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Overheating grinder

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Peter G. Shaw	03/11/2009 14:19:24
1531 forum posts 44 photos	Hi folks, I have a 20 year old Clarke 5" d/e grinder. Ever since I bought it, it has, if used continuously for more than say 15 minutes (guesstimated) become very hot to the touch. As a result, grinding becomes a long process whilst waiting for it to cool down. The first one I bought also became hot and was returned under warranty, but as this was the same, I have persevered with it. Obviously the fact that it is now 21 years old suggests that my usage of it has been ok and has made it last, but I would nevertheless like to ask, out of curiosity, if anyone else has the same problem. Regards, Peter G. Shaw
Gordon W	03/11/2009 14:50:49
2011 forum posts	Hi, Petre-I have an even older cheapo 5" grinder, and it gets hot, best advice I can give is let it run with no load to let the fan work as much as possible.The air holes are clear arn't they? Can't be doing much wrong after 20 yrs.
Peter G. Shaw	03/11/2009 14:55:54
1531 forum posts 44 photos	Gordon, There's no fan in this thing, and no airholes. It consists of a 150W motor inside a casing of some sort with a bearing at each end, then two grinding wheels. Thanks. Peter
Circlip	03/11/2009 15:35:22
1723 forum posts	We are constantly being told that "Modern" motors run a lot hotter that propper ones Peter, as long as it's not singing a tune (As in the windings rattling) you should be OK. You should save all your sharpening and grinding jobs till this time of the year as it helps to keep the workshop warm. Regards Ian.
Peter G. Shaw	04/11/2009 19:20:12
1531 forum posts 44 photos	Thanks Ian for your comments. I have to admit that yesterday I got it so hot it started smelling of the typical hot electrical smell. What brought this query on is that currently I'm grinding up an old 6mm file to create a 1.1mm or thereabouts wide tool to cut a groove, and as you can imagine, it's taking some time when you have to stop to allow the grinder to cool down. Still, if other people have hot grinders then that's ok. Thanks, Peter G. Shaw
mgj	04/11/2009 19:54:24
1017 forum posts 14 photos	No, I don't have a hot grinder. Not even a warm one!Even after prolonged use on tool steel. Not that that's a lot of help. Warm electrical smell. You are drawing too many amps somewhere and there will be a reason. If it runs for a long period, the probability is that there is nothing electrically wrong, though perhaps part of the winding could be shorting, or the capacitor start centrifugal switch is not disengaging. The capacitor can get a bit warm then!!!! Dirt internally, something in a bearing. Anything you can find that resists movement? Not a real amps/whole volts man I'm afraid. Some of the highly rated drill motors will get warm, but I would imagine that bench grinder motors are unlikely to be so designed? This might be of use - you have softened the file first by annealing? Might speed up the metal removal rate. Won't fix the grinder though.
MikeD	04/11/2009 19:55:53
5 forum posts	I use an angle grinder with various discs for roughing out - when it's dry, outside with the tool held in the workmate, that keeps grit out of the shop. My local BOC agent sells 0.8mm (thick) wheels, which are great for rough shaping HSS tools, files, etc, by carving chunks off, rather than grinding the bulk of the metal away. Once you have the tool to the approximate shape you need, then use your bench grinder, (or T&C gringer) to perfect the angles before you use your diamond laps to finish the job. If you don't have an angle grinder, look out for your local Aldi or Lidl "specials" - they quite often come up, and are really cheap, and fine for this sort of work. MikeD
Peter G. Shaw	05/11/2009 15:30:55
1531 forum posts 44 photos	Hi everyone, Right then, about this grinder. According to the instruction manual (which covers four grinders from 150W (mine) up to 550W) it is a Clarke CBG-5RSB Heavy Duty Bench Grinder. There is an exploded diagram which does indeed show ventilation holes at the bottom of the end caps, a fan, a centrifugal starting switch and a motor starting capacitor. My grinder does have the ventilation holes and a 3microfarad capacitor which as far as I can tell is directly connected to a winding. It does NOT have either a fan or a centrifugal starting switch. The inside of the machine is very clean, surprisingly so, but then, there is nothing to suck air and dirt into it. And the run down time after switch off is quite long. Nor does there seem to be any undue resistance when rotating by hand, so I don't see any problem there. I therefore conclude that despite the "Heavy Duty" tag, it is nothing of the sort, and is meant for light domestic occasional duty use, and indeed, using it in this manner it has run satisfactorily for these last 20 years. It is only when I get into long periods of continuous use does it seemingly get too hot. Internally, the field coils are mounted on a frame which itself is supported by the outer casing by a small number of pillars. It therefore makes me wonder just what the internal temperature is when the outer casing gets as hot as it does. Another reason for