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Jan 17, 2015 20:46:12 GMT
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I have a cheapo pillar drill, got it for buttons and it's been pretty handy, that I've been trying to do some very slooooow drilling with. The specs suggest that the lowest possible speed it will go is 525 rpm but I've been told that the maximum speed I should be drilling cast iron (I'm trying to drill into old tools) is 300 rpm but even slower would be better. I tried, just in case it would work, using a 240v dimmer to reduce the voltage but it doesn't slow the motor. Is there anything I can do to modify this? If I put the drill-end pulley on upside down, so have the radius pullies on the belt at the same time, would that lower the speed? I think the answer is that I'm going to have to put my hand in my pocket for a new drill (silver lining: new tool!) so in that case, can anyone recommend a decent drill that goes slow enough?
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Last Edit: Jan 17, 2015 20:47:42 GMT by Battles
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Jan 17, 2015 21:03:41 GMT
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That picture shows the lowest speed possible with the current pulleys. If you turn the drill pulley around then (a) belt wont' fit (b) drill speed will be the same as the motor - 1400rpm IMO the only way you will get the current drill to run slower is to change pulleys - smaller on motor and larger on drill. Loads of on-line calculators to help determine what size pulleys required. For example - www.blocklayer.com/Pulley-Belt.aspxTo be honest cost of new pulleys and belt could possibly be more than a good secondhand drill.
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Jan 17, 2015 21:11:25 GMT
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Yeah, I suspected that I had my /elbow mixed up with my plans to put the pulley on upside down. Looking on Gumtree and whatnot now...
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Frankenhealey
Club Retro Rides Member
And I looked, and behold, a pale horse! And its rider's name was Death
Posts: 3,874
Club RR Member Number: 15
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Jan 17, 2015 21:18:37 GMT
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If you want to modify the drill and the base plate is rigid enough you could put an intermediate step pulley in the middle of the base plate. Mount it on a rigid bearing housing and adjust the centres with lock nuts and slotted holes. You'd need to invert the motor pulley but that would give you 25 ratios and a lot of flexibility.
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Tales of the Volcano Lair hereFrankenBug - Vulcan Power hereThe Frankenhealey here
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Jan 17, 2015 21:28:51 GMT
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What kind of diameter are you drilling?
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v8ian
Posted a lot
Posts: 3,747
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Jan 17, 2015 21:55:35 GMT
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250 watt motor, I suppose it would be possible to use a 250w dimmer switch mounted in a box (400w would be better), dunno if the capacitor would start the motor, but you can hand start the chuck, ----- Just a thought, not even sure if it would work, there are better qualified people on here that can tell you more as to if or if not it would work.......
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Atmo V8 Power . No slicks , No gas + No bits missing . Doing it in style. Austin A35van, very different------- but still doing it in style, going to be a funmoble
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Jan 17, 2015 22:19:34 GMT
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What kind of diameter are you drilling? No bigger than 10mm. I've humped loads of bits, including some expensive ones I borrowed to rule out my cheap ones, using this drill on these old tools, tried all kinds of techniques and cutting compounds but the couple of guys I know who are metalwork pros keep pointing at the speed as the issue. They say I'm at least 100% out. Machine Mart have a couple of good ones for £200, going for a look tomorrow. I'm making stuff for my wife so it's not like she can give me a hard time for buying a new drill...
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Jan 18, 2015 11:20:09 GMT
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Humm. I think you should be able to make it work, assuming you are actually drilling cast iron like you say it is actually quite soft but there may be a hard skin on the casting. Once you break through that you shouldn't have problems. If you start with a small diameter drill first you might find it helps. Sound like your better off buying a bench grinder so you can re-sharpen your bits!
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MiataMark
Club Retro Rides Member
Posts: 2,954
Club RR Member Number: 29
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Jan 18, 2015 12:08:20 GMT
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1990 Mazda MX-52012 BMW 118i (170bhp) - white appliance 2011 Land Rover Freelander 2 TD4 2003 Land Rover Discovery II TD52007 Alfa Romeo 159 Sportwagon JTDm
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Jan 18, 2015 14:11:03 GMT
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As above, somewhere. Add an intermediate pulley. Even if you have to modify the drill to move the motor backwards further.
Although if the above speed controller works as well as they state it does, I may have to invest in one myself!!
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Jan 18, 2015 14:56:18 GMT
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Unfortunately if you read the specifications it is for brushed motors only so an induction motor as on the pillar drill isn't suitable.
