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Tool Time Let's talk shop. Equipment, Tips & Tricks, Safety issues - Post it here.

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  #1  
Old 03-21-2018, 06:44 PM
lellasone lellasone is offline
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Favorite Grinder Features

TLDR: I am designing a 2x72 grinder and would like to hear about your favorite, or least favorite grinder features and details.

Hi All,

After a year or so of working with a 2x42 grinder (and files) I've decided to go a head and build a proper 2x72 unit. My motivations for this are two fold. First, I've been playing with finger grooves a bit more and would like a bit more control of the radii I cut. More importantly though, there's been an upswing in interest among my fellow students and it's gotten to the point where grinder time is becoming the limiting factor in how many people can be involved.

To that end, I'd love to hear about any features you've enjoyed having on grinders you have used. Your thoughts on what larger features are worth it, things like tilting or double arms would be very welcome, but i'm also really interested in what little details or attachments you've found notable.

I'll post a CAD of whatever I synthesize out of this thread, once it's more than just my best shot at a KMG clone.

Note: I'm new around here so if there's anything I should or shouldn't be doing let me know.

Best,
Jake
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  #2  
Old 03-22-2018, 02:39 AM
epicfail48 epicfail48 is offline
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Fast and easy belt changes, fast and easy tool rest adjustment, those are the two big ones for me. Ill elaborate a bit on both.

Changing a belt should take less than 10 seconds, not counting the time it takes to get the belt to behave, and should require no tools of any sorts. Essentially, all you should have to do is change the belts is press down to release the tension on the belt, slide one off and the other on, with no wrenches or screwdrivers or whatever. Tension on the belt should also be constant even as the belt stretches, avoiding the use of something like a threaded tensioner that remains stationary until adjusted. A gas spring pushing up on a hinged arm with the tracking wheel would be ideal, since gas springs provide a constant force throughout their range, and the length of the arm could be adjusted for leverage to make releasing the tension easier.

As far as the tool rest goes, i prefer something solid and flat, no fancy adjustable angles and whatnot. Flat spot for the work, attached at a right angle to the tooling arm. The important things are being able to adjust the rest in and out to/away from the platen or whatever easily, and again without tools. Ideally, a single handwheel/lever/whatever locks the tool rest in place, and can be loosened, the rest pulled in/out/replaced, and resecured in under 10 seconds, without the use of any tools.

In case you couldnt guess, im a huge fan of the KMG design, it checks off everything id want in a grinder, with the exception of the tool rest. Adjusting the tool rest i believe requires a wrench or screwdriver. My grinder is actually based on these plans:
http://dcknives.blogspot.com/p/2-x-72-belt-grinder.html

I modified the design a bit to have a hinged arm instead of a pillar for the tensioner, but the rest of the design is solid, in my opinion. The way the tooling arm and workrest arm are setup are genius in my decision, quick twist on a bolt release either for adjustment or replacement, like if you wanted to go from a platen to a contact wheel.

Give me a bit and ill try to get the CAD files for my grinder thrown up somewhere, might give you some ideas
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  #3  
Old 03-26-2018, 07:31 AM
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Ed Caffrey Ed Caffrey is offline
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I've been a Bladesmith/Knifemaker for 30+ years. At one time or another I have used just about every 2x72" grinder available, whether in my shop, or in others.

Here are the things that I value in a grinder, in no particular order....
- Heavy duty construction- far too many "modern" grinders forget about this, and instead, are made of materials that are far too light in weight/strength. This makes them prone to vibration.
-PRECISION- This means everything..... Wheel alignment, slop in moving parts, and the most important.... accurate and easy belt tracking.
-Belt tensioning: I simply DO NOT like a grinder that uses anything other than a typical "spring" for belt tension. Gas Spring Cylinders are not a good thing when it comes to belt tensioning.
-Drive method" Direct Drive! Over a year ago I converted my KMG grinder to direct drive, and it's proven to be the best mod I've ever done to a grinder. All three of the machines I own/use are direct drive.
-VFD/Variable speed: There is nothing that lends more versatility then variable speed...period.
Lastly, adaptability..... it must be easy to change attachments, and be able to do so quickly and easily.