treating it carefully. Meyrick, you said that your grinder does not run hot. I'd be interested to know, for comparison, what the spec is for your machine, eg power rating, fan etc. Now about the present project. I haven't annealed the old file because sometime ago, I tried doing just that by putting some old files into the late evening fire, and whilst they were definitely soft, the outer part simply flaked off. In any case, I created a parting off tool by grinding down an old 4" file to produce a blade about 1.8mm thick by 10-12mm long and since this worked extremely well, I thought I would use the same technique. The idea of using an angle grinder for the initial shaping simply did occur, which is rather silly since I have indeed used my angle grinder to cut up an old 10 or 12" file for use as lathe tools. Perhaps that says more about my inability to perform lateral thinking than anything else! And finally to Circlip. Eh lad, tha hasn't seen mah workshop. It'd take quite a number of these machines to overcome the heat loss through the roll up door, the single skin walls, the single skin flat roof, the concrete floor, etc. To be honest, I've given up trying to keep the place warm - it's easier to ensure that the expensive machinery doesn't rust by using individual machine heaters or liberal doses of WD40, and for me to dress accordingly. So there we are, I don't think I've a problem - just an underpowered low spec device aimed at the casual homebased user. Regards, Peter G. Shaw Edited By Peter G. Shaw on 05/11/2009 15:32:38
chris stephens	05/11/2009 17:30:55
1049 forum posts 1 photos	Hi Peter, If it has run successfully for twenty years, can you really complain? It hasn't packed up, yet, so is still usable, besides it is somewhere to warm your hands or keep a cup of tea warm, on a old winters day. even if it will not warm the whole engineerium. chris stephens PS If you are thinking of replacing it anyway, why not keep it running and see what happens, it might surprise you.
mgj	05/11/2009 18:15:21
1017 forum posts 14 photos	I think you are probably right - about the power bit. If the stone isn't all that sharp as well, it may well be doing the decent thing and be trying to cope with demand by drawing more amps over a long period. The alternative is that with vent holes etc, it SHOULD have a fan (is there some sort of location for a press fit ali item?), but somehow it got forgotten. Mine is called a NU TOOL 550 watt grinder running twin 8" wheels. Its a pretty aged Taiwanese machine. (15-20 years?) It has vents and there is a pressed ali fan in there. Annealing - presumably you will have to harden and let down anyway, so that was just a thought. However, there are always many ways to skin a cat. My only concern, were I doing that kind of job, would be that I might locally destroy temper in grinding, so I would do the heat treatment bit - in which case the softening process might just as well be done before grinding?
Peter G. Shaw	05/11/2009 19:32:26
1531 forum posts 44 photos	Hi Chris, No I'm not complaining. I was just curious to know if other people had the same problem, and a couple have admitted that they do. And no, I'm not thinking of replacing it. In fact, I am one of the old breed of people in that I will not replace just for replacing's sake, and if I can, I will look at repair first. I will replace if I'm convinced that the replacement will be an improvement, but I do have to be convinced first. That's why until recently we had a 12 yro car which we'd owned for 10 years, a 20 yro tv and a 17yro tv etc. Keeping a cup of tea on it? No thanks, much too dangerous, and despite the fact that I am totally happy working on electrical/electronic stuff, I've survived too many shocks to risk any more. Hand warming I agree with though. Meyrick, Your comment about the grinding disks may well be right as I have been wondering about changing them: they are the original ones. Considering that both the fan, and the centrifugal switch are missing, I therefore don't think there ever was provision on this particular model for a fan, and anyway the first one was just the same so unless there was a bad batch all at the same time.... Yours with that big motor will need a fan, and in all probablity has a centrifugal switch as well. Annealing, and the tool. Well the tool has now worked successfully I'm pleased to say. It's just a pity that the rest of the job isn't as good! Your comment about locally destroying the temper is perfectly valid and I did take a lot of care in preventing the tool from overheating, ie I had some cold water handy ready for frequent dunking. The tool, by the way, was to cut a groove 1mm deep, by 1.1mm wide to take a circlip. I don't know what the scrap steel was that I was cutting, but it did machine up ok. Also, for the groove, I used slowest speed (125rpm) and lots of 50% Rocol. Anyway, many thanks for the discourse, at least I now know I'm not alone in having a hot running grinder. Regards, Peter G. Shaw
mgj	05/11/2009 20:15:39
1017 forum posts 14 photos	I bet the rest of the job is just fine Peter. I admire you for your economy and versatility. I think I'd have just machined up a bit of silver steel and done the easy solution. Less ouch hot fingers. One cat and many skins.
