I Want A New Grinder

colu41 said:
Going off of the plans I have, its a 3/4" x 4" springs that compresses 1" with 30# of pressure. I don't even know where to look for one. Or how to even search for that?
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Check here: http://www.mcmaster.com/#compression-springs/=x3b5z1

edit: Are you still planning a build similar to the photo you posted before showing the tension arm dropping inside a vertical square tube? If so, then what size is the vertical post square tube? Say it's 1-1/2" ID same as the tooling arm holder, you would want a spring that is sized to just drop inside the square tube easy without binding.

The choice of which spring needed depends on design of build. On a KMG type clone, you normally want at least a 40 lb (or more) spring with at least 3" of travel. I started looking for a specific spring, but realized I didn't know your grinder design that determines the spring. Springs are not too expensive at $10 to $15 each should cover the choice of springs.

Ken H>
 
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Thanks for that. This is the exact grinder I'm building, just different motor and vfd. And he used a spring that compressed 1 inch with 30# of load.

I may have been wrong on the size I mentioned earlier....Took a look at McMaster, and call me stupid, but I have no clue what I'm looking for right now! lol. If the spring needs to deflect 1" with 30# of pressure, what max load would it be? I have no idea.
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For an exact 30# at 1 inch of travel, you'd have to get a spring with only 1" of compression with 30lb at max compression. The 30# isn't that critical, nor is the stroke length. I personally think I'd prefer a longer stroke to the spring - perhaps 3" or so? From looking, it looks like the vertical post is 1-1/2" ID square? If so, here are a couple of springs you might look at.

http://www.mcmaster.com/mv1431030469//#9620k33/=x3ewm3

It has a 1.06" OD, overall length of 3.5", and a fully compressed length of 1.6", which is 1.9" of travel 65# per inch pressure.

http://www.mcmaster.com/#9657k142/=x3eybu

This is the one I used, but it's a bit larger OD than you can use: http://www.mcmaster.com/#96485k125/=x3f04j

Problem I have in finding your spring, is finding one with a good OD to fit, but still a long enough compression length. Maybe that's why the grinder in photo only has 1" compression length. That will work, just a bit more adjustment on tooling arm.

Ken
 
Ken H> said:
For an exact 30# at 1 inch of travel, you'd have to get a spring with only 1" of compression with 30lb at max compression. The 30# isn't that critical, nor is the stroke length. I personally think I'd prefer a longer stroke to the spring - perhaps 3" or so? From looking, it looks like the vertical post is 1-1/2" ID square? If so, here are a couple of springs you might look at.

http://www.mcmaster.com/mv1431030469//#9620k33/=x3ewm3

It has a 1.06" OD, overall length of 3.5", and a fully compressed length of 1.6", which is 1.9" of travel 65# per inch pressure.

http://www.mcmaster.com/#9657k142/=x3eybu

This is the one I used, but it's a bit larger OD than you can use: http://www.mcmaster.com/#96485k125/=x3f04j

Problem I have in finding your spring, is finding one with a good OD to fit, but still a long enough compression length. Maybe that's why the grinder in photo only has 1" compression length. That will work, just a bit more adjustment on tooling arm.

Ken
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Wow thanks Ken! I get what you mean though, I think Id also prefer a longer travel in the spring. I think I'm going to purchase that first one you listed.
I got the tool arm and platen completed today. Just waiting to order the wheels.
Motor and VFD next week! I will be welding the frame up tomorrow.
 
Looking forward to the weld process. Just be sure to clamp all the parts flat to get them in line while welding.... well, I'm sure you're well familiar with welding pulling material when tacking up.

Have fun - and don't get an "dingle ball" burns:) Oh, are you using a stick welder?

Ken H>
 
Ken H> said:
Looking forward to the weld process. Just be sure to clamp all the parts flat to get them in line while welding.... well, I'm sure you're well familiar with welding pulling material when tacking up.

Have fun - and don't get an "dingle ball" burns:) Oh, are you using a stick welder?

Ken H>
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Wire Feed. And yes I will be adjusting and clamping like crazy because the more I think about squaring everything up the more I worry that when its all done the belts just going to fly off the wheels! lol
 
I understand those wire feed welders are much nicer to play with than the old stick welders. I grew up with stick, and never really tried wire. Do you have a steel baseplate for the grinder in that batch of scrap steel you got? If so, and it's 3/8" thick or so use it for a leveling board. Lay the parts out in shape, clamp them to baseplate (or tack weld) so they won't move. Then do your tack up with spot welds on all accessible 3 sides. Once it's all tacked in place good - you should be able to weld without pulling out of alignment. Then grind the tacks to base plate free, and complete the welds. It "should" be pretty much in alignment.

There are only 2 really critical welds on that grinder - 1) is the tool arm tube to the vertical tube- that needs to be in the exact same plane. and 2) is when the vertical tubes are welded to baseplate. That really needs to be square so when motor is mounted to baseplate it's shaft is in correct alignment to frame so the belt won't be running off the drive wheel.

