Shopsmith Forums

Just bought a Mark 7 with Power Pro v2. My question is: I have a existing 220v outlet less than 2 feet from the Mark 7. My closes 110v is 15 feet away which will require a extension cord. I don't want to cut the existing plug off so I was wondering if I could make a short pig tail with the 110v plug on one end and the 220v plug on the other. Checked the existing 110v plug and the wires are on the right terminals. Looking at the Mark 7 owners manual, page A-5 which talks about utilizing 220/240v it appears all you have to do is change the plug. Is there anything wrong about using the small pig tail cord.
Thanks Jon

SAFETY! A new plug is cheaper than a new tool or appliance, or a trip to the emergency room.

I agree with RonKlein. A simple adapter pigtail is hazardous because it could too easily be used to connect a 110V-only device into 220V. Which is why it’s an electrical-code violation.

If you’re dead set on retaining the existing 110V plug on the Mark 7, at a minimum secure the adapter pigtail to Mark 7 power cord with a cord lock such as this: https://www.amazon.com/Farm-Innovators- ... B002MHC138

And then make the lock quite difficult to remove.

Jon,

Ron and Dennis have given some very good advice. I would recommend you follow it, but I want to share a bit more. The pigtail you describe is more of a mis-matched extension cord because pigtails are typically done inside of a junction box. So, if I understand you correctly, you want to make a short extension cord that will have a 120V receptacle on one end and a 240V plug on the other end. Is this correct? I have worked at companies in the past where similar, but different mis-matched extension cords were common. Typically in a lab setting. Our labs were wired quite well, but still there are many lab benches in a small space so we were always running out of power connections. It was a large communications company, so the building labs were always kind of a generic setup. We had plenty of 120V power with the power bars on our workbenches, but needed 240V for our thermal ovens and thermal streams for device testing. We always had to use an extension cord for them and many times the cord had mismatched plugs versus receptacles. To be clear anything from 208V to 277V was within specifications for a thermal oven or thermal stream, so there was no chance of damaging the equipment when we plugged into a different outlet in the lab. Long story being short, we didn't always have a 240V connection close by to each workbench, so we took whatever was available, often times it was a 208V connection when 240V was preferred. I mention all of this to say that as long as you know what you are doing, then by all means go ahead. My concern would be if anyone else could one day use your shop, e.g. what happens if a family member comes in, unplugs the PowerPro and plugs in a 120V device to your mismatched extension cord? My suggestion is they have lockout devices for extension cords for workplace safety, but they also have something called a "power cord lock". IF you make the mis-matched extension cord as you suggest and put something like a power cord lock (with padlock) on it then NO one can separate the PowerPro cord from the extension cord without having the key to open the padlock on it. This would preserve your Shopsmith original 120V power cord, but also let you plug in to 240V with safety. I highly recommend a large print label of some kind on this extension cord warning about its use/intent. Just do a Google search for "power cord lock" - below is just one example from Amazon. Hope this helps.

https://www.amazon.com/Power-Safety-Ind ... R3K2?gQT=1

BuckeyeDennis wrote: Tue Jul 29, 2025 8:59 pm I agree with RonKlein. A simple adapter pigtail is hazardous because it could too easily be used to connect a 110V-only device into 220V. Which is why it’s an electrical-code violation.

The second time I lived and worked in Europe multi-voltage equipment and devices had become somewhat common and adapters similar to what the OP describes were very common. The only difference I can think of is that they adapted a U.S. style 110V plug to a European style 220V outlet. Not surprisingly, it happened from time to time that people would inadvertently plug a 110V-only device into 220V resulting in its immediate destruction. My only question here is what Electrical Code would it violate? The NEC's authority generally ends at the outlet receptacle for circuits that have one (or more). UL only applies to UL-certified devices, which I'm pretty sure excludes the Mark 7 (and similar).

That said, I researched this once and did not find the answer. There are many multi-voltage tools on the market but I didn't find a definitive answer. My solution was the opposite of the OP's I rewired my M7 with a NEMA 220 V plug and made a short pigtail so that I can plug it into a 110V outlet if I happen to be taking advantage of its portability. I feel this was safer, and that it is somewhat impractical to change plugs if/when I want to change outlets.

