3 Points to support parts when scraping

[Richard King 2]

Hobby Machinist member Duane Dickey is attending this past weeks class and he is getting educated on how important it is to set columns, tables, saddles on 3points wwhen scraping and measuring for co-planer or parallelism. Cast iron bends and sags. If you just set a part on a table it will flex to it's own weight. Maybe not a lot, but if you scrape it as it sits, when you go to assemble or match fit it to the mating part it will be off. I am teaching today, so I can only post a few pictures now I posted more on my company forum at the top of the lists. Yesterday I showed him what's called the balance beam or bridge support. Also on the photos' we put the single point under the feed screw hole on the saddle as when the factory built the machine that is the center of gravity of the part. We originally set it at 1/2 of the appearance and it was not as accurate. The machine we tested was a Harig surface grinder that the scraping looked new. The first pictures show the column of a Bridgeport grinder.

 

[Richard King 2]

I have to scoot, class starts in 7 minutes...I'll write and add more pictures later. The ways tested on a bare table compared to on 3 points was3 to 4 times worse.

 

[Richard King 2]

Class is over, I have another in 3 weeks. I added more pictures in my company forum at the top. Thanks everyone. If you need some advice on any machine repair issue, please ask here or you can always call me . on your nickel, that is...lol

 

[ddickey]

Hobby Machinist member Duane Dickey is attending this past weeks class and he is getting educated on how important it is to set columns, tables, saddles on 3points wwhen scraping and measuring for co-planer or parallelism. Cast iron bends and sags. If you just set a part on a table it will flex to it's own weight. Maybe not a lot, but if you scrape it as it sits, when you go to assemble or match fit it to the mating part it will be off. I am teaching today, so I can only post a few pictures now I posted more on my company forum at the top of the lists. Yesterday I showed him what's called the balance beam or bridge support. Also on the photos' we put the single point under the feed screw hole on the saddle as when the factory built the machine that is the center of gravity of the part. We originally set it at 1/2 of the appearance and it was not as accurate. The machine we tested was a Harig surface grinder that the scraping looked new. The first pictures show the column of a Bridgeport grinder.

I knew about three points but I had never really checked or thought about checking. To actually see the readings change with the Kingway was quite educational and eye opening.
Thanks Dick, I mean Rich (LOL) for putting the class on, learned a lot.