40 replies to this topic

[swodem]

It’s hard enough getting a Flexi chassis flat, without a non-flat tech block contributing to some false readings

I recently got a couple of aluminum ones, that had been milled flat, but in fact, they were far from it

So using a very flat surface, some wet’n’dry sandpaper and some elbow grease, I got them truly flat and uber-smooth

I also touched up my Precision corian ones, which were dirty, but in terms of flatness pretty good. They’re smoother now

Worth the effort I think

Out of the packet


Halfway


Finished!!




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[JimF]

Thanks for posting this. I have several chassis jigs (for retro) and I use 'em hard. I find that I get much better results if I sand them occasionally as well. For the Corian blocks, I use 60 grit paper taped to a countertop and just bear down until my tru-bar shows flat. I then follow with 180 grit but that's probably not necessary. It can take a while but it's worth it. Eventually all the nice dimensional marking go away, but the holes are still there.

[slotbaker]

I'm curious, how flat is it??

 

How, and what did you check it with?

 

It looks nice and smooth, but can't tell how flat it is.

 

[Matt Sheldon]

I use a precision granite machinists block for flattening chassis pieces and final assembly. You could also use the same and put sandpaper on it and lap your other jig surfaces on it. Additionally machinist stones would get a jig block flat.

 

[swodem]

I use an engineering rule to check for flatness



Hold it in front of a light. Move the rule around to check all angles and surfaces




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[swodem]

Thanks for posting this. I have several chassis jigs (for retro) and I use 'em hard. I find that I get much better results if I sand them occasionally as well. For the Corian blocks, I use 60 grit paper taped to a countertop and just bear down until my tru-bar shows flat. I then follow with 180 grit but that's probably not necessary. It can take a while but it's worth it. Eventually all the nice dimensional marking go away, but the holes are still there.

Wow that’s coarse grits you’re using!

I start with 240, and work up to 1200
All the time they’re well wetted




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[slotbaker]

I use an engineering rule to check for flatness

Ok, cool.

 

I'm guessing that if you checked the plate with the straight edge prior to smoothing it out, you would be hard pressed to get your thinnest feeler gauge (0.0015"?) through any gaps.  If the milling is done correctly, the surface would be flat enough for our slot car use, even though it looks rough.

 

If you're interested in being super precise, and seeing as you have 2 flat aluminium plates, you could go one or two steps further to see how flat they really are.

 

As a rough test, put both plates together against the smoothed faces, and hold up to the light to see if there are any gaps between them.

If no gaps, good, then try the next check.

 

Get a small tube of Prussian blue oil paint from an artist supply store (or you might even already have it), and put a thin, even film completely over one of the plates smoothed face. Not too much, just enough to colour the surface.

 

Then put the second plate face down on the blued face and gently push down evenly then move the top plate in a figure 8 a couple of times over the bottom one, then check where the blue was rubbed off the bottom one, and deposited to the top one.

 

If there are high spots, you could lap the plates together with fine valve grinding paste, and check by blueing again.

 

Not sure all this effort is warranted for slot cars, but there might be some who want to be sooper accurate.

[Bill from NH]

Like Matt, I've always used a small granite surface plate  for checking chassis flatness. 

[kvanpelt]

I use a precision granite machinists block for flattening chassis pieces and final assembly. You could also use the same and put sandpaper on it and lap your other jig surfaces on it. Additionally machinist stones would get a jig block flat.

 

13120001.jpg

 

https://www.mcmaster.../granite-blocks

 

Matt, you win!!!!!

[Dominator]

For chassis jigs I use a flattening stone. One side is 180 and the other is 320. Here is a link to the one I use.

https://www.sharpeni...tone-P1545.aspx

[JerseyJohn]

For chassis jigs I use a flattening stone. One side is 180 and the other is 320. Here is a link to the one I use.

https://www.sharpeni...tone-P1545.aspx

nice Dom ordered one

[Matt Sheldon]

For chassis jigs I use a flattening stone. One side is 180 and the other is 320. Here is a link to the one I use.

https://www.sharpeni...tone-P1545.aspx

Basically a machinists stone as I referred to. That's a good price and should work perfect for our purpose.

