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  #1  
Old 12-28-2015, 08:15 AM
David Eye David Eye is offline
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What SFPM for Belt on Grinder

I have done much reading and searching here regarding SFPM of belt on belt grinders and realize it has been discussed, but I couldn't find a "happy medium" belt speed mentioned.

I am a newbie to knife making and I'm in the process of gathering equipment and will be getting a belt grinder.
My money is limited and don't really want to get into brand or size discussions, but I do need some info on belt speed for grinding flat bevels which will also help me make a good decision on what belt grinder to consider (price WILL be a factor). My belt grinder will have at least 1/2 HP motor with 2" wide belt.
I don't have time right now to make my own belt grinder, but I am building my own kiln.

It seems there are various opinions on belt SFPM speed.
Question:
What would be a good "happy medium" compromise regarding SFPM belt speed?

I realize there are ways to control/change speeds such as step pulleys, variable speed motors/#######, etc.
Some people seem to like very fast speeds of 5000-7000 SFPM and some people like somewhat slower speeds in the range of 3500-4500 SFPM. Even though the high speeds of 5000-7000 SFPM can remove material faster, is it really necessary? I would also think that the very fast speed machines enable a person to make a mistake easier if not very careful.

I will be doing the majority of my grinding on annealed carbon steel blades and only very minor grinding after heat treatment......if any, other than some hand finish sanding and sharpening.

I understand I don't want to overheat the belt or blade too much and a lot of that can be controlled with technique. I WILL be using high quality ceramic belts.

Any help, suggestions and info regarding belt SFPM speed would be appreciated.
Thanks, DAVID
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  #2  
Old 12-28-2015, 08:48 AM
David Eye David Eye is offline
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As an added comment:
In case I didn't make it obvious, I am basically in need of this info so I can make the proper choice of a less expensive DIRECT DRIVE unit that is pretty well fixed in it's belt SFPM speed due to design and motor rpm.
I believe the direct drive units can also be the less expensive units. I also realize I more than likely will have to do some other modifications to the less expensive units, but I do NOT want to change a motor.....good motors aren't cheap. Even crappy motors aren't cheap!
I realize better more expensive machines are capable of easier speed changes using various methods and designs.
I have a technical background, but would like to know what the suggested belt SFPM speed is for what I will be doing since I will probably have to get a fixed speed belt grinder that wouldn't be easy to change the speed of without spending a ton.
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  #3  
Old 12-28-2015, 05:34 PM
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Andrew Garrett Andrew Garrett is offline
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A pair of three step pulleys is $10-$20. That would give you three speeds. Plus, with a 1/2HP motor, a step down pulley to reduce SFM would give you much needed torque (via mechanical advantage) on such a small motor.

However..., that was not the question you asked, so I will say this:
If you can only have one speed, it must be slow because you will over heat the steel during post-heat treat grinding with a fast belt, thus, destroying your temper.

Any direct drive motor will be too fast with a drive wheel. If this was what I was limited to, I would pull the wheel (regardless of saize) and just use the shaft to drive my belt.

That's my free opinion.


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  #4  
Old 12-31-2015, 09:04 AM
David Eye David Eye is offline
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UPDATE: ( In case a couple people decide to read this thread.)

Here is what I have decided to do based on my budget and time restrictions and needs as a new knife maker:

1) I want to be able to change speeds of my belt grinder, so against popular opinion I purchased the least expensive belt grinder that I feel is still "decent" enough to do the job with some modifications. I purchased a Kalamazoo 2FS 2"x48" w/o motor and am currently sourcing a used motor @3/4-1HP.

2) I will be using some step pulleys to achieve various speeds and MAY have to replace the short drive shaft that comes on the unit.....time will tell.

3) I can see that I will have to modify the stock platen. I will have to reduce it's width and possibly attach a ceramic surface piece.

4) I may have to enlarge the work table by modification or all out replacement with homemade unit.

I personally feel that for the investment of approx. $291 + used motor and step pulleys and some minor time for modifications I am getting a very decent 2"x48" grinder than I can easily change the speed of.
Yes, I realize a 2"x72" grinder would be best in the long run, but they are just too expensive for me......even the Kalamazoo unit without motor.
I also could make one but I don't have the time and would take awhile to make.
I am currently making my own electric kiln among many other time consuming necessities I have to take care of on my homestead!

Due to my circumstances, IMO I believe I will have a very nice 2"x48" grinder that will more than suffice and even be speed adjustable.
DAVID
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  #5  
Old 12-31-2015, 06:06 PM
Cat skinner Cat skinner is offline
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David
A 2 x48 Kalamazoo is what I have and it works OK for me. It might be a little bit fast and the platen was to wide ( I put a 1 1/2 piece of steel hooked over the platen so I can slide it side to side) I got the one with the motor and 1/2 HP is a bit on the small side.
I would like to build a 2x72 but right now what I have works fine. Personally I don't see that much benefit of the 2x72 except the longer belt for flat grinding which is what I do. So anyway I'm satisfied with my 2x48
Sam
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  #6  
Old 01-01-2016, 06:21 AM
Ed of all trade Ed of all trade is offline
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Thanks for the update. Ed
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  #7  
Old 01-01-2016, 09:07 AM
David Eye David Eye is offline
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Thanks Sam and Ed.
My suspicions regarding belt speed and small motor on the 2FSM seem to have been correct.
That's why I purchased the 2FS with out motor. I want to install step pulleys for speed adjustment and use a 3/4 to 1 HP motor.
The platen has to be modified on both models and not that big a deal for me.

