MARK V Headstock shakes at high speeds

[Blair73]

This past summer I acquired a Mark V unit built in 99. It had been used very little by the original owner before he passed away and it was given to a neighbor. That neighbor also used it a little before I bought it this summer. Upon receipt I went through the entire package and other than a missing nylon connector for attachments I don't have, it was all in excellent condition.

With that all having been said I've been using the machine mostly as a lathe and it has served me well in that capacity. One issue I have been having though is that while it runs smoothly at slower speeds, once I try to take it up higher the headstock starts to shake as the project turns. I've tightened everything I can on the entire frame and rails but once I try to spin it up to approx more then half speed it starts to shutter and impacts upon my ability to turn. The same happens when I try to use the saw feature as well as the large sanding disk. It's not a matter of an unbalanced turning project.

Any help/guidance would be appreciated.

[JPG]

Belts!

Tension?

Have they taken a 'set'? Get some automotive belt dressing.

Last resort, replace them.

[Blair73]

I'm not sure what you mean by "have they taken a "set"?" but I thought I had already tensioned the belts according to the instructions but I'll have a look again. They appear to be in great shape but for the cost of new belts I'll look at replacing them.

[JPG]

Rubber belts when under constant tension for a long period of time will assume the shape it is in and will resist reshaping. Thus the portion over a pulley will assume a round profile while the length between pulleys will assume a straight profile.

When the belt is subsequently moved, the rounded portion acts like a bump. As the belt is moved, the bump(s) cause vibration.

Belt dressing helps to remove the bumps as it 'softens' the belt.

[Blair73]

Ah, now that makes perfect sense. Thanks so much. Looks like I have a bit of tinkering to do.

[dusty]

He said that he had been using the machine as a lathe. The issue then seems to be during operations performed only at higher speeds. If belt set is the cause, just turn it on and let it run at a lower speed for ten minutes or so. This should remove the set if there is any.

I'm thinking the lathe project might be mounted wrong or is offset.

[JPG]

He also mentioned having the same issue with the saw blade and sanding disc.