Making Belt Grinder need help

[JTknives]

well i have been making knives for a long time now but never had a nice grinder. the nicest thing i had was a hand held belt sander that was my dads, i used it so much i burnt out the motor over a 5 year time of making knives. im now 25 and live an a apartment and have been wanting to get back into it but using a good grinder. what made me think about making a grinder is that i worked part time a nordic track and the store just closed and i snaged a super hevy duty dc verabile speed motor reted a 3hp continuis duty but i can get more out of it if i push it for shorter amounts of time. its quite a beast in that its about 6" by 13". the shaft is around 5/8" i think. The first qusetion i have is this. because its dc i was hoping to run ac from the wall to a veriable switch like a dimer switch for your lights in your house then from there convert it to dc using 4 hevy duty diodes to rectafy the ac to dc so that i can adjust the belt speed. do you think that will work. it runs at around 3400 rpm at 130 volts dc. also my other question is it allredy has a weel type of thing atatched to the output shaft would it be ok to reshape this a little and use it to drive the grinding belt or does it need to be in conjuction with v pully and belt to drive another drive weel. i gess my last question is this, because i live in a apartment i want it to be small so i can take it out side to use but i want to use the 72 inch belts. i will post a picture of the motor later. thanks for your help

 

[A C Richards]

JT

Have you considered a disc???? Since you are limited on space this may be your answer. I started with a 9 inch disc grinder on a 1/2hp monkey wards motor. Wired it to reverse and got to grinding. Use 9 inch because I us standard 9x11 sanding sheets. Use sanding disc cement also called feathering adhesive, and trim it to the disc. I still do not own a belt grinder. I had one that was way too big and got rid of it. I now have a 1.5hp 3 phase set up with an inverter. The variable speed is great. You have a nice motor but now you need a controller. Dc controllers can be expensive. A simple dimmer switch will not work for your application. Get on ebay and see what you can come up with. Many do not like the disc. I have found it easier than a belt. I have ground up to a 24 inch sword on mine. It does not dig in on the edges. I can get an absolutly flat surface for flat grinding. If you are into hollow grinding then a belt is the only way to go. There are several plans available. I would suggest you purchasing Wayne Goddards $50 Knife shop. It goes over getting set up in the most simple way possible. He even describes making a belt grinder in this book. Covers so much material that I recommend it to all of my students. No I don't get commission but I really like this book. Just get going even if you have to just use files. I've done that too. Get back to us if we can help any further.

Chuck

 

[JTknives]

Man thanks for your quick reply. thats funny you metion using a disk. i did build a disk sander once and used it a lot. i just got some aluminum plate and shaped it into a round disk and mounted it to my motor, it was like a 1/4 3500 rpm so i could stall it but i think with the motor i have now that would be impossible. also about the power control. this motor will run on any voltage if its dc. i pluged it into a 12v 2amp wall adapter and low and behold it started up, now granted it was not real fast but it was hard to stop with my hand. i then got an ac wall jack that puts out i think 19 volts ac at 3 amps i then built a voltage doubler that took the 19 volts ac and turned it to dc at around 40 volts. man it ran nice, very quit and smooth, the onley sound i could hear was from the brushes which sould like a runing your fingers over your pants. so that is why i was thinking about using the dimmer switch to control the ac voltage and the use my device to change the ac to dc. ill see what i can come up with. I have like no money for this project so that is why i am going cheep. also the pully that is on the motor i think will work for a disk for grinding. it is qouit large and thick around 1 inch thick and completley flat, then from the center of that disk where the shaft of the motor is there is the actual pully where the belt went, the thick part i think is just weight to keep the motor spinning smooth. i think i can remove the pully part the sticks out of the thick plate and use that as a disk grinder. Could you imagen a 3-5 hp disk grinder that would be a beast. ill post some pictures when i get home tonight of the motor. I was also thinking about using the outside of the thick disk as a belt grinder where i woud just slip say a 28" belt over the outside of the disk shure it would not be a 72" grinder but it would handle what i needed a belt grinder for like handles and furniture.

