Grinder design / build

W

Wiredude

Well-Known Member
So I figured that I would start a new thread, instead of clogging up the other one.
I've come to the conclusion that my best option is to build myself a 2x72, as the smaller gringers I could afford will only lead to frustration, and I simply don't have 2k laying around at this point.

After looking, reading, and listening, I think I'm going to do something along the EERF/KMG route, most likely with a jackshaft/step pulley drive. I would prefer a direct-drive/vfd setup, just for the reduction in parts n pieces, but with cost being a major factor, the jackshaft setup is just more doable at this point. It also will alow me to use the best motor I can come up with for now, and still be relatively easy to upgrade at a later date.
It does still leave me with a few questions though. First of which is the diameter of the jackshaft. Is 5/8" adequate, or should I use 3/4", or even something bigger?
Also, with the pillow blocks, what specs should I look for? I'm sure I don't want cheap, stamped housing ones, but I'm not that familiar with them overall, and I want to get appropriate parts.
 
5/8 will be adequate if you don't have too much shaft hanging out. As for pillow blocks, most of the more affordable sets are all made in china. I treat them as a consumable myself, and just replace when they start to get too noisy. Just about any UPC-202 should be ok.
 
It sounds like you'll be building something along the line of a KMG style..... I've built a number of the EERF grinders, and those will use a direct drive situation. As Andrew said..... pillow blocks are of two types....the cheap/expendable one from China that generally have little or no shielding, or the expensive type that have excellent shielding, and usually a grease fitting. Just be aware that if you choose to go with the cheaper variety, between the lack of shielding, and the fact that you can't grease them, they make last a long time, or they may last a week or two....at least that's been my experience with them.

If you choose to go with the EERF design, I will caution you on one thing.....change the way the belt tension mechanism to a compression spring (like on the KMG). If you use the suggested tension spring setup, your belt tracking will be terrible, and the belt will have a lot of "wonder" when the machine is running/in use.

Again, as Andrew said.....keep the mininmum amount of shaft you can outside the pillow blocks. The shorter the shaft, the better too.
 
I'll go ahead add add this... I've built two grinders, a NWGS with pillow block and step pulleys for the drive train, and a direct drive grinder of my own design. I much prefer the direct drive for several reasons, though I understand it can get a little pricey when purchasing vfds.

Given the choice between a KMG and EERF, I'd likely choose the latter.

FWIW, you can get a chinese vfd and motor for less than $300 combined if you get on eBay. AutomationDirect has 2hp 3 phase motors for $166 shipped as well.
You'll need an enclosure and/or filters to keep dust out, as they aren't sealed, but these are a more economical option than something like a kbac drive.
 
Thanks for the input. I had read your posts before Ed, about the spring, and was planning to take that into consideration. Given the pics I've seen, I think the problem lies more in the pivot, and spring attachment points, than the spring itself, but either way, I was thinking compression spring or shock, depending on what I can scrounge up.
If all things were equal, I would prefer a direct drive setup, as laying a jackshaft setup over on it's side is going do be practicality impossible, however, going the jackshaft route will allow me to build a solid platform, use whatever motor I can scrounge up for now, and eventually upgrade relatively easily to something better. Essentially, if I go the jackshaft route, I can spend more on wheels and materials and have a solid "chassis " to hook a bigger, better motor to as I can afford one.
 
Given the pics I've seen, I think the problem lies more in the pivot, and spring attachment points, than the spring itself,
Click to expand...

You got it! It's all about the leverage.... a tension spring attached to the back end of the idler arm simply doesn't have enough leverage to overcome the pressure the belt puts on the idler wheel when the machine is running. MAYBE...if you built it with as much idler arm sticking out behind the pivot, and attach the spring to the end of that...you'd have enough leverage.....but making the back end of the idler arm that long creates other issues, such as with where you can place the grinder.
 
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If you go with the step pulleys, shaft, belt, and pillow blocks you will spend over $100.00. why not apply that to the purchase of a VFD? And if you go with the step pulley design, when you decide to convert to a variable speed design not only will those parts be an added expense, you will have to purchase another motor. You will notice that I said, "when" and not "if". It may be some more money now but, in the long run, it will be a savings.

Let me know if I can help you,
 
Wayne Coe said:
If you go with the step pulleys, shaft, belt, and pillow blocks you will spend over $100.00. why not apply that to the purchase of a VFD? And if you go with the step pulley design, when you decide to convert to a variable speed design not only will those parts be an added expense, you will have to purchase another motor. You will notice that I said, "when" and not "if". It may be some more money now but, in the long run, it will be a savings.

Let me know if I can help you,
Click to expand...
I appreciate the input Wayne, I was actually poking around on your site the other night, just looking around to see what you have/offer.
Yes, there will be expense in the shaft/pulleys/belts. And if/when I would go to a vfd/direct setup they would no longer be needed.
My take on it is this. I'm trying to get off the ground, and see if I have a gift or skills in knifemaking. While it would be awesome to have the best setup available to learn on, I simply don't have that level of resources that I'm willing to commit to what is at this stage an experiment. What I'm seeking to do is build myself a servicable device to use, that, if I discover I do have a talent for knives, can be relatively easily modified/upgraded. If I don't have a gift for it, or decide that I don't wish to continue doing it, I will still have a useful tool to use for assorted metal fab, or woodworking projets.
While I fully appreciate the thought that I or anyone shouldn't 'cheap out' on tooling, I feel my situation is kind of like teaching a teenager to drive, you want them in a safe, dependable car, but you probably wouldn't put them in a brand new corvette either.
 
