Community Build 1 SOSE

Well, I "started" with a carbide facing tool running between 300 and 500 rpm. I was making the cut dry. I take very small cuts/steps as I am still getting a feel for what I'm doing. Hit a lot of chatter that ended up shattering my carbide bit. :eek: I replaced it with a HHS bit and got the job completed (the facing at least). My setup is pretty conventional, a '39 belt-driven SB 11" lathe with a QCTP and a 4-jaw chuck. I have done facing with tool steel and some softer steels and haven't had any problems. I am sure I'm missing some nuance to this. :p

Thanks,

-Ron
 
303 is about the easiest stainless to turn. Without seeing your setup, it's hard to point to something that may have contributed to the problems you had. How much was sticking out of the chuck? That's the first thing that popped into my mind. Big factor in facing a bar. If you can't "swallow" it, you must use a steady rest. And have it set right. Chatter is usually the result of things not being tight, or the tool nose radius being too large. Or like I mentioned, too much protruding from chuck jaws. Are your jaws true and unsprung?
 
Sorry about not having a pic of my setup. I get on the forum from my home but my "shop" is in an extra garage at my office building so I can't just step over there. From the list of possible "wrong things" too much hanging out the chuck (probably 3.5" - 4") might be a contributor. Tool radius, probably not an issue as the tool(s) both had a very small radius. Now, "Are your jaws true and unsprung?", I believe the jaw is true but I can double check as to the "unsprung" I am sorry to say my ignorance is showing itself again. :eek: What exactly does that mean and how do I check for it?

Thanks Tony,

-Ron
 
It's not uncommon for someone to chuck up a piece of material using only the tips of the jaws, not the full length of them. If the chuck is tightened very much (overtightened by Hercules), you can see that the back of the jaws, where there is no material to grab, would tend to close up more than the ends, or tips, where the material is. What happens is that the jaws are no longer parallel, and this is because the face of the chuck body is no longer flat, and the slots that the master jaws ride in are not perpendicular to the axis of the machine. Then, after all that, when you toss in a piece of material that does reach all the way to the back of the jaws, the back tightens up but the front never touches the material, giving you less grip area. Same effect as hanging the stock out too far. You're holding the material too far away from where you are cutting. Couple that with too much hanging out from a normal grip, and it just aggravates the situation.

I've heard of people taking a short slug and putting it in the back of the jaws and overtightening the chuck on purpose to try to reverse this damage, but I don't know that it works. Both of these actions are hard on the scroll and pinions.
 
Thanks for the explanation Tony. I may make a lot of ignorant moves but fortunately my instinct was to use the entire depth/length of the jaw so I am pretty sure that wasn't part of the issue. Along the same topic, given that a lot depends on the diameter of the piece and the material it's made of, approximately how far out of the chuck would a piece be before you drill it and use a live center?

Sorry about the "learning" here in the build thread guys but it's kind of, in a way, sort of related. :p :D

-Ron
 
My rule of thumb that has served me well for years is hangout not over 2x diameter.
On the sprung jaws bit, I wasn't suggesting that you did the springing, but prior users may have damaged the chuck. It's been known to happen. Even though you thereafter chuck using the entire length of the jaw, the front isn't gripping as much as you think in that case.
 
Tony Wells said:
My rule of thumb that has served me well for years is hangout not over 2x diameter.
On the sprung jaws bit, I wasn't suggesting that you did the springing, but prior users may have damaged the chuck. It's been known to happen. Even though you thereafter chuck using the entire length of the jaw, the front isn't gripping as much as you think in that case.
Click to expand...

I will pay a little more attention to the jaws next time I'm working on the lathe to try and see if there was/is an issue with it. Thanks Tony

B34VD said:
If it will slide thru your chuck & into the spindle, I like to push the stock all the way in till just a stub sticks out of the jaws and center drill it. Then pull it out the length you need to work with and run your center up to it. Also it might be a good time to face the one side. That's all I can add right now Scrapmetal, I can't remember what part you were making.
Click to expand...

I'm making the crank (some how appropriate? :p) and the stock won't go into the spindle. :( On my SB I only have 7/8" through spindle that kind of limits me in how I deal with lengthy stock. Thanks for the tips.

-Ron
 
Don't apologize for learning on this project. That was the whole purpose in the first place. It encourages us all to stretch our skills, including how we explain what we're doing so that others can understand.

I found that making 10 identical parts made me revise my methods several times over. Things like the order of steps, do I do one step 10 times or do two or three steps on each piece while it's in the chuck? A good exercise.
 
Oh, and let me apologize if I am intruding. I am not able to share in the build itself, but if I can help with tips and how-to's, let me know!
 
As Hawkeye has said, no need to apologise for asking questions. In my eyes, its all relative to the build and there's no need to have a thread for each question that may pop up along the journey.

Tony, just because you're not building, I don't think you should be completely removed from discussions, especially when someone asks for help.
Your input and handling of questions and tips is highly valued.

Jason.

tick tock, tick tock,
home in 1 week so i can carry on with the pistons
 
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