Press Fits

[Ghosty]

I built a crankshaft from machined parts with Loctite 680. Two of the 8 joints have loosened up. I had the holes bored with a 0.376 reamer and the shafts are 0.375. Six of the joints seem solid and two loose. Should there have been more room in the fit larger than 0.001 for the Loctite to work properly? I did use Acetone to clean up the hole and shaft prior to assembly and I didn't touch anything for 24 hours to allow for curing. The close up shows the shaft no longer flush with the joint.
Grasshopper
View attachment 144112

View attachment 144113

Grasshopper,
You should have been using a 0.374 reamer, the hole needs to be smaller than the shaft.
Cheers
Andrew

 

[Steamchick]

Hi Ghosty, I agree if you want a press fit, but anaerobic adhesives usually specify a clearance, usually very small. (I think? - The Simply Bearings paper say there is an optimum gap.). There is a lot to read here, if you are interested (I have not read the first article!).
https://www.researchgate.net/public...sives_in_finite_thickness_under_high_pressureThis is a simpler explanation of "how it works" for shear strength of anaerobic materials...
https://simplybearings.co.uk/shop/files/5800-EN.pdfBut this is based on a sealant, not an adhesive. Although I understand the same principle applies? - The Manufacturers have determined Optimum gap sizes per product and application, so these should be used rather than some "good idea from Someone - like me".
Cheers!
K2

 

[Henry K]

Here is a You-tube Video on the Otis King Calculator aka slide rule.

 

[IanN]

Can you show us a photo of that Otis King? Thanx

Hi Richard,

Attached are some pics of my Otis King. I see that a link has already been posted to a video showing its use.

The slide rule in the video is a model K with two slider scales end to end to avoid "end switching" when the result of a calculation goes "off the end" of the scale. My machine is a model L which replaces the lower slider scale with a scale reading logarithms to allow the calculation of arbitrary powers and roots.

Pictures show:

1) Slide rule in box


2) Slide rule in its closed state


3) Slide rule scales extended


4) Setting up to multiply 2 by 3 - lower cursor index set to first value (2)


5) Start of upper scale set to cursor upper index mark


6) Cursor moved to set upper cursor index against second value to be multiplied (on upper scale)


7) Upper scale set of reading off logarithm of values


8) Reading the Log of 2


Ian

 

[petertha]

I admit that I'm not familiar with SolidWorks, but all of the CAD packages I have used.... If SolidWorks doesn't have this capability, it's something they should add (otherwise end users of the output are going to go crazy with dimensions like 41/128" instead of 5/16").

SW has multiple ways to define significant figures. Within the part environment, drawing environment, specific to user defined templates, based on common Unit systems... on & on. These permutations are for user defined 'display' preference. Behind the scenes, the calculations use floating point arithmetic to orders of magnitude more digits. Not significantly different than your calculator knowing PI or 1/3=0.33333333333333333 to the limits of RAM. As to the crazy fractional dimension example/comment, not quite sure what you are getting at.

 

[petertha]

Solidworks (like all current CAD packages) uses SI units for its native dimensions

Really? Or is it just a default setting in your own configuration for convenience? It seems to me I can choose from any of the common unit systems, or make up my very own unit system, or change units on the fly, or enter 1.234" in metric dimension box, or 1/3mm in an inch dimension box... At least that's how I've been using it for several years & how its presented in the documentation.

 

[ChazzC]

As to the crazy fractional dimension example/comment, not quite sure what you are getting at.

Our Design Team, who did the bulk of the detailed work in Revit (as opposed to the Engineers, Architects and PM's like me who only used it for review & comments), would occasionally forget to load the correct template or set the units correctly and a building that was 1,225' long would end up 1,224' 11-127/128" long after extending or trimming a line.

Now I'm the design team; being known to mix units since I buy nominal inch stock shapes, may trim them to convenient inch lengths & widths but then place holes on mm centers to match existing tapped holes in a machines, I also know how the edit dimensions if necessary, not unlike:

In this case it in an existing "metric" part that was being modified to suit use in an English Unit environment.

 

[djc]

...anaerobic adhesives usually specify a clearance, usually very small.

This design guide from Loctite is quite instructive and relatively simple to follow:

https://5.imimg.com/data5/AE/AX/JM/SELLER-2044578/loctite-retaining-compound-638.pdf

 

[IanN]

Really? Or is it just a default setting in your own configuration for convenience? It seems to me I can choose from any of the common unit systems, or make up my very own unit system, or change units on the fly, or enter 1.234" in metric dimension box, or 1/3mm in an inch dimension box... At least that's how I've been using it for several years & how its presented in the documentation.

View attachment 144251

Hi Peter,

It seems I didn't explain myself very clearly - apologies.

Within the CAD software there is only one set of "dimensional scales" used to store lengths, angles, and so on - there is not a millimetre standard, a metre standard, an inch standard, etc.

All length units ultimately trace back to the ISO definition of the metre as a function of the wavelength of light emitted by .... etc ,etc, etc, which can be recreaed in any lab in the world. So there is no such thing as an "inch standard" - the inch is defined as 25.4mm and so is defined in terms of SI units

If you want a dimension displayed in aliquot parts of an inch, this is calculated from the millimetre dimension which is actually stored by the software. All dimensions are stored in units of millimetres (or metres in some CAD systems)

Sorry for the confusion,
Ian

 

[petertha]

Hi Peter. It seems I didn't explain myself very clearly - apologies.
Ian

All good! Just wanted to ensure you were aware that one can flip between common unit systems with reckless abandon, even create your own unit system & set defaults using templates of favorites. Same goes for drawings. Very powerful in that regard.