Table Saw Repair

I am crossposting this from one of my other blogs because it is an electrical repair of a fairly common household tool. This can save you money if you happen to have one of these saws, or similar.

A While back, my old Sears 10 inch Table saw “gave up the ghost”, it simply stopped and flipping the switch back and forth a number of times did not get any noise from the motor. So I swapped a Delta “Super 10” Saw onto the base and ran that one for a while, until the motor capacitors failed. This being a tight budget situation required some thought on the matter as to which one to repair first. The Sears saw got the nod because I located a scrap Sears 10 inch saw that had a different top on it, but just happened to be the same motor and arbor mechanism. And having a decent table saw you can move around is almost an essential for a home renovation as well as for other projects.

The image shows the location of the 6 screws on the edges circled in red that retain the aluminum panel, there may be one or two others on that panel as the saws did have some variability. The two screws holding the protractor do not need removal as they only have a quick nut behind them and do not secure the panel in any way, so they can be left alone. The 2 screws circled in blue hold the switch.

front panel

The screws to remove the panel are circled in red.

After some initial disassembly to get at the wiring for checks, which entailed removing 8 Phillips head screws that held the aluminum plate (as well as the sheet metal end of the saw to the rest of the base). The aluminum plat is what the switch itself attaches to with 2 philips screws of about a #6 size. The switch will not come out unless the yellow safety tab is removed. Slipping the two wires off of the switch freed the plate which was set aside for the moment as some cursory checks and a wiring diagram were written down. That aluminum plate itself- which once removed revealed decades of accumulated sawdust and essentially the compact assembly of the recess for the switch, the motor start capacitor, the thermal motor fuse/reset switch and the magnetic starter. The metal bracket under one of the thermal reset screws just retains the magnetic starter in place

Saw wiring Schematic

Wiring Schematic for Craftsman Saws since the 1960’s. Rigid Saws will be similar.

Once the schematic was finished, it was simple matter of checking with an Ohmmeter the various potential culprits, which actually turned out to be the first item I checked- the switch. The parts saw was promptly pulled apart and that switch removed and once checked- it was revealed it too had issues, and was the most probable reason the donor saw was scrapped. This is a fairly general schematic as far as applications go. If you happen to have a newer power cord wired to an Asian or European wiring standard, double check the cord leads to be sure they correspond to the correct plug prongs, but most of those types will use the Brown wire for “hot” and the Blue wire for “Return” with the green wire with yellow stripe as the ground wire. In the US, the Black wire is the “Hot” lead and the return is the White wire.

However, this being a budget situation, I first tried some contact cleaner- I found later this was not even worth the effort, and hindered the efforts to clean out the sawdust. With the switch still showing no continuity when “on”, I decided first to take apart my old switch, which was melted from a fire (I actually bought the saw for the price I did because it had been too close to a fire, and it showed- which made people not take a second look at it in spite of the price at that garage sale. The fellow was pleased that the saw was going to good home- mine, and that I was not afraid of the melted nature of the cord or the switch and knew how to deal with them safely. I did get my money’s worth of work out of it initially before it started to act up. Once I had the original switch taken apart, it was actually very simple in design compared to some I have taken apart over the years and saw how easy it would be to effect repairs on the switch.

The Switch Taken Apart

The switch taken apart

The one thing I would suggest if you decide to try this yourself, first put the switch in the refridgerator or freezer to chill it and thicken the grease that holds in the plastic pin which is missing in the photo. The image is missing the plastic button portion that rides against the moving contact. Chill the switch first and work quickly. you should not lose that button. Doing the repair outside is taking a risk and I admit I got lucky. The button must have shot out of the switch when it warmed inside of the solar gazebo where I parked the box of spares for the moment.

The problem is sawdust filters into the switch in spite of that foam seal. Both switches were fully packed with sawdust. Now getting the switch apart is easy, with a diagonal cutter or small screw driver, just bend the corner tabs that hold the rocker portion to the lower phenolic portion- bend them out enough for the tabs to be clear of the phenolic shoulder each anchors to. Gently peel the foam seal off the phenolic and tap out the saw dust. Compressed air might be a consideration if and only if you have the button and the copper piece that rocks to make the switch contact. It is that missing piece that rides on the back side of the rocker to make and break contact within the switch. As you can see, this one is quite pitted and therefore not used, since the original switch had better contacts, I took the best parts of both switches and combined them into one switch. If you are only dumping out sawdust, this whole process takes less than 5 minutes. Some degree of pitting is normal, but there is also a point where the pitting is just too extensive to even consider reuse. Dressing the contact with a “point file” might get some additional life out of the switch, but at some point an inevitable replacement will be needed. The switch is rated for 15 Amps, so you can replace it with a heavier switch to extend the life of the contacts of the new switch.

On reassembly, the rocker just sits on the pivots- make sure the botton contact is over the button contact on the switch body. Then reapply the foam seal and gently place the rocker assembly over the switch body- it is self aligning in most respects so all you need do once the top is in place on the body is push the tabs back over their resting places and the switch is ready to go back into service.

