An Upshur Farm Engine

[kuhncw]

You are getting a lot of nice work out of your Taig machines. 

Chuck

[crueby]

Nice work! Watching along...   

[Kim]

You're moving along on this quickly, Ron!

Did you do any stress relieving on your cold rolled steel?  If not, you might want to do that.  It can have a tendency to go banana shaped when you machine it.  I also know that some people just make it then bend it back straight again after machining.  That hasn't worked as well for me, but some people seem to do it OK.

Kim

[john mills]

I like to do a rough machine leave enough to finish machine after it has moved after rough machining ,
if you have to bend it be cause it bent to much it is easier to get it straight if you finally finish machine it straight
as the last operation.
John.

[crueby]

You're moving along on this quickly, Ron!

Did you do any stress relieving on your cold rolled steel?  If not, you might want to do that.  It can have a tendency to go banana shaped when you machine it.  I also know that some people just make it then bend it back straight again after machining.  That hasn't worked as well for me, but some people seem to do it OK.

Kim

Kim, whats it take to stress relieve crs? I've done it for brass, don't know the process for cold rolled.

[Hugh Currin]

Kim, whats it take to stress relieve crs? I've done it for brass, don't know the process for cold rolled.

I built a bearing mount recently and had some trouble. It's made of CR 1018 and looks like this:

I cut the large hole for bearings first. SOP so the larger stock is easy to hold in a lathe four jaw. Very nice fit. Then went about hacking off the outside curve in the mill. When finished the hole for bearings was definitely not round. So I tried again by first annealing the 1018 stock. I'm not sure which reference I used but the temperatures can be found here.

For annealing just heat up to temperature, leave at temp for an hour or so (guidelines give time at temp versus thickness of part, but it's an hour or two). Then turn off the oven and let cool overnight. (Avoid the temptation to open the door and look inside.) For 1018 temperature is 870-910 deg C. For stress relieving it is 500-700 deg C, but let cool in still air rather than overnight in the furnace. I don't know the colors to go for if using a torch for heating.

On the second try I cut the outer curve first and made a jig to hold it in the lathe for the hole. So I'm not sure how much the annealing helped, but the part came out well.

For a crank it may be best to cut the basic shape leaving dimensions a good bit oversized. Then stress relieve, followed by finish cuts.

Thanks.

[RReid]

Chuck, Chris - Thank you!

Did you do any stress relieving on your cold rolled steel?

Hi Kim. No, I didn't, at least not yet. I had meant to order a bar of hot-rolled, but through an act of carelessness ordered cold-rolled instead. Now that I've got it I'm using it as a "learning opportunity". It's a smallish part, not expensive, not terribly time intensive, so I think I'll plunge ahead and find out for myself what happens.

As for stress relieving, I'm not sure I have any good way right now to get it up to the ~1100F needed, and hold it there for 1 hour or more. My coal forge is long gone, my oxy-acetylene torch is at my Son's in TX (anyway, hold it for an hour?)  , I don't even have a charcoal BBQ anymore! I'm sure I could find a way, but I'm not going to sweat it now. If I make a pretzel I'll hang it on the wall and order the right stuff, or build the fabbed version, for which I have stock on hand already.

John and Hugh - Thank you for the comments and suggestions. I will certainly do what I can as far as trying to leave myself some extra material to remove post-warping. 

[Kim]

Kim, whats it take to stress relieve crs? I've done it for brass, don't know the process for cold rolled.

Hugh gave a good answer on this, but I'll tell you how I do it.  My method isn't nearly as technical or accurate.  I just use my torch (Oxy-Acetylene) to heat up the part till it's nice and red hot.  I play the torch up and down it, trying to keep it evenly red for a while (feels like 20 minutes, is probably more like 5-10) then I just let it sit on the fire bricks and cool.   I'm sure an oven would be much better and let you more accurately deal with soak time.  But this has worked pretty well for me.  I've had good luck with it anyway.

Maybe someday I'll get an oven!  Or make one like Hugh!

Kim

[crueby]

Thanks guys for the info on stress relieving.


Ron, you mentioned you had intended to buy hot-rolled instead. Does the hot-rolled version not need stress relieving like cold-rolled does?

[RReid]

Ron, you mentioned you had intended to buy hot-rolled instead. Does the hot-rolled version not need stress relieving like cold-rolled does?

That's right. the cold rolling process itself introduces most of the stress we're talking about needing to relieve. On the other hand, in hot-rolling the temperatures involved are high enough that (1) the material is in a more malleable state during forming, and (2) the stress-relieving step is accomplished by default. I think there are still some stresses locked in, but far less and so less of an issue. But you are left with that ugly and often troublesome surface scale.

There is also something called stress-free steel available, but apparently only in round bar form. Brian Rupnow has discussed using it to good effect for crankshafts, but it does require extra work to produce a flat bar.

[Hugh Currin]

There is also something called stress-free steel available, but apparently only in round bar form. Brian Rupnow has discussed using it to good effect for crankshafts, but it does require extra work to produce a flat bar.

I agree with hot rolled having far less residual stresses than low carbon cold rolled steel like1018. Hot rolled shouldn't tweek as much.

Did you mean "stressproof" steel? I haven't used it but it looks like it would be a good choice.

You might be OK cutting the crank leaving a good margin. Then once you have it all to rough shape take it to finished size. Most of the warp will occur during the first large cuts.

It'll be interesting.

Thanks.

[crueby]

Ah! That explains a lot - had gotten some hot-rolled a couple times, stopped getting it after having problems with the scale, never used enough to realize it didn't have the stress issues.

I've used the 1144 Stressproof a number of times, on both crankshafts and engine blocks - works very well. Its a little harder to machine than the 303 stainless, and it is NOT stainless so it can rust, but fine for non-wet applications. As you say, only available in round bar.

[RReid]

Right, stressproof, not stress-free (as if such a thing could exist).

Got the crankpin turned before lunch. Not much I can do about leaving material there, since the centers for turning it will be removed preparatory to turning the main shafts. So it's finished to final size. It'll be interesting to see what happens after I hack off the surplus material from both ends and start turning the mains.

[RReid]

As mentioned above, I turned the crankpin this morning. I worked it down slowly, alternating between using left and right turning tools to face the web cheeks, and a parting tool to turn the OD.


 

So far, so good.


I cut away most of the waste material outside the main shafts with my trusty ankle grinder and a hack saw. Then remounted it on the other set of centers. The block of aluminum is a light tap fit between the cheeks, and is secured with a bit of Loctite. Once the turning is done I'll remove it.


My plan is to work this down slow and easy also. Once I knock the corners of the first end, I will turn it around and do the same to the other end, plus take it down a little farther on the OD. I'll continue swapping ends like that until I get to the final size. Hopefully this will help mitigate the warping tendency.

This is where I left off for the day.

[crueby]

Great progress, watching along...