Powermatic 74

[Mike Barton]

I am going to look at a Powermatic 74 tomorrow, geez..12 inch blade with a scoring blade separate, 3 Phase 7.5 HP ...

I am returning to woodworking now that the nest is finally empty... I am currently using a Delta Contractor Saw that is perfecly fine and has a Unifence...

Am I looking at too much saw with the Powermatic ? Or is there no such thing as much too much saw ? It is VERY well priced. And I can re-power or get a phase converter.. I have 220 single phase on both floors of the shop.

Mike B

[Van Huskey]

You can never have too much saw. 30 years ago they were $5000 saws, close to $10K when they quit making them. Bottom line it is a GREAT saw if it is in good condition and I wouldn't think twice about picking one up IF you feel like dealing with 3 phase. If you are considering re-powering be aware it has 2 motors so factor that in the price.

[Don Jarvie]

If its priced right then it may be worth getting a 5 hp single phase and sell the 3 ph.

Your never going to need another saw for sure.

[Mike Barton]

So here it is sitting in the trailer....HEAVY !!!!... but getting ready to unload... I'll shoot some more pictures later if my fingers survive unloading this beast... a Model 74 but does NOT have the scoring blade and extra motor....Extension table is sheet metal over 2 x 4 frame so would need to be upgraded but if I keep it I would build a new one and incorporate my router.

Has the original "T-Square" fence.

Anyone have any experience with static 3 phase converter ? Internet research seems to be saying my 7.5 HP motor would be running at about 5 HP with the converter...that make sense ?

The question again....clean it and upgrade it or keep my really nice Delta with the Unifence ?

[Van Huskey]

... a Model 74 but does NOT have the scoring blade and extra motor....?


Huh, wonder if it was the 74A that got the soring blade, or if it was an option...

I would fix her up and sell the Uni but thats me.

[David Castor]

Regarding the 3-phase issue - my suggestion would be to look into a 240 V variable frequency drive. They can produce three-phase power output from a single-phase input. Some smaller ones are specifically designed for this, but probably not a 7.5 hp.

You can also use a model designed for three-phase input on single-phase power by derating it. Looking at the Yaskawa website, they recommend that when running a three-phase VFD on single-phase power, size it so that 50% of the VFD rated output current is equal to your motor full load amps. Even on single-phase input power, it will still produce three-phase output to the motor.

You might check EBay for used VFD.

[Ryan Hellmer]

I have run a tablesaw off a VFD. Here's what my research has shown me; Static is a big no-no, VFD works fine if (1) its used single speed or (2) variable speed with the proper motor, Rotary is the way to go.

That being said, I like my VFD but it only runs one tool. Also, to get a VFD to run even 5HP is going to be a shiny penny. Rotary converters are more expensive but can run full power and multiple motor loads without damaging your motors (I bet that 74's motor isn't a standard off-the-shelfer).

Rotary converters are actually fairly simple to build. I found a place online that sells a plug and play kit, all you need to supply is a 3 phase idler motor. As you may know, salvage 3 phase motors are easy to come by and pretty cheap. I am about to pull the trigger on the kit (once my 10HP idler motor gets here). I would check with a salvage yard or HVAC company as they will likely have 3 phase motors sold for scrap that still work like champs. You may be able to get one for free.

Once you have a rotary in place you can expand your collection of 3 phase tools at will.

Ryan

[Stephen Cherry]

Here is a drive:

http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/PC1-75.html

I have a 7.5 hp saw and have been working on a phase converter. I bought a 15 hp motor for 175 dollars, some start capacitors, and some run capacitors. It works OK! Next I am going to get a metal enclosure, push buttons, thermal overload, etc to make it work right, and safely.

http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

It's possible to buy a phase converter panel on ebay; you supply the motor.

Any specific questions, feel free to ask.

nice saw!

[Van Huskey]

I forgot to say:

YOU SUCK!

That is an excellent score!

[Mike Barton]

OK here it is, a much better pic...needs some tlc and cleanup..... if you thought I sucked before... let me tell you the price....120.00.....

Unfortunately the phase converter and a new fence will add up a bit...

[Van Huskey]

let me tell you the price....120.00.....

Unfortunately the phase converter and a new fence will add up a bit...


Major suckage... just major. That is probably near the scrap value of that much iron...

[Mike Barton]

Reading just enough to be dangerous it appears that a Static phase converter will deliver 2/3 of the rated HP. If I can live with reduced HP, and it's starting at 7.5 are there any safety or life of the motor issues with a Static Converter ?

Thank you for the info so far.....

[Karl Card]

OK here it is, a much better pic...needs some tlc and cleanup..... if you thought I sucked before... let me tell you the price....120.00.....

Unfortunately the phase converter and a new fence will add up a bit...



you suck worse than anything that has sucked before.....

[Don Buck]

I came across a great deal on a 20" bandsaw with a 2 hp 3 phase motor. I explored the cost of a new motor, heaters and switch and decided to to keep the 3 phase (I might find more 3 phase bargins!) I went with an American Rotary 5 hp I as know little about 3 phase and found the folks at American (tech service 262 268-7014) very helpful in determining the best arrangment. The installation wasn't too bad as I found a used 3 phase distribution panel with breakers and disconnect on the internet for around $100. You can probably get by without the boxes but it is safer to have the slow burn fuses in the disconnect.

Good luck.

