-
The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
FNG Building a GIB
- Thread starter Bob Ohlemann
- Start date
- Joined
- Mar 30, 2012
- Messages
- 86
So are you going to be using this strictly for knife making? It looks like you're pretty handy in the metal work area, so I would assume this might see double duty?
Are you still happy with the 3450RPM or do you wish you'd gone with ~1700RPM?
I plan on making a few knives on mine, but it will be far from the main purpose and more suited to just general shop use and am debating motor RPM.
Are you still happy with the 3450RPM or do you wish you'd gone with ~1700RPM?
I plan on making a few knives on mine, but it will be far from the main purpose and more suited to just general shop use and am debating motor RPM.
- Joined
- Dec 5, 2013
- Messages
- 1,180
I think I already posted in your thread but, I have mixed feelings on my motor configuration. I use my grinder for a lot of things but 90% of the use is on knives. I find I use the slower end of the spectrum more often than the high end and for that I would actually prefer to have a 1700rpm motor. That said, I do grind my profiles and rough in the bevels at high speed using ceramic belts and for that I would like to have about 50% more top end speed. I believe the ceramic belts (Norton Blaze 50 grit) would perform better if I were using them in the SFPM range for which they were designed which is 6k-8k.
I am planning to build another GIB in the near future and I will definitely use a 4-pole motor and a 5" drive wheel. I will experiment with running the motor above 60hz to see how that suits my needs.
Bob
Using a direct drive setup, the belt speed in SFPM approx. equals the RPM when using a 3.7" drive wheel.
As PTDoc has posted several times, as the RPM of the motor exceeds the nameplate RPM, the torque will go down. Also, over 130% to 150% of nameplate RPM the efficiency drops quite a bit. Heavy hogging requires max torque, which means for heavy hogging at high belt speeds, you really need to use a motor/drive wheel combo that will give max desired belt speed at no more than 25% over speed. This is 2100 to 2200 RPM motor speed for a 1725 RPM motor. With this in mind, a 7" drive wheel will be required for 4,000 SFPM.
The advantage of a 3450 RPM is it only requires a 15% over speed at 4,000 SFPM with a 4" drive wheel.
Remember, at low RPM grinding requires a gentle touch so the low torque doesn't give any problem.
Tim Gunn in this thread gives a LOTS of good info: http://www.bladeforums.com/forums/s...a-box-motor-questions?p=14189435#post14189435
After reading Tim's thread, I I "think" I still prefer the 3450 RPM because the low HP at low RPM isn't a problem because torque required is low when "gentle" grinding.
Ken H>
As PTDoc has posted several times, as the RPM of the motor exceeds the nameplate RPM, the torque will go down. Also, over 130% to 150% of nameplate RPM the efficiency drops quite a bit. Heavy hogging requires max torque, which means for heavy hogging at high belt speeds, you really need to use a motor/drive wheel combo that will give max desired belt speed at no more than 25% over speed. This is 2100 to 2200 RPM motor speed for a 1725 RPM motor. With this in mind, a 7" drive wheel will be required for 4,000 SFPM.
The advantage of a 3450 RPM is it only requires a 15% over speed at 4,000 SFPM with a 4" drive wheel.
Remember, at low RPM grinding requires a gentle touch so the low torque doesn't give any problem.
Tim Gunn in this thread gives a LOTS of good info: http://www.bladeforums.com/forums/s...a-box-motor-questions?p=14189435#post14189435
After reading Tim's thread, I I "think" I still prefer the 3450 RPM because the low HP at low RPM isn't a problem because torque required is low when "gentle" grinding.
Ken H>
Last edited:
- Joined
- Feb 6, 2010
- Messages
- 1,427
Ranger Bob, You make your own wheels on a lathe, right? You could make a 7 inch drive wheel that would fit the GIB without hitting the baseplate. If I could have found a larger dive wheel I would have used a 1725 RPM motor on mine. It would produce about 3171 SFPM. Larry
- Joined
- Dec 5, 2013
- Messages
- 1,180
Bringing up this old thread again. It's been about a year now since I did this build and started my big knifemaking adventure. It is amazing how much I've learned in that year and I am really excited for the coming year. I have decided that I need another grinder. I've been thinking it for a while but there are always so many tools to buy that it was on the back burner. Lately my wife, Karen, has been enjoying some time in the shop with me and she has become pretty competent at getting blades all the way to HT. She's not grinding any bevels yet as I do that after HT but, she is scribing, cutting, and grinding the profiles and drilling and chamfering all the holes...and placing the blades into tool wrap.
This has increased the need to have a second belt grinder in the shop so we aren't waiting on each other. I gave serious thought to getting a machine that was ready to go straight out of the box but, I just couldn't justify it. I've had the opportunity to use most of the best brands of grinders over the last year and honestly, none of them performs any better than my GIB. Add to that, I already have several attachment arms setup to work with my GIB and it just makes sense to build another.
