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Gerald_D
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Username: Gerald_d
Post Number: 86
Registered: 11-2005
| | Posted on Friday, May 26, 2006 - 10:31 am: | 
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The MechMate drawings will call for a machine shop with a milling machine to form the inverted V on the top edge of lengths of standard angle iron for the x and y rails. Pretty easy and economical - if you have access to a milling machine shop. But you may want to consider a variation on the following......
Grinding in radial arm saw or table saw
Then a quick test in a table saw.....
  
Don't try this if there is sawdust in your table-saw! 
This is not the way that I had my rails made (they were milled), but I am just throwing this in here as food for thought......... |
Gerald_D
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Username: Gerald_d
Post Number: 396
Registered: 11-2005
| | Posted on Wednesday, November 08, 2006 - 08:00 am: |
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The grinding in the table saw was surprisingly easy (20 minutes) A 175mm wheel protruding 26mm above the table surface gave the 2x45 degrees, albeit very slightly concave. Then some draw filing with a fine file and a bit of emery stone (20 minutes). There is scope for refining this process, but already the results are an A-class "pass".
If I had to do a lot of these, I would use a thicker(wider face) stone of a finer grit, but the 3mm thin cutting disc (coarse) was not too bad. The biggest job was to make a centralising bush for the disc in the table-saw.
Can I suggest you guys try it with any old piece of flat bar before you believe me? |
Evan Curtis
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Username: Evan
Post Number: 15
Registered: 12-2005
| | Posted on Tuesday, November 07, 2006 - 07:22 pm: |
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As you’re pushing the plate through and the grinding wheel is wearing down; how do you keep the edges parallel and square? Do you have to adjust the fence? Or is the wear on the wheel so minimal as to not matter? |
Gerald_D
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Username: Gerald_d
Post Number: 393
Registered: 11-2005
| | Posted on Tuesday, November 07, 2006 - 08:03 pm: |
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It was a thin "cut-off" wheel only 3mm thick. Not designed for feeding material from the side. And the grit is quite coarse and fairly loosely bound in the wheel. Unfortunately our table saw construction is such that a thicker blade/wheel doesn't go past the nose of the (left-hand) threaded shaft.
With the first couple of cuts, the wheel seemed to wear a lot because the cut was quickly getting lighter. Realise that all four edges are done with one setting (the plate is flipped over and end-for-end). Therefore 2 meters of edge per setting.
For the first couple of cuts I only lifted the wheel and didn't move the fence. When it got close to final shape I re-measured the wheel diam to do a final calibration. To my surprise, there was only 3mm lost on the diameter.
The last cuts were very light and all 4 flipped passes seemed consistent. The original edge was down to 1mm wide and looked absolutely consistent side-to-side and end-to-end. The fence was only moved twice, the wheel was raised less than ten times, therefore less than 10 passes per edge. (Had to do it during lunch-break when they allow me in the workshop)
Realise that I am not trying to get a 100% perfect slide by NASA standards. It must be an economic, wear-resistant, stiff slide suitable for a short-stroke z-axis on a router. Because this slide is harder and thicker than our SB's one, and because the wheel diameters are bigger, I will be able to pre-load the eccentrics quite a lot without causing excessive wear. |
Evan Curtis
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Username: Evan
Post Number: 16
Registered: 12-2005
| | Posted on Tuesday, November 07, 2006 - 09:45 pm: |
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As I've thought about it and reading your process I see now how it could be quite accurate (more precise than SB's) If you scribe four layout lines one on each side along each edge then grind and file to the line, it might help in ensuring accuracy. The pictures you've posted look great. It appears you left a small (about 1.5mm) flat face along each edge there by ensuring the edges remain at least as parallel as the flat stock was when purchased. I'm going to have to rebuild one of my Z axis in the near future, now I have to decide between using a linear bearing slide as on the Original Mechmate and this V-Bearing slide. I really appreciate all you've shared with us. |
Gerald_D
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Username: Gerald_d
Post Number: 394
Registered: 11-2005
| | Posted on Tuesday, November 07, 2006 - 10:06 pm: |
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Evan, try it on some scrap flat bar stock first. I did the draw filing only to remove the right-angle marks left by the wheel. The amount removed by the file is very tiny and I wouldn't try to file to a scribed line. I don't even think the draw filing is necessary at all if the stone is finer. My draw filing started on the SB years back, and I regard it as my personal input - much like scraping bearings and beds (don't expect everyone to know what I'm talking about here hint) |
John_H
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Username: John_h
Post Number: 1
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 12:43 am: |
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Hi all,
I dont own a SB but I'm assuming this project
is a completely seperate machine all it's own?