I am not a stranger to the ways of knife making, i have made a number of damascus steel knives where i forged the blades from cable, files with rebar, and anything else i could find. i love making knives and it bringes in a little extra income.

One more thing befor i go, This is for A C Richards, did you realy make all thoes knives on your site with a disk grinder?

Thanks for letting me ramble on with my questions.

 

[A C Richards]

Jt.

All the knives on my site were made with a disc. As I said in the previous post I don’t even have a belt. Well I do but it is powered from my dremel. I hope you do not feel I though you were a novice by suggesting the $50 knife shop. I did not get my copy until I had been forging for over 10 years. It has so much information that anyone can use it, and Wayne makes so much from nothing. His shop is full of machines he either made or modified for knifemaking. Wade Colter is another disc user, look at his stuff. I understand his disc is run my a washing machine motor. If you can put together a belt grinder for less than $200 you will do better than anyone I have met. Just the conact whell will cost you about $100 minimum. If you have access to a machine shop and welder etc. then you can do it, if not it will be even more. The disc you should be able to get up for less than $100. I think you should invest in an actual disc right now. Maybe barter for one, Machinists love custom knives. If you had to buy one you could get it for about $70 from K&G or Texas .Knifemakers supply. You may try a router controller, it may be better than a dimmer. You can get one from Harbor Freight for aobut $20. I understand how no budget cuts into things. Just got to plug along. Good luck and let me know if I can help out.

Chuck

 

[JTknives]

O no i was not affended i was just letting you know a little more about me thats all. it funny i was allredy thinking about getting that book it looks great, one think i have learned from making knives is that you never know it all. also here is the picture of my motor. so you think i could have a disk made for my motor or just buy a disk grinder. i would love to use this motor as it is a beast.

let me kno what you think of this motor, it is an semi open case so i will have to blow the dust out every once and a wile

 

[A C Richards]

You could buy a disc from K&G or Texas Knifemakers, for $79 here’s the link to K&G http://www.knifeandgun.com/catalog/equipment_186657_products.htm

Or you can have one made. I like mine on the heavy side but then I also have a 1 inch arbor on my motor. You have a choice on yours, pull off that pulley or use the other side and leave the pulley for mass. It will help keep things running. Looks like you do have a standard 5/8 shaft so the choice is yours. Buy it or get one made. I can tell you it will cost more to have one made. It took me about 3.5-4 hours to make my last disc. In machine shop terms that is $240 plus materials and the piece of steel was $60. SO I basically paid $300 for my disc. The motor was another story. I did the work so it just cost me time. In the end I have a VERY Nice disc.

The motor is nice and compact for a 2.5hp. I think I am reading it correctly. It looks like it came off a treadmill. I do not like the open part. You could make up a filter to go over the holes but still keep it blown out. Have heard of a few fires in open motors, my first motor was open, kept it blown out and it worked fine.

Chuck

 

[Greg Obach]

great post by the way

do you have your disc mounted vertically..... or is it better to have it horizontal.... so your looking down on it..

also... i think you could use the top motor.....but you'd have to build a box for it... or the grinding dust would eventually kill it..
-- building a box wouldn't be a big deal..

oh...do you by chance have any pic's of your disc grinder set up...

thank you
Greg

 

[JTknives]

thanks, would you requmend that i use that rubber disk pad between the metal and that paper or just the paper on the disk. also that pully it solid steel so it has quite a bit of weight to it to keep everything running smooth, but it threds on the the shaft and its tight i dont know how to get it off. Because the shaft is on the moter is threded and not keyed do you think it would be better to just have a flat plate made that i can atach the the pully by drilling and taping the big pully and dril holes into the steel plate and use long bolts to atack the plate to the big pully. It would kinda look somthing like this. i could probabley also have a slot milled in the back of the plate so that the small pully would sit inside the steel plate a little and make shure it was centered.

 

[Mike Hull]

It looks like the makers of exercise equipment lie about motor ratings as bad as compressor makers.

Here's a 1HP variable speed. True rating. The toolbox is 14x20.5", the disks are 9" for scale. The other two motors are 1hp AC units.
They must depend on the heavy flywheel for the rating, but I've noticed in the past that motors from treadmills, etc., are way smaller than regular lesser HP rated motors from other fields.