Don

[Greg Loxtercamp]

Your comments about this saw not having a scoring motor is interesting. A 12/14" Powermatic without a scoring motor is a model 72...with a scoring motor is a 74. I have a model 74...that is, with a scoring blade. Mine is the gold paint model...circa 1985. It is a 7.5hp 3ph as well, with the 3/4 scoring blade. Mine was not $120, but rather $450, but that came with two glue-edge rip blades, a high quality melamine blade, two combination blades, a 8" dado set and, of course, the scoring blade set (all quality blades), so my suck-factor should be near yours... :)

Regarding a phase converter... I built one before I got this saw and started with the purchase of a 5hp motor. I got a box (a large 3ph service disconnect), a large starter (for the run caps and idler motor), a smaller contactor for the start caps, run & start caps. I put it all together and found that it works very well. I recently upgraded the circuit and integrated a voltage switch that will automatically switch in/out the start caps. I was worried that a continuous pressing of the 'start' switch would have the start caps in too long...with the possibility of them exploding (and making a mess of things).
Yes, some of you would state that my 5hp phase converter shouldn't power a 7.5hp saw, but it works well. I noticed after I installed the voltage switch in the converter, that when I start my 7.5hp saw, the start caps get switched in for a second. I am not concerned about that as it is a fairly low start load and comes up to speed quickly. Also, the idler motor only supplies the third leg so, two of the three legs are tied directly to the line, so the smaller idler motor only effects one leg. The generated leg may droop in voltage under full load (very infrequent, if ever). If this was on a CNC machine, then I'd be worried about the third leg voltage droop, but on a motor, it should be fine.

You mention that you need a new fence. That is either a Beismeyer or the Powermatic fence. Why would you want a new fence?

Good luck and give us an update!

[Jeff Duncan]

That's a good score, whether or not you should keep it only you can decide, but here's a few things to consider. There's a general 'bigger is better' vibe that goes with machinery, but that's not always a good way to go. Would you want to drive an hour commute to work in a Freightliner? Sometimes it's better to size the machine based on your needs.

So the obvious advantages of a bigger saw are increased power for heavy cuts, increased capacity with bigger blades, and a stoutness that is just very nice to work with.

Some downsides....dealing with 3 phase power and how to get around it. Much farther operator reach to push stock past the blade, some guys find this problematic. Bigger blades....ie more expensive blades, can't use that nice collection of 10" blades you've put together, unless you get them re-bored which would eliminate the advantage of increased capacity. Not to mention if you use one, needing to buy another dado blade. If you've invested in aftermarket accessories like miter gauges and/or tenon jigs they most likely will not work on your new saw.

So you have to decide whether or not the pros outweigh the cons for your needs. I've run a lot of saws and currently run a Uni and a Wadkin 12", and they all have their place. If I was going to pick a saw for my personal home shop I'd have to stick with my Uni or a PM66....they're just such great all around saws. For heavy duty use in a production shop I prefer the bigger machine to be able to withstand the abuse I throw at it.

that's my 2 cents....good luck,
JeffD

[Chip Lindley]

Mike, a static phase converter should not be considered. VFDs for 7.5hp are wayy expensive. Look into a RPC that will run your Model 74 and you will be set for any machine up to 7.5hp. You just never know when these $120 bargains may pop up! BTW, YOU DO SEVERELY SUCK!!!

My ARCO Model R RPC starts any 7.5hp motor, plus any other 3ph motors totalling 20hp. In a one-man shop that means I can run a 7.5hp 3ph machine and a 5hp 3ph DC simultanously with no problem. I gave $650 for my Model R on CL. That's not so bad considering it included a Cutler-Hammer Size 2 magnetic starter and about 40 feet of #8-3 w/G hookup wire. I have my RPC set up with an X-10 remote to control the magnetic starter coil. Nice to turn it on or off at the touch of a button.

Look into a "real" RPC rated to run at least a 7.5hp machine and you will be all set!

[Karl Brogger]

Heck of a find!

Be careful when running it by hand. I've only used one without a feeder a few times, and found it very awkward because of the blade being so far forward in the field of the table.

I'd also keep the uni-saw if you can afford the space. Great dado saw, and having two saws in general can be very convenient.

[keith jensen]

Mike,
Nice!! From what I understand, the motor life is going to suffer using a static phase converter. You might be better off with the rotary as a couple others noted earlier. Were you able to test the motor when you bought it?

If you are replacing that fence, please box up the one that came with it and send it my way!
Keith

[Chip Lindley]

Great find Mike! YOU DO REALLY SUCK!!! On a big saw like that, an RPC is the only way to go! You will have the means to run any other 3-phase machine you should find for such a pitance!

I love my ARCO Model R. It will run any 7.5hp motor plus any others up to a total of 22hp. In a one-man shop that is plenty for my largest machine and a 5hp DC running together. Should it turn into a 2-man shop, two big machines could be run at the same time plus the DC.

I spent $650 for my used RPC, which came with a commercial Cutler-Hammer Size 2 mag starter and about 30 ft. of 8-3 wire. I hooked up my RPC to an X-10 remote to turn the magnetic starter coil on/off. I love it! The X-10 stuff is cheap enough, so extra components can be kept on hand in case a part goes South. Small investment; Small headache. In a small shop you can run a 10-4 extension from your RPC to your big PM74. No need for hard wiring.

You've saved enough on your scoring saw to pay for a good RPC. There are good used bargains out there for a fraction of NEW. Keep an eye out on eBay, CL and local bargain papers.