24 votes
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Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

The photo you have is not for the standard jigsaw blade. Standard blades teeth point upward and cut upward for the obvious reasons: less wobble, more control, center of force near the handle. This is ...
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16 votes

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

If you think what happens as each tooth cuts material then the blade is put into tension as it cuts, this means that the blade is likely to stay straight, but any unevenness between the teeth side to ...
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12 votes
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How to work on big CAD project in team?

It's a massively important question. Short response: apply the concept of encapsulation. Divide into subsystems During development, assign design-ownership (distinct from project manager role, ...
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  • 1,367
11 votes

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

To enlarge slightly upon Solar Mike's response, a jigsaw that cuts on the upstroke tends to yank the saw shoe down into firm contact with the workpiece. This guarantees that the cut angle will match ...
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9 votes

How can the vendor be approved/disapproved based on validation test data?

TL;DR: It depends, but probably not You might argue that "all 15 samples are within spec, so the supplier should be approved". Not so fast: depending on the parameters of your full production run, ...
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9 votes
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Line balancing - How far do companies go?

I can answer for the Chemicals Sector I'm familiar with: Overall line balancing is quite poor between processing operations. 10% difference would be surprisingly good. 50% difference isn't uncommon. ...
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8 votes
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Material selection for weight scale

Which of the following materials will be most suitable to manufacture the disc for the stiffest/strongest possible part. It seems that you need a material that will transform a non-uniform load into ...
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  • 3,587
8 votes

Why are mass-produced metal parts machined by rotating the part against a stationary tool?

You can be sure the resulting surface is round. If you used a router and rotated the bit around the piece then you would get inaccuracies due to the movement being harder to control. Using a lathe-...
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7 votes
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How do the dimensions of a ductile iron casting change as it cools?

Ductile iron is actually likely to expand during the casting process, as shown in the table found on the Casting Wikipeda page, which is in part cited from this casting text by Stefanescu. However, as ...
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7 votes
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Does every engineering design needs to have a complete theoretical backing or may experimental data suffice?

Are any designs based solely on data from trial and error used in critical mainstream engineering? Usually not. And the reason is that trial and error is expensive and time consuming. As engineers, ...
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  • 2,511
7 votes
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What is the name for a removable sewn bag stitch?

It is called "chain stitch" and was the stitch used in the first designs of sewing machines, because it is easy to produce mechanically. The fact that it can be pulled out unless the end of the string ...
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6 votes
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Measuring longer distances with high accuracy

To get that sort of accuracy over that scale is not trivial and probably won't be cheap. For smaller size up to a few meters a portable CMM would be an option (here's an example). These have accuracy ...
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  • 1,025
6 votes

Work hardening?

Work hardening is done to increase the strength of the material, not the stiffness. You change the yield stress to be closer to the failure stress of the material. If I understand it correctly it ...
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  • 1,002
6 votes
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Purpose and name of fine pitch marks on a cast metal part

these are part-tracking marks. they indicate which cavity in the mold the part was cast from, in which mold set, in what molding machine, in what year, month, day and shift. this way, a part that ...
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5 votes

How do I cut a crack into a polymer/plastic?

Since you used some specific words in your question, I will respond a certain way. Cracks are generated by mechanical action, and cannot be machined in. They may, in certain brittle materials, be a ...
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  • 241
5 votes
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Is it feasible to forge multiple, smaller parts in the same forging operation?

I've previously worked in the forging industry and you can certainly forge multiple parts in a single stroke of a large press but there are problems. The obvious ones are the size of the available ...
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  • 294
5 votes

Measuring longer distances with high accuracy

Even the best metal tape measure is susceptible to significant thermal expansion over large distances. Try a laser measurement device ('electronic tape measure') instead: http://www.engineersupply....
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5 votes
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What's this mystery symbol on a manufactured machine?

My best guess after a couple minutes of Googling is that this is a CMC certification which stands for ...
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5 votes
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How to obtain an homogeneous mixture of 10 000 tons of minerals, each one in a different pile?

This happens all the time in the minerals industry where people need to blend material from different stockpiles to produce a supposedly uniform product for a processing plant. Depending on the size ...
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  • 9,382
5 votes

Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

To expand on Solar Mike's answer and to help explain part of niels nielsen's answer, the saw blade is normally designed to essentially squeeze the material between the teeth and the shoe. This ...
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4 votes

How do I manufacture a fillet?

On a mass manufactured part, one solution is to cast the piece and shape the die (with an inside fillet) to form an outside fillet. Of course, if you want your casting to have an inside fillet, you'll ...
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  • 4,501
4 votes

Measuring longer distances with high accuracy

For high accuracy over long distances it's typical to use general surveying techniques. You use a total station (like this) which will get you 1.5mm accuracy in a single shot. They're no laser tape ...
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4 votes
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Why can't red flint glass be produced?

It seems likely that costs associated with the material prevents economical production of red glass. Rather than a matter of possibility, it may be a matter of viability. Without knowing more about ...
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  • 3,971
4 votes

Can graphene really be made in a modest lab at home?

The short answer is, anyone can make graphene, but knowing you did or doing anything with it requires a bit more equipment. I work with people who work with graphene. This is not the only way to ...
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  • 126
4 votes
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Real world applications where one would use a force function in PLC programming?

A "force" in a PLC is the act of forcing a memory bit on or off from the PLC programming software. It is used exclusively for testing. Forcing a bit on or off over-rides all other PLC logic. You can ...
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  • 7,444
4 votes

What are the challenges in building a 'sports car' frame and body?

The main issue is practicality. The vast majority of car buyers have certain expectations in terms of comfort, features and interior space which are pretty much essential in their choice of vehicle. ...
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4 votes

Is CNC milling on metals always followed by heat treatment?

No. CNC machining is done in a huge variety of industries and applications, many of which do not benefit from heat treatment. CNC machining - and metal cutting in general - is an incredibly broad ...
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  • 41
4 votes
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What is the manufacturing method used to make aluminium C channel

Aluminum sections are extruded from billets heated to 800-925F under high pressure and then pushed through a die. During the entire process temperature is carefully controlled, because depending on ...
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  • 20.9k
4 votes
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What does "bedding-in" mean in casting technology?

According to p.33 of this presentation 'bedding in' is a process of packing the molding sand by ramming the sand around and under the pattern until the sand is tightly packed and even with the parting ...
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  • 248
4 votes
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Why laser cutting speed suddenly decrease when cutting sheets from 1 to 3mm thickness then stabilize?

To see why this graph can only have a hyperbolic shape, it can help to take a look at the energy balance of the laser cutting process with absorbed laser power $P_A$. $$P_A = \underbrace{vtw}_{V_M}\...
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