Unit had lots of vibration which I determined to be from a out of balance blade. If it was cranked on a cement floor and left it would walk all over till it came up against something.
So I decided to sharpen and balance the blade and did so unfortunately getting the blade aligned on the X of the blade adapter is a bit tricky and unfortunately did not seat so when I started it up and started to cut it started making a racket about 60 feet into the first cut. I took blade off and located the problem, called MTD and ordered a new blade adapter and then I got to thinking I could improve the design so I clamped the upper adaptor (a casting?) up in my milling machine and located the centers of the former locating protrusions and drilled them all the way though and out the top with a 1/4" carbide spade drill. Next I tapped them 5/16X18 TPI all the way through the casting and inserted 5/16X18 TPI 1" bolts (Grade 8s) and utilized anti vibration nuts to secure the other end. This will allow me to remove the bolts should they shear off like protrusions did and the bolts snug up on adapter since it is threaded if they do shear I just unscrew the remaining, replace the Grade 8 Nut (about ten cents at Tractor Supply Co.) and I am good to go. I secured the main 3/8" bolt with a Grade 8 Lock Washer. Cranked the mower up, no vibration and ran a full tank of fuel through it cutting grass today and it works like a champ.
I had already replaced the blade adapter by ordering new but just wanted to see if I could improve original design and so far it appears to work with less chance of a screw up remounting the blade. I used to work Product Engineering for the Army Small Cal Weapons Lab so I am used to problems surfacing in actual use that did not show up in testing and coming up with a fix. You can test to H&G and get no problem but give it to the troops and they will do things you never dreamed of to a weapon.
As the old saying goes if you have a spare you will never break the original so that is the logic I am going on. Will see how long this lasts.
Having a lathe and a mill has been a God Send the last 30 years.
