Casting kit measurements

[Ryan]

I'm just wondering if the majority of casting kits available use fractional measurements and BA taps, drills etc? is that just part and parcel of the model engineering hobby ( unless of course designing your own)?

I work in metric and have metric taps mainly. I have metric and imperial drill sets but to what extent are reamers used? Does one require an extensive collection of imperial reamers (which compared to metric would be of limited use for my other projects outside of model engine building)?

 

[Jasonb]

Depends where you are based and where you buy the castings from.

UK - mostly BA but steam fittings in ME & imperial measurement with a few that have double mesurements in metric as well
Europe - Metric
US - UNC and UNF & imperial measurement

You will find some imperial kits use fractional measurements others use decimals, metric will obviously be decimal.

 

[deverett]

If you prefer to work in the Metric system, there is no reason why you cannot adapt Imperial measurements to the Metric system.

Screw sizes are easily interpolated between the two systems - there are any number of thread equivalent charts freely available here and elsewhere. e.g. If a 6BA screw is suggested, you would change that to M3.

Changing Imperial measurements to exact Metric equivalents for castings is no problem, but if a piece of steel is listed as 1/8", that would literally be 3.175mm. You would obviously use 3mm steel. If doing this, check other measurements. One example that springs to mind is loco frames, frequently (in the UK) specified as 1/8". If you use 3mm plate, axles will need to be adjusted to take into account the thinner steel used.

Using, say, 6mm rod instead of 1/4" is quite acceptable. Strength is not normally an issue in the size models most of us make. So, your Metric reamers would be the ones to use. If you do use Imperial stock, then you will need Imperial reamers. If that is the case, just purchase what you need at the time rather than a set, many of which may not be used.

Dave
The Emerald Isle

 

[Tin Falcon]

What they said !!!

Stuart turner kits BA hardware.

PM research kits model sizes like 5-40 3-48

some folks like there own hardware better for aethetic purposes. like using studs instead of bolts or hex head instead of screw heads.

part of this hobby is adapting and overcoming.

Tin

 

[chrsbrbnk]

Most of the prints are not done by pros and some are really out dated I've got one that has fractions and decimals combined like .5/8 wasn't really sure how to think about that.

 

[Jasonb]

Fractions and decimals can be an indication of the tollerances needed for the part.

1/2" would just be a nominal size
0.5 would be +/_ 0.02"
0.50 would be +/- 0.01"
0.500 would be +/- 0.001"
0.5000 would be +/- 0.0005"

 

[Tin Falcon]

The Import kits s( bar stock) assembled by Sieg and sold by LMS and Grizzly IIRC are metric .

Tin

 

[Ryan]

I just revisited this post as I'm intending to start building something more complicated than the EZ.

I've noticed that pretty much every fastener below M4, except for hex head screws can be purchased in Australia. Has anyone found a supplier of M2-M3 hex heads?

Apart from the absence of those fasteners, there's no reason I can't exclusively work in metric.

 

[Jasonb]

If you want scale looking hex heads and nuts to match then "standard" metric will look very large even if you can find them in teh smaller sizes.

I get my metric nuts and screws from Germany although one of the English model engineering suppliers stocks a limited range from the German maker.

http://www.modellbauershop.de/schrauben/modellbauschrauben-hoher-kopf-ghw-1000.php

If you download their catalogue it gives the hex sizes which are typically 1 size smaller so M4 has 5.5mm hex, M3 has 4.0mm hex,