Blade adjustment problem sudden drop

[tvarch]

Hi all, I hope someone can help me with a problem that has me stumped.
When I lower the blade on my B3100 it will drop suddenly once it reaches a certain height. After the drop it will lower as it should. When i raise the blade it will go up a certain distance and then stop. If I lift the motor an inch or so the mechanism re-engages and the blade can be raised to full height.
I have stripped down the saw,cleaned,. etc... but can not fix the problem.
I do not think the threads on the aluminum arbor are stripped because the blade will raise and lower normally except at a certain point.
Any ideas??

[Black wallnut]

Where in the range is it doing this? I'm stumped on what might be causing this problem.

[tvarch]

Black Walnut- it is happening in the middle of the range. My blade drops if less than an inch above the surface. I am stumped too. I haven't yet taken the motor out and looked inside the aluminum arbor but I cant see why it would be stripped if the blade adjustment works in the rest of the range.

[mnmphd]

The behavior is consistent with stripped or damaged threads on the
lift screw. However, I find it hard to believe this is the real problem.

[natausch]

Its possible that the thread of the adjustment screw itself is stripped; instead of the bushing like most people see.

[tvarch]

Here is a photo of the threaded shaft with motor raised.
I can't see a problem but maybe one of you can.

[Black wallnut]

Check your bevel locking lever, perhaps the problem is in that assembly.

[pelligrini]

Here is a photo of the threaded shaft with motor raised.
I can't see a problem but maybe one of you can.

A few of those threads in the middle portion of the shaft look to be slightly flat. I suppose if the aluminum threads are worn too, it might be slipping on those worn threads on the shaft. You did mention that the dropping happened in the middle of the range.

You might get under the saw and start lowering the blade to see what is slipping. I've got a feeling that the aluminum threads are worn, and you'll see the blade raising arm slide down over those worn threads.

[Pappy]

Like Erik suggested, watch from under the saw as someone lowers the blade for you. If you continue to use the saw without fixing the problem, every time it drops the damage is going to get worse.

[tvarch]

Thanks all,
Looks like I will need to take the saw apart to get to the bottom of the problem.
No complaints, I have had the saw 16 years it doesn't owe me much.

[pelligrini]

16 years of use isn't too bad.

Did you see it slipping from below? If it's what I think it is a helicoil insert will probably fix it. Please keep us posted on what it turns out to be.

[LCHIEN]

my guess is that it sounds like the aluminum threads are stripped in the motor bracket.

[tvarch]

I finally got the motor out of the saw. Once you've done it it doesn't seem so difficult.
Sure enough the aluminium threads are stripped. Have a look at the photo.
Now I am off to find an insert.
Thanks again for your help everyone.

[pelligrini]

Hehe, I've found that getting stuff apart usually isn't as hard as getting it back togeather properly.

Hope everything goes as painlessly as possible and you get your saw up and running again. You might consider changing out the belts while you've got it apart.

[LCHIEN]

keep us posted on progress, Tvarch.