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[4]

Cast Iron Selection For New Gear

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tfleming

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#1
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?
 

rgray

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#2
I might think of brass for that. So much cooler
 

Uglydog

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#4
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
 

Billh50

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#5
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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Bob Korves

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#6
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.
 

Tony Wells

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#7
I will second the Durabar, esp: Dura-Bar: 65-45-12
 

chips&more

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#8
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.
 

Tony Wells

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#9
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.
 

Billh50

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#10
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.
 

Tony Wells

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#11
It's an art, and one I have had only limited success with. I knew a guy who was an old hand at Crucible Metals who was a whiz at it. He tried to teach me, and part of it stuck. Color is a big part of of it, but the breakout of the sparks I think is very telling and maybe more important. You could still do pretty good, even with limited color vision, I believe.
 

4gsr

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#12
Do a little filing on the broken gear. Then try to file some cast iron on the same machine. Either the filing will be the same or they will be different. If the filings are dusty or powdery, it is cast iron. If the filings have shape to them, like filing a piece of steel, then it is steel. Let us know what you determine.
BTW- as I said in my post on the other thread, let me know about the cast iron or if you want to use ductile iron, I have a source for getting my hands on just about any size anyone would ever need. And you won't have to pay Speedy metals prices or shipping! Ken
 

tfleming

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#13
Thanks for all the responses guys. I am going with the G2 Dura-bar from 4gsr. The rest of the gear train all is in reasonable shape, sans some honest wear. To be honest, I don't have a problem making all the gears if necessary. Based upon the grain structure of the broken areas of the teeth on the original gear, I believe them to be cast iron. In any case, I appreciate all the feedback. One thing for sure, when I get this old girl back into service, she won't be doing any massive production work. I will be working her, but nothing dramatic.................and unless I have a brain cramp, I don't expect to "crash" it either! This will be my first attempt at cutting a gear, so I am looking forward to the project.
 
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