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weight to speed?

13K views 46 replies 12 participants last post by  mkoukkgou333 
#1 ·
Any body here know how to decide what speed a certain router bit should be used at? I'm contemplating buying a large diameter 1/2" bit but my makita router does not have speed control.
The manual just gives a vague "match weight to speed" but no specifics.
Any weight / speed charts out there?
I'd prefer actual charts rather than seat of the pants "feel
 
#2 ·
here.....

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#9 ·
I bought this 3 3/4" Forstner bit for a one off project and in the drill press at it's lowest speed it scared me. A 2 3/4" router bit spinning at a suitable speed would also scare me and I'm not easily scared but am accident conscious.
 

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#10 ·
I cant work this out. In the USA, variable speed controllers for up to 15 amp machines are $20 or less.
In the UK, The ONLY controllers that take 15 amps are $70 and more.
The exact same pictures of the 15 amp on the amrican sites are used on the UK sites, but are then only rated for 8 amps.
 
#12 ·
Bob I thought your standard circuit was 230 volt and 7.5 amps. Is that not correct? If I remember the formula correctly then 7.5 amps at 230 volts should equal 1725 watts which is about what that Makita would be running if it was on a 110 volt 15 amp circuit here. All of our routers will run on a standard branch circuit here. Maybe Harry could respond to that. I know he's more knowledgeable on the subject than I am. If I got all that right then that might explain why you can only find an 8 amp controller.
 
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#18 ·
Yes Charles, that Makita router is rated at 1850 watts and because amps equal watts divided by volts it becomes:
1850 divided by 230 which equals 8 amps. I know that the purists will point out that the formula relates to direct current but it's close enough.
 
#13 ·
Well that has stirred the waters a bit.
UK (and Cyprus) electricity standard power circuit is 230 volts 13 amps wall socket. All power tools are supplied with a 3 pin socket that contains a 13 amp fuse.
I used an online calculator and input 230 volts and 1800 watts and it told me 15 amps. I believed this untill having read this reply.

It looks like I was misled.

I have just looked out the instruction book that came with the router and it does not state supply requirements, only that it must be fitted as per the data plate on the machine.
The machine itself is buried inside a fully enclosed router table and I am just too busy to take it all apart at the moment.

I've tried looking it up on ebay.co.uk (which is where I bought it) but it appears to no longer be sold in the UK.

Its a makita RP1800 running on 230 volts 50 cycles. If anyone can work that out please let me know.
 
#16 ·
...at 1800W/230V, doesn't that equate to just under 8 amps...?
 
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#19 ·
Gotcha...I had forgotten that 50Hz draws more current than 60Hz...about 1.2 times the power...

I'm with you...go with the specs on the box for 50Hz machines...
 
#24 ·
I think we may have a problem Bob in finding anyone with experience using a controller on EU type power. You may have to decide if you want to be the guinea pig. I can tell you from experience that even at recommended speeds listening to one of those very large bits come up to speed is just a bit intimidating.
 
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#25 ·
Charles, the main problem with me being a guinea pig is that I would have to buy in the UK. That means 3 or maybe 4 weeks before it arrives. then, if it goes wrong, it would cost more money to send it back than it cost in the first place. which would leave me 2 months down the line out of pocket not just for the box but the large bits as well. Thats almost a couple hundred dollars.

I'm going to have to shelve the project untill I can find a definitive answer.
 
#27 ·
Bob...are there other items that a speed controller could be available for you, for example, a fan or other such device...? Maybe instead of looking for a router controller just a plain ole controller for an 1800W motor...? I dunno...fan, exercise equipment, food blender... just grasping at straws here...

Maybe a call to an electrical supply shop...?
 
#28 ·
Hi Bob, I notice that in most posts, you give the amps and or wattage, but not the volts. That would clarify the issue somewhat. I think most of the amps or watts are stated for startup. Running takes less unless the bit is large, then the amps will rise because the load is heavier. I think you either need a local electrician or to contact the route maker for their take.
 
#29 ·
Bob did say he was on 230V
 
#31 ·
@sunnybob,
What you can get is an AC motor controller kit. It may require a very small amount of soldering, which I assume you can manage - there are only a few components (as in 5 or 6).
Locally (also 220/230V country) a 2000W kit costs about 10 Euro (may need an enclosure - small metal box, two grommets, cable in and out). If you want to go big, a 10KWatt kit is around the 30 Euro mark. The kits are based on a diac-triac pair, pretty much like what is built into variable speed machines.
If you feel up to it, you can just get the components, but you might have to fiddle with a mounting board and heat sink.

I made a 1000Watt controller for a small motor to drive a British-made Multisharp drill bit sharpener. Cost about 5 Euro, but I had a case, etc.
 
#33 ·
Thank you all, I have finally had everything explained to me by a UK expert.

The controller issue that was concerning me was the apparent mis match between the watts stated on the controller, and the watts stated on the makita.
I seem to have gotten completely misled by doing calculations with online services that could not tell the difference between voltage and cycles.

At 230 volts and 50 cycles, my makita only needs 1400 watts, NOT 1800. so I can now buy the controller with confidence.
Thanks again.
 
#39 ·
that's not how it works. 230 Volts at 8 Amps is actually 1840 Watts regardless of the frequency. P=E x I which is the power in Watts is equal to the Voltage times the Amperage.. routers use brushed motors.. btw, an induction motor designed for 60 Hz will get too hot at 50 Hz because it don't have enough inductance, which is why a motor for 50 Hz. is larger, more iron.. a motor designed to draw 1800 Watts at 230 Volts at 50 Hz. WILL draw 1800 Watts. btw, that's peak wattage, not average!.. from an MSEE..:wink:
 
#34 ·
I had a feeling that was why you were only able to find 8 amp controllers in 230 volt. This question comes up occasionally so it's good to know the definitive answer.
 
#35 ·
@Cherryville Chuck I'm trying to work out in my mind why the 50 cycle renders more powr output. Is that because the current is flowing for slightly longer each cycle? The difference in frequency would yield 16% increase in current flow, plus the higher voltage. I'm curious in part because I'm thoroughly familiar with 115 volt, 60 cycle electrical practices and theory, but completely ignorant about 220-230, 50 cycles.
 
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