I have a mastercraft mitre saw. The blade blocks midway when I am

something is not quite right with that model number and doesn't follow normal Mastercraft format. I wonder if that is the Serial Number?

https://www.google.com/search?q=Mastercraft+RX9938+Mitre+Saw+manual

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did you put blade in backward ?

Simple question, is there something inside of the blade and the blade guard blocking its use? Sometimes a piece of wood or plastic lodges itself in between and is hard to see.

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try a little locktite

There's a slide pin on the back of saw.

Sounds as if the blade is dull. Or perhaps bent. A dull or bent blade blade will 'grab' the wood, rather than cut it, resulting in binding, or kickbacks.

Solution; replace the blade with a fine-toothed, good quality blade. If the blade is new, then check that the blade is bolted tight on the arbor. If the blade is loose, it can result in kickbacks.

Also, check that all the bolts/fasteners/locking mechanisms on the saw are tight, and in good working order. Sometimes a tool new out-of-the-box will have loose screws/nuts/bolts that need to be tightened up.

Also, when cutting, use a smooth, slow, motion, being sure to give the saw the time it needs to make the cut.

you have to stop the blade turning. Grip it with some locking pliers but it might damage the blade. Or jam it with a piece of wood/ stone and undo the nut.

I have the same question.

most of these saws have a push/lock tab on back side of motor housing that pins the shaft for blade change. if you cant find, use a 4/4 wood block to wedge old blade so you can loosen bolt.. hope this helps....chris