Thread: Jointer/planer cutter speed.

Originally Posted by Amrjon

So, Is this simple case of 1415rpm being the correct motor speed to give the correct cutter speed and potentially doubling it being a bad idea?

Correct.
Double the speed means
- the cutter head bearings won't like it,
- 4 times the force needed to hold the blades in place - or conversely the blades fly out of the cutter head - this is the most significant issue
- blades going blunter faster
- more fine dust and
- more noise.
- probably burnt wood as well

Keep looking for a used motor 1415 - 1440 SP motors are pretty common.
BTW it helps to give a more specific location in your details than Australia.

Thanks Bob,

Those are the sort of logical answers i was expecting, just thought I'd check in case there something more to consider.

Thanks for your response.

On checking the details more closely today it turns out the pulley wheel already on the 2850 rpm motor I was planning to use is 86mm vs the 160mm wheel on the current motor. If my calcs are correct that will produce a belt speed 1.08x the current speed, so with a new belt to suit I should be all good.



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Amrjon,

Couple of other things to consider, as well as getting the speed of cutter correct it also important to ensure the drive will transmit the power required. First I am assuming that the power output of the two pole motors is at least equivalent to the original motor and the smaller drive pulley is the exact same V section as the original.

I would suggest checking the V belt section power capacity using a reputable belt manufacturer's tables as V section size, pulley diameters and centre distances all influence how much power can be transmitted.
Capacity of new drive should not be less than that of the original drive, that is if you require equal performance.

With the small drive pulley there will be a smaller arc of contact between pulley and belt for transmission of power. To ensure correct transmission of available power (and avoid belt slip/burnout) belt tension will need to be increased significantly and I believe you will find that belt life and bearing life will decrease.

Cutter speed is usually about 5000 rpm in the machines I've used (3-phase, 5-10 hp, 120mm cutter diameter, 3- and 4-knife heads)

Tip speed (of the knives) may be a more useful guide than cutter head diameter as clearly the tip speed will vary according to diameter.

Providing the pulleys are compatible with the belts I don't think there would be much of an issue. However I would suggest that if you are going from 3PH to 1PH you up the power a little if possible as my impression is always that the 415V motor has more grunt than a 240V motor of the same power. I know that sounds illogical, but if you doubt it start a bench grinder with a 240V motor and one with a 415V motor of the same power. The 415V motor reaches speed more than twice as quickly.

A while back I substituted a 1.5HP 240V motor for a 1HP 415V motor in a small jointer. It worked really well as did a similar conversion in a Tough lathe. Must keep the cutter speed the same if changing the number of poles.

Regards
Paul

Another option would be to keep the existing motor and use an Electronic VFD (variable frequency drive) to run it.

Pete

Thanks for the replies.
The single phase motor is rated 1HP up on the current one so power should be OK.
Im pretty sure the pulley sections are the same but good point about the reduced belt contact on the smaller pulley. Given that Ive already got the other motor sitting there and the speed will match Ill give it a go.

Thanks for the cutter head speed info too. I might try to calculate what mine will be for comparison.

Originally Posted by Bushmiller

However I would suggest that if you are going from 3PH to 1PH you up the power a little if possible as my impression is always that the 415V motor has more grunt than a 240V motor of the same power. I know that sounds illogical, but if you doubt it start a bench grinder with a 240V motor and one with a 415V motor of the same power. The 415V motor reaches speed more than twice as quickly.

I have heard this before but after measuring the HP output of some 20 single phase (SP) and 3 Phase (3P) motors I have yet to observe this claim. The HP output of motors depends on the load so a 2HP rated motor might deliver ~1/2HP when free running 1HP under a light load, 1.5HP under a medium load and 2HP on high load, and usually will go to 2.5 or even 3HP for a while when really pushed before stalling.

The issue of the 240 V SP motor reaching speed quicker has nothing to do with its ultimate power output but because the 240V only has one phase and generates the other phase using the main input phase and a large capacitor. This is usually enough to produce the counter forces needed to accelerate the motor. A 415 V 3P motor has 3 phases to work continually against each other, which is why no capacitor is needed, and why it produces a quicker acceleration. Once similarly power rated motors are up to speed they will develop the same power.

The 3P motor does provide smoother power than a SP motor but that is happening at the frequency rate of ~50 times pr second. For small SP motors driving machinery with inertial components like, blades, flywheels, pulleys etc these are enough to smooth the power out. On bigger motors it does make a bit more difference which is one reason SP is not used for large motors.

What may happen is cheaper SP motors may claim a bit more power than they are capable of generating but I have yet to see this in my measurements even with some pretty junky motors.

Ok, the calculator has been in action, and if I have it right the 'new' single phase 2850rpm motor will give me 1 additional HP and an 8% increase in cutter speed compared to how she is set up at preset - and i need to watch out for belt slipping.

And Ill be at around 4460rpm on a 100mm diameter cutter, which will be ~25% slower blade speed compared to elanjacobs example above.

Of course that's all talk at present, I haven't even turened it on yet! I am however much better informed than a couple of days ago which was my original objective - so thanks again to all.

Amrjon

I don't think that will give you any trouble at all. Let us know how successful the conversion is. My jointer may be quite similar to your machine and with the increase in power (less than you are intending) it has never even looked like slowing down even with some 'orribly 'ardwoods.

Regards
Paul

OK the 'new' motor and an actual new belt are on and she seems to be working well. Plenty of power and no sign of any slipping on a quick test. I successfully made a nice little pile of wood shavings so it looks like I'm in business.

I dont think I'll be able to resist giving this machine a birthday and a new paint job down the track though. The base (1/2" thick cast iron!) has a very cool art deco look about it that would look great with a two colour paint job to highlight the features.

Wow, check out this beauty.

Jointer Thicknesser in NSW | eBay

No association, other than I would love to own it.

Wadkin is the King.

Regards
Paul

Originally Posted by Amrjon

OK the 'new' motor and an actual new belt are on and she seems to be working well. Plenty of power and no sign of any slipping on a quick test. I successfully made a nice little pile of wood shavings so it looks like I'm in business.

I dont think I'll be able to resist giving this machine a birthday and a new paint job down the track though. The base (1/2" thick cast iron!) has a very cool art deco look about it that would look great with a two colour paint job to highlight the features.

Amrjon

You are very lucky to find a hyco jointer like this! Do you have any photos of the new paint job? How do you find that guard ? It's not like what you see on most jointers?

Cheers stew