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Jan 18, 2015 16:37:33 GMT
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i slowed a 240v grinder down once so i could polish a car with it by fitting a 110v plug on it and running it on one of them yellow 110v transformers under powering the motor made it run slow for polishing, not sure if it would work on your drill
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Jan 18, 2015 17:15:51 GMT
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Sound like your better off buying a bench grinder so you can re-sharpen your bits! I could live with a lot of re-sharpening if they were making any impact but they're not. I've tried a number of techniques and had a pro-metalworker have a go on a drill with the same specs (not the exact drill but the same pulleys and motor specs) and the same cast iron tools and he was like "this is never going to happen - it's just a bit ruining machine!".
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v8ian
Posted a lot
Posts: 3,747
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Jan 18, 2015 20:32:12 GMT
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Cast iron is exceptionally abrasive when machining it, I think its self lubricating to an extent, If you are only drilling one size a decent carbide drill might be a good investment, It could be worth getting the rake ground back too, not a normal job for the average bench grinder, a "Green" wheel is more like whats needed but giving the drill a dollop of Trefolex cutting compound might help.
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Atmo V8 Power . No slicks , No gas + No bits missing . Doing it in style. Austin A35van, very different------- but still doing it in style, going to be a funmoble
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MrSpeedy
East Midlands
www.vintagediesels.co.uk
Posts: 4,786
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Jan 18, 2015 21:17:56 GMT
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You could get a pair of 'taperlock' pulleys to replace the ones you have, and then a belt to suit.
To achieve 300 rpm, you need a reduction of approx 4.6:1, so, if you have a motor pulley of say 60mm you need approx 270mm on the drill spindle
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Jan 19, 2015 12:03:11 GMT
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You could get a pair of 'taperlock' pulleys to replace the ones you have, and then a belt to suit. To achieve 300 rpm, you need a reduction of approx 4.6:1, so, if you have a motor pulley of say 60mm you need approx 270mm on the drill spindle I'd need to extend upwards outside the drill case to accomodate that, it's only about 120mm wide. I started looking at replacement motors over the weekend, if I can get the dimensions right it looks viable. They're still not the type of motor that allows variable input to vary the speed but it would be a decent start. I was working on the basis that if I could half the RPM that the motor has stated I'd be in the right ballpark. I'll report back if I do this.
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93fxdl
Posted a lot
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Posts: 1,991
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Jan 19, 2015 15:39:44 GMT
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Cast iron is soft to drill, if anything you need a slightly blunt drill, to stop it from digging in, are you sure It's cast iron ? A possibility is that it got "chilled " which gives a very hard skin, might try a carbide tip masonry drill to get through Ttfn Glenn
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Jan 19, 2015 16:13:27 GMT
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Cast iron is soft to drill, if anything you need a slightly blunt drill, to stop it from digging in, are you sure It's cast iron ? A possibility is that it got "chilled " which gives a very hard skin, might try a carbide tip masonry drill to get through Ttfn Glenn Hi, Yes, what tools are they? most tools are not cast iron but Cast or even forged steel which are case hardened for a lasting service. A grinder will be needed to at least break the surface skin. Colin
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Jan 19, 2015 23:38:56 GMT
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I'll stick some photos up. There are two batches of tools, the newer ones (very new, rescued from the skip at an offshore engineering firm where they're binned after a single trip subsea) were surprisingly easy to drill despite being hardened steel (or whatever). The older tools are seriously old so I've been told they'll be cast iron. Got no other information to go on and it seemed plausible when I was told it.
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Jan 21, 2015 18:49:21 GMT
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You need to reduce the gearing, and some of the suggestions already posted seem pretty good to me. I think you'd be wasting time trying to simply slow down the motor electrically- as the whole point of slowing the drill down is to either make use of a larger Drill, or break through a more resiliant material- hence you need the Torque- Gears are essentially torque multipliers. By simply reducing the power, you'd just stall it. Think of trying to drive at half throttle in fifth up a steep hill, compared to dropping it down to second before applying the same amount of throttle. The first approach just won't work. Hope that makes sense. Apologies if you already know, but to work out the speed at which you should run the drill, apply the following formula as a guide. [(material cutting speed in metres per minute*) X 1000 ] Divided by [Pi X (diameter of drill) *The material cutting speed is specific to the material and the type of tool used. There is a table here which should help you en.wikipedia.org/wiki/Speeds_and_feedshope this helps Dave
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1986 BMW 628csi, 2003 Alfa Romeo 147, 1992 Jaaaaag XJ40, 1982 BMW R100 cafe racer.
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