Heck, you've got that all figured out anyway - just pardon an old man "building" in his mind {g}

Ken H>
 
Ken H> said:
I understand those wire feed welders are much nicer to play with than the old stick welders. I grew up with stick, and never really tried wire. Do you have a steel baseplate for the grinder in that batch of scrap steel you got? If so, and it's 3/8" thick or so use it for a leveling board. Lay the parts out in shape, clamp them to baseplate (or tack weld) so they won't move. Then do your tack up with spot welds on all accessible 3 sides. Once it's all tacked in place good - you should be able to weld without pulling out of alignment. Then grind the tacks to base plate free, and complete the welds. It "should" be pretty much in alignment.

There are only 2 really critical welds on that grinder - 1) is the tool arm tube to the vertical tube- that needs to be in the exact same plane. and 2) is when the vertical tubes are welded to baseplate. That really needs to be square so when motor is mounted to baseplate it's shaft is in correct alignment to frame so the belt won't be running off the drive wheel.

Heck, you've got that all figured out anyway - just pardon an old man "building" in his mind {g}

Ken H>
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No no, you keep giving me great tips. Whether theyre in your head or not they all help. I'm just super excited with this project!
 
So I decided to go with the longboard wheels. And just ordered a 4" alum drive wheel. But my problem is the bearings bore size is .3. What size bolt is going to fit that? 19/64 is the closest I can think of. Not sure if this is work able or if I should try to bring the bearings back and try different ones.
 
If you've got standard skateboard/longboard wheel bearings they "should" use a 5/16" bolt for axle ok..... but 5/16 is .3125 - that's only 12 thou over your .3 - the thread size is max of .3125 and minimum of .303". If the threads are a tad tight on all thread, chuck in drill and file just a bit with drill spinning all thread. That should knock a few thou off and make the 5/16" all thread work just fine.
 
Skate axles are indeed generally 5/16" even though bearings are metric spec 8mm ID. Some high end skate trucks use true 8mm axles to remove some of the slop. 5/16 will work just fine.
 
Ken H> said:
If you've got standard skateboard/longboard wheel bearings they "should" use a 5/16" bolt for axle ok..... but 5/16 is .3125 - that's only 12 thou over your .3 - the thread size is max of .3125 and minimum of .303". If the threads are a tad tight on all thread, chuck in drill and file just a bit with drill spinning all thread. That should knock a few thou off and make the 5/16" all thread work just fine.
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Boogaloo said:
Skate axles are indeed generally 5/16" even though bearings are metric spec 8mm ID. Some high end skate trucks use true 8mm axles to remove some of the slop. 5/16 will work just fine.
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Thanks guys. I didnt know how exact it needed to be. I'll pick up some 5/16s. Then the platen assembly will be complete and just need to make the hinging system for the tracking wheel. Kind of confused on that but, i'll figure it out.
 
So I got the rest of the hardware I needed. I'm trying to put the wheels on the platen attachment and it doesn't seem to be working. I got spacers that fit perfectly, washers and everything. The spacers ride on the inner piece of the bearing, but when I tighten it down, the wheel doesn't spin very well at all. Do these bearings need to be worn in? Or am I missing something?
 
Nope, bearings should not need "wearing in" at all. There is something binding when you tighten the nut too much. There should be a spacer between the bearings inside the wheel so when you tighten on nut, there is NO pressure at all on the bearing itself - only on the spacers.
 
Ken H> said:
Nope, bearings should not need "wearing in" at all. There is something binding when you tighten the nut too much. There should be a spacer between the bearings inside the wheel so when you tighten on nut, there is NO pressure at all on the bearing itself - only on the spacers.
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Hm. I was kind of thinking of that. How will I know the exact size spacer I would need? Pretty hard to measure that.
 
Some skateboard bearings come with a wide inner race on the bearing that acts as a spacer. Other bearings might not have this spacer. I'd think perhaps if you push the bearings into place in the wheel, look inside the axle hole and see if you see any space between the bearings. If there is some space, guesstimate the distance, but that much spacer (washers, tube cut to length, etc), press bearings back into place - do they seat all the way? Does the spacer fill all the gap? If bearing doesn't seat all the way, it might be possible to take a tad of spacer out.

That would be my first "guess" at trying anyway.
 
I just did some research. I think I need 8mm x 10mm spacers. Theyre the most common for longboard wheels. $3 for 4 so, I might just try that tomorrow when the Skate Shop is open.
 
There ya' go - since there is a skateboard shop close by, you can get exactly what you need.

Ken H>
 
Ken H> said:
There ya' go - since there is a skateboard shop close by, you can get exactly what you need.

Ken H>
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Thanks. Yes I got pretty lucky having them local. I ordered my 4" drive wheel, the motor and vfd last night. I should have everything I need. Just need to piece it together now
 
Super newb question but. How far should the flat of the platen be from the outter edge of the wheels? Right now my platen is set up about an 1/8" inside the outter edge of the wheels. Should it be flush? Platen protrude slightly outside the wheels?
 
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