How to Diagnose a Bad Power Cord or Switch
This article outlines the basics of power tool and appliance electrical diagnosis. You can use a multimeter to test tool and appliance cords and switches, the two parts usually responsible for electri...
Electric Power Tool Parts 101
This article defines the basic parts of most power tools, explains how they work, and what to look for when they stop working.
Discussion
Discussion for the Skil SHD77M (F012SD7702) 7 1/4" Magnesium Worm Drive Skilsaw
fixin some shd77 for stone countertop company. lot of water use. thier rusty. thinking thier shorting out between field and armarture rubbing. can i sand out rust and paint to seal it??
Most of the parts for the Skil Model 77 types 14-16 are no longer available. As I remember the big difference between 14-16 types & type 17 were the motor parts and the gears and most likely the main housing ( basically the whole saw). It was nice when Skil had factory owned service centers, you could take a 77 in for repair and for $89.00 they would make it a new saw.
Has anyone tried substituting type 17 worm gears in a type 16 skilsaw? I have a model 77 '50th anniversary issue' worm drive and the gears are shot. Apparently the type 16 gears are no longer available, but since these saws didn't change much over time, I'm hoping the newer ones fit. Anyone?
Hi Kent,
In answer to your question. The type 16 and type 17 gears are both different sizes and the housings are not the same. You might try some local repair centers to see if they have any of the older gears.
WJA
The previous owner wasn't mechanically / electrically inclined. Said it didn't work.
It runs but generates a lot of sparks in the motor housing. The brushes seem to be fine...I'm not sure how I should verify that they need to be replace.
Any suggestions about the problem? Brushes? Other?
I am replacing a bad armature on a Skil Mag HD77 worm drive saw. What else should I replace in addition to the armature assembly? Are there any special tricks?
I was cutting a redwood 4x4, new blade, the skil HD77 just stopped running, checked breaker, cord, oil,brushes are good everything I can think of the saw just won't run, any ideas?
Thanks,
Sammy
With the saw suddenly dying like that I would suspect either the brushes or the switch. Check the brushes first. If they are almost worn away then they are probably the problem. If the brushes look OK then open the handle and inspect the switch. You can test the continuity of the switch with a multimeter set to test ohms.
The sparking you are seeing through the rear vent holes on the saw is caused by a bad armature. Many different things can cause the armature to go bad but the most common causes are using too long of an extension cord that is too small gauge or cutting in a manner that causes the saw to pull more amps than it can handle. (Such as deep cuts in concrete, etc.) The armature will need to be replaced.
There may have also been damage to the field. When you open the saw you will want to look for signs of burn or melted insulation on the armature and field. The field can also be tested with a multimeter set to test impedance (ohms). To test the field take an impedance reading from one side of the coil and then the other. The number you read from each side should be within a few ohms of the same. If it isn't the field is bad.
The armature is part #2610931892 and the field is part #1619P02674. Both of these parts are available from http://ereplacementparts.com.
Good luck with your repair!
-Mark
Reply: Brushes
josh
Most likely the armature. It's about $60. Look for a little black spot on one of the commutator bars or connections, all it takes is one and the whole thing is no good.
I am looking for some parts on a skilsaw. I can't seem to find the right model number on the parts page. The model number is a 77 not the HD77. serial #1B504000. This is an older saw. What I am wondering is if the the parts are the same? What model number is the closest?
Thanks Paul
I had a saw just like yours, but parts were getting harder to obtain, alot of the parts are no longer available. But I do have the parts list. Ill attach it here.
Good luck!!
My SHD77 Skilsaw turn on, but blade stops turning the moment I try and cut with it. In other words, while I would not recommend it, you can turn on the saw and almost stop the blade with your two fingers! Is this a "gear" problem, or more likely "armature"?
That's pretty strange! If the saw is [I]that[/I] weak then I really doubt you have motor problems. The blade might be slipping between the clamps. Those HD77 saws us a diamond knockout instead of a round arbor on their blades. If you are clamping the blade between the clamps but not using the diamond shaped knockout on the blade, you could get some pretty nasty slipping.
Reply: SHD77 Wormdrive
cmoorejack
Hey guys,
one more thing it might be is the nut that tightens the worm gear on the armature shaft...if you unscrew the black plastic nut on the end of the tool you can gain easy access to the nut..push in the lock pin to secure the assembly and tighten the nut..and that should put you back in business..[it is rare for the nut to loosen but it does happen once in a while..]
Hope this helps:)
cmoorejack
I have a Skilsaw Model 77, type 16 (in fact it's the '50th anniversary issue'. I need to replace the worm gears. Are they available? Can I use the ones listed for the model 17?
The gears for the type 16 and type 17 are different and not interchangeable. Unfortunately the manufacture has discontinued the parts for the type 16. So either find a type 16 with good gears or time to purchase a new one.