View Full Version : Variable Speed Grinders? 1.5 hp vs 2 h.p.?


Steve
10-05-2006, 11:54 AM
So, how do you like your variable speed grinder? Are they necessary?

How about 1.5 h.p. vs 2 h.p,?

I love my variables, have two, one is an old Bader with 2 h.p. motor the other is a newer BMIII with 1.5 h.p. In my opinion I need 2 h.p., or at least appreciate the extra power at times. Most of the time 1.5 h.p. is OK, but in tapering tangs, grinding away the inside of a handle slab, etc., the machine will slow down, and I only have the platen for the smaller machine, so I just make do. Not a big deal but a little irritating.

The variable speed is nice when doing handle materials that like to "burn" and you can slow things down and take it a little easier. I seem t get more control with a little slower speed, though you lose some of the efficiency of the higher speed. Just grinding a boot knife this morning and goofed up a bit when I was pushing a little too hard on high speed and "slipped."

Any comments on the above types of machines and why, or why not, you like a variable?

Brett Schaller
10-05-2006, 10:29 PM
I LOVE variable speed. I have a Hardcore with a 1.5HP motor. 1.5 is perfectly adequate for me, but I'm not a full time maker who runs it all day. I like to grind the blade bevels at about 40% speed. Slower, but it gives me more control. My grinding (and confidence) have improved markedly since I got the Hardcore.

Steve, I've seen your knives and I refuse to believe you've ever slipped! (I know, you slipped on your subhilt DVD, but I don't think it was a real slip -- I think it was just a computer generated special effect.)

Frank Niro
10-06-2006, 12:59 AM
I have two variable speed 1 HP the motors run at 3450 r.p.m. The drive pulleys have a 3" diameter. I run one full speed for flat and conture grinding and for hollow grinding I run that one at 50% for all of the grinding. It may be slow but I only do folder blades and it works for me. Frank

Charles Vestal
10-06-2006, 07:07 AM
Hello Steve;

I have a Bur-King 1.5 HP and like it alot but when it comes to tampering tangs i have found, as you have, that it will not keep up. So I have to go to my Square Wheel non-variable speed grinder to taper the tangs. The Square Wheel Has a 1 HP motor but it does a pretty good job.

I rarely go above 70% speed on the Bur-King when grinding blade bevels and it seems to work well, I don't want to grind faster than I can comprehend that I'm making a mistake.

Take Care
Charles

Steve
10-06-2006, 09:12 AM
I LOVE variable speed....... Steve, I've seen your knives and I refuse to believe you've ever slipped! (I know, you slipped on your subhilt DVD, but I don't think it was a real slip -- I think it was just a computer generated special effect.)

Sorry, it's true, not badly enough that I couldn't fix it, but it had me scared for a minute there! Probably run my variables at about 70% most of the time. Polishing is full-bore, though, usually, gets more work done, faster.

Thanks, everyone for your input, it's helpful.

joe sangster
10-06-2006, 05:23 PM
I have 2 Bader 111 variables , one is 1 1/2 & other is 2 hp. I would get both as 2hp if doing it over. For the most part , 1 1/2 hp is sufficient but the 2 hp always is ! Joe

christian609
10-18-2006, 09:44 AM
I love my variable speed setup for my KMG. Slowing down to a crawl with the turn of a dial for finishing is very nice. I only have a 1 horse motor and i do see the need for more power when stock removing thick stock and when tapering tangs the motor seems to bog down at times. When i move into my first home i will have 220 put in so i can get a 2 horse motor. By the way steve i just ordered your new video and cant wait for it to get here.

Steve
10-18-2006, 10:29 AM
It's looking like one common suggestion is to get the 2 hp motor, if you can. It'll cost more, but in my mind it's worth it. (They can range from $1680 1.5 h.p. vs. $1890 for the 2 h.p. Bader from one supplier, for example, others range from $1685) If it's a big financial burden, and you have to go with the 1.5 h.p., don't worry, it'll do the job, you'll find it just a bit light on power for an operation, or two - mainly tapering tangs or heavy grinding.