 

[pso]

Hello JT

I have been investigating building my own budget disk grinder for a while. Some people here said that Grizzly sells replacement parts for their machinery. I called Grizzly's customer service and found that the 9 inch disk for the following goes for about $16 (www.grizzly.com/products/G1014Z). The guy on the phone thought that it was meant to fit on a 5/8 inch shaft. Hope this helps.

Phil

 

[A C Richards]

My disc is mounted vertically so i can see the edge as i am grinding. this way I can judge where my grind is and at what angle I am holding the blade. SOme like the horizontal version. I think it is a matter on what you learn on.. JT. I would really look inito using the other end of the shaft. It looks long enough to get a disc onto and that $16 disc sounds interesting. To build a disc that bolts to the current pully would be way too heavy unless you use a very thick piece of Micarta or even aluminum. It just would not hold up as well as the steel. i have use both alum and Micarta and like a plain steel disc.

Chuck

 

[A C Richards]

It looks like the makers of exercise equipment lie about motor ratings as bad as compressor makers.

Mike nice picture, my 1hp DC looks just like the one on the right, Just your shop is much much claener than mine, :thumbup: I like your controller too, Need to pick one of those up for my DC unit. Looks like you like discs also.

CHuck

 

[A C Richards]

Greg I will take some pics tomorrow of my set up.

CHuck

 

[Mike Hull]

It looks like the makers of exercise equipment lie about motor ratings as bad as compressor makers.

Mike nice picture, my 1hp DC looks just like the one on the right, Just your shop is much much claener than mine, :thumbup: I like your controller too, Need to pick one of those up for my DC unit. Looks like you like discs also.

CHuck

Chuck, that's an older photo. I have two Leeson DC VS 1HP disk grinders up there now, along with another controller. The 1750RPM AC units are OK, but one slip and you're toast, or your work is. Variable speed is so much nicer.

You can get the controllers(and motors) from Minarik Electric. It's their MM20,000 series.Mine are NEMA 1 enclosures with heat sinks, but I sealed the various gaps with silicone after tuning the motor speed, torque, etc(you can do the same with tape if you wish). They have them all over. make sure you tell them you're a knifemaker and they give you the OEM discount. If you need, let me know and I'll give you the number of the one in Phoenix and the managers name. He gives good prices.

 

[Mike Hull]

Chuck, here's a new photo(today).

Edited to add: Sorry, I'm not trying to sidetrack the thread, just showing possiblities.

 

[JTknives]

do any of you use a what is called a small table right in frount of the disk. or do you just use the disk with out anythng to rest the blade on?

HOLY HOLY HOLY HELL, I just got a 35 Amp bridge rectifyer to turn my 110ac into 110 dc and last night i tryed to plug it into my wall plug. i thought i had a goot hold on the moter but i gess not, i just put the plug in for like 1/4 to 1/2 a sec and i could beraley hold on to the motor because of the tork. so just now im at lunch i decided to try it agen but i put the motor on a chair and i sat on it and held it with one hand while i pulged it in, i had a 100 W light on next to we which dimed to half brightness wounce i jamed the plug from the motor into the wall. the motor gave cuite a good kick at start up. then once it got going i did not even need to hold it, it would just sit there and the light came back to full brightness. but holy hell the motor is powerfull i had a pice of wood wwich i tryed to stop the motor with by pushing it onto the big flat pully. the motor slowed a tiney bit but mo mater how hard i pushed nothing changed except for the pece of wood smoking. i must say this motor is defintley at least 2 hp. i had a 3500 rpm 1/2hp motor with a disk a wile ago and i could stop it with not much effort at all, i mean not with my hand but while i was grinding. i am in love with this motor. as for speed control i dont know, the dimmer switch would work but it is not rated for the amps my moter pulls, so for right now im going to have 3-4 speeds by using 100w lamps eather in series or paralel to change the total amount of resistence in the circuit therfor reducind the total amps pulled. If any of you know of a dc speed control let me know. I am an electronic repar tec so i can probabley build on if i had the plans. thanks

 

[pso]

Hello TJ

Please use a meter to check the voltage that you are getting out of your rectifier. 110Vac into a rectifier does not give 110Vdc. It should give you about 310Vdc or 155Vdc, depending on how your rectifier is configured. You do not mention any sort of smoothing capacitor. Your meter may give some reading lower than 310Vdc or 155Vdc, with the meter set to the DC range, AND some AC voltage when set to the AC range.

