Surface Grinder - Convert to belt or not ?

Kosa_PL

Kosa_PL

Joined
Aug 25, 2013
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1,220
Hello everyone,

As recent time I obtained a new item to my shop called surface grinder I have some question...

Can I convert my belt grinder to belts?

My surface Grinder is a Jung F50R (Variable speed).
This fat bastard weight 1.300kg, and have wheel 225x25x51mm, power up/down feed, step 1,8mm per pass ( better is to make this step by hand on wheel...)
Got this for 1.450 USD :D ( with transport and 45L of new HLP-32 hydraulic oil)

Jk3ZVe.jpg


Graduation feed up / down is 0.002mm for the division. And 0.2mm to 1 turn.

What precision / Ra factor I will get with belt conversion instead of grinding wheel? ( And much safer grinder because there is no more ceramic wheel, what can desintegrate like frag grenade.)
Also my grinder will be equipped with MQL cooling (DIY Fogbuster) and Mobilcut 320 grinding fluid (full synthetic micro-emulsion)

Will I achieve the same results like when using Ceramic wheel(grenade) ?

What are pros and cons of belt conversion?


And the photos of main part of interest in belt conversion.
8q7GZn.jpg

95UgQB.jpg

YzJ8Ix.jpg
 
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I'd leave it alone. I always have seen an x-y table under a belt as a 'poor man's surface grinder.' Therefore conversion to said would be the same. No offense to those that have them... But the key here is nothing moves or flexes.

Good find. I don't do folders so haven't bothered shopping for one yet (get by with the mill...) but gauging from pics and such, price seems great. I've seen just the magnetic chuck that size go for as much $$

Cheers.
 
IMO the only reason to convert is for hogging damascus billets, and there's plenty of other ways to do that.

There's a reason you don't find "belt surface grinders" in the wild, they defeat the purpose of what a surface grinder is built for, which is dead flat and parallel. No matter what you do, you've got too much flex in a wheel, and too many variables in the belts and splices.

One thing people think you get with a belt, is the ability to get finer finishes. This is absolutely not the case. With a standard course 32A type stone, I can get the equivalent of a 400 grit belt finish, when properly dressed. By changing the dress feed and speed, you can get various finishes. This is with a course stone, and they make fine stones if necessary that'll give extremely fine finishes.


With a properly dressed course stone, and coolant, you can hog at insane rates also.


I'd highly recommend learning to use the machine as is, and then decide if you want to try belts later. If you do go the belt route, I highly recommend designing the belt mod in such a way as to not compromise the functionality of it's use with stones. You can buy surplus stones very cheap, and they'll last years of use each.

For the record, I now have 3 surface grinders running in my shop. 1) 6x18 Hydro Feed with Belts or Stones (I only use belts for damascus work) 2) 6x12 manual with mag-sine chuck for cutting nail nicks and tapers 3) 6x12 manual with standard stone configurations for fine work


Honestly, I could live without the belts on the big one, and did for years.
 
Like Javand said, hogging is the main advantage of belts. I also use them for fittings in softer materials like brass or copper that tend to gum up the wheel. I even use them for wood.

But wheels can't be beat for getting things dead flat and there is pretty much no limit on the finish you can get with them.

I would only convert to belts if the change from belts to stones can be done quickly. Doesn't look like this is going to be easy looking at the design of your grinder.

Sure is a beauty though. :thumbup:
 
I have been in many machine shops and have never seen a belt surface grinder conversion. Why is that?
Used properly they do a better job. The ceramic wheels will out last the belts by a long shot.

Nice buy too.
 
Personally I don't like worrying about dressing the wheels, my surface grinder belt conversion is easy to maintain. I also have a higher durometer wheel to address the flex issue, it's 90 duro. I like the quick change ability of the belts, and they are a lot cheaper than stones by a lot.
 
Andre stones ( made in Poland :) ) cost 40-50 PLN per one.
Thats about 10-12$.
Cost of 4-5 belts.

And here is result of grinding 2,5mm 80CrV2 hardened to 62 HRC.... Without cooling, deph of cut 0,02-0,05mm
Grinding wheel : 200X20X51 99A60K7VE01






What caused this ;_; ?


And what wheels do you suggest ?
 
