Casting a straight edge

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Harold_V
Posts: 19592
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Casting a straight edge

Post by Harold_V » Tue Nov 01, 2022 1:37 am

Talk about taking the long way around things!
Some time ago I purchased a B&S 6" x 18" surface grinder off eBay. The machine was equipped with a radius dresser and rapid traverse for the wheel head, which, on a surface grinder, is a very welcome feature, as the feed on the head is exceedingly fine (for high precision). The price was right, including shipping from the east coast. However, the grinder had issues that I didn't expect.

It had been taken out of service and was sold by a machine tool dealer in Pennsylvania. Fortunately for me, they hadn't removed any of the maintenance documents from the machine that had been kept in the electrical cabinet, so I contacted the original owners who were more than cooperative, sending me the missing manual and the custom wrenches that are a part of the operation of the machine. In addition, they included a couple dozen wheel hubs, which didn't fit the B&S but are a fit for my #2 Cincinnati cutter grinder. These folks were exceedingly generous, not only with their time, but they wouldn't accept payment for shipping. A win/win situation in pretty much every way.

Down to the problem.

When I tried operating the machine, the wheel head tilted as it advanced. That was mystifying until I dismantled the machine and discovered that the hydraulic cylinder had been attached improperly. Remedy? Simply realign the attachment point, which is made adjustable for obvious reasons.

One of the things that was not obvious (because I couldn't do any grinding) was that the ways for the table are not parallel. They're out by .005" over 32", which renders the machine relatively valueless as is. I can't help but think that the machine was worked on by someone who had no knowledge, or it was sabotaged so a new machine could be provided. My intention is to make the correction by scraping the flat, although I hope to touch up the V as well, depending on what I discover once I have a straight edge at my disposal.

The general condition of the machine is acceptable, so I deem it worthy of spending my time trying to get it operational, and in keeping with my work ethic, I tend to do everything myself. It's a way of me expressing my ability on the machines, and it's a great way to keep me active (I'm now 83). I had intended to build a model steam locomotive, but the time spent building our house and shop was far greater than I had anticipated, so I don't see that happening. Doesn't mean I won't eventually try, but more so for the experience of making castings that are not, nor have they ever been, available. What better way for an old guy to spend his time in the shop, which has proven to be a good reason to get out of bed each morning.

I have made a pattern for casting a straight edge that will suit my requirements for the flats of the grinder. Fact is, I should be able to use it for the V way as well.

I have almost no experience with casting. What little I've done has been plagued with issues that I must overcome. I understand the need for risers, often referenced as feeders, to prevent shrinkage. That is my quandary. Gray iron of a given chemistry is known to cast without shrinkage, but I don't have the capability of analysing my heats, and the brake rotors I use for feed stock appear to create shrink areas if not properly risered.

Anyone here have any thoughts on how this should be gated and risered? I welcome any input, especially from someone who has some practical experience in pouring iron.

The pattern will be mounted on a board, along with the runner gates.

H
Attachments
Straightedge1.JPG
Straightedge2.JPG
Straightedge3.JPG
Wise people talk because they have something to say. Fools talk because they have to say something.

Andy R
Posts: 384
Joined: Wed Sep 26, 2007 2:18 pm
Location: So. Calif.

Re: Casting a straight edge

Post by Andy R » Tue Nov 01, 2022 7:06 pm

Harold,

You wrote:
"I had intended to build a model steam locomotive..."

Why not start?
You will enjoy it. And who knows? You might finish it too.

Sorry about not being helpful about the gating question ... Hopefully somebody knows.
Regards,
Andy

Harold_V
Posts: 19592
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Casting a straight edge

Post by Harold_V » Wed Nov 02, 2022 1:14 am

Andy R wrote:
Tue Nov 01, 2022 7:06 pm
Why not start?
I plan to, Andy, but before I can, I want my shop to be fully operational, and that's what I'm spending my time on right now.

Years ago I decided I'd build a model of UP's 833 in 1.6" scale, the prototype having been on display in Pioneer Park in Salt Lake City. I like large engines and that one was readily available. Now, of course, it is no longer on display in Pioneer Park, nor am I a resident of Utah, so that doesn't really matter, but I'm still fixated on that engine, especially the boxpok wheels, which have never been faithfully modeled. I can see how they can be, so if I get the shop finished and still have the ambition, my first project will be patterns for the boxpok wheels. I see them as a huge challenge, one I'd enjoy conquering.

Thanks for your comments, Andy.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

K. Browers
Posts: 89
Joined: Wed Mar 21, 2007 11:57 am
Location: Philippines

Re: Casting a straight edge

Post by K. Browers » Wed Nov 02, 2022 6:26 am

Hello friends
This night come in handy. casting the way the hobbyist does it is old school really old school so here is an old book.. :D

https://archive.org/details/generalfoun ... ?q=foundry

cheers Karel

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rmac
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Location: Phoenix, Arizona

Re: Casting a straight edge

Post by rmac » Wed Nov 02, 2022 10:56 am

Unfortunately, no help from here regarding the casting process, but I do have a general question. Once a blank is cast and cleaned up, how do you make sure it is really straight?

I've heard of a procedure whereby three blanks are lapped against each other in a particular sequence that renders them all perfectly straight after some time. Is that what you're planning? Or do you have somebody grind them straight somehow? Or ... ???

-- Russell Mac

rrnut-2
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Location: New Hampshire

Re: Casting a straight edge

Post by rrnut-2 » Wed Nov 02, 2022 3:12 pm

Watch Vintage Machine (Keith Rucker) on You Tube on making straight edges straight.

Jim B

Harold_V
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Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Casting a straight edge

Post by Harold_V » Wed Nov 02, 2022 4:16 pm

rmac wrote:
Wed Nov 02, 2022 10:56 am
Unfortunately, no help from here regarding the casting process, but I do have a general question. Once a blank is cast and cleaned up, how do you make sure it is really straight?
Once cast, stress relieved and machined, the flat is hand scraped, using a large surface plate as a reference (flat) surface. High quality surface plates are generally flat within .000050".

Hand scraping is the process that has been traditionally used when ultra flat surfaces are required.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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rmac
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Re: Casting a straight edge

Post by rmac » Wed Nov 02, 2022 4:41 pm

Harold_V wrote: Once cast, stress relieved and machined, the flat is hand scraped, using a large surface plate as a reference (flat) surface.
Aha! Got it. Thanks.

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