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View Full Version : What the heck is "semi steel"?



kenc
10-24-2003, 06:56 PM
I am looking for a decent quality - but cheap ($60 tops) 8x3 castor to use for an English Wheel top wheel. I've been looking through MSC's catalog and notice some wheels are noted as "semi-steel". Now, I have seen "semi-steel" attributed to some cheap Chinese lathe chucks and was wondering what "semi steel" is since I'm unfamilier with the term.
If it's a Chinese name for cast iron I'm not interested!

Forrest Addy
10-24-2003, 08:23 PM
The Chinese use semi-steel for the same reasons we do. It's an economical material having properties suiting a variety of applications. As for alloy or country of origin, let all your judgements based on merit or politics be clear-headed and unconfused.

Semi-steel is any of a variety of ferrous alloys. Here's one common definition: "SEMI-STEEL - Cast iron (not steel) of high quality, obtained by using a large percentage of steel scrap with the pig iron." This isn't really satisfactory because alloy constituants aren't broken out nor are subsequent heat treatments discussed. I doubt if refined standards exist for semi-steel as they do for malleable iron which is closely related.

Semi steel is a foundry product featureing many of the characteristics of cast iron (fluidity in the melt, castability, low cost, machinability) and steel (strength, impact resistance, and some ductility) that suit it well for lathe chucks and caster wheels among other things.

That semi steel contains recycled steel not not a detremental factor. All metal products contain some select scrap these days. The alloys we ail depend on are made up in the melt as part of the metallurgist's art.

Presonally I don't think a castor wheel is a good choise for an English wheel. I suggest you make them from 1040 or some other hardenable steel that can be taken to a high polish. Otherwise every bruise and nick the soft semi-steel wheel picks up over time will be transferred to the work.

wierdscience
10-24-2003, 08:55 PM
I made my english wheel top out of a cast steel caster wheel,it worked but not for long.

The english wheel as I understand it works because of the very small contact area between the wheel and the work piece,mine worked okay until I noticed a small groove around the circ. of the caster,I looked closer and saw that it was a slight radius and that it effectivly increased the contact between the top parts,so I chucked it and turned the od again and that solved the problem until it grooved out again,I finally found a large ball bearing outer race and turned the wheel for a shrink fit it now works great.

kenc
10-24-2003, 10:49 PM
Thanks Guys,
Unfortunately a piece of 4140 or similar large enough to turn an 8x3 wheel out of would cost an arm and a leg - at least from the places I know. It may be more economical to pay the $135 plus $30 shipping from the guys who sell hardened 4140 wheels on ebay.
Ken

CCWKen
10-24-2003, 11:21 PM
I got some casters from Northern Tools. I used 6x2 and if I recall, were about $7 or less. You'll need to put new bearings in them. The stock "bearings" are like the old Model T rear axle bearings. (Split sheet-metal race) You can bore the 1.190" out or use metric bearings.

Like WS says, don't expect longevity. They do shine up to a nice finish though.

Forgot to mention: I built a smaller version for use on small pieces out of two old ball bearings. For the size, This works great for rolling dings out of smaller items. Both bearings are flat-faced now but I've got some old self centering bearings that I was going to try as the bottom dies. If I can get my new PC up and going this weekend, I shoot some pics and post them.


[This message has been edited by CCWKen (edited 10-24-2003).]