angle plate fabrication -- how good is 'enough'?

"Good enough" is up to you and your applications, of course.

You could always make 3 and scrape.

I bought a hand-scraped cast angle on eBay. I didn't trust it, and after checking on a surface plate, it was obviously not flat on either face. I just bought a utility angle plate that I'm going to cut in half. Then, I'll have 3 angle plates that I can scrape in against each other. I'll have to see how long that takes.

Jon

And many of us would like to hear your experiences.

I cut up some of the cheap Enco cast iron squares into 4 x 5 x 1 pieces, and scraped them to a few tenths using them against each other and a granite surface plate a la Connelly. Took me some hours per piece. Anything 5 inches long is easy compared to something feet long.

As others have said, "good enough" is your call. However, when you check your parts with your square, you will always be second guessing yourself as to where the error came from. Was there some dust or a chip, or was it your angle plate, or is your mill out of square, etc.

In tool making, the gauges, guides, bushings, datums, etc. should usually be two to five times (or perhaps even ten times) more accurate than the tolerance on your part....

Garbage in, garbage out.

Regards,

Robin

As long as it suits you and is within specs for your intended purpose........However, to one or two folks in this forum unless its dead on and perfect to the millionth decimal point all it will do is reflect is your shoddy work habits and your integrity , whose concept is, if its worth doing its worthwhile doing it "exact" and there is no such thing in their many years of being a machinist as good enough!

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Grant, If you lay your angle plate on its side, you can surface grind the other side so it is parallel to the side that is down. Now flip it over and surface grind the side that was on the bottom. Great now you have two surfaces that are parallel to each other, but maybe not at 90 degrees from horizontal when the plate is in its normal position. So take your dial indicator and base, and a piece of round scrap and set up the indicator to measure the angle plate side at the top with the angle plate up against the piece of round stock and that against the indicator base. Note the reading. Now do the same on the other side. If the reading is identical, sides are at ninety degrees from the bottom. If not put the angle plate back on its side and shim to make it right. Cigarete paper works for small amounts. Repeat until the sides are as close to 90 degrees as you want. Now check the side you want to improve on the angle plate. Shim and grind accordingly.

I hope this is enough that you understand what I am trying to convey. If not call me.

Dan

I decided to track down the error. It turns out that the angle plate I made is actually much better than I'd thought. It's the chuck on my surface grinder that has the error - uh oh. I guess I'll have to jury-rig the coolant pump again and spend a couple more hours grinding it in again. Thought I had it about right last time. Dag nabbit.

GWE

Grant Erw> OK, today I made my first angle plate. Had to have a little one for

On 16 Oct 2004 07:53:54 -0700, snipped-for-privacy@krl.org (Dan Caster) calmly ranted:

I can just hear it now, as you speed home to shim the jig.

"Honest, Officer. You don't need to search my vehicle. This pack of ZigZag papers is for my _machine_, not me."

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In the top of my toolbox is a mirror, a razor blade, and a pack of ZigZags. Best and cheapest setup aids for 99 and 44/100ths % of my work.

Bob

On Mon, 18 Oct 2004 04:00:57 GMT, "Robert Murray" calmly ranted:

I'll pretend that I don't know what you're talking about.

P.S: No straw?

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Naw, that's what hundred-dollar bills are for ............