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3:42 AM
July 9, 2011
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Not sure this has been mentioned before, but I always have a ball of Plasticine in the shop handy, I learnt this trick working in a large Toolroom, we made our own Punches and Dies, first on the lathe leaving them oversize, we then heat treated them , from there to the cylindrical grinder we finished the diameters to size, then we had to grind the overall length, we did that by clamping in a vee block, this is where the Plasticine comes in to play, a lot of punches were only .030 dia or even in some cases smaller, without the Plasticine wrapped around the punch as soon as the grinding wheel (46 grit) touched the tip of the punch that was it the punch was scrap, with the Plasticine around the punch we could lower the grinding wheel say .500" and feed into the side of the wheel and it would never snap, so when you are boring a hole and it starts to chatter wrap a big chunk of Plasticine it cant do any harm even if it touches the job you are machining, as an example, I had a friend in Edmonton who was having trouble machining large Aluminium castings (for a Harley project) on his lathe the whole thing was screaming like crazy, terrible finish, he place Plasticine around the chuck the back of the casting and around the cutter, next time I saw him he was ecstatic, it does work, and its cheap,
7:44 AM
April 19, 2011
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Where do you get it ?? Is Plasticine a trade name or a generic name for the product ?? I've heard of it before but don't know where to get it.
Also is it a very expensive product or relatively cheap ?? 
Do you have any links to suppliers ??
~Chris
10:42 AM
July 9, 2011
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Sorry Tenn,
Plasticine, a brand of modelling clay, is a putty-like modelling material made from calcium salts, petroleum jelly and aliphatic acids. The name is a registered trademark of Flair Leisure Products plc. Plasticine is used extensively for children's play, but also as a modelling medium for more formal or permanent structures.
In England as a young boy we called it Plasticine, in North America I guess its Modeling Clay, its not expensive, and I would think any toy or craft store might stock it,
……..Edmund……..
11:51 AM
October 10, 2010
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holmes_ca,
I'm having a senior moment today. I'm not understanding how the plasticine is being used or how it helped in the situations you described.
12:52 PM
October 11, 2010
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I'm having the same difficulty. I guess that if a long rod is extending out of a lathe spindle or cylindrical grinder, having the rod covered in a thick layer of plasticine will absorb the chatter. I'm probably not visioning this correctly but the plasticine would interfere with coolant, gum up the grinding wheel and if the work is rotated rapidly then centrifugal force will dislodge and hurl it across the room. It makes more sense to use the tail stock center, as well as the steady and fallow rest.
1:05 PM
July 9, 2011
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Titaniumboy,
sorry about my ramblings, I try to explain things and keep it as short as I can, at the same time giving as much detail as I can,
Example: your having a chatter problem for some reason or other, the chatter is caused by a resonance that takes place because of the feed or speed or flimsy tooling, in some cases you can rectify the chatter by reducing speed or feed or by using a sturdier cutting tool holder, or shape of toolbit, if these changes don't work try plasticine and mold it around the project being machined and the holder of the cutting tool, the Plasticine absorbs the resonance, I cannot vouch this will solve the problem in every case, but it has worked for me,
Imagine you have a .030 dia pin sticking up say 1 inch above the top surface of a vee block on a mag chuck of a surface grinder with no support, and you need to grind off the top .005 thou, as soon as the wheel touches the pin it will snap off (break off) and that's the end of that punch, if you hand mold a piece of Plasticine around the top face of the vee block and pin when the wheel touches it will not break off and you can grind any amount off the pin, and the same applies when working on any machine if chatter is taking place,
I would just like to add I cannot guarantee this will always work,
Hope that gives you a better explanation,
………….Edmund……….
7:40 PM
April 19, 2011
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Now we're talking I can understand pictures
.
Thanks for the added info Edmund that helps a lot.
~Chris
7:46 PM
July 9, 2011
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Alexander m,
you make an interesting point, Plasticine flying across the room, never thought of that, but this particular subject tips and tricks is not in the machinery bible, it comes with experience, if you Persevere you will get it eventually,
I really don't know what else I can add to my previous posts to reveal the mystery,
………Edmund…….
8:14 PM
July 23, 2010
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Great idea, Edmund. From an engineering standpoint, the plasticine (that's what we always called it when I grew up in Ontario; it's like a modeling clay that doesn't harden, kind of like Play-Dough, but closer to clay in texture) adds a ton of damping to the piece being machined, allowing it to absorb and dissipate vibrational energy across a wide band of frequencies. Very cool indeed.
-Chris
9:17 PM
October 11, 2010
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It is most certainly a ingenious idea now that we understand how this would work. This reminds me of a similar method for tool holding by Tormach, the super soft jaws. I have never used this system so I can't say how effective it is, the video makes it look quite amazing but I fear that the substance is sightly gummy even when hard so it may twist or bend when cutting forces are applied. This substance is quite expensive at $100 for the kit and $14 for 10 oz. A possible alternative would be to make a lead holding fixture. What I have in mind is to take an aluminum block and mill out a rectangular void to use as a mold, then fill it with molten lead and when it's slightly cooled a steel part can be pressed in. When it has fully cooled it can be mounted in a milling vice or a round bar of lead can be used in the lathe. The beauty of this is that it can hold odd shapes with the part half buried in lead and there is no fear of damaging the vice and you can also freely cut, mill or drill into the lead. There are a number of places where lead ingots can be found aside form online, gun stores have them for people who cast bullets and also recycling plants how accept car batteries will sell lead, expect it to cost 50¢ per lb. or less.
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