Thread: Building your own grinder: cheap and easy

I got the idea for this grinder when I was working on a 7 day set that needed regrinding. I did the first one by hand, but it was a lot of work because of all the damage. the thought of doing 6 more like that was not appealing so I went looking for something better that would not break the bank.
I finally came up with an electrical sander costing all of 30 dollars, and easy to make.

This is one of those e-z sharp appliances that you can find in many hardware stores. These things are advertised as wet grinders, but they are worthless, and often not even trued. I've tried using the as wet grinder for de-pitting a wedge, and they suck. But luckily, you can turn them into something useful.

the first step is to remove the water resevoir. This is not necessary if there is plenty of room between the stone and the sides / bottom of the reservoir, but even then it is more convenient.
As you can see, this is a high precision job, meticulously executed with a hacksaw and a pair of pliers



The next step is to coat the stone with double sided tape. don't worry too much about any hairline gaps theat might be left they won't make any difference.



When that is done, you remove the coating of the tape, and fix a strip of rubber over the tape. The strip is the same width as the stone.
The purpose of this ruber is to make sure that the sandpaper is cushioned, and that any minor bumps in the stone do not cause scratches when grinding. The stone on this thing is bumpy and uneven (after all, it was cheap) so this is really needed.



On top of that you put tape. Go at least twice or thrice around the rubber band with 1 continuous piece of tape. This is to make sure the rubber stays on, and to provide a flat and stable surface to fix the sandpaper to.



Now it is time to fix the sandpaper. you can do that by putting small patches of double sided tape on top of the black tape. Use only small patches so that it is easy to replace the sandpaper. And if the tape becomes rumpled after a while, it too can easily be replaced.



And on that double sided tape you can mount the sandpaper. whether you need 1 or 2 strips depends on the length of paper that you have, but be sure that there is a bit of an overlap, and make sure that the overlap is in the right direction.



And voila: here you have a very cheap grinder that will do a reasonable job. I restored that entire 7 day set with it, and you can see the results here:
http://straightrazorpalace.com/galle...7-day-set.html

It died pretty much immediatly when that set was done. The gearbox was made of plastic cogwheels, and I had accidentally run the motor into its thermal protection a couple of times.

The grinder should only be used in 20 - 30 minute intervals, and then given an hour at least to cool off. It will depend on the way the grinder is built, but for 30$ or les, you cannot expect much. It had thermal protection, but after I used it for an hour+ and the protection kicked in for the first time, it lost a significant amount of torque. I suspect I shorted out a good number of coils.

Also, it pays to use good sandpaper. Don't use wet / dry because it clogs up faster if used dry then plain dry paper. I found aluminium oxide paper to be excellent. silicon carbide might be better still, but I haven't tried it yet.

This is by no means an equal alternative to a Bader or KMG belt grinder. Grinding pitting damage from a wedge will take some time. But at least the amount of time will be reasonable, and you won't get a tennis elbow in the process.

Great idea, I like this kind of thinking.

Charlie

I love the enginuity of the guys on this site - and proves once again that necessity is the mother of invention!

Very nicely done, Bruno - sorry to hear it crapped out on you at the end though. Any plans on building another grinder from a different motor/set of plans?

Mark

I got this one for free. I already had one, but I tried this one first because it was the crappiest of the 2.
I have since converted the other one to a grinder as well, and it still works fine. I now take care not to use it for more than 30 minutes at a time. So far so good.

Our old washing machine is standing in my garage with the idea of hooking it up there. But I am thinking of taking out the vari-speed motor and building myself a real grinder.
The plans for a real grinder are stickied in the Forge, but so far I haven't had the time to really look into it.
Maybe somewhere later this year.

This one is dirt cheap, and you can build it in less than an evening.

I think your grinder was a real grinder. The seven day set you did looked really good. I think that tools used for your avocation need not be the latest and greatest. As long as they make your hobby more enjoyable, that is all that matters. If you were depending on the grinder to earn money and put food on the table it would be a different story. I like to tinker and figure out different ways to get things done with what I have. I like hearing and seeing other people’s ideas and contraptions.

And yes Rube Goldberg is a hero of mine.



Charlie

If there is a harbor frieght near by check em out,they have buffers and grinders under 50$ and there good for the money. I have a buffer I paid 47$ has the extended shafts so your blades and hands arent all in the grinder. For the money its great they have alot of sales thats when to buy. They have a web sight too.http://search.harborfreight.com/cpis...ffer&Submit=Go

Bruno-thanks alot for this idea.I would never have thought of this myself but have used your work here to make my first wooden wheel with 400grit wet & dry attached on my 1/2 HP bench grinder.
it works a treat for pre polish and I can't wait to try it with higher grits.


Cheers John

I want to make one of these.The idea of using a wet grinder is cool because of the low RPM so it is harder to over heat what you are grinding.
Slawman

The Idea of variable speed and reverse using scrap or disposable items at hand I like alot, so I wanted to tell you guys that I have built a few grinders, two of which use the motor and variable speed clutch from a Tread mill, never have I bought one, both were given to me to haul away, they both worked like new, the shafts and bearings have been helpful in building knife making grinders, but those are another story.

To me Parts is parts and I too have wanted to use the digital motor from a front loader washing machine, boy, those turn up some RPM!!!