I have two of these in two different grinders. They were both (and/or my grinders' collets) a bit out of whack..
One of my grinders normally runs rather smoothly. But with this mandrel chucked in it, it vibrated so bad that the cutoff discs frayed, the switch fell apart, the power leads broke off, and the case "ultrasonically" welded itself together in two spots. I had to tap it with a hammer to get the halves apart.
After repairing the grinder, I chucked this mandrel back in and "turned" it true with a thick cutoff disc in another grinder while this mandrel was spinning at 25K rpm. You can easily see where the high/low spots are, due to the black finish. When there's no more black, it should be better. After making it concentric and removing a bit of unnecessary mass from the head, the vibrations went away. I also noticed the discs did not sit flat, so I took the screw out and faced the part that the bottom of the disc sits on, too, using the same method. Unfortunately, I had no way to face the bottom of the disc retaining screw in situ, but it was close enough to begin with that the discs now sit perfectly flat, and I did not need to fudge with it by, say, adding a cardboard washer or an O-ring between the disc and the retaining screw. The grinder is now super smooth and working fantastic with this mandrel. I think I'm gonna dedicate this grinder to cutoff discs, changing them out only with the mandrel screw. I'm afraid I might lose some smoothness/concentricity if I re-chuck the mandrel.
These mandrels are made of carbon steel and the screw and threading are fine. They are solid. They are cheap enough that I would recommend them. Just have another grinder or Dremel tool handy, I think after going through this, I would true up any large mandrel in situ on any tool rotating at ridiculous RPMs, unless it were chrome plated and extremely well balanced to begin with. It's very fast and easy. Just keep both grinders oriented the same direction when you grind: tip to tip, butt to butt. If you try to "69" it, the cutting disc will just loosen, itself. This makes me wonder how reversible air grinders keep the cutting disc in place.
If I still had access to a lathe I would've made my own, but this is a high quality choice as well. Fits snug in all the wheels I've put it in so far and I have yet to experience vibration due to an off center disk. From the first time, the threads were flawless and hold tight even after getting warm when the disk gets used too much. 10/10 would buy again (unless I get a lathe of course)
These ones are terrific! Great balance, nice machining and finish, the threads are smooth. I went through a few others and they did a terrible job at centering the discs. These ones are great, definitely the one to buy!
NO concentricity issues AT ALL. FINALLY a brand that makes a properly machined mandrel! Just ordered 2 more.
No more wobbly cutoff wheels, nice and true. My previous one I bought at a discount store warped from the heat of cutting after about 30 seconds. This one has held up nicely.
Feature Product
- Mandrel mounts a Type 1 cutoff wheel with a 3/8" arbor hole onto a grinder that accepts a 1/4" shank
- Fits 0.035"- to 1/4"-thick wheels
- Carbon steel provides strength for extended tool life
Description
Steel mandrel for mounting Type 1 wheels. Constructed for cut-off wheels with 3/8quot; arbor hole. Suitable for 1quot;- 3quot; wheels
I believe and stand to be corrected this item is unsuitable for the thicker and heavier grinding 1/4 inch discs as specified. This is due to the thicker the disc the less threads are engaged. This is exasperated by the un-threaded internal recess and the extra weight of the thicker discs. I would recommend using this mandrel safely using cutting discs of a thickness 0.035"- to 1/8" or 0.8 mm to 3 mm. Very suitable for this task.
worked well on the underside of my Nissan Altima 1999!
Fits my dewalt Die Grinder
Holds the 3 inch die blades tight.
I was happy with this mandrel. the topscrew works better than the one my employer issues us to use for die grinders. topscrew has the built in girth to center and hold the cutting disc.
Nice addition to the tool box
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