Having built my 2x72 grinder http://www.bladeforums.com/forums/showthread.php/1430390-Another-home-built-grinder I was wondering what is the best compromise belt speed for a single speed grinder. I have a 6 inch pulley off the motor (1440rpm) to a transfer shaft and need a pulley size on that to drive the 4 inch belt drive wheel. I was thinking that a 4 inch transfer pulley off the 6 in motor pulley would give a (possible???) belt speed of round about 2000fpm where a 3 inch transfer pulley would give about 2970 according to a chap who did the math for me.
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Belt speed calculation.
- Thread starter Von Gruff
- Start date
kuraki
Fimbulvetr Knifeworks
- Joined
- Jun 17, 2016
- Messages
- 4,679
6:3 doubles your RPM to the drive wheel. 2880 rpm. A 4" drive wheel at 2880 rpm is 3,015 FPM.
6:4 increases your RPM 150% to 2161 rpm. A 4" drive wheel at 2161 is 2262 FPM.
Depending on the HP of your grinder, I would likely use 2 different pulleys. A 3" and a 6". The 3" at 3,015 FPM is not blazing fast but respectable for roughing. You can finish knifes at that speed but it can be frustrating. A 1:1 transfer would let you drop down to 1,507 FPM for finish work and changing a pulley isn't the end of the world.
6:4 increases your RPM 150% to 2161 rpm. A 4" drive wheel at 2161 is 2262 FPM.
Depending on the HP of your grinder, I would likely use 2 different pulleys. A 3" and a 6". The 3" at 3,015 FPM is not blazing fast but respectable for roughing. You can finish knifes at that speed but it can be frustrating. A 1:1 transfer would let you drop down to 1,507 FPM for finish work and changing a pulley isn't the end of the world.
It may not be as easy to change ulleys on this particular set-up as on others as the transfer pulley is on a shaft through the pillow blocks. The 6 in pulley on the transfer shaft will be shifted to the motor shaft under the table top so if I use a 4 inch pulley on the transfer shaft will that be a reasonable compromise speed to do both roughing and finishing. I realise it isn't ideal.
Ken the motor is on a hinged plate and I investigated that scenario but the cost of near $500 for the pulleys is more than my pension will allow but in any case there is only an inch of motor shaft so not enough length to take the width of the 3 step pulley.
Von Gruff - I didn't click on your link until now and I remember the 2X72 you're making. Seems like I might have commented on it on one of the gun forums (castboolits??). Take a look at the top of your table saw frame - if you could widen that slot a bit you could fit a 3 (or 4) step pulley just fine. I checked pulley prices, and unless you missed a decimal point meaning $50 rather than $500, the pulley less expensive.
http://www.ebay.com/itm/130679377366? this link will give 2 pulleys for around $41 shipped.
Of course, I don't know what's on the motor below the table.
Ken H>
http://www.ebay.com/itm/130679377366? this link will give 2 pulleys for around $41 shipped.
Of course, I don't know what's on the motor below the table.
Ken H>
The 5/8 inch output shaft under the table is only an inch and a 1/4 long with a collar and nut as it was to run a saw blade in its original form so not long enough for the stepped pulley althought it takes a single pulley, and yes I did mean $500 not $50.
If you look at what the shipping to NZ would take that pulley to it would still cost a minimum of $125 if they shipped two for that price.
If you look at what the shipping to NZ would take that pulley to it would still cost a minimum of $125 if they shipped two for that price.
Am starting to think of that as a possible fix but still would like to know a compromise setup for a single speed option for the costs at this stage. As I get further into this it is probable that I may do a double pulley system but for now it is not financially feasible for me to do so.
So still wanting to know what size pulley for the transfer shaft with a 6 in output pulley and 4 inch belt pulley to make a reasonable belt speed for all purpose work even though I now it is not ideal but then how many of us starters have an ideal set-up.
So still wanting to know what size pulley for the transfer shaft with a 6 in output pulley and 4 inch belt pulley to make a reasonable belt speed for all purpose work even though I now it is not ideal but then how many of us starters have an ideal set-up.
With thanks to ripi for the 3 in pulley and some good conversation I have my grinder up and running properly. There was a bit more to do than I thought as when I got the pulley set-up sorted I found that the motor was not up to the task so I got a better one (4 pole 1 hp) that required a little more work and machining. With its different mounting pattern causing a need for different belts (that had to be ordered in) and having a 3/4 in shaft instead of the 5/8 shaft of the original motor, I had to have the motor pulley turned out for the larger shaft.
