Getting the most from my 3/4 hp motor

easterngray · Post by **easterngray** » Wed Mar 11, 2009 5:36 pm

Some of you might recall a post I had a while back looking for feedback or suggestions for a 9" thin kerf cross cut or combo blade. I think it was Dusty that suggested that Freud had one. Well I ordered a Freud, very reasonably priced at less than 40 dollars, and I am "pleased as punch" as my Mom would say.
I wanted the thin kerf 9" in order to get the most from my 3/4 HP 500 - why drive a 10" blade when for my purposes a 9" will do? I have had some real "bogging down" problems when ripping, even with a brand new 10" thin kerf combo blade from SS, yet when I put a 9" ripping blade on - no problems. Well with the new 9" TK combo blade I can also rip with no bogging down. Is it possible that the one inch of blade really causes the motor to work that much harder? I don't know - but I do think that with the 9" thin kerf blade I am getting the most performance from my 3/4 HP headstock. Alec

JPG · Post by **JPG** » Wed Mar 11, 2009 5:56 pm

As I have said b4, The 10" blades were Not thought of during Greenie/Goldie days even though later goldies did have the 1 1/8 HP motor. The 1 1/8 HP motor does a good job with 10" blades but the 3/4 HP - Well maybe not!

The increase in speed (at the circumference) is about 11% whereas the HP increase is 50%. This would imply that the 1 1/8 HP motor with 10" blade is a better performer than a 9" blade with a 3/4 HP motor. This IGNORES any blade design factors. Bottom line, If you have a 3/4 HP motor, get the best performing 9" blade you can(as Alec seems to have done).

dusty · Post by **dusty** » Wed Mar 11, 2009 5:59 pm

Very interesting! I would expect a similar report from someone changing from standard to thin kerf but not from 10" to 9".

Now, I don't have the 3/4 HP motor on the Mark V and I do run thin kerf exclusively (of late) so that may be why.

This may be just what I need for the Crafter's Station. I don't use it a lot as a saw but I think I'll do so for a while just to get a performance comparison. It'll have to be done in real time though. With wood costing what it does these days, I can't let myself start making sawdust of it just to test a theory.

There will soon be a new young "Dusty" in the family (a great grandson due any day now) so projects won't be hard to justify. A few words dropped in the right places and I got one (project that is).

foxtrapper · Post by **foxtrapper** » Wed Mar 11, 2009 7:32 pm

easterngray wrote:Is it possible that the one inch of blade really causes the motor to work that much harder?

Absolutely. You lose force exponentially as you move out from the center of the blade. That 1" (actually 1/2") makes a very appreciable difference.

Or to put it another way, you get a lot more torque out of a long wrench than a short one.

bucksaw · Post by **bucksaw** » Wed Mar 11, 2009 8:18 pm

I run a 10" Freud thin kerf on my Greenie 3/4 hp with no issues. I've never used a Shopsmith blade but it could be that Freud just makes a better blade. I also run Freud blades on my Grizzly cabinet saw (standard kerf) and my old Craftsman radial arm saw (thin kerf with negative hook). I should mention that I just got done rebuilding my headstock and switched to the PolyV drive system and replaced all bearings (including the motor) so my Greenie might be running with a little less resistance than a Greenie with some miles on it.

dusty · Post by **dusty** » Wed Mar 11, 2009 8:44 pm

bucksaw wrote:I run a 10" Freud thin kerf on my Greenie 3/4 hp with no issues. I've never used a Shopsmith blade but it could be that Freud just makes a better blade. I also run Freud blades on my Grizzly cabinet saw (standard kerf) and my old Craftsman radial arm saw (thin kerf with negative hook). I should mention that I just got done rebuilding my headstock and switched to the PolyV drive system and replaced all bearings (including the motor) so my Greenie might be running with a little less resistance than a Greenie with some miles on it.

For the record: For years the Shopsmith Cardide Blades were manufactured for Shopsmith by "Freud". Many of us who swear by the Shopsmith blades were using Freud or said another way "If you don't like Shopsmith blades you might not like Freud".

easterngray · Post by **easterngray** » Wed Mar 11, 2009 8:52 pm

Bucksaw you make a good point. When I restored my Goldie (a 1960) I kept the Gilmer drive and installed new belts - no new bearings and I didn't do a thing to the motor other than install a new cord and new switch. I like the SS 10" blade plenty - it's just that I bogged down with it when ripping. As I said, with the old (but sharp!) SS 9" rip blade and the new Freud 9" TK combo - no bogging down. Alec

2manband · Post by **2manband** » Thu Mar 12, 2009 4:00 pm

Maybe I'm over-simplifying this, but by switching to a smaller blade, aren't you just reducing the tooth velocity and increasing torque? Wouldn't slowing things down with the speed changer have the same effect?

charlese · Post by **charlese** » Thu Mar 12, 2009 4:24 pm

Good Question, 2 man!! Very astute! BTW where are you living now days?

JPG · Post by **JPG** » Thu Mar 12, 2009 5:02 pm

2manband wrote:Maybe I'm over-simplifying this, but by switching to a smaller blade, aren't you just reducing the tooth velocity and increasing torque? Wouldn't slowing things down with the speed changer have the same effect?

As foxtrapper pointed out, there ARE two things to consider. [Exponential???]

1)The circumferential speed(Teeth/time if you will).

2)The distance from the center(Lever arm if you will).

Slowing down the rpm's WILL compensate for #1, but will not compensate for #2. The Power gain by adjusting speed will be far short of the 50% larger 1 1/8 HP motor.

Yes you can get the job done if you also slow down the feed. It just takes longer.