- David

I believe that the NEC requires that plugs and receptacles be used in accordance with their NEMA ratings. But I have no idea where my old copy of the NEC is, so I Googled it. Here's what the AI summary says:

In the National Electrical Code (NEC), the requirement that plugs and receptacles be listed for their use can be found in several sections, particularly within Article 406 - Receptacles, Cord Connectors, and Attachment Plugs.

Specifically, NEC Section 406.3(A) states that receptacles must be listed and marked with the manufacturer's name or identification and voltage and ampere ratings. This ensures that the receptacle has been evaluated and found suitable for its intended purpose by a recognized testing laboratory.
Additionally, other sections in Article 406 and other parts of the NEC may detail specific listing or approval requirements for different applications or types of receptacles, such as:

406.9(B)(1): Regarding receptacles in wet locations, requiring an enclosure that is weatherproof whether or not the attachment plug cap is inserted and specifying that the outlet box hood must be listed and identified as "extra duty". It also states that nonlocking-type 15- and 20-ampere, 125- and 250-volt receptacles shall be listed weather-resistant type.
210.52(C)(3) or 210.52(C)(2) depending on the NEC version: Regarding receptacles in countertops, it specifies that receptacle outlet assemblies listed for use in countertops or work surfaces are permitted to be installed in those surfaces.

In essence, the NEC's definition of "Listed" in Article 100 underpins these requirements, stating that equipment, materials, or services must be included in a list published by an acceptable organization that evaluates and inspects products and ensures they meet designated standards or are suitable for a specific purpose.

As for the NEMA ratings themselves, the charts are clear and unambiguous. Wikipedia has a good overview: https://en.wikipedia.org/wiki/NEMA_connector.

I thought that the NEMA ratings on plugs and receptacles were just that "ratings". In other words, they specify max voltage and amperage, but they don't explicitly indicate the intended application. For example, I installed my Mark V 240V on a NEMA L6-20 plug which is listed as a welder or plasma cutter in the Wikipedia chart. My point is it is up to the owner/electrician to choose the appropriate product that meets voltage and amperage specifications, but the applications can be varied. Short of a relevant NEC section that says it is a no-no, I still stand by what I recommended to the OP. In fact, any homeowner is allowed to do their own electrical wiring. Expectation is that it follows the NEC, but we all know that some do not do so. The only time it is a problem is a) when the house is sold and a building inspector catches it or b) there is a fire or other catastrophe because of it. I am curious as to what the relevant section of the Mark 7 owner's manual says about conversion to 240V. Can someone post this please? Do they recommend cutting the 120V plug off. and replacing it? IF the plug is rated only 120V then perhaps a reason NOT to follow my earlier advice. Also, I really wish Shopsmith would provide separate neutral and ground connections on their equipment. Even my Mark V, wired for 240V from the factory, doesn't have a separate neutral. I hope the new Mark 7 is double insulated inside. I digress...

P.S. For the work example I gave up above, the mis-matched extension cord was constructed by electricians we had at the facility. Presumably they followed the NEC for our unusual request or they wouldn't have built them. One time, we needed another one made and one electrician did ask questions but once he saw the input ratings on the oven we were hooking it up to, he agreed to proceed.

Why not just get an appropriate length extension cord that is used for higher current window AC units? I know that most high current 120-volt devices say to not use an extension cord, but the issue usually (besides wire gauge being too small) is the fact that you have added one additional plug / socket to the circuit that could lead to heat buildup and some voltage drop. This 15' /12-gauge AC extension cord from Lowes isn't particularly expensive so why not give it a try? Run it for a while with a load on the saw and check the intermediate connection for excessive heat.

https://www.lowes.com/pd/Utilitech-Appl ... 5013598303

An alternative course of action.

Replace the M7 plug with a 250v 20A plug. NEMA 6-20P

Make a 'cheater'(adapter) with a 125v 15A NEMA 5-15P plug connected to a 250v 20A NEMA 6-20R receptacle.

The erroneous use condition is plugging a 250v appliance to a 250v receptacle being sourced by 120v. Not good, but less disastrous results.

The adapter is only needed for portable use away from the shop.

jimbeaux wrote: Wed Jul 30, 2025 9:58 pm Why not just get an appropriate length extension cord that is used for higher current window AC units?

Certainly an option, but remember that the DVR motor in the PowerPro produces more HP (2HP) when on 240V.