Well last night my wife made the final push by asking about ordering a new grinder as my Christmas gift. I should take a moment to point out how lucky I am because she just got me a new bandsaw and drill press for my birthday last week. I think she kind of wanted to order a off-the-shelf unit but, after we talked about it she agreed it made sense to build another one. We got all the components ordered last night; GIB kit from Jamie, KBAC-27D from Electric Motor Wholesale, 1.5Hp motor, 5" drive wheel and 4" idler from Ebay.
There will be a few differences on this build. I will use a 1.5hp motor instead of the 2hp so I can run the grinder on a standard 115v outlet. The motor is also an 1800rpm unit that I plan to run with the 2x jumper enabled. There may be some other small differences but mechanically it will be set up the same. I'm going to get my wife involved in the build as well; at least as much as I can, she works some pretty long hours. I explained to her that tapping holes would be the perfect way for a 100mph, type-A personality to relax.
I will not document the entire build but, I will post up here with any variations I make to this grinder. I also have an idea for a new tool arm that I am going to try. It is based on Nathan's assertion that lengthwise grinding has not been explored enough by knifemakers. It will utilize small wheels and a highly adjustable flat platen.
Bob
This has increased the need to have a second belt grinder in the shop so we aren't waiting on each other. I gave serious thought to getting a machine that was ready to go straight out of the box but, I just couldn't justify it. I've had the opportunity to use most of the best brands of grinders over the last year and honestly, none of them performs any better than my GIB. Add to that, I already have several attachment arms setup to work with my GIB and it just makes sense to build another.
Well last night my wife made the final push by asking about ordering a new grinder as my Christmas gift. I should take a moment to point out how lucky I am because she just got me a new bandsaw and drill press for my birthday last week. I think she kind of wanted to order a off-the-shelf unit but, after we talked about it she agreed it made sense to build another one. We got all the components ordered last night; GIB kit from Jamie, KBAC-27D from Electric Motor Wholesale, 1.5Hp motor, 5" drive wheel and 4" idler from Ebay.
There will be a few differences on this build. I will use a 1.5hp motor instead of the 2hp so I can run the grinder on a standard 115v outlet. The motor is also an 1800rpm unit that I plan to run with the 2x jumper enabled. There may be some other small differences but mechanically it will be set up the same. I'm going to get my wife involved in the build as well; at least as much as I can, she works some pretty long hours. I explained to her that tapping holes would be the perfect way for a 100mph, type-A personality to relax.
I will not document the entire build but, I will post up here with any variations I make to this grinder. I also have an idea for a new tool arm that I am going to try. It is based on Nathan's assertion that lengthwise grinding has not been explored enough by knifemakers. It will utilize small wheels and a highly adjustable flat platen.
Bob
- Joined
- Jul 4, 2010
- Messages
- 866
Bob, It will be fun to play along. I've tried to interest my wife in joining me in the shop, but no go so far. Jess
- Joined
- Mar 30, 2012
- Messages
- 86
Ok, bear with me as I'm far from an electrician, I'm assuming you still picked up a 3ph motor?
How would changing from 2hp to 1.5hp change the voltage requirements?
- Joined
- Dec 5, 2013
- Messages
- 1,180
I dunno. I just know the manual says you need 230v for a 2hp but can use 115v for a 1-1/2hp or less. Motor is 3ph and I am no electrician either.
Bob
- Joined
- Dec 17, 2014
- Messages
- 30
Most higher HP motors are 230v because the amperage required for higher HP 115v motors exceeds what can be delivered over most household 115v circuits. Baldor does make 2 115v/230v 2hp motors, but they draw 22amps in 115v configuration, which exceeds even a 20 amp circuit.
This is spot on info. Someone is going to chime in that Travis Wuertz runs a 2 hp on 120v. ��
- Joined
- Dec 5, 2013
- Messages
- 1,180
I considered turning a bronze bushing but it's really not necessary. I just went with a standard 1/2"-20 bolt with a washer in between the arm and riser and a nylock nut to be able to adjust the slack out. It has worked fine for over a year and I did the new grinder the same way.
Bob
- Joined
- Apr 8, 2014
- Messages
- 682
Bob, I've got a GIB build in progress and also plan on using a 1.5hp 1800rpm motor on 115V with the KBAC-27D. Still debating on drive wheel size, 5" or 6". What can you tell me about your new set up? Do you like it and are you happy with the 5" drive wheel?
Thanks for any info!
- Joined
- Sep 21, 2013
- Messages
- 1,574
I've given this some thought as well. Advantages of a disc but with 2x72 belts.
- Joined
- Dec 5, 2013
- Messages
- 1,180
Sorry man, I've been so busy I didn't notice your post. In fact, I've been so busy I haven't finished the grinder yet. Still need to build the stand and mount it.
Bob
- Joined
- Apr 8, 2014
- Messages
- 682
Thanks anyway, hope things slow down for you so you can get caught up. I'm still waiting for my GIB kit to arrive and at this point I'm pretty sure I'm going with a 1.5hp motor running at 1750rpm and a 5"drive wheel. My understanding is that with this setup and the 2x setting on the KBAC-27D I will get the same top speed as a 3450RPM motor and more torque at lower speeds. If anyone thinks I'm making a mistake with this approach, I'm open to suggestion.
Thanks!