How To Slow Down A Mitre Saw To Cut Metal - Cold Cut Saw Conversion 

Great seeing someone adapt a tool to meet their needs, Bravo

AC motors designed to run on a certain voltage (120vac in the USA) depend upon back EMF (ElectroMotive Force) to limit current draw. EMF is generated by the spinning of the rotor (which is a spinning inductor). Inductors resist the increase in current. When back EMF is reduced due to lower voltage input or if the rotor is not spinning, current draw from the line goes up generating lots of heat. That's why your transformer approaches and exceeds the boiling point of water. Also, the saw's motor heats up, too. EMF is sometimes called CMF/CEMF (CounterElectro Motive Force). Not the best way to control motor speed. DC motor speed control is done by voltage adjustment (cheapest method).

great explanation and fantastic math,,, I am struggling with the same problem.Thanks for your info

Cool video! I might have to try this...

Awesome !!! Thanks for sharing

Thank you.

I liked the video just from the thumbnail, but when I saw the cattle skull belt buckle.... I subscribed!! Haha, keep it up dude!

Brilliant!

Good ole craftsman

Impressive!

You sound quite a bit like a fellow named Jeremy that was into building belt sanders and such, If you are glad you're back if not take it as a compliment since you seem pretty darned smart like he was.

I think you would have better luck cutting if you blocked your part out about 1.5 inches from the fence. Were the fence is now it is trying to lift the part and clime down the part. Moving the part out will put it in a more neutral position were most of the force will be back toward the fence and down to the table..

One other thing, on re-winding microwave transformers: They're usually constructed a bit differently than most other transformers. Instead of having the laminated iron plates of their cores riveted together, there will be two thin weld beads running down the joints where the primary and secondary halves join. I have no idea why they do it that way, but but it makes them an excellent choice for hobbyists to tinker with. The welds aren't very deep and you can easily remove them with an angle grinder, allowing the end to be removed. (Try to leave the half of the weld bead toward the end piece intact, so it will still hold the plates of the smaller end together.) Once the end has been removed, you can slide the secondary coil out without having to chop it up. Of course it's a lot easier to wind on a new secondary coil, but you can also experiment with different numbers of windings quickly and easily. The end plate doesn't have to be welded back on; just held firmly in place. I use a bar clamp for testing, then black vinyl electrical tape for semipermanent assembly. I haven't noticed the heat buildup problem you mentioned, but I'll be looking out for it now that I know it's a possibility. (I haven't tried using any to run powerful motors, but a transformer will get hot if you try to pull more power through it than its' primary is designed to handle. Depending on the wire gauge and number of turns in the primary, they can also get hot when plugged in with no load applied.) Good luck, and thanks again for the video!

I think that if you add a counter-weight at the back you can eliminate the loss of depth-control.

Great video!! Haven"t heard of winding a transformer before, very interesting to see I also loved the background tracks as well. How would this compare to a router speed controller or a Variac? I am looking at both of these options to slow down a portable table saw [universal motor] to cut mild steel (for the same clean repeatable cuts you are after, and without spending the money to get a dedicated machine)

A variable voltage transformer (little heat) from Amazon costs $100 and do the same job as you made.

You should use a saw blade with negativer tooth angle, which presses down on the steel instead of pulling up.

That belt buckle 🤠

Still great video buddy! So what I would do man and forgive me but get a shock absorber off the hood of an old car or something like that. That has a screw adjustment or (pressure relief valve) and if it's blown that's even better it'll be smooth as hell and most likely work just right. As for me I'm gunna try doing this with my band saw. I have a porta band cordless flexvolt that I'll be jigging up to an aluminum plate frame making it a auto horizontal bandsaw chop if you will. Also I'd like to ask you some pointers on making a mill with my radial arm saw... Lol I wanna make a c channel and put some bearing rollers inside it and hang my radial arm saw off it and make a mill... I know crazy as hell but I'm doing it any thoughts?

Thank so much for your great details video

Great video and looks simpler than Jeremy Fielding method where he replaced the motor. I've been thinking of converting my Dewalt mitre saw and this looks relatively straightforward and I have a microwave transformer. The math will hurt as I don't understand electronics well enough yet. What gauge wire did you use for the secondary winding and how do you determine that?

Doesn’t the increase in amperage mess with the motor?

Decrease the amplitude, what you 've been doing will destroy you're motor. To decrease the rpm's one should lower the frequency of the sinus wave. A frequency converter is what you need.

Makes my brain hurt trying to figure out what you are doing. Not a criticism, just an observation. Amazing how you figure all of this out. Congratulations.

One cutting steel isn't it important to have a balance between the speed and material feed rate, meaning you could go for a higher RPM provided your feed rate will set appropriately. With a miter saw The freezer feed rate

Have a 10" Skilsaw 3810 miter saw that turns at 5200 rpm . I got a transformer from a microwave but how did you determine the primary coil had 90 turns on it? The label on the transformer says MD-803AMR-1. Thanks for posting this video, will help out greatly when I know the turns on my coil.

