Horizontal Belt Grinder

[cfellows]

I did my very first real CNC work today on my newly converted Enco Mill/Drill. Took me over 8 hours of redrawing, reprocessing with CAM and cutting test pieces using MDF until I finally got it right. What a learning curve!

So, on to the real subject at hand. Ever since I first saw one of these, I've wanted one.

So, I've decided to add one to my small, already crowded shop. The two pieces I started with, above, will hold the small drum on the outboard end of the grinder and be used for grinding very small, inside radius's. The slotted ends will accept interchangeable drum sizes fitted with 7/8" OD x 3/8" ID ball bearings on each end. The overall design is really pretty simple. Here are drawings done in Visio...

Mine will use a 2" x 48" belt.

Chuck

 

[cfellows]

This is the motor and drive pulley I'll be using for the grinder.

It's a 100 volt, DC motor that's rated at 3/4 HP at 2500 RPM. I have a full wave bridge rectifier installed inside the switch box so I can plug it into 110 volts AC and it runs fine, although it's a bit torquey on startup and will jump pretty hard if not fastened down. Running at 110 volts, I should get close to 2750 RPM. The drive pulley is 3.5" diameter x 2.25" long. This should give me a surface speed on the belt of about 2500 feet per minute. Higher would be better, but the belts should last longer at the lower speed.

Chuck

 

[Herbiev]

Looking great Chuck. You'll wonder how you coped without one.

 

[rodw]

Awesome project Chuck. I just bought a linishing belt for my bench grinder. I am not sure if you can get them in the size belt you will use but see if you can also get some scotchbrite belts. Absolutley awesome for alluminium and will polish steel to a high shine...
http://www.machineryhouse.com.au/A36203#

 

[cfellows]

Thanks, guys, nice to see some other folks validating my thoughts that I have a need for one of these! I'd like to make it convertible from horizontal to vertical so I could replace my vertical 2" x 48" belt grinder, but so far I haven't figured out an easy way to do it.
Today I pretty much finished up the interchangeable roller bracket.

Still have to bevel the inner edges of the vertical piece to clear the belt and drill the through hole that mounts it to the base, but for now, I'm going to move on to the tension idler assembly. I plan to finish that up before I start on the base/cabinet.

Chuck

 

[cfellows]

Today I got started on the Belt Tensioner / Idler.

The vertical piece is 3" x 1.5" x 1.25". The bottom piece is 3" x 1.25" x 3/4" and is attached to the vertical piece from the bottom with two, 5/16" Socket Head Cap Screws. Tomorrow I will notch the top of the vertical piece to accept a 3" x 3/4" x 3/4" steel arm that will hold the idler pulley. It will swivel up and down with an adjustment screw to provide belt tracking.
Chuck

 

[Wizard69]

Looks like you are off to a nice start!

By the way you aren't the only one thinking that such a tool will come in handy! It is on the list of things to do.

 

[cfellows]

Looks like you are off to a nice start!

By the way you aren't the only one thinking that such a tool will come in handy! It is on the list of things to do.

Thanks, Wiz. By the way, I found some price references from back in 2008... $950 - $1400 depending on options and accessories. So far, I've spent $2.50 for screws, the rest of the stuff I've had on hand. May have to buy a few more bearings, but that should be it.

Here's one last picture for the day.

I made a 1" roller. I plan to make a 3/4", a 1.25", a 1.5", and a 2". I can also make more as the need arises.

Chuck

 

[barnesrickw]

Any ideas on a motorized hacksaw?

 

[kvom]

What CAD and CAM are you using? 8 hours seems like a lot for that, but since it was a first part maybe not excessive. What problems did you have?

 

[cfellows]

Any ideas on a motorized hacksaw?

No, I owned one once that I had bought and refurbished. I wound up selling it because I liked my 4 x 6 band saw better. Never thought about it much since then.

Chuck

 

[cfellows]

What CAD and CAM are you using? 8 hours seems like a lot for that, but since it was a first part maybe not excessive. What problems did you have?

I was using Autodesk Inventor with their new HSM Express CAM plugin. The main problems were figuring out the navigation through the CAM and getting the pocket to come out the right size. There are a number of places where you can specify amounts of stock to leave, ostensibly for finish operations or for milling cutters that aren't exactly the specified size. I was also kind of designing as I went, so I changed the position and length of the slot several times.

I do have to say that having the CAM as a plugin is convenient. It's easy to make changes to the part then just reprocess it, all in the same software. HSM Express is only 2.5D, but I think it will be satisfactory for most of my needs, or at least until I get a little more experience with CNC. I can see that I have a long, steep hill ahead of me.

Chuck

 

[BaronJ]

Hi Chuck,

Keep at it ! What you have so far is looking good. I'm watching with interest.

 

[cfellows]

Thanks, Baron. This thing is coming together pretty quickly.

I had a pretty productive day in the shop. Managed to get the belt tensioner assembly mostly finished. Here is the idler pulley for the tensioner:

The pulley started out as a 2" diameter piece of aluminum rod, 2.5" long. It has a 5/8" hole bored straight through, then a 1/2" ID ball bearing recessed into 1.125" pockets on each end. A 1/2" bolt will thread into the supporting arm with the jam nut to lock it in place. I formed the crown on the pulley by turning a 3 degree taper on each end in about 7/8". Then I used a rasp, a file, and 320 grit sand paper to smooth the transitions while spinning it in the lathe.

Here's the assembly so far:

The support arm is hinged on a 3/8" bolt in back with a 5/16-24 Jack Screw for the belt tracking adjustment.

Still have to figure out the tensioner spring arrangement, drill a mounting swivel hole in the back, and mount a handle on top of the support arm before I can call this part finished. Then I'll be about ready to start putting this puppy together.

Chuck

 

[BaronJ]

Hi Chuck,

The photos make that crowning look a little severe.

As far as tensioning is concerned, would a cam arrangement work there ?

Something like a disk with the tensioner mounted offset.

 

[cfellows]

Hi Chuck,

The photos make that crowning look a little severe.

As far as tensioning is concerned, would a cam arrangement work there ?

Something like a disk with the tensioner mounted offset.

I did a lashup this morning with all the parts fired it up. I think you're right, the crowning is too severe. I wasn't sure how to calculate the correct slope so I may have to adjust it.

I don't quite understand the disk arrangement you describe...

Chuck

 

[BaronJ]

Hi Chuck,

Forget my ramblings about a cam arrangement. I looked at the video but the spring tensioner simply passed me by. Then just having scrolled through the post again... Doh.

Sorry :wall::wall:

 

[cfellows]

Getting Close! Here's the mostly assembled grinder, parked in it's new home. This space on the end of my Table Saw stand was previously unused and the grinder fits in there nicely.

Here's some photos of the rest of my garage/shop. You can see it's a bit crowded...

Now I have to build the spring assembly for the tensioner arm, the backing platen for the straight bit, and the adjustable table assemblies for both the straight part and the end roller.

Chuck

 

[cfellows]

Here's a short video of the grinder. Not finished yet, but the running gear is done...

[ame]http://www.youtube.com/watch?v=KkdHQBYd9Wc[/ame]

Chuck

 

[BaronJ]

Hi Chuck,

If you think your workshop is a little crowded, I daren't show you mine.

Its coming along real nice. That spring clamp and pinching the spring from it is a good idea. I would add a screw tensioner so that you have some control over it.