garydyt Posted April 12, 2008 Share Posted April 12, 2008 I was wondering what to look for when buying a knife grinder ? What brand ? How much to pay for one and etc. Any info on knife grinders would be helpful. Quote Link to comment Share on other sites More sharing options...
Glenn Posted April 12, 2008 Share Posted April 12, 2008 go to the top of the forum and click on user cp click on user profile go to the bottom of the page, enter your location, and save. We would like to know where in the world you are located. Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted April 12, 2008 Share Posted April 12, 2008 A big deal in looking for a belt grinder is what belts are availeable for it. Belts make a huge difference. 2" x 72" belts are a good size for a couple of reasons. Number one they are long enought to have enough abrasive surface that they last longer than shorter or narrower belts. The other big reason is there a lot of companies that make belts in that size in a large nnumber of grades of abrasives. Not hard to find from 36 grit which is really coarse to upwards of 2000 grit which is almost too fine for a lot of things. The second option tolook for is a speed cotrol of some sort or another. Some of the cheaper grinders run too fast for most knife making. That last option is what rasies the price out of range for a lot of folks. If I had to choose new grinder for the shop and had a limited budget I would buy one of the grizzley grinders in 2" x72" even though it does not have a way to control speed. Quote Link to comment Share on other sites More sharing options...
Hollon Posted April 13, 2008 Share Posted April 13, 2008 Can't you just put a larger pulley on it to change the speed of the belt sander? Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted April 13, 2008 Share Posted April 13, 2008 Grizzley is direct drive on the motor. Quote Link to comment Share on other sites More sharing options...
canman Posted April 13, 2008 Share Posted April 13, 2008 What speed would you run a belt sander for knife work? Canman Quote Link to comment Share on other sites More sharing options...
Normark Posted April 13, 2008 Share Posted April 13, 2008 Hey Gary... Asking what kind of knife grinder is best for knife grinding is like asking what kind of car should I buy.. First question I would ask you is: How much money do you have ? How much money do you want to Spend ?? Knife grinders can be had for as little as $250 for a Multi-tool that fits onto a standard Bench Grinder, or right up to $2500- $3500.00 depending on Specs and Add ons. Forum member Askdamice just picked up a nice Grizzley 2X72 grinder for about $500.00. Albeit it is a pretty basic machine, it will get the job done and then some.. It is certainly not a toy.. For what you get it is a fine Grinder and I want 2 of them... I would say pay as much money as you can possibly afford so the grinder will last you longer before you outgrow it.. Probably one of the best grinders on the market is the KMG. These come very basic, however they are the Abrams tank of the knife grinding world. Direct Drive one speed systems are good. Pulley drive systems are better as they allow for some speed control, however Grinders with a VFD (Variable Frequency Drive) are the best bet and the Best in the long run, although much more expensive initially. A VFD Grinder will allow you complete control over the grinder, letting you dial the grinder down to a slow Crawl, or dial it up for high speed grinding.. For the beginner grinder,, a high speed belt, that will take a finger off without slowing down can be Very intimidating . I remember flipping the switch on one ,waiting for it to wind up and literally Sweating because the machine was running so fast... That's when I bought a VFD Grinder... However once you get use to them they are fine... The speed control is needed when you are doing some real delicate work.. I've slowed my grinding down alot and now grind at about 40% power. My suggestion to you is buy a grinder that can be upgraded.. Start with a Pulley Drive system with a motor no less than 1HP. When you've outgrown it and can afford a VFD, simply swap the motor out and away you go.. That's the beauty of the KMG.. you can change the drive motors fairly easily, while still keeping the Grinder body you started with.... Hope that helps... ttyle Eric O/ST Quote Link to comment Share on other sites More sharing options...
