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Thin cuts

gleber

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I am mechanically inclined, but not a machinist. I've always wondered how very thin cuts are made. For example, many tall case suspension springs are mounted in brass blocks at the top of the pendulum rod. How do you cut such a paper thin looking cut in the block? It may be obvious, but not to me.

Thanks,
Tom
 

novicetimekeeper

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how did they do back cocks in the 17th century? I'm not sure the pole lathes would have run a slitting saw.
 

Jerry Kieffer

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I am mechanically inclined, but not a machinist. I've always wondered how very thin cuts are made. For example, many tall case suspension springs are mounted in brass blocks at the top of the pendulum rod. How do you cut such a paper thin looking cut in the block? It may be obvious, but not to me.

Thanks,
Tom
Tom
Actually its a great question.

Slitting saws work great in a Lathe or Milling machine, but are not practical for deep paper thin slots where professional appearance is desired.

I know what you mean when you say paper thin slots, however actual paper thin slots (.002"-.003" / .05mm - .075mm) are sometimes required. In Model Engineering I have had to go down
to .001" or .025 mm.
Even had saw blades existed this thickness, they would not have been stable enough to make a straight deep cut. When using thin blades, they need to be stabilized per the first attached photo.
In this case, only the blade required for use is exposed by the holder. The blade is .005" or .125mm thick and is used to slot screws.

For long thin slots, the slots are the first thing that I cut. I first select a slitting saw blade wide enough and stable enough to make the required slit in a flawless straight line regardless of desired thickness.. A very basic illustration example can be seen in the second photo. Once the slit has been cut in a unshaped work piece, a piece of shim stock of the desired thickness is placed in the slot. At this point, the slot is pressed together with a machine vise or press per third photo. When the shim stock is removed, you will now have your required slot that can be
as thin as .0005" or as thin as shim stock can be purchased.

From this point I then machine the rest of the work piece as required in either the lathe as shown or the milling machine.

Jerry Kieffer







DSCN2097.jpg fullsizeoutput_736.jpeg fullsizeoutput_737.jpeg fullsizeoutput_738.jpeg
 
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novicetimekeeper

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Tom
Actually its a great question.

Slitting saws work great in a Lathe or Milling machine, but are not practical for deep paper thin slots where professional appearance is desired.

I know what you mean when you say paper thin slots, however actual paper thin slots (.002"-.003" / .05mm - .075mm) are sometimes required. In Model Engineering I have had to go down
to .001" or .025 mm.
Even had saw blades existed this thickness, they would not have been stable enough to make a straight deep cut. When using thin blades, they need to be stabilized per the first attached photo.
In this case, only the blade required for use is exposed by the holder. The blade is .005" or .125mm thick and is used to slot screws.

For long thin slots, the slots are the first thing that I cut. I first select a slitting saw blade wide enough and stable enough to make the required slit in a flawless straight line regardless of desired thickness.. A very basic illustration example can be seen in the second photo. Once the slit has been cut in a unshaped work piece, a piece of shim stock of the desired thickness is placed in the slot. At this point, the slot is pressed together with a machine vise or press per third photo. When the shim stock is removed, you will now have your required slot that can be
as thin as .0005" or as thin as shim stock can be purchased.

From this point I then machine the rest of the work piece as required in either the lathe as shown or the milling machine.

Jerry Kieffer







View attachment 621561 View attachment 621562 View attachment 621563 View attachment 621565
That could be a similar approach in the 17th century, they could have cut a wider slot, closed it up onto a piece of hammered iron then finished the part.
 

Jerry Kieffer

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Hessel & Tom

Thank you for the comments.

However, Tom brings up an interesting point.

As we all know, that back in the 17th century, most work was the result of the cottage industry where one person made the same part everyday over a life time. As such, you become quite good at what you are doing after 10 years or so.
Again however, there were some truly creative masters who achieved so some highly efficient and effective methods. Unfortunately, these masters took their methods to the grave to protect their livelihood.

We know this because the commonly known less efficient methods of the time, generally published in repair publications are not practical to produce the workmanship and sometimes the results found in many surviving work examples. While in todays world we can purchase million dollar machines to produce anything, Its not very practical for most.
We are left with being as creative as we can.

Jerry Kieffer
 
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gleber

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Thanks all for the great and very informative feedback.

And, yes Jerry, I am keenly interested in how they did this kind of work in the 17-19th centuries without such convenient access to the types of precision tools we have nowadays. They must have truly been craftsmen. I would love to be able to go watch one of them for a day, or at least see highlights since I imagine a lot of their work was painstakingly slow and spanned weeks if not months on some parts.

Tom
 
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