4x36 conversion to 2x72 belts

G

GaryPogueCustomKnife

Joined
Oct 8, 2013
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188
I have been dying to get my hands on a 2x72 belt grinder, but just cannot afford one. I keep thinking about building one, or getting very very lucky and finding one on craigslist for cheap. Either of these things has not happened so I figured i might be able to convert the one i have now. I figure it wont cost to terribly much for some small idlers or caster could be sent out to be machined to specs. I have a rough idea on what i want to do. I created the drawing in ms paint below. It is a basic design of the conversion. I will make the new part of the frame out of tube steel and bolt it on the original platen.



Here is the base grinder

http://www.harborfreight.com/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.html

It currently has a 3/4 hp motor mounted on it, but that may be switched out to a better one if I find one in an auction or on craigslist.
I seen an old post by Zaph1 ( i hope he doesnt mind this) when he converted his grinder. I just want some friendly advice and guidance and also some thoughts on this conversion. I am worried about the tracking, mainly because it is on the original idler and I will be adding two more. Keep in mind this is just an idea, that may turn into something real. This is also just to tide me over til I can afford a real grinder.

Thanks,
Gary
 
Can't you just shovel people's driveways to save up money for a grinder? It would be easier than what you propose.

Bob
 
RangerBobTX said:
Can't you just shovel people's driveways to save up money for a grinder? It would be easier than what you propose.

Bob
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Tried that, but 99% of people either do it themselves or have another guy they hired to do it for them sadly. I have tried many times, but nobody hires me. I made a whole 30 bucks last winter from two people, both on separate days.
 
I would think by the time you rebuld that machine and source material and parts you could almost build a no weld grinder. I built mine for 500 bucks and that's including the 300 bucks I spent on wheels
 
i would say the biggest problem with that design is with the 4x36's motor. It is way underpowered even for running a 4x36 belt, its only 1/3 hp. I can bog it to a stop easily, and thats only sanding wood down to flat . I also have the 1x30 h.f. 1/3hp but with that small a belt runs good. Craftsman 2x42 with 1/2hp, or 3/4hp + would be a better candidate.
 
mxlj said:
i would say the biggest problem with that design is with the 4x36's motor. It is way underpowered even for running a 4x36 belt, its only 1/3 hp. I can bog it to a stop easily, and thats only sanding wood down to flat . I also have the 1x30 h.f. 1/3hp but with that small a belt runs good. Craftsman 2x42 with 1/2hp, or 3/4hp + would be a better candidate.
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Mine has the 3/4 Hp motor, but like I said it is easy to find a good used motor
 
Gary, how would you fit the motor? The hf 4x36 that I have also has the 1/3HP motor. Sounds like yours is a totally different machine. Is the 3/4hp the same size as the 56c frame motors? The 1/3 is a tiny little guy. Mine stalls very easily, although the belt does run nice and slow.

I wouldn't mind building something off of this grinder, but with the motor mine has it would be pointless. Hopefully Zaph will chime in and describe how he did his.

Do you already have the 1x30? If so, I'd keep working with that until you can swing the Craftsman. I truly understand the want for a 2x72. My wife and I both have good paying jobs (thanks be to God), but I believe I'm just as far off from a really nice grinder as you. As far as good tools go, I feel like I've always had to make do with what I have, or can afford without making a big impact on the family.

Whatever the outcome, I wish the best for you.

Edit- just looked at the link for the HF grinder. Looks exactly like mine. If mine is the 3/4hp (I'm at work right now) then it's grossly optimistic, or a flat out lie. Mine certainly isn't the same form-factor as a 56c. I'll have a look when I get home.
 
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Like the others, I have that machine, and no matter how they rate the motor it is not powerful enough. You say replacing it would be easy... I think not.

In any case, this is no small undertaking, and unless you have experience building precision machinery, you'll be wasting money better spent on buying parts for the precision machinery. For example, in your extremely crude drawing you've added two extra wheels. What were you thinking those would be? Real idler wheels rated for use on a grinder aren't cheap. Also noted your design doesn't have any obvious means of applying tension to the belt. It doesn't seem to have a platen either. Nor a tool rest.

In short, if you actually build that thing I would bet it would not serve your purpose.

Save up and buy a real 2 x 72, or at least the parts for a real one. That thing looks like a total money pit with no option to get the money back out.
 
I think the platen is under the 4 in the drawing. The tension might come from the factory tensioner, but I highly doubt it would be sufficient.

Realistically, about the only things going for the idea, as far as I can tell anyway, is that the existing base is "free", and that it would run slower than the 1x30. That doesn't solve the fact that it would bog down very easily.

Too many problems I'd reckon, unless you have the skill/parts/time/patience/whatever else, that would be necessary to get it working right.