Since my original cord was melted, and I had a replacement cord, I simply undid the strain releifs and pull out the old cord. to undo those strain reliefs used, it is just a matter of squeezing the small tab that is visible towards the other portion of the strain relief that surrounds it with a plier or water pump plier just enough to allow for the relief to be rocked out of it’s hole. The replacement cord, which was salvaged from a plastic based Craftsman saw, just slipped into place. Both were 16 Gauge 3 conductor cords, so no issues there. If you replace with something that came from a different tool or source- make sure it is at least 16 gauge- 14 will work as will 12 gauge. If you are running the saw on an extension cord and simply want to incorporate that as the power cord- locate suitable strain reliefs- you will need 2, and enlarge existing cord routing holes and install cord. Then install the strain reliefs leaving a little slack between the 2 strain reliefs. If you are running a 25 to 50 foot cord- 12 or 10 gauge conductor will be a really good idea.

Reassembly is straight forward, the 2 slotted screw that hold the thermal reset fuse have a small brakcet that holds the mag starter in place. the screws only need to be snug- just enough to hold things in place while you are doing assembly. Now, neither saw had any issues with the mag starter or the start capacitor- if the start capacitor had vented at all, there would be the aroma of Hydrogen Sulphide (rotten eggs.). If a capacitor fails on startup, you will have large amounts of smoke billowing out of the saw cabinet in the vicinity of the switch. If there is a problem with the “Mag” starter, or if it gets wired incorrectly, the motor will run slow, noisy and hot. For this reason: only undo the wires that attached to the item needing immediate repair. The only other caveat just make sure your blade angle indicator is not stuck under the aluminum panel when reattaching the aluminum panel to the saw.

The industry part numbers for some of the parts are listed on the image, and these should be simply industry numbers in most cases- not Sears part numbers, so they can be located through motor repair shops, some online vendors, etc.

I did power the saw up after putting the saw back on it’s original base (4 bolts) and it started right up as if nothing had gone wrong with it. Considering the original handles for blade angle and blade height had melted off, I saw it as a good time to pull the handles off the donor saw and install them on the good saw. The correct handles made all the difference in ease of use, but if you are having some trouble with either adjsutment being stiff, just apply some motor oil to the threads of each adjuster and crank them to their extremes, and as always- store a table saw with the blade fully retracted below the table surface.

Since my saw dates from the 1970’s, I expect the saw should last at least another decade or two before needing work on the switch again. The capacitors usually have a date code inked on them somewhere, so if you really wanted to know the age of the saw, you can figure your saw was likely made about 6 months after the date code on the capacitor.

If the saw squeals on startup- the bearings are dry. The Sears 10 inch saws, the Rigid table saw of similar design and the Delta “Super 10” are direct drive motors- in other words the blade arbor is the motor shaft. (Some people do not like this approach, but it saves weight and costs and is reasonably durable. They may not be adequate for a large manufacturing plant, but houses have been built with less of a table saw or none at all.) The bearings are not within the scope of this post, but if you pull the end bells off the motor, you can see the bearings. If they just make noise, but are still smooth in rotation, you could try regrease the bearings (if ball bearings) by gently pulling the dust seals off one side of the bearing with a flat dental pick or small screw driver- use care not to damage the inner race sealing lip and then repacking them much as you would a wheel bearing- use a short fiber grease or one with Molybdenum Disulphide and pack it full -after applying some solvent to remove the old grease residue. Once repacked, then it is only a matter of straightening the old dust seal and slipping it back on the bearing once you are sure there is no damage to the inner seal lip that rides on the inner bearing race. Never apply compressed air to a “dry” bearing that both races are secured against rotation or damage that can affect the life of the bearing can occur.

Older saws sometimes use ball bearings to support the arbor, and these are usually marked on the outer race as to what their part number is if you choose to just replace them, and then it is only a matter of slipping them off the shaft or out of the arbor casting- which is aided by a wood mallet or plastic faced hammer. Older saws used sleeve bearings/bronze bushings, which if they run dry will make noise, and these are just a matter of a few well placed drops of oil to take care of them in most cases- unless there is too much radial play. In that case those need to be driven out and new sleeve bearings of the correct size gently driven in. There should be minimal axial play (side to side or end to end of the arbor shaft), but there should be about 0.010 inch clearance so the arbor can spin freely. This is adjusted by loosening the arbor pulley and moving it closer or away from the arbor casting.

Further adjustments and tweeks will likely come later as they take some time to perform them correctly, and my saw is still in adjustment, plus some of the adjustements that can be made on other saws cannot be made on this saw due to how it was manufactured.

http://www.youtube.com/channel/UCdjcUtAAJ-CZVwaabB6SBpA

The associated blog for above youtube channel

http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

http://passivesolarproject.wordpress.com/
The passive solar blog- outgrowth from some projects of mine.

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