Machining Question

Jonathans

Jonathans

Joined
Jan 9, 2008
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I am designing a pedestal for my new belt grinder that will allow me to flip it to horizontal.
While I have metalworking experience, I have limited machining knowledge.
I am hoping someone here can help me.
If I bore a 1.25" hole in 1/2" aluminum plate for a .75" shaft that is supported by a uhmw bushing, how do I secure the bushing in the plate? Pressure fit?
Thanks
 
Jonathans said:
I am designing a pedestal for my new belt grinder that will allow me to flip it to horizontal.
While I have metalworking experience, I have limited machining knowledge.
I am hoping someone here can help me.
If I bore a 1.25" hole in 1/2" aluminum plate for a .75" shaft that is supported by a uhmw bushing, how do I secure the bushing in the plate? Pressure fit?
Thanks
Click to expand...

A swag (scientific wild a** guess).

A quick search shows a plastic bushing so a pressure fit might even be the same size as the bushing since it compresses.

Is there a bearing in the bushing, you don't want it to lock up if the fit is too tight.

AFAIR a press fit is *normally* .0005" bigger than the size of the bearing. I could research this easily if need be.

You could prolly cut the hole as much as .002" big and locktite it.

Pics? A bushing with a flange can have button head bolts at the edges. Now I'm rambling.
 
How about set screws?

If it's not close enough to the edge for set screws, press the bushing in place then drill and tap a hole at the edge of the interface(parallel to the hole in the bushing, half the should be in the plate, the other half in the bushing) . Put a screw in there and it should hold it in place.
 
No more pressure and movement than it will get you dont even need a bushing. Here is the grinder I built.


And yes it goes horizontal too.
 
nwmetalbug said:
No more pressure and movement than it will get you dont even need a bushing. Here is the grinder I built.


And yes it goes horizontal too.
Click to expand...


What do you use those little drill bits for?:eek: Seriously, what does the drill look like that uses those things??
 
Well done! I really like your rotation mechanism. looks solid. What RPM motor did you go with in your direct drive setup? Hoping to get started on building one soon.
Stuart
 
I use a 1800 RPM motor and can drive it at 200% with the VFD with the 5 inch drive wheel its plenty fast for what I do.
 
NWMetalbug, that is one of the better designs I have seen. Thanks for sharing that. I suppose that you are correct that with the minimal movement of switching from vertical to horizontal, little wear would occur on the aluminum, even over many years. I also have the option of welding it up with steel.
Kloepper, I like the idea of running a screw half and half as you suggest
Dave, I'll have to play with uhmw a little more to see how well it responds to any compression.
Thanks guys
 
You can't locktite UHMW, it won't stick. It also doesn't work well with press fits, it's too mushy.

The best joint with these materials and this configuration might be to turn the UHMW into a hat shaped section so that it has a flange. You can then run some small screws through that flange into the steel to hold it in place.
 
Im not sure why you want to use UHMW. I used stainless for all my rotating parts only because I didnt want to paint them aluminum would be just as good.
 
you can buy bronze bushings with or without flanges from mcmaster carr. If you wanted a really fancy bushing you could look to misumi. They offer bushings with flanges and mounting holes. If you use the bronze bushings you can drill and ream your hole to about .0005" to .001" undersize and press in. You can also do the same with your UHMW bush.
 
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Here are a couple of pic's of how I setup mine to flip. Used 1"od rod and bearing bought them on Amazon.







 
Thanks again for all the excellent suggestions. It really helps a lot.
If not too difficult, I prefer to use a bushing just because it will provide a tighter, neater, finish to the project.
I can't say that it is necessary. I planned to use uhmw as it is a material I am familiar with, has very low friction, and requires no lube. Not to mention that I have an abundant supply of it. I am a beginner hobby machinist, and want to incorporate a limited number of details in the project as part of my learning process. I don't learn well from texts, so try to learn through projects I work on.
Regarding your setup Plas62, Couldn't you have made the shaft fixed to the base with the two pillow blocks on the grinder?
Great setup.
 
Plas62, That is a really cool way to flip your GIB. What part of the grinder rests on the table to hold it level? Does the lower tool arm opening touch the frame of your table or is the motor supported by the pan you installed underneath? I know there has to be clearance to put a toolbar in the lower receptacle. Very nice build!
 
LarryZ10 - See pic #2. When the grinder is in the vertical position the base plate of the grinder rests against silver colored square tubing. When in the horizontal position the base plate rests against a vertical stop which is attached to the "pan". The tool bar holder does not contact the frame in the horizontal position.

I have tapped holes in both pieces that I run a bolt into, just finger tight to ensure the grinder does not flip on me when in use.

Johnathans - I probably could have attached the rod directly to the base and just used two bearings, but since I don't have a welder this was the simpliest way to do it. It also gave me a couple extra inches of height by using the bearings on the base of the grinder
 
I really like the use of the pillow locks as I can easily mount those to the bottom of the grinder, and they will perform really well. The shaft then can just be inserted through bored holes in the supports and secured with a good set screw.
Plas62, after having used your setup, do you still feel that it was prudent going with the 1" shaft?
 
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