I'm on a farm, and I'm a little person learning to do big work.

I was having so much trouble controlling a direct drive circular saw due to the gyroscopic twist when starting it up, my "adopted brother" found me this wonderful worm drive Skilsaw. It's an old solid metal case, the thing weighs like three times the Ryobi direct drive, but when it's running, it doesn't feel like anything at all! I love the darned thing.

We replaced the blade for something newer, as I've got some cabinetry to tackle - but neither he nor I can get the blade to tighten down. If there's no real drag it cuts fine, but the least thing makes the blade just stop. No jerk or bounce-back, the shaft spins but the blade is obviously not tight to the shaft.

This scares me, but I really want to be able to fix ths so I can get back to cutting. Any help would be appreciated!

Edit: Thank you all for your suggestions!

I got the bolt off (yes, reverse thread) and yes, the diamond knockout is knocked out. So it's a problem with the blade thickness. I got a hefty washer on there, threaded the bolt back on, tightened the you-know-what out of it, and the difference is obvious without even running it - before, I could hold the blade with my fingers and spin the shaft with a wrench. Now I tried holding the blade with a pair of slip-joint pliers and couldn't get the bolt to budge.

I'm leaving a photo here of how it looks, and will check back in a bit - let me know if what I did is in some way dangerous or unsafe.

Note to the respondent who noted the dangers of worm drive - thank you! I already knew, and have a healthy terror of kickback. Scariest thing I ever did with a circular saw was stand on the top rung of a ladder and cut notches into roofing plywood - and that was a direct drive, and I definitely self-medicated with a bit of Tito's that night, well after I was finished. :)

You people rock, and if I haven't forgotten I'll post shots of the finished bed frame. Thank you all!

side view washer on shaft

  • I forget - is that a left hand thread blade retaining bolt? i.e., backwards from normal "tighten/loosen?
    – Ecnerwal
    May 1, 2016 at 12:21
  • 1
    Backwards threading. May 1, 2016 at 13:29
  • Thank you both! Reverse threading, like I noted below, is something I check for in anything where you have to tighten down something that spins really fast and can rip your head off. :) Very likely either a thinner blade (will a washer solve that?) or the diamond knock-out like shown below. I'll have to get the saw out and check, will add to the data soon as I know more.
    – Blanche
    May 1, 2016 at 17:52
  • Thank you again! After adding the washer and tightening like I noted above, I went back to the bed frame project, and cutting was a dream. No blade binding, it didn't feel "wrong," it's grand to have my favorite saw back!
    – Blanche
    May 11, 2016 at 4:35

3 Answers 3


Does the old blade have a diamond shaped hole? My 77 is a few miles away, but my recollection is that it uses that configuration. Some new blades won't have it at all (and thus are not suitable), others will have a round hole and a pre-cut diamond hole that punches out to engage the diamond shape on the saw clamps.

Here's the manual, which suggests both the "left hand thread" and diamond arbor as correct recollections on my part:


Here is a blade which appears to have the diamond hole possiblity, but not yet knocked-out.

Saw with diamond knock-out

Here is one with the hole cleared to the diamond shape:

Diamond-shaped hole saw

Note that the worm drive saw, while you prefer the feel/heft of it, can be rather more dangerous than a direct drive saw if it's jammed and kicks back. Most people treat them with a healthy dose of respect - or learn to eventually.

  • Thank you! I knew about the reverse-threading, it exists in other kinds of hand tools, and with good reason, inertia being an unpredictable bitch at times. :) But I didn't think of the diamond knock-out, and will check. It's exactly the kind of thing I wouldn't have looked for. Your response is greatly appreciated!
    – Blanche
    May 1, 2016 at 17:48

Some things to consider.

  1. Some of the newest blade, especially the thin cut carbide tipped ones, are quite a bit thinner than the blades from 20 or 30 years ago. It is possible that the truss washers on either side of the blade just do not tighten down enough on a super thin blade.

  2. You may have made a mistake assembling the blade mount. The truss washer on at least the outside end of the shaft usually has a flatted hole on one side so that it fits down on the flat on the saw shaft. It is possible you had this rotated around the wrong way and the bolt went tight but the washer did not seat tight down to the blade.

  3. Maybe there is debris or rusted threads down in the bottom of the threaded hole on the end of the saw shaft. This could prevent the bolt from entering the shaft the required amount to tighten up the blade.


Make a washer out of cardboard. Older saws aren't designed to tighten down on the newer thin blades. That Diablo blade you've got is thin. I had the same problem.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.