I can't fabricate. Hell, I can't even weld, so making my own grinder from scratch is unlikely. It's tempting to hope for an easier way. Speaking for myself, I think I'll just need to be satisfied with a 2x42 for the foreseeable future. And the day that I even get one of those will be a good day. ;)
 
Tryppyr, I would definitely make a actual design and get it on paper. I will incorporate the current wheels and frame into the build. It may look like a Franken-Grinder, but it would be better than what it is now. As for the motor, I could make a be mount If I can't modify the one I have now.the sketch I made is just an example on what I'm thinking in my mind, by no means at all the final design. The left side is where the drive wheel and pulley is located. i also have lots of scrap steel tubing and just scrap in general at my grandpas house, he has half a pole barn full of usable stuff. i have access to it since he passed, that will make a significantly cheaper end cost. I should have said that earlier. And if it doesn't turn out, I most likely use em on a nwg one i can afford to build one.

Thanks,
Gary
 
Gary, while I wish you all the luck in the world, it is wisely said that fortune favors the prepared mind.

Think through this before you begin. That HF 4 x 36 may be useless for grinding metal, but I use mine all the time for flattening the edges, flattening wood blocks and scales, and generally shaping handles. Once you've torn yours apart it will do none of those things, and unless you're VERY fortunate, it won't grind metal either.

Several folks here are saying much the same thing to you. We're trying to help. You might want to consider what we're saying, rather than dismissing it. At the very least put together a detailed plan of what you're trying to attempt so you know what to look for in grandpa's barn.
 
I think this could work. I have a few people who have experience fabricating things. I have also split a 4 inch belt to 2 inches and it tracks better than the 4 inch does. Zaph claims his machine worked, I do t know why mine wouldn't. But if it doesn't, well I will just un bolt it from the original frame and use it like before. Heck, the new frame could just be taken off so it could use different belts for different jobs (like sanding wood or handle shaping). I am not trying to sound like a jack@$$ here but I really do think this is possible. I am willing to find out if this will work or not, anything is possible.

Gary
 
Gary, I just checked my sander. It is the "3/4"hp as well. Honestly, the 1/4hp Delta motor in my 1x30 seems more powerful. Of course, that's probably a result of the additional speed.

Not sure if it tells anything, but the Delta is rated at 2.5 amps, and the HF 3/4hp is rated at 3.2 amps. The Delta is 3450rpm, while the HF is 1700rpm. I'm beginning to wonder if the (slightly) more powerful motor will fit into the 1x30 chassis. A much slower motor + a little more power would actually make this a halfway decent machine.

In any case I'll be watching this thread. :)
 
GaryPogueCustomKnife said:
I think this could work. I have a few people who have experience fabricating things. I have also split a 4 inch belt to 2 inches and it tracks better than the 4 inch does. Zaph claims his machine worked, I do t know why mine wouldn't. But if it doesn't, well I will just un bolt it from the original frame and use it like before. Heck, the new frame could just be taken off so it could use different belts for different jobs (like sanding wood or handle shaping). I am not trying to sound like a jack@$$ here but I really do think this is possible. I am willing to find out if this will work or not, anything is possible.

Gary
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This is the point where you should just go and prove everybody wrong! You asked what we thought and we told you. We have the experience of age but you have the imagination of youth. Go build the thing. You will certainly learn something along the way. I have no doubt it can be done actually. I just don't think it is worth doing but, sometimes the reasons for doing something aren't always clear. You seem to need to try this so, I say go for it.

Bob
 
Strigamort said:
Gary, I just checked my sander. It is the "3/4"hp as well. Honestly, the 1/4hp Delta motor in my 1x30 seems more powerful. Of course, that's probably a result of the additional speed.
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I think the real prolblem is which horses are used a the basis for comaprison. HF apparently used a horse that was walking to the glue factory, whereas other manufacturers use horses that pull plows or wagons.
 
I had one of these , used it for a few years shaping titanium backspacers, kydex sheaths and grinding other metal. That motor will fill up with particles very quickly.

Yes they rate it at 3/4 horsepower , but I could stall it shaping kydex sheaths.
 
tryppyr said:
I think the real prolblem is which horses are used a the basis for comaprison. HF apparently used a horse that was walking to the glue factory, whereas other manufacturers use horses that pull plows or wagons.
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I have a 3/4hp Baldor buffer and it is a beast! I can't imagine the Harbor Freight motor has a tenth the power.

Bob
 
I figured there was something causing drag when it stalled under almost no pressure flat sanding a scale. Nope. All systems were go. Well, I guess "go" is a poor choice of words. :D

I looked at Zaphs build thread on his grinder. He used a 4x36 made by a reputable manufacturer sold by Menards. I think he said something about 9amps,but I could be wrong.

According to an online calculator, the HF motor rates at .3 continuous HP. Sounds right to me.

So, I'll agree that you should do it if you want to. I've gone my own way many times and been pleased with my results. If it sucks, what do you have to compare it to? Yup, a 4x36 that doesn't work at all for what you want. My only stipulation for how I'd go about it is to absolutely plan to upgrade the motor. I truly believe that it won't work for grinding steel, and very possibly may not be powerful enough to even spin the belt.
 
tryppyr said:
I think the real prolblem is which horses are used a the basis for comaprison. HF apparently used a horse that was walking to the glue factory, whereas other manufacturers use horses that pull plows or wagons.
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Shetland ponies...
 
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