Making Molds On a POS Manual Mini Mill

It's called a "spring tool" or "gooseneck tool".
OX Tool made a video on this. His explanation is exactly right. If you make a holder that looks like his version, and it doesn't eliminate chatter, make the round hole in the top larger and try again.
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Turns out that spring tools were common in the 1890s, for use on shapers and planers. The main problem then being solved is cutting-edge damage due to hard inclusions in the steel or cast iron of the day - the cutting tool deflected instead of being damaged, and so simply resumed cutting, not needing to be reground.
Later, spring tools were found to be useful for threading and parting on the floppy lathes of that day, reducing or eliminating chatter.
The original round gooseneck pattern allowed lateral deflection, useful for evading hard inclusions, but the sideways motion yielded drunken threads and parting problems. There were various solutions, but the simplest solution is simply to make the spring neck rectangular, so the holder is stiffer laterally than radially (parallel to the long dimension of the holder).
There are very many patents. Here are some. To get copies, enter into Google Advanced Patents, proceeding the number by "US" and dropping the commas and semicolons.
US Pats 1,146,546; 2,242,033
Joe Gwinn
Reply to
Joe Gwinn
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If you do not thread often with the compound you may find replacing it with a solid block of steel may help with parting.
Another is placing a jack under the parting tool.
Probably number one first thing to try if parting is a problem is snugging up all your gibbs so they "just" move easily when properly lubricated.
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Parting isn't a problem, especially after I surface-ground the worn bottom of the compound slide so I could adjust the gibs closer. I mentioned it as an example of an operation that chatters if my lathe's speed is too high.
Reply to
Jim Wilkins
Maybe, but I can do some amazingly aggressive fast parting if the tool is up to it. I think that a limp loose machine, bad grind, and poor tool position are more likely to chatter than being a little off on speed. I'm not saying speed can't be a factor. Just that there are things one can do to increase the range at which it works ok before doing a motor swap.
In your case you made your machine less limp and sloppy.
... and of course its all just my opinion. I'm not a master machine builder.
Reply to
Bob La Londe
When I was first taught to part on an old Southbend in metal shop class I was taught to use a low speed and that worked fine but the tutor didn't explain why. Later in a machining class for students potentially intending to do it for a living and taught by a time served and still practising machinist I asked about what surface speed to use and he said it was a cutting operation like any other so to use the recommend surface speed if the lathe was up to it and the one I was using certainly was, no problems parting at the same speed as turning. These days almost all my parting is done with as insert parting blade on my Harrison M300 which is a 13x40 and I don't bother to slow it down, on a less rigid machine I would slow it down most likely.
Reply to
David Billington
Maybe, but I can do some amazingly aggressive fast parting if the tool is up to it. I think that a limp loose machine, bad grind, and poor tool position are more likely to chatter than being a little off on speed. I'm not saying speed can't be a factor. Just that there are things one can do to increase the range at which it works ok before doing a motor swap.
In your case you made your machine less limp and sloppy.
... and of course its all just my opinion. I'm not a master machine builder.
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I bought the "Machine Tool Reconditioning" book, a surface plate, 0.0001" indicator, straight edge and cylinder square. So far I've risked improving/damaging only the ways of the AA lathe and the lower surface of the SB's compound. Maybe some day I'll take on the others. I've learned their limitations and design around them.
The book was valuable to fit the warped heatsink of a thermoelectric module controller to a spreader plate, on the space comm laser project. The heatsink wasn't thick enough to flycut flat. I figured that quietly fixing the problem myself was better than telling the project manager he chose and bought deficient equipment, after he had proudly told me what a good deal he got on it.
My shop let me assume all control over the fabrication of most projects, so that I was only rarely caught between an electrical and a mechanical engineer who didn't understand each other's field.
Reply to
Jim Wilkins

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