Dial for Drill Press Speed Control?

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SteveHGraham
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Dial for Drill Press Speed Control?

Post by SteveHGraham » Mon Oct 29, 2018 5:44 pm

I have never used the Dumore sensitive drill press I found on Craigslist. I need to set it up.

Problem: it runs at 3 million RPM all the time. I want to control the speed. I was going to get a Foredom pedal, but it occurred to me that this might be a stupid idea. Seems like a control with a dial will work better, because I'll be able to set it at certain speeds with repeatability. I could even measure the speed at various dial settings and mark the dial so I would be able to get the speeds I wanted without fiddling around.

Good idea?
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10KPete
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Re: Dial for Drill Press Speed Control?

Post by 10KPete » Mon Oct 29, 2018 5:55 pm

Yep, that's what I'd do. Remember, if a motor has brushes, you can run it through a light dimmer.

Pete
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SteveM
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Re: Dial for Drill Press Speed Control?

Post by SteveM » Mon Oct 29, 2018 5:55 pm

I'm no motor expert, and the real experts might contradict me, but you might be able to get by with one of those router speed controls.

Might be good to borrow a strobe to measure the speeds and mark them on the dial in case you need to set it to only one million rpm.

Steve

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SteveM
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Re: Dial for Drill Press Speed Control?

Post by SteveM » Mon Oct 29, 2018 5:56 pm

10KPete wrote:
Mon Oct 29, 2018 5:55 pm
Remember, if a motor has brushes, you can run it through a light dimmer.
Learned something new today.

Problem is, I forgot two other things.

Steve

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SteveHGraham
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Re: Dial for Drill Press Speed Control?

Post by SteveHGraham » Mon Oct 29, 2018 6:28 pm

I have read that the router and dimmer controls tend to be primitive and have issues. Wondering if that's true.

It looks like there are a lot of old speed controls on Ebay. I found one that has a switch with one position for variable speed and another for full throttle. That would be nice for the old Themac grinder I bought.

Here is what I read, over at PM:
The router speed controls sold years ago worked quite well. Unfortunately they have driven off the market by cheapo import "speed controls" sold by the bale to relablers. These speed controls while they will electrically reduce the free running RPM of a series wound motor, exert virtually no speed regulation. Slow the motor -fine - then apply the load and the motor practically stops.
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10KPete
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Re: Dial for Drill Press Speed Control?

Post by 10KPete » Mon Oct 29, 2018 6:52 pm

That hasn't been my experience. I have a plain old hardware store turn-the-knob dimmer in a box. With an outlet and a power cord. Highly portable.
I use it with my routers, tool post grinder, die grinders, Biax scrapers, the lot. While I may not try for the slowest possible speeds (that would be problematic) I can easily reduce speeds to 25%-30% with no meaningful reduction in power.

Pete
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SteveHGraham
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Re: Dial for Drill Press Speed Control?

Post by SteveHGraham » Mon Oct 29, 2018 7:13 pm

I decided to try an NOS Dayton speed control. It was too pretty to pass up, and it was considerably cheaper than a Foredom.
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BadDog
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Re: Dial for Drill Press Speed Control?

Post by BadDog » Tue Oct 30, 2018 1:26 am

I have an old variac, and a passing thought once or twice to try that on my little Dumore, but never tried it.
Russ
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tornitore45
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Re: Dial for Drill Press Speed Control?

Post by tornitore45 » Tue Oct 30, 2018 6:23 am

Variac will work fine on Universal Motors (AC/(DC) motor with brushes)
If a dimmer gives poor performance try placing a 100W incandescent light bulb additional load (in parallel to whatever you are trying to control)
There are different types of dimmer loosely classed for electronic or inductive loads in addition to lighting loads.
Mauro Gaetano
in Austin TX

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SteveHGraham
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Re: Dial for Drill Press Speed Control?

Post by SteveHGraham » Tue Oct 30, 2018 12:38 pm

BadDog wrote:
Tue Oct 30, 2018 1:26 am
I have an old variac, and a passing thought once or twice to try that on my little Dumore, but never tried it.
Have you seen what old variacs are bringing now? I believe I paid $45 for an old NOS Superior Electric, and now I'm seeing prices up in the hundreds. I'll bet hipsters discovered them.

I think you have to buy new Chinese now.

My variac only had two prongs, so I had to modify it to accept modern plugs.
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tornitore45
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Re: Dial for Drill Press Speed Control?

Post by tornitore45 » Tue Oct 30, 2018 12:58 pm

Variac's are autotransformers. No isolation. If the input leads are reversed the set up is even more dangerous than usual since both output leads are hot when set at zero.
Is important to have the plug polarized, and wired right. A GND prong connected to the metal case is highly desirable.
Mauro Gaetano
in Austin TX

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SteveHGraham
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Re: Dial for Drill Press Speed Control?

Post by SteveHGraham » Tue Oct 30, 2018 2:07 pm

I thought it was odd that my variac had no ground, but I suppose things were different in 300 B.C. when it was made. It has a ground now.
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