I have ground out a couple of blanks and got most of the chisel grind done on a salami knife for myself. I have a few orders in hand so will be busy enough over the next few weeks.
A big hat-tip to ripi for much more than the pulley as he has given me a great deal of encouragement along with numerous bits of steel and handle material to try different options to the rasp/file and slasher stees I have been using to date.
I wanted to step up a little from the (short handles) slip jaws I had been using for getting the blades out of the fire when heat treating and had been unable to find a set of blacksmiths tongs so did for me what is the next best thing and added a couple f lengths of 1/2 in tube to the handes of a simple set of pliers that have proven to work very well for the intended purpose.
A length of pipe acts as a heat shield to even out the heat transfer and protect the blade from hot spots in the fire
And an old (12in x 3 in ) fire extinguisher tank is an ideal quench tank for the canola oil. I can sit it on the fire to bring it to temp for the quench
I have ground out a couple of blanks and got most of the chisel grind done on a salami knife for myself. I have a few orders in hand so will be busy enough over the next few weeks.
A big hat-tip to ripi for much more than the pulley as he has given me a great deal of encouragement along with numerous bits of steel and handle material to try different options to the rasp/file and slasher stees I have been using to date.
I wanted to step up a little from the (short handles) slip jaws I had been using for getting the blades out of the fire when heat treating and had been unable to find a set of blacksmiths tongs so did for me what is the next best thing and added a couple f lengths of 1/2 in tube to the handes of a simple set of pliers that have proven to work very well for the intended purpose.
A length of pipe acts as a heat shield to even out the heat transfer and protect the blade from hot spots in the fire
And an old (12in x 3 in ) fire extinguisher tank is an ideal quench tank for the canola oil. I can sit it on the fire to bring it to temp for the quench
Good to see you posted again Von Gruf and with a good solution. I do like your solution of the pliers with tubing handle - great idea.
Now, what did you wind up with for grinder speeds? Motor RPM... 4-pole, 1750 rpm? OR - are ya'll on 50 cycle? Pulley sizes and drive wheel size to calculate belt speeds.
Ken H>
Now, what did you wind up with for grinder speeds? Motor RPM... 4-pole, 1750 rpm? OR - are ya'll on 50 cycle? Pulley sizes and drive wheel size to calculate belt speeds.
Ken H>
It is a 1400rpm motor Ken with a 1 1/2 in pulley on the motor to an inch pulley on one end of the transfer shaft that has the 6 inch pulley on the other end that is all under the bench. The 6 inch pulley drives the 3 inch pulley on the shaft through the pillow blocks on top of the bench that has the 4 inch drive wheel for the belt. Complicated I know but the way the original saw was set up had the transfer shaft underneath to get the saw blade running in the right direction and I am not able to turn the motor arround under the top (space limitations) and it wont fit on top running in the direction it does so I am stuck with the set up the way it is.
I am going to call the electrician today (5.30am just now) and see if he can reverse the direction of the motor and then I may be able to fit it on top of the bench so it has just the 6 inch pulley on the motor driving the 3 inch that has the 4 inch wheel for the belt. That would be the best solution I think.
I am going to call the electrician today (5.30am just now) and see if he can reverse the direction of the motor and then I may be able to fit it on top of the bench so it has just the 6 inch pulley on the motor driving the 3 inch that has the 4 inch wheel for the belt. That would be the best solution I think.
Sounds like it's a "Double" jackshaft setup - interesting. Since you've got the 3 pulleys now (thanks to John) and with the motor rewired to run other direction allowing use of only one jackshaft. If you need assistance on calculating belt speed, just holler. I've got a spreadsheet that calculates different pulley setup for belt speed.
Ken H>
Ken H>
Have it all arranged now with the motor on top of the bench. It took a bit of juggling of pulley positions etc bit I have the 6 in pulley on the motor (1400rpm) driving the 4 in pulley (it is a little bigger in dia than I had thought) that drives the 4 inch belt pulley. If need be I could make a larger belt pulley if more belt speed would be better.
I have the electrician arranged for Wed to reverse the direction of travel for the motor.
I have the electrician arranged for Wed to reverse the direction of travel for the motor.
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