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It was made to comb mail #7: The pattern is assembled on the follow block

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Blog entry by Patternguy posted 02-23-2017 12:01 AM 1223 reads 0 times favorited 5 comments Add to Favorites Watch
« Part 6: Next step: good setup ensures accurate positioning Part 7 of It was made to comb mail series no next part

Part 7 Assembly

You cannot tell from the picture, but each rib has been pinned to the block. Pinning the ribs in position allows the spacer blocks to be removed for the next step, which is to fit pieces of material between the ribs. The material, shaped with a large radius will form the “webs” that will tie the ribs together.

This illustration shows some views of the follow block with the completed pattern in position.

Here is another view of the block and pattern, after the ribs have been tied together.

Remaining details are added and the pattern is ready for a coat of lacquer.

I always hated the last step, which is painting a beautiful piece of mahogany…GRAY!

The pattern was used to cast an aluminum match plate because a wood pattern like this would never survive a day in the foundry.
Match plates are the high production version of a pattern. Technically, they are precision castings, made from a plaster mold of the pattern it is duplicating. Plaster is used because of its ability to transfer detail, its consistent shrinkage rate, and its cost.
Match plates are pretty much what the name suggests, a flat plate cast with the cope side of a pattern on one side, and the drag side of the pattern on the other, where both sides “match” at the parting.

This casting went on to be part of a large mail sorting machine. It was designed to move back and forth against a pile of mail, “combing” the mail into position to be fed to the next step.

I hope this all made sense.
(I might just stick to pictures if I ever share the story about building the Ark of the Covenant:)



5 comments so far

View Kelster58's profile

Kelster58

298 posts in 352 days


#1 posted 02-23-2017 12:20 AM

That is so cool. Thanks so much for sharing this series of posts. Very informative.

We used to use bees wax to create “draft” in out patterns. Often times we would get the wax preformed in the shape of a fillet or radius. Is that still in use?

Do you add the sprues, gates, and risers as well?

-- K. Stone “Tell me and I forget, teach me and I may remember, involve me and I learn.” ― Benjamin Franklin

View Patternguy's profile

Patternguy

53 posts in 503 days


#2 posted 02-23-2017 03:03 AM

Yes, wax fillets and sheet wax is still used in traditional pattern making, but tradition is dying fast.

Look at large electric motor frame and all the fillets around the cooling fins. I used to spend days rubbing fillets, counting by the number of 200 ft. length bags I would go thru.

Gating is still the path to getting metal into the mold and has not changed that much. (Except that gating is often 3D models that were printed overnight)

View MerylL's profile

MerylL

70 posts in 1183 days


#3 posted 02-23-2017 04:25 AM

I really like seeing these and the explanations. It is quite a fascinating craft and art. Yes… it was so beautiful, and pow! grey paint.

View Bluepine38's profile

Bluepine38

3371 posts in 2897 days


#4 posted 02-23-2017 04:09 PM

A lot of work to make sure all the details are correct, because without the details, it would not work.
Thank you for sharing.

-- As ever, Gus-the 78 yr young apprentice carpenter

View GlenintheNorth's profile

GlenintheNorth

238 posts in 348 days


#5 posted 02-26-2017 05:37 PM

This was a great series. I want to learn to do this stuff but there isn’t a way near me that also ensures the bills are still paid!

-- MFia-made man. But that doesn't mean I don't dig my 45. Minneapolis/St. Paul, burbs.

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