I've built 5 small fixed bridge desktop sized
machines, But I'd like somthing a bit larger.
I'm interested in how you're working on the flat
bar. I'd be concerned that the fine grit will
do some damage to a table saw.
What about a piece of angle iron bolted upside
down alongside a cheap grinder. That provides
a 45 angle, then an adjustable block to provide
enough tension to slide the flat bar through
in several passes.
Here's a crude sketch...Hope it make sense.
John |
vadeem
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Username: Vid1900
Post Number: 10
Registered: 10-2006
| | Posted on Wednesday, November 08, 2006 - 03:49 am: |
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I cut aluminum on the tablesaw without worry about damage all the time.
I always clean out ALL of the wood dust before starting. I also turn off my main dust collector and switch to just a plain shop-vac. |
John_H
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Username: John_h
Post Number: 2
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 04:36 am: |
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I also cut aluminum on mine. Mine is a 150.00
table saw. I imagine some of us use 5-6-7 hundred
dollar saws.
Relative to an aluminum shaving, the fine dust generated from an abrasive cut-off wheel (aluminum
or silicon oxide) WILL damage your motor bearings.
I know this from experience.
What I'm interested in is a way to create the necessary angles for bearings to ride on in an
on-demand, as needed fashion.
I believe a setup like I described may work very
well, accounting for a trial & error test or two.
I have seen some surface hardening compounds in a
can, but haven't tried any. |
vadeem
Registered
Username: Vid1900
Post Number: 11
Registered: 10-2006
| | Posted on Wednesday, November 08, 2006 - 06:49 am: |
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Thanks for the tip before I runined my $$$ saw! |
John_H
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Username: John_h
Post Number: 4
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 08:17 am: |
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You wouldn't likely ruin it just doing it a few
times, but it's definitly Not Good for the motor
in the saw. This aluminum (or silicon) oxide
dust is harder than the bearings. and so small
that easily gets into places one can't see.
I'd do it on my cheap saw...it's on the way out
anyhow. But I'd hesitate on a nice expensive
shop saw.
Anyway, It'd be nice to be able to make up a section of rail, maybe several feet long, as it
was needed.
John |
Gerald_D
Registered
Username: Gerald_d
Post Number: 397
Registered: 11-2005
| | Posted on Wednesday, November 08, 2006 - 08:20 am: |
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The bearings on my grinders and table saw are identical in terms of seals - I can't see why grind dust will be a bigger issue for the table saw bearing instead of the grinder bearing. We are not talking of using the table-saw as a production 40 hour/week grinder - this is a quick light job. No worse than using a belt-sander near your table saw.
The biggest damage to the saw is caused by the burr that the grinding makes on the bottom edge of the rail. This burr scratches across the table. A bit of thin plywood under the rail will stop that. |
John_H
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Username: John_h
Post Number: 5
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 08:45 am: |
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I Absolutely Agree.
I would like to set up a small scale "production"
type of arrangement, just to see and test out how
well it'd work.
Here's what comes to mind. Imagine if this "V" track
were about as cheap as drill rod material, with
about the same tolerances. And the bearings were
well..not as expensive as they are now.
That combination would VERY useful to a lot of people. And there's really no good reason such
a combination doesn't exist. It's a big world full
of people trying to figure out what to make so they can survive, but strangely enough, nobody
makes what there's a demand for?
It can't be that hard to make a relativly straight
bar that is angled on the edges.
I'll throw away a $35.00 grinder if it fails.
What do you think of the grinder idea anyway?
I see you're the only one who's actually tried to do this.
John |
John_H
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Username: John_h
Post Number: 6
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 09:12 am: |
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I should have mentioned from the start that
I'm VERY impressed by the section you made
already. I haven't seen anyone else try this.
John |
Gerald_D
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Username: Gerald_d
Post Number: 399
Registered: 11-2005
| | Posted on Wednesday, November 08, 2006 - 09:18 am: |
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John, in principle, your scheme is solid. Adjustment for progressively deeper cuts would be tricky.
Also, I would add a support edge for the back of the rail (bottom left corner in your diagram). Imagine what happens down there if you are putting 4 bevels on a flat bar.........
Little $35 grinders are often very under-powered - that isn't a problem if you have time. Taking lighter cuts will force you into a good finish. Also, the larger the stone the better - I don't know if $35 grinders can safely take bigger stones.
The experimenters must watch the legal speeds on stones, wear eye protection, maybe even gloves for that sharp burr...
