drill speed reducer

[Michael GilliganParticipant @michaelgilligan61133]

Posted by lee hawkins 1 on 09/12/2014 13:24:55:

I contacted somebody who sells electronic moter speed controlers, but he said the ones he sells only reduces the voltage, I would get the speed down but Lose the torque

.

Lee,

It sounds like you need to talk to a different seller

The very common SCR based speed controllers do not simply reduce the voltage.

Here is a construction article from 1980, which describes one. [Crude but effective]

>>> ignore the half page between 50 and 51 … that's a different project !!

Yes, you will lose some torque, and yes the power will reduce with reducing speed: But there should be plenty available to do the job. … If you are worried about the drill overheating, use a cooling fan.

MichaelG.

[Peter G. ShawParticipant @peterg-shaw75338]

I have to agree with MichaelG re SCR based speed controllers. Back in the late 1960's/early 1970's I bought a kit, possibly from J. Bull, which was even simpler than Michael's version consisting, from memory, a SCR, diode, capacitor and variable resistor. There may have been a couple more components but there certainly were no transistors.

As far as I can remember, it worked by comparing the drill back emf with the voltage developed across the capacitor: when the capacitor voltage exceeded the back emf, the SCR was triggered. The result was that under low speed, low load conditions, the drill skip cycled, but as soon as a load was applied, skip cycling stopped with the drill then receiving much more power, effectively up to about 70% of maximum I think was the quoted value.

My present mains powered hand held drill is an ancient 400W Black & Decker which has a 2 speed mechanical gearbox, allied to a pistol grip variable speed controller. As far as I can determine, this speed controller works in a similar manner to the one described above: certainly it is capable of generating quite high power at low speeds.

I have over the years had a lot of B&D kit, and one thing that B&D have always said is that if the temperature starts to rise, simply remove the drill from the work with it running. The internal fan will then cool down the internals after a few minutes of off-load running.

Regards,

Peter G. Shaw

 

Edited By Peter G. Shaw on 10/12/2014 12:32:59

[Neil WyattModerator @neilwyatt]

You could try a light dimmer switch – ann old trick for small hand drills – but I fear it might go POP with a drill the size of the Wolf (I have one too, rarely use it but how could you get rid of such a beast?) one here I have is rated 40-250W.

The Wolf plate is blank in the Amps box, but even my mid-size B&D drill is 550W.

Neil

[martin perman 1Participant @martinperman1]

Lee,

How big is this piece of plate because I have drilled 50 mm holes with a hole saw through 3/8" plate on my mill drill, use slow speed and plenty of tapping fluid as coolant and take your time, it didnt wear away the cutter.

Martin P

[lee hawkins 1Participant @leehawkins1]

Brilliant! thank you to you all, lots of information posted here most appreciated

I think I will give the electronic controllers a miss, I can wire motors and things in but circuit boards and stuff scramble my brain

Been digging around in my work shop or big shed,today and came across a Bell cement mixer motor and,the pulley wheels.

I have a Idea

lee

[Ian S CParticipant @iansc]

Lee, is there a tool hire outfit in your area, if so you should be able to get something suitable for a half day hire.

Ian S C

[mick70Participant @mick70]

can you not just get another set of step pulleys?

did this with a drill press mate got of ebay was designed for woodworking so we put 4th set of pulleys on it and worked great for steel.

have used my 25yr old sip drill press for doing 86mm holes in 15mm plate before took a while as did it nice and slow with plenty of cutting fluid.

also kept stopping to let things cool down.

did 15 like this.

Edited By naughtyboy on 11/12/2014 12:36:08

[Enough!Participant @enough]

Posted by lee hawkins 1 on 09/12/2014 18:42:47:

3/4 hp drill press would bump through it no problem with Starrett Dual Pitch hole saw, I have used them all the time over the years, their brilliant as long as the speed is not too high

I hope you're right – for you ….. it certainly never worked well for me. Things bog down real quickly once you get below tooth-height and the swarf has nowhere to go. Filling up the tooth gaps translates into abysmally little feed before having to withdraw to clean out the saw and the narrow annulus that it cuts. If you don't fully clean it, things just bog down all the quicker at next pass. The use of cutting fluid, as advocated by some, makes matters worse, if anything, leading to a gooey mess in the slot that's hard to get out.

Personally I'd lean towards trepanning it if I couldn't mill or turn it out.

If you do attempt it I hope you make a video (with a clock visible) and post it.

[Ian S CParticipant @iansc]

A tool similar to a gasket cutter run at slow speed if HSS, or at the 450rpm if you can manage a carbide tip.

I'd try making a cutter using a carbide tip from an old circular saw blade, I have not tried using one of these tips for this sort of cutter, but have used them on lathe tools, both external, and boring tools, even works well on the Super Adept.

Ian S C

[Gordon WParticipant @gordonw]

Big hole saws, and little ones for that matter, are difficult things to use. A few ideas I have used – Drill a few holes just inside the circle , this helps get the swarf out. Drill from both sides. Use thin suds as coolent, not oil. You must use a bench drill. piller drill or the lathe, don't try hand held drill. Slow as possible, make a bigger pulley if needed. Using the lathe with the job mounted on an angle plate I have found best. It is a slow job. D*** spell checker gone away again.

[lee hawkins 1Participant @leehawkins1]

OK, I have cut the holes out the steel plate

I was going to have ago at posting up some pictures of my setup, but not sure how to get the pictures on here,

Thanks

lee

[Les Jones 1Participant @lesjones1]

Hi Lee,
Have a look at these two threads on posting pictures. Posting pictures 1 Posting pictures 2

Les.

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