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long slender machining


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  #1  
Old 08-24-2005, 09:53:46 AM
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Question long slender machining

Trying to machine a rear wheel spoke with follow rest and can't get away from chatter. Diameter of material is 1" and trying to machine to .750. What spindle speed should i use with the rest?
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  #2  
Old 08-24-2005, 10:53:17 AM
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Craig A Craig A is offline
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Default Re: long slender machining

When that happens sometimes it's as simple as holding a gloved hand on the piece to act as a dampener.
We have even resorted to using wood blocks, a piece of rubber belting and a vee block to gently support a shaft to prevent chatter which has the same dampening effect.
The cutting tool angle and rake can affect chatter also but a slower speed will usually reduce chatter.
See what happens.....
Craig
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  #3  
Old 08-25-2005, 08:31:51 PM
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Talking Re: long slender machining

thanks craig i'll give it a try
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  #4  
Old 08-25-2005, 08:45:29 PM
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Default Re: long slender machining

I would add how tight are you gibs? A loose tool carriage will cause it big time. Also, carbide chatters more than high speed steel cutters, and larger radi on the tool causes more chatter. Sometimes moving the cutter slightly above center also helps. Fred
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Old 08-26-2005, 01:33:11 PM
Steve Adams Steve Adams is offline
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Default Re: long slender machining

Craig!!! you of all people should know that you NEVER wear gloves around rotating equipment! Not lathes, not mills, not drills, not grinders, Nothing! BAD, BAD, BAD! A friend of mine who has another shop across town had to deal with the loss of one of his guys who was KILLED on one of their lathes because he was wearing gloves. There was a burr on the part that caught his glove, pulled his arm in that came off at the shoulder, and by that time it had smashed his head off of the spinning chuck, which proceeded to spay blood and brains up the wall behind the machine. They found what was left of the body in the chip tray. It was so bad the fire department had to hose down the shop. I apologize for the graphic description, but I can't emphasize enough the gravity of the situation. This was on a 20X60 TOS. When I was still working for someone else, I had my back to a guy that was working on a 20X60 lathe and I heard the machine bog a bit and then switch off. when I turned around, Bob was standing there with no shirt on. it was wrapped around the part he was working on and he had caught his sleeve.This guy was big and luckily had the strength to pull back until the shirt ripped right off him. As I stood there asking if he was okay, the welts started coming out and after 5 minutes he looked like he had got 50 lashes. I was shaking thinking how close a call it was. NO GLOVES!!!!!!!!! if you have to do something like that to reduce chatter, use a SHORT piece of emery cloth.
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  #6  
Old 08-26-2005, 04:11:21 PM
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Default Re: long slender machining

AMEN! Steve.
I know most people (including me) are guilty of it at one time or another, but you should NEVER touch a moving part! No gloves, rings, watches, long sleeves.
To reduce chatter support the part the best you can, slow the RPM and increase the feedrate. You might try grinding your tool bit with a slight negative rake on top. This helps to keep the part from trying to climb up on it.
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  #7  
Old 08-27-2005, 12:02:59 AM
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Default Re: long slender machining

I ALWAYS wear leather palmed gloves when working around machinery and always will. There's something about HOT parts on my hands that I don't like.
One doesn't, indiscriminately, just GRAB a rotating part without seeing it IS burr free and, besides, I said HOLD a gloved hand on the piece, not grab it.
Loose fitting clothes are another story. Even my Dad got his shirt wrapped up in a lead screw because he didn't have it tucked in.
No long sleeves? I don't care WHAT you are doing.....you have to think and use your head.
People die in the shower too and I can only assume they aren't wearing anything.
Be that as it may, unfortunately, accidents do happen.
As far as dangerous equipment goes, in my opinion, a press in inexperienced hands has 'em all beat.
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Old 08-27-2005, 09:04:33 AM
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Thumbs up Re: long slender machining

Thanks for the info guys
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  #9  
Old 08-27-2005, 09:43:00 AM
Steve Adams Steve Adams is offline
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Default Re: long slender machining

Experience combined with complacency in an industrial enviroment can be just as dangerous as inexperience.
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Old 08-31-2005, 01:47:06 PM
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Default Re: long slender machining

The advice I have always been given by my elders with machining experince is this: Chatter, decrease speed and increase feed. I will also add that the tool must be on center with the part you are turning. If you are using carbide check the cutting edge with a loop to make sure that it hasn't cracked away. I am one who thinks using any gloves on ones hands next to a spinning shaft is asking for an amputation.