chris stephens	05/11/2009 22:19:22
1049 forum posts 1 photos	Hi Peter, Re your second para. 12 year old car, that's not old, my every day transport is a 37 year old bike, which I have used for the last 110,000 miles. Hate to think how many modern bikes i would have worn out by now. I did not mean you to keep the tea on a running grinder, that would be silly. I suppose yours is round on the top, if so, junk it and buy a nice flat topped one, much safer for mug. chris stephens
Peter G. Shaw	05/11/2009 22:40:27
1531 forum posts 44 photos	Meyrick, Yes I could have used silver steel. I do have some 3mm, 6mm, 10mm & 12mm square stuff. And some gauge (guage?) plate. All of which cost money. And yes, I'm a Yorkshireman! But the old files are effectively free. And anyway, don't forget, the main model engineering body is the SMEE - Society of Model and Experimental Engineers. Seriously though, one of the reasons I'm into this hobby is simply to see if I can in fact do things - such as convert old files, make a new part for something, etc. So a lot of it is experimenting, and despite the Yorkshireman tag above, I don't particularly mind scrapping and starting again if the first, or second, or.... attempt turns out wrong. After all, that to me, is what it's all about - increasing ones skill and knowledge. So re-using an old file like this, when a bit of silver steel would have been easier, has done just that. Chris, I presume you mean a motorbike, especially if you know how many miles it's done. FWIW, my brother has a 1973-ish Triumph T120. Don't know the miles though. The car, by the way, was changed because the replacement towbar it needed was the last straw. As a car, it was fine, although bits were no longer working correctly, but I was advised that it was unsafe to tow the caravan. Yes mine is a round top grinder. Flat topped? Didn't know there were any. Anyway, if I did get one, I'd use the flat top for more important things, like the cheese toastie being kept warm. (I was going to say bacon buttie, but I don't eat 'em.) Regards, and goodnight, Peter
Allen Paddock	05/11/2009 22:41:37
24 forum posts	Hi i have a 20 year old 6 inch grinder and it runs cool for sharpening the odd few drills and lathe tool but stay on there a little more than that and it gets hot. Always have done sometimes you can hardly rest your hand on it but if it packs up i will just sling it in the bin and buy a new one.
chris stephens	05/11/2009 22:57:00
1049 forum posts 1 photos	Hi Peter, I hope, having mentioned the sacred name SMEE you are contemplating joining this august body. You could always do a guest lecture on Cheese Toastie warming. All the best chris stephens
Gordon W	06/11/2009 10:04:13
2011 forum posts	Hi Peter, spelt rite this time! I'm amazed you have the instruction book after all these years. Was going to suggest angle grinder also,best thing for lots of metal removal. The modern? thin cut of wheels are great, also for cutting tool steel blanks to length.
Circlip	06/11/2009 11:28:13
1723 forum posts	By ell Peter lad, tha deserves Yorkshires highest award, FC and Bar, (Frugality Cross). As tha tried resharpenin t files by pickling em?? Aye, an keep thi powder dry, dowant tell em abart usint files fo cutters, fytin thi way tert front on car buwit sales is bad enuff bart damn kids gerrin under foot. They mek damn good wood chisels anorl. Brok one of me Grandads that i left me, by ell, a did weep, saved bits tho. Keep upt good work lad, best wishes fromt reyt side oft Pennines. Regards Ian.
Peter G. Shaw	06/11/2009 11:33:14
1531 forum posts 44 photos	Allen, Thanks for the support, and yes, as you say, after 20 years & £32.95 it doesn't owe me anything. Although, having just dismantled it to look inside, all there is, are two bearings (replaceable), one armature which is extremely unlikely to go wrong - I mean, it doesn't even have any wires, and a fixed double coil set of field windings which are the most likely cause of any irrepairable failure. But, after 20 years, I really don't see why it shouldn't last me out - say another 20 years? 30 if I'm very lucky, but unlikely. Chris, I wouldn't dare join such an august body. I mean, how can a C&G Full Technological Certificate "compete" against people with IMechE plus half the alphabet after their names? After all, I once read a very interesting engineering discourse along with calculations on the support mechanism of the strapless evening gown! Somehow, I don't think Cheese Toastie warming would be half as interesting! Gordon, Never noticed the spelling mistake. Instruction books. Ah yes, well, somehow I've managed to keep them for just about everything I've got. How it started I have absolutely no idea, but once I cottoned on that it was a good idea, I now have a "system", eg all the engineering manuals are in the garage/workshop. All the household stuff are in the house in a big folder. All the electronic manuals (non-household) are in the hut. And so on. I'll have to look into these thin cut disks. Although I have an Aldi 2200w angle grinder with a metal cutting 9"/230mm disk, the disk is something like 6 or 7mm thick which does make cutting stuff up rather wasteful. Regards, Peter
chris stephens	06/11/2009 11:37:31
1049 forum posts 1 photos	Hi Peter, On the subject of recycling old files, there was some debate awhile ago in woodturning circles about this. The general thought was that using 20-30 year old files should be OK, annealing grinding hardening etc, but younger ones might be made of cheaper steel and just case hardened. This would of course preclude their use as "chisels" and parting tools. chris stephens

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