Cast Iron Selection For New Gear

tfleming

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Some of you may have seen my post over on the antique machine section about the old Lodge and Shipley lathe I recently picked up. The small spindle gear is missing about 8 teeth. I have decided to make a new gear for it, and wanted opinions on cast iron selection. The gear itself is 4.116 OD, 12 DP, and 48 teeth. It is the drive gear for the feed gear train. I am debating between Type 40 Gray cast iron or Ductile iron. The Type 40 is easier to get and is a bit less expensive. Any thoughts or comments on choice here?
 
I might think of brass for that. So much cooler
 
4gsr has some large sticks of Durabar he was trying to move at a very nice price.
I wonder how that would work?

Daryl
MN
 
There are various grades of durabar. Some are cast gray iron and some are cast ductile iron. durabar is a brand name. Attached is a property sheet for various grades.
 

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Beyond repairing the gear:
When it crashes next time, think about what you want to see fail first. It can be very helpful to have a "fuse" in the system that is relatively quick, easy, and cheap to repair, and hopefully will fail first. Many times it is a shear pin in the lead screw drive, though there are other choices as well. After making a new gear you will not want to break it or any of its sisters. Some of the gears are often much more difficult to replace when they fail. Sometimes machines are designed that way, and when the fuse breaks a stronger one is put in its place, which can cause issues like your broken gear. Look for previous modifications. Sometimes machines are built with the attitude that "real machinists do not make mistakes." I would rather think "smart machinists would rather replace a roll pin than have the lathe down until they can make a gear." YMMV.
 
I will second the Durabar, esp: Dura-Bar: 65-45-12
 
You could try “spark testing” the broken gear to find out what the factory used for the material to make the gear. The internet has info on the subject…Dave.
 
Someday, those handheld XRF guns will be cheap enough for us. If you are tight with a scrap yard and they have one (many do now) they can tell you pretty accurately what it is. Spark testing is a great thing to learn. A little tricky, but pretty good to know.
 
I have never been good at spark testing. I think I might be slightly color blind as most sparks look the same color to me.
 
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