Wire,
A TEFC motor is ideal, BUT! I have a 2hp from the 1940's that a buddy gave me with oil ports on it that I've run on & off for the past 20 years along with a few other open motors and have yet to burn one out from steel shavings. If I have a compressor, I blow them out once in a while

The first motor I bought was a used 1 1/2 HP 1750 rpm open motor that I bought for $30.00 bucks, two Air cond/heat step pulleys for about 25.00 total, the old fan belt off of my pickup truck and I put the motor on a hinged board to hold it taunt.

It ran my then, adjustable speed www.cootebeltgrinder.com that I had up and running for well under a $1000.00 There is some pics on Norman Coote's site of how to build the motor on a hinge. I still own that Coote and three others. :biggrin:

Best of luck whatever you do. I hope i and the others have helped give you some ideas for your machine.
 
Total up the cost of the shaft, pulleys, belts, and motor you'll have in the 3 step pulley setup (don't even consider a single speed - those take a VERY skilled person) - see just how close you come to the 3 ph motor/VFD cost of less than $300..... I did it for around $250 by using a 3450rpm motor. The only problem with 3450 rpm is you do lose some torque at low rpm where you don't use much torque anyway.

Ken H>
 
Ok. Got the motor issue beat to death at this stage. May see how things go, I do have a fairly large NEMA 4X enclosure I could mount a non-sealed vfd in. I think there's a couple extra 3/4 k/o punched in it, but for purposes of my use, those can just get covered in duct tape... I think it's like 10x14x6 or something like that... Anyhow, gotta check a local source or 2 on motors when I have a few bucks and go from there...

I do have a couple of frame design related questions if some of you would like to offer some info or opinions.
I would like to build my machine to be able to accept the "standard" KMG, 1-1/2" square tool arm. From what pics I've found, it appears that most KMG/ish machines have 2 toolarm slots, stacked on top of each other. I'm guessing something along the lines of 3/8" or 1/2" between them...
Again from what I've seen, it appears that most people use the upper toolarm almost exclusively, and the lower slot is almost never used for anything other than a workrest.
Is this more or less correct? Unfortunately at this point I have yet to get to meet up with someone who actually makes knives to be able to see more than pictures, so any input is valuable.
 
If the VFD is not NEMA 4X rated itself it will have to breathe. They have to suck air through them in order to cool the electronics. If you put it in a box you will have to provide a fan and filtration on the intake and outtake. I considered this when I first started building grinders and decided that it was more economical to get the correct product for the job.

Let me know if I can help you.
 
Most of the non enclosed VFDs have a built in fan for SOME circulation. I run one for a 3 phase mill and/or surface grinder, and just have it in a wooden cabinet with a few small holes drilled in the bottom, no filters. Gravity more/less does the work of keeping dust out, though it's in one of the less dusty corners of the shop, and as for cooling, it's never overheated. Granted, it does have probably twice the volume of your NEMA enclosure (at least), thus a little more room to breathe. If it was closer to my grinder, I might think about fitting a filter in the bottom.
 
Heh, yes, seen that very vid, part of why I am considering going the step pulley route... trying to figure out how to do the frame at this stage, mostly in terms of what materials I have, what I need to achieve, and how I can make the 2 meet.
 
if you want, i will quote you a plug and play motor and VFD, everything wired and programmed, just plug in the power cord.
 
scott.livesey said:
if you want, i will quote you a plug and play motor and VFD, everything wired and programmed, just plug in the power cord.
Click to expand...
I'll let you know. I'm not at all worried about the wiring aspect of a Vfd setup. While I'm not actually an electrician, I've worked in and around the electrical business for almost 20 years, between supply, construction, and now control panel construction / wiring (hence the handle).
Right now I'm kind of trying to get together a plan for the chassis, and the materials needed.
 
Ok, change of topic, somewhat...
Who can fill me in a bit on wheels? In digging around of the web, and here, I see most people using aluminum wheels, though I also see most people recomending urethane, or rubber surfaced wheels for contact use. I assume there's areason for this, but I'm curious as to what it is. I've also seen some 'glass filled nylon' options on ebay, and the cost is lower. I know a couple of my Kershaw edc knives have that as scales, and it seems quite durable. I'm just not sure what direction to look in, or why...
 
Rubber coated wheels typically give a better finish when grinding (using as a contact wheel, that is), since they have a little give to them. They can also potentially track a little better as they grip the belt more, but if the grinder is set up correctly with proper tension, I think this would be negligible.

Aluminum wheels tend to be the best compromise between price and durability, IMO. The plastic/nylon wheels will probably work ok for occasional grinding, but if you're using the machine as a production grinder, I'd probably go aluminum or rubber.

If money was no object, the idlers and drive wheels on my grinder would be rubber coated. The next best option, IMO is aluminum. I like the sets that eBay seller vwjackstraw is putting out. Some of the highest value/quality wheels out there IMO. Just behind that would the the sets from oregon blade maker.
 
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