Install a blade specifically made for miter and circular saws. Freud diablo metal demon for instance . Make life easier.

How many amps are you pulling on primary side of the transformer now? Thank you.

Reduce spring strength, to manouver miter saw more easily. You do not need to reduce motor power and torque, by lowering voltage input to motor. All you need to do is to install very low feed rate system for blade. Very easy with some welding and small 50 W, electric motor.

curious what size wire did you use for the secondary winding?

Really good video. Hopefully your read some of your comments because I do have a couple stupid questions. If you search RU-vid on how to modify a standard compound miter saw to make a cold cut saw, most videos basically point to a blade choice. It is hard to find videos on what to do with the electrical side of things and actually slowing the motor down which is exactly what you did (what I was looking for). That is where my questions start. With your transformer method, what was the effect on torque? Did it maintain the torque or was there a significant loss? My next question is, how well would a VFD work? I bought a cheap compound miter saw on offerup for $40 to make a cold cut saw and I figured if I ruined the saw I would only be out $40 which I'm not worried about. It was also an older Delta so it's an all metal chop saw which Is a good thing in my opinion. Would it be worth it to use a VFD? Again, excellent video and thanks for going a little deeper on the electrical end than most!

Could you use a Variac Transformer?

I know a man with one eye who drilled out an abrasive blade to fit his arbor----of center a smidge caused the blade to "blow up"

It’s a universal motor. Get a 48v dc battery charger Lots of torque half speed on DC

Sounds like you should've bought a 10" abrasive high speed wheel?

Excellent video. I love seeing smart young people do projects such as this one. Love the math on simple paper and pencil. If more boys would learn valid things in schools, our world would be a much better place. IMO, a man, husband, father needs to be resourceful and skilled in many ways, lucky are those women who have husbands, boyfriends, who fit these characteristics, and are hands on, logical, practical men, but I have found that few women appreciate men like these. Ladies, if you have a man like this, you have a nice gold nugget and you may not even know it. Likewise, can be said about smart women or children in general who have learned from hands on fathers, mothers. One thing I would have mentioned, at the start of the video, where it shows taking apart the tool, is a note to make sure to UMPLUG FIRST!, and for the use of a microwave transformer, is a word of caution that working with microwave transformers can be lethal if one does not understand the mechanics of it. Unpplugged no problem, but I am afraid some person may just plug it on in stock form and electrocute himself with the output. Explaining that using a microwave transformer with the secondary windings modified to STEP DOWN, is safer, lower turns and heavier wire lowers voltage but increases current without the use of math would be prudent for those not familiar with electronics or electrical circuits, the thing that makes a microwave XMER lethal is the STEP UP windings where it generates alternating unfiltered dirty and killer energy in the KILO VOLTS!

Did you do 32 or 36 turn

What brand blade are you using? Freud-Diablo 10 X 50 X 1 Ferrous CERMET CSB, Multi, One Size (D1050CF) calls out max speed of 3000 rpm.

Hows the torque on the saw? Those motors get touchy sometimes dropping the incoming voltage

Add a large resistive load like a 500w or 1000w tungsten lamp with the dimmer

use a cardbord former in begiining of transformer, stop wire shaving first few turns

Lo hice y funciona

...I just use a abrasive disk rated at 6000 rpm and my chop saw is rated at 4600 and I use a cardboard (pop can box) shim for the side of disk without metal protection and a C clamp or wood clamp to hold down...get your files ready to clean the metal though

What size and type of wire used on secondary?

how has this held up? I assume motor life is significantly reduced.

Thank you. How many turns did you end up with?

We got 230v What transformer do i need to have? 230v to? May be i can buy a transformer.

When you just drop the voltage like that, are you not worried about overheating the motor by drawing significantly more current under load? Good old P=IV, the motor power (P) is fixed and you've just substantially reduced 'V,' so 'I' going to go up proportionally, is it not?

Haha Your handy!

Cold cut saws require light pressure this is not true the chip load on a cold cut saw is very high commercial units normally habe a 3ft handle for leaverage

The rpms not much difference I would just leve it

Why speed up 300% Couse the saw dont saw?

I don't think the average DIYer will do this instead of just buying a cold cut or use an angle grinder to cut steel. If you have a better way to convert the average chop saw, then make a unit that can convert or ..... just saying. The video is interesting but hardly practical to the average DIYer to do.

Righty tightly lefty loosely.....LEFT HAND THREADS...??

Hot damn son, I hope you don't grow up to be some left wing bat. That was awesome.

Go buy the right tool

Metal boxes for outlets. There is a electric shock aroun a corner for you. Ever heard of pvc boxes?

Sorry, but the formula and the calculations are wrong! Is not possible what you did there !

lol so much wrong with this…