# Tool Question - obsolete Black and Decker Rotary Hobby Shop



## TimR (May 22, 2011)

The local thrift store has a Black and Decker Rotary Hobby Shop tool for $12 and they're open tomorrow.

I'm tempted. This thing cost $80 when it came out in 1982, with inflation that's 192.77 in today's dollars.

But it's a 1982 tool with no accessories. It's just a motor with flexible shaft and collet. I have bits left from a Dremel that burned up long ago, not sure if any would fit. Top speed is 1900 RPM. It runs but is obviously unrepairable if anything goes wrong.

Anybody have an opinion on it?


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## Hrawk (Oct 25, 2010)

Be sure to see it running before outlaying any cash. No way to know what condition the brushes are in.

As for the tools, most of them are a pretty standard size and can be had cheap from online sources.

Kinda sounds like one of these which you can pick up at Harbour Freight for $35

http://www.harborfreight.com/bench-grinder-with-flex-shaft-43533.html


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## TimR (May 22, 2011)

Thanks. That bench grinder looks like a better value, although it's pretty big for my basement room.

Here's a shot of the B&D tool:

http://books.google.com/books?id=f9kDAAAAMBAJ&pg=PA72&lpg=PA72&dq=black+and+decker+rotary+hobby+shop+9416&source=bl&ots=fr1uUnw-t6&sig=Y_Fo0lG6Vk0BuxA-iyOG_tyGo34&hl=en&sa=X&ei=GKWVUYnOBYbM9ATRr4HoCQ&ved=0CDsQ6AEwAw#v=onepage&q=black%20and%20decker%20rotary%20hobby%20shop%209416&f=false


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## quemado (May 10, 2013)

I think it depends on how serious that $12.00 is and how much you want it. If it works but you only get a month out of it, will you be satisfied you got your monies worth? If your needs are simple, and $12.00 is not that serious, you may be in luck. If not you threw away 1/3 the cost of the Harbor Freight model.


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## ash (Apr 23, 2013)

I'd leave it. 1900 rpm isn't much use. Motor technology has advanced a long way since 1982 and most cheapo Harbor Freight tools would be better.


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## bullseyeben! (Apr 24, 2011)

Not too sure what sort of rotary tool it is,but today I got a new dremmel rotary tool.. she spins @ 35,000 rpm...so im assuming it ain't a hand held tool? Cheers


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## bullseyeben! (Apr 24, 2011)

Ok just seen it, id save for the above mentioned


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## TimR (May 22, 2011)

bullseyeben! said:


> Not too sure what sort of rotary tool it is,but today I got a new dremmel rotary tool.. she spins @ 35,000 rpm...so im assuming it ain't a hand held tool? Cheers


In 1982 maybe it wasn't as easy to make a handheld motor like a Dremel. So you had a big motor and a flexible shaft. I suppose there are advantages, it's less tiring to hold just the cutting part rather than the whole motor, and sometimes you have clearance problems with the Dremel equivalents.

But you've brought up another issue, speed. How much do you need? (Is it like ammo, where the answer is "all you can carry and a little more?") What is the advantage of 35,000 RPM? My handheld coping saw probably moves about 60 strokes a minute, and my handheld sandpaper block maybe twice that. <grin>


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## LVO (Sep 25, 2011)

TimR said:


> Thanks. That bench grinder looks like a better value, although it's pretty big for my basement room.


The grinder is actually incredibly small. It's not a full size unit. 8 3/4 wide. it's pretty slick, IMO


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## Hrawk (Oct 25, 2010)

TimR said:


> But you've brought up another issue, speed. How much do you need? (Is it like ammo, where the answer is "all you can carry and a little more?") What is the advantage of 35,000 RPM? My handheld coping saw probably moves about 60 strokes a minute, and my handheld sandpaper block maybe twice that. <grin>


Now it comes down to cutting speeds. The smaller the bit you use, the higher the speed you need.

For each cutting tool material and material being 'machined' there are optimum speeds you should aim for.

Without going overboard here (I kinda want to but I wont), you need to match the speed of your machine to the tool you are using and the material you are machining. Dremels (rotary tools), drill press, routers, grinders, mills, lathes etc will always perform better when running at optimum speeds.

Speed is usually calculated in feet per minute or mm per minute. This is based on the cutting edge of the tool. This is calculated on the diameter of the tool.

For a large tool, say a sanding drum or a router bit on a dremel, you will want a slower speed otherwise you will create way too much heat, load on the machine, and end up burning the piece you are working on. If you are doing engraving or using really small carbide burrs or drill bits, you will want a much higher speed to reach optimum.

This is why these tools have such a large range of speeds available to them, to adjust to the tool size and the material you are working on.

A quick example. Milling aluminium. Aluminium machines best at a surface cutting speed of around 100-150 meters per minute. Now if I was using a tool with a 20mm diameter, I would want my speed at around 1500rpm. If I was using a 1mm tool I would want that speed at around 30,000 rpm to give roughly the same machining rate.


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## ash (Apr 23, 2013)

In addition to Hrawk's advice above, the fact that it's a hand-held device complicates things even further. Hand held rotary cutters need to be extra smooth with low and consistent cutting loads so that you can control them without skipping, or excessive vibration. Even if you had tool bits ideally suited to the speed in question, a 30,000rpm machine would be a lot easier to control and use for long periods than a 2,000rpm one.


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## Jeff Lazerface (May 7, 2013)

if its 10 bucks or less, pay no more than that.


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## Winnie (Nov 10, 2010)

Finally, something I know something about.
I make my living using variations of this type of tool.
Everything comes down to heat. Small bits do have a smaller feet per minute rate but they also have far less blade area. Less blade doing the work means extra load on those blades. Smaller blades also concentrate their energy into a very small area so they do cut very efficiently but again, the end result is heat and wear. Small bits/burs wear out much faster than larger blades. The only way you can step up the speed is to cool the bur while cutting. My burs spin at 500,00rpm but I also have an assistant and evacuation to handle the water and air needed to cool everything. The only time I would consider stepping up the rpm on a rotary tool is for touching up a really small area and then only with a very light touch.
The big difference between the 1982 unit you're talking about and one made today is magnets. The motors these days are smaller and much more powerful for their size.
Each rotary tool you use will have it's own feel and quirks. It's part of the game and it still beats a pocket knife.
I used Dremels and Dremel-tye tools from that era and they work fine. Likely the construction will be a good deal better that the Harbor Freight version.
Buy it and spend your extra savings on decent burs.


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## Winnie (Nov 10, 2010)

Correction: I said 500,00. I meant 500,000rpm.


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## TimR (May 22, 2011)

I went back and looked. It has an 1/8th inch collet, so it will fit the Dremel bits I have lying around.

Unfortunately I only had $9, and it was a consignment item so they wouldn't bargain. If I don't change my mind I might buy it next Wednesday when they open again.

Standard hand drills run between 1200 and 2500 RPM. So I seem to already have a tool that will do this. They're awkward to use this way, though, and I hate to put too much side load on their bearings.

It seems to me that the flexible cable drive may be convenient at low speeds, but unreliable at 20-30,000 RPM.


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