For long lengths, one is going to need a long table to carry the weight - you don't want the rail to droop over a table, lifting the center section away from the wheel. |
John_H
Registered
Username: John_h
Post Number: 7
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 09:40 am: |
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Well then a $100.00 grinder. I became Very
interested when I saw you'd actually done it.
If attention and care were put into a tool/jig intended to do only beveling edges, it may be worth the trouble. It could even be stepper driven very easily.
To try and do a "quick & dirty" on such an important part of the machine is no good.
I saw your part you'd made and that's what got
me going. I'm working on a Z-axis for my machine
as we speak and I wished I could use the "V"
bearings. PITA to get them though!
I gather you're the guy who's designing this
machine? E X C E L L E N T !
John |
Gerald_D
Registered
Username: Gerald_d
Post Number: 400
Registered: 11-2005
| | Posted on Wednesday, November 08, 2006 - 10:43 am: |
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What's stopping you from making your own V-rollers? |
John_H
Registered
Username: John_h
Post Number: 8
Registered: 11-2006
| | Posted on Wednesday, November 08, 2006 - 11:17 am: |
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I tried to figure out how to make the rails
first, and whether it was worth the trouble.
But to do it Precisely was going to require
a jig and I just sorta put it off.
When I saw your section the light came back on.
I'm sorry I haven't done my homework correctly here but if I understand it your project is a
stand-alone machine all it's own?
You're offering the plans alone and the end user
does the best he can.
You don't offer any parts.
I'm pretty sure I'm right with that but I will
ask directly.
I'd like to be a useful contribitor, that's why I ask. I think this may be one of the very best idea's I've seen.
I don't know about SB, but I've been rig-matizing
machines for many years and may be useful in some way.
BTW those are impressive too!
John |
Gerald_D
Registered
Username: Gerald_d
Post Number: 401
Registered: 11-2005
| | Posted on Wednesday, November 08, 2006 - 11:47 am: |
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"If attention and care were put into a tool/jig intended to do only beveling edges, it may be worth the trouble. It could even be stepper driven very easily." Apparently, that is how ShopBot make their rails. I've heard they use belt sanders instead of stone wheels, and they drive them down the rail with steppers. I guess that they control pressure and time in contact with the abrasive rather than the exact dimensions of the finished rail. Nothing really wrong with that, the exact dimensions of the rail are not critical - they just have to be consistent (parallel).
Yup, I am not supplying parts. I would really like to see guys like you standing up and offering parts to others in your area while I take a back seat. It would be nice to get a self-supporting community going. |
fabrica
Registered
Username: Daya
Post Number: 35
Registered: 10-2006
| | Posted on Wednesday, November 15, 2006 - 02:53 pm: |
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My machine operator has around two days of free time starting from tomorrow. I had a chat with him yesterday and he confidently said that he may be able to do the rails with the Shaper. But it is going to be a very tedious and time consuming job.I will keep you guys posted of the developments. In the mean time your suggestions on this issue are welcome before we start on the job (to make my life less miserable). |
Gerald_D
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Username: Gerald_d
Post Number: 454
Registered: 11-2005
| | Posted on Wednesday, November 15, 2006 - 03:16 pm: |
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Relax fabrica, go and watch some cricket!
I believe that your "shaper" and my "milling machine" are the same type of tool (different terminology in your country?). Just let your machinist do one rail first. Can you take photos for us?
Did you see how this thread developed 2 days ago? |
fabrica
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Username: Daya
Post Number: 36
Registered: 10-2006
| | Posted on Wednesday, November 15, 2006 - 03:31 pm: |
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In my country when our team is involved in a cricket match most of guys do not turn up for work (including me).
Definitly I will keep you guys posted with the photos on a regular basis. |
Greg Waggy
Registered
Username: Gawnca
Post Number: 51
Registered: 11-2006
| | Posted on Wednesday, November 15, 2006 - 08:39 pm: |
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Gerald, I thought/think that tread was going good. |
fabrica
Registered
Username: Daya
Post Number: 39
Registered: 10-2006
| | Posted on Friday, November 17, 2006 - 04:23 pm: |
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This is the sample V rail that we did with the existing shaper which ahas a stroke of 600 mm. We did this just to get some confidence. I will post a better picture tomorrow since I am still to learn the finer point of using the micro mode of my dig camera.
 |
fabrica
Registered
Username: Daya
Post Number: 40
Registered: 10-2006
| | Posted on Friday, November 17, 2006 - 04:28 pm: |
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To do this rail we used a shaper which has a
600 mm stroke.
 |
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