 

Another thing to remember is to wipe your chassis block often. Cutting debris can and will hold surfaces up enough to have voids. I wipe mine down often with 70% alcohol and my granite block with lacquer thinner.

[MSwiss]

Its hard enough getting a Flexi chassis flat, without a non-flat tech block contributing to some false readings
I recently got a couple of aluminum ones

You don't have a U.S. Navy surface plate?

I feel poorly for you.

What's happens to racers that fall off in front of you, after you spent all that time flattening your chassis?

Start looking for the bow & arrow? Lol

[boxerdog]

Have you got a CR part number for that??

[swodem]

You don't have a U.S. Navy surface plate?

I feel poorly for you.

What's happens to racers that fall off in front of you, after you spent all that time flattening your chassis?

Start looking for the bow & arrow?

1. Obviously if they come out in front of me they’re gonna get ‘flattened’ too

2. US Navy property, you better send that to me and I’ll say nothing

3. I hate to think what the Navy actually paid for that!!

4. Can I send you some new socks?

5. Interesting mod on the pliers....

6. Yep the archery gear will come out if it happens over and over!!


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[MSwiss]

Ref #5 - A slightly better pic of them

Bryan Warmack sent them to me.

He modified them for some important bending operation.

What it is/was, escapes me at the moment. Lol

[Tim Neja]

It seems Kevins granite blocks will work great!! Not TOO expensive if you go tool grade B which will definitely be accurate enough for what I build!!   Plus as a bonus--I can use the 18 x 12 one to check my 1/10 scale F-1 chassis too!! 

[Matt Sheldon]

Ref #5 - A slightly better pic of them

Bryan Warmack sent them to me.

He modified them for some important bending operation.

What it is/was, escapes me at the moment. Lol

20190801_074611.jpg

Duffy had a pair Bryan sent him too.

[Guillermo Suar]

It seems Kevins granite blocks will work great!! Not TOO expensive if you go tool grade B which will definitely be accurate enough for what I build!!   Plus as a bonus--I can use the 18 x 12 one to check my 1/10 scale F-1 chassis too!! 

 

 

Even cheaper:

 

https://www.grizzly....-No-Ledge/G9649

 

[Phil Hackett]

 

 

Even cheaper:

 

https://www.grizzly....-No-Ledge/G9649

 

 

 

This is overkill but it's cheap overkill. That makes it OK. You just know someone is going to have  a labratory grade surface plate for building chassis. That extra 150 millionth of an inch flatter is going to make a .000001/second difference per lap. 

 

Didja know granite is mildly radioactive? It's also heavy... 9 x 12 x 2 is 25 pounds listed in the ad.

[Bill from NH]

I bought a couple tool grade surface plates the size in Tim's post, from Lee Valley Tools in Ogdensburg, NY.  About 15 years ago. I paid around $35 for the two of them, included shipping. Now they're about $60 each. If taken care of, not abused, & cleaned, they'll last a lifetime. Grizzly's price is a very good deal.

[swodem]

Yep well that’s all very well, getting engineers blocks to work on your chassis when you’re setting it up (clap, clap). We probably all have one of those of some style. Even a piece of marble benchtop offcut is really flat these days

Good luck getting one of those suckers in your pit box tho

My post was about getting your setup boards flat. Because one of mine wasn’t.


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[slotbaker]

My post was about getting your setup boards flat. Because one of mine wasn’t.

How much was it out?

What size feeler gauge could you get under your straight edge?

[swodem]

I didn’t measure it
For me it was most obvious the milling wasn’t right - like the mill but wasn’t dead vertical

The second pic, (repeated below) should explain




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[Dan Searcy]

I use an engineering rule to check for flatness



Hold it in front of a light. Move the rule around to check all angles and surfaces




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I don't know how to use a metric rule.....