Normark Posted April 13, 2008 Share Posted April 13, 2008 Hello Canman... You run a knife grinder anywhere from Full blast for hogging, right down to a crawl for blending in grinds.. Then every speed in between... To me a grinder at full speed and only full speed is Very limited in use, however I'm spoiled by a VFD.. I feel though they are worth every penny and will pay off for the amount of things you can do with them... ttyle Eric O/ST Quote Link to comment Share on other sites More sharing options...
Normark Posted April 13, 2008 Share Posted April 13, 2008 Hello HollonCan't you just put a larger pulley on it to change the speed of the belt sander? Not to be critical or anything.. However.. Belt Sanders are for Wood.. When used on steel we call them Belt Grinders... And yes there are Pulley Drive systems that allow you to change the speed of the grinder.. These are the best bet if you can't afford a VFD.. Hope that helps.. ttyle Eric O/ST Quote Link to comment Share on other sites More sharing options...
Ian Posted April 13, 2008 Share Posted April 13, 2008 I might be way off the mark here, but we've used dimmer switches of a high amp rating to dial in the speed of the forge blower (which is a motor after all) could somthing similar be done to create a variable speed grinder? Even proper dedicated speed control boxes are available here, but they're expensive. Still if they'd work they'd convert a current cheaper non VS to VS right? So long as the control box and cheap grinder worked out at a decent saving on a true VS grinder I don't see a downside. Thoughts? Quote Link to comment Share on other sites More sharing options...
brucegodlesky Posted April 13, 2008 Share Posted April 13, 2008 One way to slow down a Griz is to mount another motor underneath the bench, put a large pulley on th emotor and mount small one on the buffer shaft of the Griz. You'll need an on/off switch for the lower motor. Worked for me.just don't run both motors at once :-) Quote Link to comment Share on other sites More sharing options...
Mike BR Posted April 14, 2008 Share Posted April 14, 2008 Hand-held power tools generally have universal (brush-type) motors. The speed of these motors is determined by the voltage, and they can be controlled with a dimmer switch. Stationary tools usually have induction motors. The speed of these is determined by the frequency of the AC supply (60 Hz in the U.S. and 50 most other places). The motors slip slightly from their theoretical speed, but get very inefficient if they're overloaded to the point they slow significantly. Running one on reduced voltage from a dimmer switch would in effect overload it from the time you turned it on. It would probably quickly overheat, stall, or both. The speed of an induction motor can be controlled with a variable frequency drive (VFD). This rectifies the AC power to DC, and then "chops" or "inverts" it back to AC at the frequency you choose. You should be able to plug a grinder with a standard induction motor into a VFD and control the speed. But a VFD costs a lot more than a dimmer switch. Quote Link to comment Share on other sites More sharing options...
Normark Posted April 14, 2008 Share Posted April 14, 2008 Hey Ian.. Yes, ,that is what a VFD is.. Variable Frequency Drive.. Used to speed control motors,, however I think you need to use a motor that is able to use the VFD.. The controllers are several hundred dollars in themselves.. I use a Penta Drive on my 2X72... ttyle Eric O/ST Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted April 14, 2008 Share Posted April 14, 2008 Seems to me a large pulley on driving motor and small on the driven speeds things up,,,, Quote Link to comment Share on other sites More sharing options...
Dodge Posted April 14, 2008 Share Posted April 14, 2008 Seems to me a large pulley on driving motor and small on the driven speeds things up,,,, Exponentially ;) Quote Link to comment Share on other sites More sharing options...
brucegodlesky Posted April 14, 2008 Share Posted April 14, 2008 ya, I was backwards. Sorry about that . Quote Link to comment Share on other sites More sharing options...
Glenn Posted April 14, 2008 Share Posted April 14, 2008 How to figure pulley diameters: D x N = d x n D = diameter of the driven pulley d = diameter of the driver pulley N = rpm of the driven pulley n = rpm of the driver pulley Slip and creep are not considered and omitted. Driven speed should be increased by 2% for belt slip. Source: Millwrights and Mechanics Guide Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.