Forrest A
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Old 04-26-2015, 10:26:45 PM
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Default Re: long slender machining

Run the cutting tool slightly above center .
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  #12  
Old 04-26-2015, 10:36:00 PM
Ray Freeman Ray Freeman is offline
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Default Re: long slender machining

The cutting tool shape will make a huge difference. On jobs like that I'll use high speed steel thats sharpened to use the least horepower.Deep slicing action chip breaker and sharp.
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Old 04-27-2015, 09:22:36 AM
gvasale gvasale is offline
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Default Re: long slender machining

No one has asked about the lathe. Some lathes don't do a great job with certain follow rests and tool holders, aside from the speed & feed requirements.

---------- Post added at 09:22 AM ---------- Previous post was at 09:20 AM ----------

And, sorry, but would it not have been easier to use 3/4 stock in the first place?
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Old 04-28-2015, 11:17:17 AM
steve mallette steve mallette is offline
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Default Re: long slender machining

Mr. Case : I will try to attach a page from an old German book i have, titled technisches Hilfsbuch circa 1917. It shows a means of machining a slender shaft. I don't think I would go to the effort as I always use Craig A's method .. YMMV
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Old 04-29-2015, 12:06:42 AM
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Tanner Remillard Tanner Remillard is offline
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Default Re: long slender machining

Not to mention this thread is 10 years old...... But for anyone new reading this, when I experience chatter I first do what was already mentioned, slow down the RPM or increase the feed rate, or both. If that doesn't do it, a smaller radius tool bit helps a lot. The bigger the tool nose radius the more chatter you are likely to have unless you have a nice rigid setup. I have experienced that sometimes if you already have chatter marks in the shaft, that you have to get under the chatter marks for it to take the chatter away, or the shaft can simply "follow" the chatter marks that are already there and keep chattering. In other words, if you take too light of a cut, the pre existing chatter marks in the shaft will pretty much bounce off of the tool causing it to chatter more. Sometimes you have to take a deeper cut to get under it with a sharp tool nose radius and lower RPM. It can take a lot of playing around but usually the sharper tool nose helps a lot and solves most situations. If I have to turn down a long section of smaller diameter shaft I will usually use a carbide threading bit because of the small tool nose radius, and I get good results. Use a steady rest whenever possible, it will also help tremendously.

Last edited by Tanner Remillard; 04-29-2015 at 12:18:56 AM.
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  #16  
Old 04-29-2015, 09:38:35 PM
John C Walker John C Walker is offline
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Default Re: long slender machining

As far as the glove thing goes, an old fellow told me once that the only thing you can efficiently do with gloves on is piss your pants
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Old 07-25-2015, 01:17:04 PM
Bob Phillips Bob Phillips is offline
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Default Re: long slender machining

Have enough boring bar extended out the right of the tool holder to chuck a chuck on the extended boring bar as a counter weight...
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Old 07-25-2015, 02:44:18 PM
JonH JonH is offline
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Default Re: long slender machining

Rather than cutting the entire length down to your 0.75 diameter, start at the tailstock end and machine about an inch or so to diameter. Keep working toward the headstock an inch or so at a time until the entire shaft is to diameter. I machined 2 brass pins like this to 0.1" diameter 0.3" at a time for a length of about 2". Never had any problem with deflection or chatter although on a part like that, I would not expect chatter anyway. Hopefully after 10 years, you've got your parts made. Just thought I would throw this method out there for anyone else faced with cutting long, skinny parts.

Jon
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