Casting Layout Paint

[cubman]

Hi All. I have been lurking for a while and have just joined. I am starting my second ic engine, First from castings. A 1/2 scale IHC Tom Thumb. My first question of what I'm sure will be many, is what do you folks use for layout paint on rough castings. I'm thinking of using white latex. I have Googled it with no results. Thanks, Larry

 

[b.lindsey]

First of all, welcome to HMEM. I would assume that most of your layout work will be done once the relevant surfaces have been machined flat, faced off, etc. In that case I would also think that layout blue (Dykem or similar) would work fine. Maybe I am not understanding the question.

Regards,

Bill

 

[Jasonb]

I tend to just give the castings a spray with white acrylic auto primer, this is ideal for iron castings when doing the basic layout to work out how much needs to come off the faces, grey or red will also be OK. Once the face is machined then as said above layout blue or a marker pen works fine.

Welcome to teh forum, hopefully you will post some progress of your Tom Thumb, I'm currently doing an IHC famous, you can see the build in "engines from castings"

Jason

 

[cubman]

Thanks for the replies. Perhaps I'm being overly cautious. Not having experience with castings I don't want too ruin a casting. Not sure if a replacement is available. I would like to have an overall layout before removing metal. I did face the bottom of the base and made a mounting plate like Putputman shows on another thread. I would like to mount the base to the plate with the datum line shown on the dwg. parallel to the base edge. Larry

 

[Mainer]

It is possible to get white Dykem, though I don't know who carries it.

 

[Jasonb]

Your not being over cautious, it good practice to asess any casting to make sure it will fit the drawing. If you were to rush straight in and machine one face you could find that there is not enough metal on the opposite face due to distortion, excess shrinkage or someone in the foundry getting carried away when fettling the casting.

I tend to remove any large moulding lines or remnants from casting gates etc then give the casting a quick spray with a can of primer before setting it up on a marking surface and running a height gauge and square over it. You may have to shim up under one or more corners to get the layout lines to run true or to average out the draft angles on each side. You can then scribe on some basic layout lines into the paint, if you feel the lines may get rubbed off during machining its worth adding a light dot punch dimple every 1/4" - 3/8".

The casting can now be transfered to the machine and setup so the layout lines are true to the machine axis and you can safely machine away to establish a datum face. You can then accurately set out from this datum face either with traditional marking out or use of a DRO.

Jason

 

[Jasonb]

It is possible to get white Dykem, though I don't know who carries it.

The thing with painting the casting is it gives a good surface for the scriber to mark into, the rough nature and sometimes hard surface of an iron casting can be hard to mark and a thin coat of dykem will not show the line off well.

You can always blue the white/grey painted surface. Or use typewriter correction fluid as a white marking liquid

J

 

[Maryak]

Being a cheapskate - a paste of chalk and water works fine when allowed to dry on the casting.

Jason's comments about assessing and aligning before cutting are priceless and can save the hip pocket nerve from severe damage.

My machining of castings has only been done at 12" : 1' (see above - cheapskate). Even after following all Jason's advice, it's pucker up time until the 1st cut is proven successful.

Best Regards
Bob

 

[Tin Falcon]

I

t is possible to get white Dykem, though I don't know who carries it.

MSC has a variety of colors in various sizes
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1705086&PMT4NO=100583152
Tin

 

[2manyhobbies]

One of the first things that I do is paint the castings with some sort of spray paint. This was a tip from my Dad and he said he does it for the following reasons: keeps stray oil from soaking into the cast iron when working with the castings (easier to clean and paint later), keeps them from rusting, and as Jason pointed out provides a good surface finish.
Brad