Radial arm saw raise and lower (loose?)

9 years ago

I'm hoping to get some help with my tuning my radial arm saw. Not sure if the is the correct forum but hopefully someone can provide some advice.

The two pictures are of the same piece, but the bottom is a close up.

This is what controls the lift of the arm.

The problem is that when I switch directions it takes about half a turn before it engages going the other direction. I've narrowed it down to whatever is going on inside that piston thing.

Could it just be that it needs to be greased, or is it that something inside might be worn down or loose?

This is an old radial arm saw that I inherited from my grandpa. I'm trying to restore it and get in back in perfect working order .

Any thoughts?

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chas045

9 years ago

I had/have an old 'Wards model. It always responded as you describe. I got it new and I don't believe there was an adjustment for that. I don't recall that it caused any issues for me as I would be checking height anyway and additional adjustment in the same direction would respond appropriately to rotation count if I cared.

If I recall correctly, even that enclosed area ends up with Lots of sawdust and I suspect grease would be a bad call.

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Comments (8)

User
9 years ago
Three areas in which to look.

Gear backlash between the two bottom gears. Backlash is the distance between the gear teeth, if that distance is too much, the control handle will be sloppy.

Second, turn the handle and watch the play between the threaded rod and the bottom gear. Those two parts should not have any play.

The third place is the play in the small gear when you move the handle. Again, should be no play there either.

I suppose there could be some play at the top of the threaded rod, but you may need more disassembly to check that area.

If there is play anywhere, connecting pins/whatever(fixing the gears to the shafts) may be loose or broken. There should be ab adjustment to remove excess gear backlash, but that could have to be made with shims under/behind a gear..
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chas045
9 years ago
If I have not forgotten, I believe This site would be useful for other info on your saw.
bmelz
Original Author
9 years ago
Thanks HandyMac there is no play from the handle (wheel) to the threaded rod. I believe the play is inside that cylinder. It appears to be a closed system, but perhaps I can disassemble further.

also, based on chas045s experiences, this might be a common or even designed behavior.

I might try to disassemble above the threaded rod to see what I've got. I just wasn't sure if this was a common issue fixed with some grease somewhere.
PRO
Sombreuil
9 years ago
there are enough places for lost motion to occur; handle/shaft; shaft/gear; gear/gear; gear/shaft; shaft/column. All these can naturally add up to 1/2 turn.

Casey
bmelz
Original Author
9 years ago
I can manually turn the threaded rod. From past that point is absolutely where the slack is coming from.
bmelz
Original Author
9 years ago
I have been able to determine that it's that wedge at the bottom of the cylinder(above the threaded rod) notice there's a slight gap at the bottom of it? I guess I can try to wedge something in it, but would need to wedge something on the front side as well (which might be difficult to access).

I'm going to leave it for now but may dismantle and rebuild during future maintenance.
jemdandy
9 years ago
What you described is called "back lash". Do what others have mentioned and that is rock the adjustment hand wheel to and fro and observe where the 'play' is. i think you have spied the main one and that is the elevator nut on the lead screw. The mating threads may not have a tight fit, but the other biggie is that the nut is not held tight and has a lot of play. This may have been made this way to avoid binding along the entire length of the screw. Try this. Use shims to reduce the up and down play this nut has. If you find that a tight nut binds, remove a couple of thousandths thickness until it runs freely and this will be about the best you can achieve. To eliminate play requires redesign of the elevator mechanism adding anti-backlash features.