Kosa_PL said:
Andre stones ( made in Poland :) ) cost 40-50 PLN per one.
Thats about 10-12$.
Cost of 4-5 belts.

And here is result of grinding 2,5mm 80CrV2 hardened to 62 HRC.... Without cooling, deph of cut 0,02-0,05mm
Grinding wheel : 200X20X51 99A60K7VE01






What caused this ;_; ?


And what wheels do you suggest ?
Click to expand...

I have some assumptions why , but I'm going to ask these days my friend who work on same grinder ... . This blank was grind on the same machine :)



11jw49l.jpg
 
Your wheel is improperly dressed, and/or you're building up heat causing the work to warp into the wheel, which is breaking down the wheel unevenly.


Bear in mind, that for thin knives, you need to be taking very small DOC with full engagement. 0.02 mm is your max without coolant, on hardened steel, especially high alloy steel such as you're grinding.. You also don't need to be feeding the full width of the wheel per pass in Y-feed.


You can take extremely heavy cuts with a stone, coolant, and a fine pole chuck, if you have the proper stone dressed properly, but it will still likely induce warp, and isn't recommendable on hardened steel. I'd recommend 0.0013mm or less in this application.
 
And a next question.

Do I need to balance such small wheel ?
( balancing shaft cost 190 EURO...)
 
Not in my experience. Just tighten it down good, and dress each time you replace the wheel.

You have to make sure when you dress it, that you're engaging the entire circumference of the wheel before you stop. You'll be able to hear when it's cutting all the way across once you're familiar with it, but before that, look at the wheel and make sure the face of the wheel is reasonably uniform in color after dressing.. Usually a low spot that isn't being engaged will be darker colored.

Usually finish problems are related to improperly dressed wheels, although with the above, I can tell you were definitely having expansion problems from too heavy a feed. With un-hardened steel, it's ok to feed heavily and cause some less good finish when hogging, and then clean up with finishing passes, but in the case of thin hardened steel, you must take delicate feeds and maintain a good finish while you remove metal.


If your finish starts to get wavy, you need to redress your stone, however, if the stone is secured, and properly dressed, you shouldn't have to redress while working, if you find your finish goes from good to bad quickly, it's likely that the stone isn't securely tightened, and the down-feed is pushing the stone mount on the spindle some, causing it to be out of concentricity.

When dressing, only remove 0.05mm or 0.025mm per pass across the stone, as many times as it takes to get it dressed properly.
 
you dont need to balance small wheels, but you DO need a surface grinding diamond dressing tool. You stick it on your chuck , set it so that it just kisses the stone, and run it in and out the length of the stone, that makes the stone perfectly parallel (flat) with the face of the magnetic chuck. Also, very small bites are what you want for a good finish, dont start with the wheel working the whole width.
 
I had converted my surface grinder to belt but you will get a nicer finish once you learn how to use the stones , I watched a couple of you tube videos and it helped me out a lot. your wheels defiantly need to be dressed and feed on hardened steel is .001"-.0015" at the most for a fine finish with out warping, also the way you dress the wheel will affect your finish. I saw one video where the guy was balancing the wheels, but that is a little beyond my capability.
 
Not to hijack this thread but why after grinding both sides I removed the blade to check thickness and put it back on there are high spots. I'm thinking my chuck isn't flat. I put it back in the same spot and clean the chuck before I put it back.

Thanks
Bill
 
I was present when they grind my blank in the picture .On one pass they grind around 5mm. surface of knive ,maybe even a little less.
 
William Schrade said:
Not to hijack this thread but why after grinding both sides I removed the blade to check thickness and put it back on there are high spots. I'm thinking my chuck isn't flat. I put it back in the same spot and clean the chuck before I put it back.

Thanks
Bill
Click to expand...

Maybe too quickly passes ??? Or blade was little bent before grinding , or you have bent blade during grinding . Magnets are very strong and they align blade when installing on chuck ....
 
Kosa_PL said:
Integrated wheel dresser :)

Click to expand...


The diamond dresser there guarantees that the wheel is dressed only, you need it dressed AND perfectly parallel to the surface, if the wheel axis is not square with the magnetic chuck the wheel will touch more on one side than the other.

And regarding the blue photos I think you are hogging too much per pass, surface grinders need patience :)


Pablo
 
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