The problem with all the "johnny come lately" grinders is that they rely on gimmicks and "bells and whistles". A grinder is just that....a machine to grind, and do it in the smoothest, most adjustable manner possible.

Right now, the the style, build quality, versatility, and overall best quality belongs to the KMG. If those who build/offer grinders would pay attention to the materials and overall build quality of this machine, they'd be far ahead.


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  #4  
Old 03-26-2018, 11:50 AM
lellasone lellasone is offline
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Epic Fail,
Thank's for the response, and I'd love to see the CADs you ended up with.

What you said about belt changes really rings true, It's something of an ordeal on the setup I use now.

If you don't mind my asking, what do you like about gas springs for providing belt tension?

That link is interesting. The actual design plays against my tool-set (have access to a cnc machine shop, but no welding gear), but it seems like a good source of ideas.

Ed,
I'm curious if you have any thoughts on aluminum as a building material. My current design uses 3/4" steel plate, mostly for vibration/rigidity reasons. I'd love to use 1/2" aluminum instead, both for weight and for ease of fabrication, but I don't have a good sense for what kind of vibration to expect.

In terms of belt tracking, is the does the KMG rocker fit the bill for easy and accurate in your experience? or are their other systems that tend to work better.

If you don't mind my asking, what do you dislike about gas springs for belt tensioning?

Many thanks for your response, its given me a lot to think about.

All the best,
Jake
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  #5  
Old 03-26-2018, 02:17 PM
epicfail48 epicfail48 is offline
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I like gas springs because they provide a constant force throughout their range, i.e a 30lb gas springs will supply 30lbs of force no matter where it's at in it's compression. Compare that to a regular spring, which changes the force delivered based on where in it's extension or compression it is.

If you have a well setup machine shop at your disposal, check out the Sayber OSG:
http://sayberosg.com/forum/index.php

Free plans for a pretty solid machine meant to be cut from aluminium plate, it's what I would've gone with if I could've had the parts cut cheap
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  #6  
Old 03-27-2018, 09:05 AM
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boatbuilder boatbuilder is offline
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where do I find the cad drawings on this grinder
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  #7  
Old 03-27-2018, 12:12 PM
s mcfall s mcfall is offline
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i used 1/2 aluminum for my grinder build, built a bader type grinder, waterjetted the pieces out...spring tension....works great!
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  #8  
Old 03-28-2018, 03:59 PM
SDhammer SDhammer is offline
 
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What is the benefit to a direct drive? I have a variable speed KMG, but drive it with a belt, with the motor located on a shelf below the unit.
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Old 03-29-2018, 02:02 AM
epicfail48 epicfail48 is offline
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Took me a bit to remember to post this, but heres the CAD files for the grinder i built:
https://www.dropbox.com/s/7tzewzym96...20v8.step?dl=0

I borrowed fairly heavily from these plans:
http://dcknives.blogspot.com/p/2-x-72-belt-grinder.html

Though i did tweak things a bit, namely making the tensioner mechanism a hinged arm, rather than the shaft arrangement. I also decided to rework the drive wheel mechanism, the drive wheel in mine sits on a shaft fed through 2 bearings and driven by a pulley since i prefer belt to direct drive. Admittedly, the CAD files are missing a lot of hardware, but the pictures of the finished unit should help to fill in the blanks:

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  #10  
Old 04-17-2018, 03:30 PM
Larry Peterson Larry Peterson is offline
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Location: I was born and raised in Spanish Fork, Utah. I now live between Manti and Ephraim, Utah. We built a home here about 10 year ago.
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This is a good post. I have one grinder set up with a belt drive and the other is direct. I thought I liked the belt better. would Ed or anyone care to elaborate on any advantages of the direct motor to drive pulley? There are a few advantages to larger control knobs, rear spring tension, and other little tweaks but I interested in the "belt v direct drive" issue. I also mount the grinder base on a piece of rubber matting and bolt it down really tight. In my own mind, I think it helps dampen vibration.

I appreciate the effort to share and the willingness to teach on this forum. Thanx, LP
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