I see a couple of things.

#1 is that the guide wheels are pretty far away from each other as well as the wheel. that means it will not get as close to the end of the rail as it could.

#2 the height adjust mechanism does not prevent one side from going high while the others goes low. it might offer an easy adjustment method, but I don't see how it prevents the transference of hieght from one side to the other.

Of course I could be missing something ???

Dave

Sean,

I agree with Gerald and Dave. It is free to rock. If you were having trouble with the eccentric changing on you, why don't you just add a thumb screw to lock it in place once the correct height/depth is set?

Yep. you guys are right....I hadn't actually started to play with it in the shop when you have already realized that the turnbuckle doesn't hold station. I should have learned last time I tried a proportional dividing adjuster. If I use 2 turnbuckles, then it would work - but that's to much work. I prefer the lock screw idea better:) See what happens when I have to much free time while the kids are napping - I get drafting happy.

Have a good weekend.

Sean

Interesting concept Sean.
The first thing that comes to mind is KISS. :) You're going to use this thing for 40' of rail (gross) and then it will sit in the corner. :eek: Also I'd have to agree with Dave regarding the distance between those rollers as well. While making mine I tried to keep the rollers as close as possible (10"). The more distance between these the more scrap material you end up with.
As for adjusting the bottom eccentrics, on mine you can see the slots in the eccentrics for holding them in place until you tighten the bolt. On the verticals ones the levers work great.

Greg,
I agree with KISS. I was trying to make it a little more friendly since I am making 2 machines to start with, possibly a third by the end of the year. SO, a production model was in my head for future use. You have sold me on the eccentric with the handle for vertical adjustment. I was just concerned with it vibrating to much and changing the grinding depth.

The next challenge is I don't have a mini-lathe in the shop. Yet! Off to buy another tool tomorrow so I can turn those bearing centers. It's a shame I sold my entire machine shop a couple of years ago before I relocated to florida. That Mitsutoyo 3 axis tree mill would come in handy about right now.

Thanks for all your input and wisdom. You keep up this good work I might have to hire one of you guys!

Sean

Sean
I can't tell you how many times I kept looking at the lathe on the Harborfreight website. Even after getting the coupon for 20% off from Gene (THANKS!!!) :) I didn't want to spend that kind of money. J.R. made his look so good with all the fancy turning. I thought about using 3/4" bolts and trying to knurl the pressed on portion but it sounded like a a real PITA. As it turned out the local Lowes hardware store sold 3/4" steel dowel. It was slightly out of round but 2 minutes with my file and the problem was solved. I took the edge off before I "pressed" them into the bearings. A brass hammer, some WD40 and everything went smooth. They are tight enough that I'm not worried about them coming loose, but not so that I worry about them deforming the bearings.

one last picture
 

Forum,
Just so I can sleep better, here is the skate that I will send to the shop to build....any questions, comments or (hey Sean - your missing something? Thanks for all your help.
Sean

Greg,
I must have missed your post, because I did the same thing! I went to Lowes and found the 3/4" round bar as well. I will be working on this week. Gerald, if your watching, I am going to build a true MM first, with the proper rails. In my heart I don't want to deviate from the design that works so well. I was attempting to save a little labor in the shop, but when I really calculated all the drilling and prep time, grinding the rails is actually a time saver by about 10 man hours. I like this design more each day. Sean

the skate looks like it will work, but...

if you review this whole thread, there is a drawing of bearings that would allow you to use the entire length of the angle.

also, if you have machine shop experience, you can easily make a jig so that the skate of any style runs the full length of the rail, just by adding an exit runway. Not important for the one off machine, but for production, it would be very handy.

Dave

I don't like that 8-wheel arrangement that lets you get all the way to the tip of the rail. Get your hand-pressure wrong (ie. apply pressure to the wrong end of the skate) and the rail is destroyed/scrap. All this for trying to save about 300mm [12"] of cheap angle iron? Imagine trying to get all 8 bearings to carry equal load . . . . . .

To talk about the skate in general, I don't see the need to have adjustments for both:
- adjusting the top wheel height by eccentrics/levers, as well as
- screws to move the grinder from side-to-side.
One of these methods should be sufficient - my preference is to move the grinder because it is less sensitive and more rigid.

Also, do we really need wheels on top for making one set of rails? Can't the bottom of the skate just rub on top of the rail? How about brass screws up into the bottom of the skate and let the screw heads rub on the rail top? (the grinding throws up a small burr which will chew the brass to some extent, but rather not have a hard "screw" which could wear down the narrowing reference surface on the top of the rail)

Double plastic handles would be a total luxury - I would manage to produce one set of rails without handles, or maybe just one crude steel bar...

Clamping the grinder by only using its handle screw holes would be a non-starter for me - the only rigid place to hold a baby grinder would be directly behind the disk onto the gearbox. With most of these grinders now coming from the East, those screws are likely to be metric. (The Bosch is 4mm)

The four main rollers would logically sit on the same eccentrics that are going to end up on the Z-slide. No need for special eccentrics for the skate. A pair of 6001.2RSR bearings would make a nice roller. Those bearings could be re-used if making your own V-wheels as per M1 20 120.

I am toying with a design and laser cutting for the skate, but I am not yet convinced that everyone can easily find the same Bosch grinder. Also, I don't know if the grind-wheels/disks have the same thickness/offset/depression around the world.

Gerald,
Interesting you brought up just a simple screw for the vertical adjustment - I was toying with that last night instead of using the bearing w/lever due to the "one off" nature of the skate usage. This also allows for a much smaller form factor and less salvage. But what's a couple of bucks for angle iron? I was playing with a UHMW/delrin treaded screw, but I like the idea of brass even more due to the heat exposure. I did find my screw was to small of a diameter if I shifted the eccentrics all the way to one side....the screw falls off centerline. Time to try a 1/2-20 tomorrow or larger to ensure a good contact surface.
Sean

I agree that as a tool, it is not required one uses all the angle iron, and it is easy enough to buy longer and cut off the ends, but...

there was talk about renting or passing around a skate so anyone could use it, so the investment in time to make a "better?" unit might be worth it.

the second application is a production shop that would be making rails all day long. After a while, the scrap pile will get to be pretty big.

Dave

In a production shop the concentration lapses after a while and somebody is going to push down on the wrong end of that long skate (or actually is going to support the weight incorrectly as the car runs off the rail) . . . .

If I were to seriously do production, that skate would be motorised and run on its own permanent rails - ala the knife grinders.

Guys just keep that brain storm process. It is a pleasure to see how a project grows and develop with good and smart craftsman.
I am just waiting to make my first order.:)