1.5hp or 2 hp

[Steve Nunn]

ok, got most of the 72" grinder built -took longer than I thought it would. I am now at the stage where i cant really build any more until I have the motor and know which way it rotates.

What size motor would you recommend I fit?

I have been on the lookout on fleabay for a motor for quite some time, but they always seem to go for just slightly less than Machinmart sell them for. So I am going to go and get a new motor. There is only about £5 difference between the two. I want it to be powerful enough but I dont want an overkill (assuming 2hp is an overkill, which it may not be)


Any advice greatly received.
thanks

steve

[Bogflogger]

More is better!

[imagedude]

I'd spend £275 on a 2HP, 3 phase motor and an inverter.

[Singeblister]

more power

Just out of interest , does the 3 phase inverter suck a lot of electricity or is it just to change to some other type like ac dc ..... lol sorry don't now much about it.

[ZDP-189]

Both single and 3 phase induction motors are bi-directional. The direction of rotation depends on how you connect them to the mains.

As for power, 1HP'll do ya. 1.5 will work better, 2 will be the most you will ever need. I do heavy grinding on a 2x72 belt using only 1HP.

If you are budget limited, consider that for about the price of a 2HP single-phase motor, you can buy a 1 or 1.5HP 3 phase motor and a sophisticated variable frequency speed controller. Some sanding and grinding tasks are much easier at slow speeds, especially when using a finer belt on a hardened and tempered steel blade.

[ZDP-189]

In case I wasn't clear, the speed controller also converts single phase to 3 phase. 3 phase motors are cheaper. Hence additional economy and utility for the same price.

[mikesknives]

i bought a 1hp 240v 3 phase a invertor off ebay £250 pounds and it runs smooth as silk and was fairly easy to wire up.

its a little more money for the motor but you then save by not having to mess about buying extra pulleys and shafts to turn a cheap MM motor into multi speed plus you save time no(no belt changes) plus you save space (no extra pulleys and shafts mount a drive wheel straight off the motor shaft) and infinatly variable speeds plus soft start plus motor braking i could go on.
more expensive but more features.

it always gets mentioned and i'll bring it up again theres no such thing as a cheap knife grinder theres cheaper options but nothing to compare to a real machine so it depends on how serious you are only hobby want to make great knives spend the money just messing around making one or two compromise but expect frustration.

now i expect a flurry of posts from people about how thier grinder makes great knives and it cost tuppence and somemore to say theres nothing wromg wit files but i didnt get up before i went to bed to be murdered by me dad and its just my personal opinion.

mike

[Zeubest]

now i expect a flurry of posts from people about how thier grinder makes great knives and it cost tuppence and somemore to say theres nothing wromg wit files

Everybody have his own idea about what is cheap or not. So what ?
If you're happy with your grinder, then, it's perfect.
Some are making their own grinders to save money, some because commercial ones don't fit precisely their needs, some others for the pleasure of making it.

The only point that makes me feel perplex is when a grinder costs more than a brand new pro one, like :
http://www.coutellerie-thiers.com/en...s/jolivet.html
Standard machine costs around 1300€ + VAT

For the question

1.5hp or 2 hp

: 2 hp !
Pro machines often have 3 hp motors.

[Steve Nunn]

looks like its a 2Hp motor. The motor i am looking at is about £74
(somewhere around there). Whilst i have every feeling that I should go withthe 3 phase and variable speed drive, not sure about the extra money).

However, having said that I am now going to have a look at the difference in
price.

What I didnt say is that it wil also be variable speed through the use of pulleys. Havent calcuated the speed yet because I havent bought the pulleys, but there will be approx 4 speeds.

Steve

[mikesknives]

steve i looked at these while i was designing my grinder i don't know wether its any good for you.

mike

[Steve Nunn]

Thats natty, i going have a ratch about for them to see if they are cost effective.

thanks

steve

[ZDP-189]

Steve, a grinder is one machine that really doesn't suit pulleys. Technically, it's fine, but when grinding a knife, I move up (and often down and up again) a series of belts from coarse to fine. In doing that, I need to change the speeds to match. It just takes too long to change belts on a V-pulley. I have a 4x48 linisher running a three speed belt and I have changed speeds a total of 3 times a year - mostly I run it on the wrong speed.

I know your mind is probably made up already. If you are determined to use a pulley system, I recommend you build a levered quick tensioner into the pulley so you can change the speed easily.

[Razorback]

I'd say either one would work. I have a 1 1/2 hp and I'm totally satisfied with it. If you can afford a 2, why not go with it.
Scott