You would probably have to connect a bunch of light bulbs in parallel to prevent them from blowing out since your motor current would exceed the current the bulb is meant to carry. Also, the resistance of a light bulb is highly dependent on it's temperature, varying by as much as 10:1.

I would not recommend trying to build your own motor speed controller. I have worked in the R&D department of a company that manufactures AC motor drives. I can tell you that, at the power levels involved, the circuit layout is very critical and it takes a fair amount of experience to get right. Just working from a schematic, you are likely to get all kinds of glitches or it may just blow up "for no good reason". You will also have difficulty buying parts at a price low enough to make it worth your while since you will be buying in very low quantities compared to the manufacturers.

You are probably better off saving up and buying a proper DC controller or to use step pulleys.

Phil

 

[A C Richards]

JT. If that motor is that stong then you really need to get that pully off the front. You can put the disc on the back shaft but man it would be really nice. Here are a few pics of my grinders. The disc is 9 ich in Dia 1 inch thick with a massive boss. The motor is 1hp 220 3ph with an inverter you can see behind. I have the disc attached to my mill table. It makes a really sturdy base and i can move it up and down as I need. It really makes it nice when you need to get a little closer to your work for fine control. I have made an adjustable table for the front of my disc and I only use it for grinding fixtures etc. I do the blade free hand with no table. The other grinder is my only belt. It was designed and made by a friend of mine. It is really a nice little grinder and can be used with any flex shaft tool with a 1 inch handpiece. I had to turn down my dremel down a little. I have another friend who actually ground a small hunter on it. I don't recommend it but it did work.

Chuck

 

[A C Richards]

The inverter or (VFD) makes the motor variable speed and changes single to three phase. I really love the Variable speed but have only been using it for abaout 3 years. First with 1 hp DC then went to the 3 ph motor and inverter. It really makes a huge difference in control. I hooked all my 3 phase eqip to it. Love the control it gives me. Here's one more pic of the little belt. Could only post five on the last post.

Chuck

 

[JTknives]

I have never sean a rectifyer double the voltage, but yes i did check it it was 111 volts on the out put. also i am going to use a filter cap to get rid of the 60 cycle hum, which if you want to get tecncale wold actualy be a 120 dc pulses a sec to the motor which the cap will provide a pulse between the other pulses to smothe out the power. I just did not have a cap to filter my dc voltage last night, i just snaged on from work, its rated at 200vdc and 1000mfd. its small but should work ok. the onley thime i have seen anything higher than 111 volts out of a rectifyer is when it feeds strait to a cap to charge it up, it will then messure around 130-135 from the little ac spikes that come throught the power line

About the using tha lamp. the lamp just adds restince to the motor so that the current draw is less. because

Volts x Amps = watts, Volts / resitence = amps

so say the moter is a 130 volt 15 amp motor that means that it should have a restince of 8.66 ohms so say you connect a 100watt lamp to it it should have a rating of 110vac which is around .9 amps its pulling it will change the total resistince of the motor and make it more then the 8.66 ohms so if the resitence goes up then the amps go down so if i double the the resitince to 17 ohms i would be pulling around 7 amps of power which sould give me some where half the speed. In our shop we use this technek to trouble shoot tv's to see it the tv is trying to pull to much power. as for parts we have a shop full and we get dealer prices from the manufactures so it quite cheep.

i will probabley just use it at full speed sience the lamp speed control would be comberson to use. but other than that im very happy with this motor.

A C Richards, you think i should remove the big flat pully from the motor and replace it with a disk. the big flat pully is some how threded onto the shaft. the shaft has threds on it and i would imagen that its quite tight. also i was thinking of maybe keeping it on and using the wide part of the big end of the pully ans using the disk glue to glue a gringing belt around it so i can do handles and gards.