I have an older Bader Bench Model with 2 h.p. variable motor and a newer BIII with 1.5 h.p. Someday, I'll have two BIII's - both with 2 h.p. motors, I hope.....

I hope, too, that the DVD is helpful, Christian.

Don Cowles
10-18-2006, 03:02 PM
Steve, I have two grinders; a Burr King and a KMG- both have 1 1/2 HP variable drives, although one is DC and the other is AC. I rarely run them over 50% speed. The 1 1/2 HP is adequate for what I do, but just barely. I can easily lug things down when tapering tangs, for example, and just have to back off on the pressure a little.

I would agree that, given a choice, 2 HP would be better.

Steve
10-18-2006, 04:25 PM
Burr Kings are so smooooooth!
Have never used a KMG, would like to try one.
Yes, like you say, a 1.5 is adequate, but there are those times when a little more "oomph!" is nice. Thanks.

Ansoknives
10-25-2006, 02:37 AM
I say allways put as much HP in as possible..I run a shopbuildt variable speed grinder at 2.2 KW ...thats 3HP...I woulndt go smaller but I am not sure the VSD works the same as yours....normally I can do everything I need to do on this one.....especially since I started bandsawing out my blades...before I got the bandsaw I used this grinder to hog steel while profiling blanks and I COULD get it to slow down.......I have another two speed grinder 3HP/4HP that will eat ANYTHING I trow at it for that purpose...

SamLS
10-25-2006, 03:27 PM
One thing you may want to consider is the actual drive ratio when using an AC motor and the current capacity of the VFD not the HP rating. Its not uncommon to have to use a 3 or 5 HP VFD on a 1.5 or 2 HP motor especially if you want to lug the motor by taking intermitent hogging cuts. Its even more significant to oversize the VFD if your running single phase into the VFD ( your supplying 33% less energy to the drive so you cannot expect 100% rated output from the drive).

A typical 1800 RPM AC motor has the same bearings as its 3600 RPM brother in the same frame size which means mechanically it will go 200% more than 1750 RPM. So with an AC motor you can speed up and slow down to take more advantage of its torque curve with a properly sized VFD. This is different than DC controls where you typically just slow down from base speed. I believe the error has more to do with machine and control setup and selection than actual lack of horsepower. The problem is when you take most AC motors and utilize them in the manner common on home use knife grinders with VFD's by slowing them down and supplying single phase power you don't have 1.5 or 2 HP you have the equivalent of 1 or 1.3 HP respectively before you even start slowing it down assuming you sized the drive based on HP which many do. Some of you may want to experiment with sheaves, drive wheel diameters and VFD settings for given sfm belt speeds if you think your underpowered at 1.5 HP. Check the current ratings on the motor and VFD especially if your wired single phase. It will take about 66lbs of pull on the belt to slow down a 2 hp 1750 motor when geared for 3500 SFM.

wildbill254
04-05-2007, 05:47 PM
Just got in my new 1 1/2 hp DC motor and Controller from Bader.

What a difference it makes. I've used my single speed with different drive wheels to slow the speed for 11 years. WOW, variable speed is the only way to go.

If you have a single speed, the "upgrade" is $906.00 (shipped to Ohio). I know others have it cheaper, or you can order from other suppliers and build it yourself, but Paul sent me the motor and controller wired and with the bracket and heat sink. It took me 10 mins to remove the old motor and install the new one.

Well worth the price (to me the electrical challenged) and by the way they are going to raise the prices soon on all their equipment. At the time a stripped machine with only the variable 110v motor and no drive wheels was $1380.00 + 100 or so shipping. I thought about that also and having 2 machines two work with, but Momma prevailed.


Just my thoughts,
Bill

Steve
04-06-2007, 10:42 AM
Thanks for the report, Bill. I really enjoy the convenience of the variable speed motor.

michaellovett
04-07-2007, 07:20 AM
I just got a 1.5 hp vari Burr King after 30 years of using a single speed. Wow! My 2 hp Bader III is non-vari, as is my other Burr-King. I'm thinking of putting a 2 hp Vari on the Bader. Is there a power difference between Dc, and Ac? Cost. I know nothing about electric contraptions. Rob Fink has a great price on 2 HP for the Bader. Mike