indicates you expect a fillet weld on the inside of the shaft. You probably want to put the symbol on the side-view.

 

[jor1492]

Thanks checkerhater but with that tolerance I think that the 2 pieces could be fabricated to the same dimension, and that case the shaft can not fit with the hole.

thanks keyen by the observation.

 

[tbuelna]

One thing to consider is that drawings typically define the characteristics of a product as delivered. In your case, there is no hole left in the plate to inspect after welding. So what you should specify instead are any dimensions/tolerances required by the finished product. And leave it up to your fabricator to figure out the best way to produce a product that conforms to your drawing requirements.

 

[3DDave]

As a point of interest - if the hole and shaft are exactly the same size the two parts will fit together. The reason such fits can appear to fail in actual parts is that there are errors in measurement that fail to detect that parts will interfere.

An example piece for honing/grinding capability that I came across once was a pin in a cylinder. There was a rubber plug to seal one end of the cylinder. It was easy to assemble the pin, put it part way into the cylinder and then seal the end with the plug. At that point the assembly could be set upright on the pin. The remaining air in the cylinder would act as a cushion and the cylinder could be spun freely, like a top, which it would do for a long time. At no point would air leak between the cylinder and the pin. The clearance between the two parts was on the order of a few millionths of an inch or less.

 

[pmarc]

H/h fits are quite frequently used in industry. In fact, in ANSI B4.2 standard there is a table with preffered limits and fits depending on desired application (below is a link to a document containg some data from that standard).

https://mdmetric.com/Ch6.8wGO.pdf

As always, real life is an art of making compromises. Too tight fit may cause issues during assembly (although often there are ways to deal with it by designing components properly). With too much loose between parts, there may be, for example, problems with potential unwanted perpendicularity error of the plate relative to the shaft axis.

In some cases, as tbuelna mentioned, the decision on the amount of considered loose may be left up to a fabricator. But in some cases it will not work - imagine that the components are delivered by two separate fabricators.

I guess only designer knows enough to choose the best option.

 

[CheckerHater]

As a point of interest - if the hole and shaft are exactly the same size the two parts will fit together.

Interesting question - if hole and shaft both pass respective GO gauges, shouldn't they fit?
Especially if the Rule 1 is in place.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[3DDave]

CH - it depends on how long the shaft has been out of the freezer and how long the plate was out of the oven. Not that I've ever heard of Inspectors placing certain parts on sunlit windowsills before measuring them. Or my favorite for slightly over sized holes - place a ball bearing on the hole and give a little tap with a hammer so the NO-GO gauge now no-goes.