I haven't received my 2FS yet, but looking at the photos of it I MAY cut off some material on the right side of the platen and then shim/spacer over the entire platen to still be centered. I would like to achieve the condition of the platen to be no wider than the belt ON BOTH SIDES OF THE BELT for grinding proper bevels while creating nicely located riccoso's (spelling?). Adding a ceramic platen piece (or metal piece as you did Sam) onto the existing platen will also help with the riccoso grinding/location issue and the issue of soft material used for the factory platen.
Thanks again for your help, Happy New Year.
DAVID
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  #8  
Old 01-02-2016, 04:44 PM
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Andrew Garrett Andrew Garrett is offline
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I have an old 1HP farm duty motor that I used for many years on my first grinder set up. It was also a 2x48 (Multitool II). I still use it for sharpening (now bolted to a Delta 9" bench grinder).

The switch is bad (always on) I had been plugging it in and out in lieu of a switch. Other than that, good motor (bought it from Tractor Supply if memory serves.

Let me know if you're interested.


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  #9  
Old 01-02-2016, 07:04 PM
David Eye David Eye is offline
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Andy,
Thank you so much for the kind offer regarding purchasing the motor you have.
I would like to exhaust my local possibilities first though, if that's alright.
I am going to look at a 1HP TEFC 3450rpm motor I located not too far away on Monday.
If I end up not buying it and also end up not finding another motor locally in the very near future I will contact you for sure.
Thanks again,
DAVID
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  #10  
Old 01-05-2016, 10:51 AM
David Eye David Eye is offline
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UPDATE FOR ANDY:

Thanks again regarding your motor offer, but I found a nice used/repaired TEFC 1HP 3450rpm motor locally and decided to purchase it. I found it at an electric motor repair place and he even threw in an adjustable speed pulley.

DAVID
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  #11  
Old 01-05-2016, 05:01 PM
David Eye David Eye is offline
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Quote:
Originally Posted by Cat skinner View Post
David
A 2 x48 Kalamazoo is what I have and it works OK for me. It might be a little bit fast and the platen was to wide ( I put a 1 1/2 piece of steel hooked over the platen so I can slide it side to side) I got the one with the motor and 1/2 HP is a bit on the small side.
I would like to build a 2x72 but right now what I have works fine. Personally I don't see that much benefit of the 2x72 except the longer belt for flat grinding which is what I do. So anyway I'm satisfied with my 2x48
Sam
Sam,
I received my Kalamazoo 2FS today and have been looking it over well.
It WILL need many small modifications, but an important one is to create a 2" wide platen surface by either modifying the existing platen as I described or doing what you did by adding a piece to the surface and "hanging" it over the top edge of the existing platen or maybe even screwing/bolting it to the existing platen. I know there are ceramic pieces made for platens (for another reason), but I would prefer to not purchase one right now if I don't have to.

Your method would be the easier and simpler modification.
I'd like to ask you why you went with a 1.5" wide piece instead of 2" wide?
I'm thinking if I go with a 2" wide piece of stock I would then just adjust my tracking accordingly instead of moving the new platen piece. If I hang it over the top edge versus screwing/bolting it down, I could kind of lock it in over the top by sizing the width of the "hook" or slot to fit between the two 90 degree bends in the existing platen that extend back on both sides. I would choose a thick enough piece of stock to allow for the rocasso (spelling again!) and any angling/cocking I may have to do sometimes depending on blade size and design.
How thick is the piece of stock you used?

If you have any thoughts on this please let me know.
Thanks,
DAVID
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  #12  
Old 01-13-2016, 03:11 AM
zccyfiberglass zccyfiberglass is offline
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Thanks for the update. Ed
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  #13  
Old 02-25-2016, 07:19 PM
Cat skinner Cat skinner is offline
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David

Sorry for the late reply I somehow missed your last post on here. I used the 1.5 inch piece because it was what I had at the time, its 1\8 thick. I use a jig to grind so when I switch sides on the knife I just slide my backer over to the other side of the belt. Maybe not the best solution but it works for me. By the way I shut the grinder off to do that (:
Sam
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  #14  
Old 02-25-2016, 08:12 PM
David Eye David Eye is offline
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Thanks, Sam, I appreciate it.
I opted with a 2" wide piece since I had to buy it anyway.
I will be bolting it on with flat head screws/bolts and make countersunk holes for the heads.
One hole will be low below the work table and the second hole very high up.....so things will be fine and flat behind the working area of the belt by the table platform.
I am also enlarging the work table and installing a spring loaded lever for the work table instead of the cheap stupid bolt and nut arrangement from the factory. This way I can easily change the angle of the work table and lock it down without using wrenches.
I am also making a simple angle iron knife jig/holder.
DAVID
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  #15  
Old 02-25-2016, 08:56 PM
Cat skinner Cat skinner is offline
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[QUOTE
I am also enlarging the work table and installing a spring loaded lever for the work table instead of the cheap stupid bolt and nut arrangement from the factory. This way I can easily change the angle of the work table and lock it down without using wrenches.Quote

I bought a 3 by 12 by 1\4 piece of mild steel for a work table works great.

I would like to see some pictures of what you come up with to replace the bolt nut arrangement. A wrench is not very convineiant .
Sam
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