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Discussion Starter #1
Reassembling B43G, having trouble installing crank gear for cam. JD manual says to heat gear on hot plate to 250 deg F, grab w / large pliers and install.
I can get the gear about halfway on shaft, but it cools too quickly and sticks.Then I have to use a puller to get it back off. Obviously it's not getting hot enough, I would imagine the gears are hardened, and heating beyond a certain temp would affect the hardness.
Anyone have any experience with this ? Boomer?
 

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I'd go to Harbor Freight and get an el cheapo non-contact thermometer. Point, squeeze trigger, read, done! Not dead nuts accurate, but probably +/- 15 degrees which is waaay closer than what you need!

Heat treating of gear: Heat treating is a multiple step process and temperatures vary depending on material and desired harness. Parts are typically heated to a high temperature (1800ºF) and rapid cooled...quenched. This produces the maximum hardness off the material, but tends to make it brittle, So now it's annealed. This is a lower temperature and a slow cooling process. This softens the material somewhat but makes it stronger and less brittle.

So, temperatures! Annealing is usually performed around 1100ºF. A hot plate or electric range will have difficulty in reaching this temperature, but gas stove will! As long as you stay below, let's say, 900ºF you'll be fine. I'd recommend shooting for no more than 350º/400º just to be safe. When heated, a drop of oil can be placed on the surface. When the oil turns black, you're around 400ºF!

Another method and the best, IF you have the tools, is to measure crank journal and "set" a telescoping gage to 0.003"/.005" larger than crank. Heat gear until gage falls through bore. Again, this is only if you have a mic and a set of telescoping gages. Bob
 

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Discussion Starter #3
Bob; Thanks for the quick reply, it jogged my memory (or what's left of it ) I have a temp gun, so all I need is a hotter heat source. Gas grill? Also have heat gun that supposedly will go to 1200 f
Is anti seize a no-no in this instance ? You obviously know your metallurgy !
Ted
 

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Correct in that anti-seize is a no-no! Any liquid on the crank will tend to draw heat from from the gear making it shrink/collapse quicker. A powder will work better. Get some powdered graphite, put it on crank, and rub hard with fingers/hand. This...hopefully!.. will inbed it into the pores in the metal, as small as they seem. Next, get a dry rag and wipe shaft down. If you ever need to remove the gear for whatever reason, the "plates" of graphite can pile up on the shaft and do MAJOR damage to shaft and/or gear! After wiping with rag, a quick wipe with your hand will verify no loose particles remain.

You'll be in good shape with temp gun. Whatever your heat source, turn cam gear over often to get an even heat. Don't rush things, there's a fair amount of metal there and you should get most of it up to temperature...350º/400º. If it happens to get hotter don't worry. you've got quite a bit more to go before you change the harness.

Feel free to post more questions/uncertainties. Bob
 

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Another option is your kitchen oven! Set to 375, cook for a bit, remove and check temp with temp gun. Bob
 

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350C I think is where you lose hardness and add temper to steel.

I know when I did a p-218 ring gear I had to be quick setting the hot gear on the flywheel, setting plywood on top of it and giving it a whack with a deadblow. It took 2-3 tries. I wouldn’t worry about the hardness though, if you didn’t have steel it would be plastic so hardness doesn’t appear critical.

I also heated the ring gear in the oven. A 250F heatgun will be lucky to get that gear to 200F.
 

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Discussion Starter #8
Well this morning I got a hot plate and my IR temp gun , got the gear heating with the hotplate at max heat. After about a half hour I checked and the gear temp was about 250f so to speed up the process, I covered the gear with a small metal pan. after another half hour, I checked the pan temp , and it was 500+ f, took the pan off, the gear was 620f +/--, so of course I grabbed it with the pliers and put it on the crank .When it cooled , I noticed that it had changed color,some areas were a bluish purple, and others were copper colored . Thought maybe the temp got too high, but according to the temps Bob posted on post #2, I was way below 900f, So hopefully it's ok.
Also, cleaning up a few small dings on the gear teeth, with a fine file, I noticed that for a hardened gear, it filed very easily. Don't know what to make of that.
Any thoughts ?.
 

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Color is a relative way to determine temperature, it's close but not completely accurate. One person's eyes may see dark purple while another see almost black or dark blue!

620 is a little hotter than I would have liked to see, but not knowing the exact specs of the original heat treatment, I can't say if any damage was done or not! We don't know the exact composition of the metal nor the original heat treat temps. You can heat treat for strength or hardness or a little of both and this is determined by material & temp.

Bottom line here is it's been heated, installed, and done! Whatever hardness/strength you have or lost is there. Run it is about all you can do right now. Bob
 
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