Help square up my belt sander tooling arm

[Nilaman]

I have been using a pheer 454 belt sander for about six months now, and to date I haven't had any challenges with it.

Over the last three-four weeks I have been working on surface grinder attachment. After gathering all the needed parts and putting everything together to the best of my ability, I have found a small problem with it: One side touches the belt before the other.

After spending some time troubleshooting this problem, it appears that when I tighten down the screw style handle on the tooling arm to secure it to the belt sander, the business end of the tooling arm kicks out to the left slightly - but just enough to allow the surface grinder plate to be skewed. Incase it matters, I'm using 1.5" steel tube stock and can't lose the ability to slide the tooling arm into the receiver.

Anyone have an idea on how to make it seat flush every time I tighten down the screw?

 

[12345678910]

pichers would really help



Solid tool arm

Two screws

 

[Nilaman]

Pictures:

This is the tooling arm setup.

This is the arm before I tighten it down

This is the arm after being tightened down

 

[DukeHarley]

Something is not square or a mounting hole is not square(90 degrees) to the mating surface.

Jay

 

[Brock Cutlery]

Can you put a shim inside the tube?

I would be interested in seeing the surface grinder.

 

[DukeHarley]

Is there any way possible the the arm isn't straight(bowed) or it's go a twist in it?

Jay

 

[Nilaman]

I tried shimming it with no success. I'm wondering if I may have to make another way to mount it to the grinder.

Once I get everything all flush and working reasonably well, I'll post my setup.

 

[P.Brewster]

The square shaft/square receiver mechanism is inherently imprecise. I build my tool rest arm with a sliding linear bearing to address this problem. I used this http://www.igus.com/wpck/3596/drylin_w The creative use of shims is probably the best way to remedy your problem without rebuilding anything.

You've got your tool arm in a square hole. The square hole is created by 4 pieces of metal, which I'll name as follows: Bolt plate (vertical plate with bolt hole), jam plate (vertical plate opposite the bolt plate), top plate (self explanatory) and bottom plate (self explanatory). When you tighten the tool arm locking bolt, you are jamming the tool arm into the jam plate. Gravity is jamming the tool arm down into the bottom plate, at least at the front end of the receiver.

I would attempt to pinpoint the exact problem. It may be one or more of the following:
* Jam plate is not parallel/perpendicular to other related components.
* Tool arm is not in fact forced into parallelism with the jam plate when locking bolt is tightened.
* Jam plate is not straight.
* Tool arm is not straight or square.
* None of the above, but something else is misaligned.

To diagnose, try swapping/rotating the tool arm and the work rest arms in every possible way.

 

[Nilaman]

Thanks for all the helpful replies!

So far I'm still SOL. I've tried shimming it and haven't had any success, but I suspect that's due to my shim material. I'll have to look for something more durable.

I'm starting to wonder if it has more to do with the tube stock I'm using not having sharp corners. The aluminum doesn't give me this problem.

If I had more time today, I would take apart the bolt plate and look to see if there is anything I can do with it.

I'm wondering if I can just temporarily clamp the arm to the grinder...

 

[mike-E]

i think it might be the stack of washers under your wheel. a single machined spacer might do the trick.the wheel mount hole could also be drilled/tapped out of square. when the grinder is running does your belt maintain equal distance from the edge of the wheel around the circumference? edit; it's just the tube that's giving you problems didnt see it before. is the tube straight? can you lay a straight edge on it? is it sagging from weight possibly? how much clearance in the socket? can you drill/tap the socket for a second lockdown handle to push against the backplate from two points?

 

[P.Brewster]

To expand on my previous comment, I would: Disconnect/unbolt everything from your tool arm and work rest arm. Now you have two square pieces of steel. Insert both into their respective receivers, and tighten the bolts. Put a square on the top-right corner of the tool arm and check for coplanarity of the right faces of the two arms. Perform this check at various locations - next to the receiver, and farther out on the shafts. Then try swapping the arms, and/or rotating the arms, and repeat the check.