# Erector set part number "BZ" Boiler Plate



## BGHansen (Aug 30, 2022)

Back with another reproduction Erector set part string. This one is p/n “BZ”, boiler plate. The part was a sheet metal plate with a number of slots & holes, formed into a 90-deg. curve; screwing four of them together formed a tube. In models, it resembled a large boiler or tank.

Now the obligatory Erector set history lesson. . . The part was first made in 1927 and continued to be produced through 1932. Eleven of them were included in a set. They were stacked end to end to elongate the tube as in the Oil Truck model. If 4 of them make a tube, and the tube was 3 sets of 4 long, why only include 11 in a set (instead of 12)? A “hole” was left so your hand could fit into the tube to hold the nuts while screwing the parts together.


Oil Truck Erector set model from 1927-32.  The oil tank was made from 11 "BZ" boiler plates




I figure on making maybe 8 or 10 sets of 11 parts; not a big World-wide demand for them. My motivation for making them is I NEEDED 11 of them to complete a set that’ll head to eBay. I sold the one pictured below for $750 on eBay a few years ago. I had the parts to make up another set that’s missing the BZ’s, so, POTD!


Sold this 1927 No. 8 Erector set for $750 on eBay a few years ago.  I have most of what's needed to put another together.




The part is pretty simple, roughly 4 ½” x 4 3/8” blank with three slots ~11/64” x 0.350” on opposite edges and 11/64” holes centered on the other edges. I have a Tormach mill and could have written a routine to drill/mill in the slots, but went a more manual route. My plan was to cut blanks to size on a Tennsmith shear, then set them in a holding fixture to punch the slots and holes. If I was making one, I’d have manually laid out the part, but I’m looking at more like 100 so a punch fixture was the plan.

Going through my scrap stock, I found a piece of ¼” aluminum that was just a little too small to cover the whole part. Decisions, decisions, sacrifice a larger piece of stock to make a hole guide, or do an undersized guide. With short-sided guide, I’d clamp the part in place, punch half of the holes, then flip the blank to do the opposite side. I ended up using the smaller piece of stock for a hole-punching fixture.

Started by squaring the stock on the Bridgeport. The scrap stock happened to have two ¼”-20 tapped holes in place spaced 4.75” apart – PERFECT for this part. After squaring the stock, the surface where the blank will nest was milled down by 0.010”. That’ll help position the stock side to side in the holding fixture.

Next, I drilled 1/8” clearance holes in prep for making the slotted punch guide holes with an 11/64” end mill. The center-edge holes were just spotted and finished on the drill press, didn’t want to drill into my mill vise!


Milled a 0.010" depression in the fixture plate for nesting the sheet metal blank.  Drilled some 1/8" holes for the elongated slots and center round holes



Milled the punch guide slots and checked fit with the punch.




My original plan was to punch the 11/64” round holes with a Roper Whitney #5 Junior. Problem was the #5 wouldn’t fit over the ¼” aluminum guide plate. So, on to plan “B”. Instead, I drilled 1/8” holes in the aluminum plate and used a transfer punch to mark the centers. The blank would need to be flipped to locate the opposite side slots; the round holes were punched with the blank loose from the fixture after transfer punching their centers.

In use, I first loosen the two button-head cap screws, set the blank in place lining up the edge of the blank with the milled depression in the fixture, flush the stock with the edge of the fixture and tighten the clamp screws. Then on to the Roper Whitney #218 press with an 11/64” x 0.350” slotted punch; the milled slots in the aluminum position the punch to the blank. Mark the 2 center holes with an 1/8” transfer punch. Then loosen the two clamp screws, flip the blank around, reposition in the holding fixture, tighten the clamp screws and knock in 3 more slots. Lastly, knock in the two 11/64” hole with the #5 Junior.


Sheet metal blank clamped in place.



Knocking in the slots



Transfer punching the center holes, then knocking them in with a RW #5 Junior




The curling is done with a slip roll on a Harbor Freight 3-in-one sheet metal slip roll/shear/brake. Last step is to prime and paint with glossy black.


I'm able to do the curl with one setting on the slip roll.  Just run the blank back & forth a couple of times to get a nice, uniform curve



Bunch of parts ready for paint.



I timed myself at 25 minutes to knock in all of the holes for 10 blanks. Not too bad, but it took me 30 seconds to flip the blank to knock in the second set of slots. So, on to plan “C” or as my dad would have said, “If you do it right the first time, you won’t have to do it again”. That’s be overly-detailed in another post.

Thanks for looking, Bruce


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## BGHansen (Aug 30, 2022)

Part 2!

I didn’t show the mods to the fixture, but I made an extension for the fixture so all 6 slots could be knocked in without reclamping the part. The added aluminum piece was doweled in place and secured with 3 cap screws. Then milled the added surface to extend the depression for nesting the blank.


Punch fixture after adding a 1" extension.  Now the blank is clamped in place ONCE, and all 8 holes/slots knocked in place without removing the part.




The #5 punch wouldn’t fit over the ¼” aluminum plate, but I have a Roper Whitney #XX punch which has a ¾” gap between the punch and die. Problem was I didn’t have an 11/64” punch/die, but I have the tools to make a set!


Started the RW #XX die with a length of 3/4" O-1.  Broke out the Starrett and adjusted my Set-Tru chuck.  Measured the thread on a stock die in prep for single point threading (3/4" - 18 thread)



Faced, center drilled and drilled an 11/64" hole in the die blank.  When punching sheet metal, the hole size matches the size of the punch, not the hole in the die.  You also need to provide clearance between the punch & die based on the material being punched and material thickness.  Punch/die clearance should be ~20% of material thickness for steel.  I'm using 0.015" - 0.018" sheet steel so the total clearance should be 20% of 0.015-0.018" or around 0.003".  I was shooting for an 11/64" hole, but it's not super critical.  I can make an 11/64" hole and turn the punch to size.  I couldn't (without making a very small boring bar) make a 11/64"-0.003" hole.  So, my plan was to make the punch fit the die instead of the opposite.



Turned shoulders at the start and finish of the 3/4"-18 thread and put a slight taper on the face of the die.



Single-point threaded the 3/4" - 18 thread checking things with a thread pitch mic when it was getting close.  Verified the final fit with the RW #XX punch.



Turned the relief at the bottom of the die.  Didn't show it, but cut it off in the band saw and faced the parted side to length.



Drilled a clearance hole in the back of the die.  The section with the 11/64" hole is about 3/16" thick.  Then back to the mill in a square collet block to cut a screwdriver slot for installing/removing the die.  Note that I write the width of my collet block on the collet block.  It's handy for getting to the center of a collet; in my case the center line is 0.864" from the edges.  I brought the slitting saw down to paper-clearance to the collet block and Zero'd Z.  Then moved off the collet block and advanced 0.031" (half of a 1/16" wide slitting saw) and rezero'd Z.  Then moved Z to the center of the block.



On to the punch.  Chucked up some 1/2" O-1 and faced with a parting tool at an angle to get a nice "prick" on the end.  The "prick" helps the punch find a center punched hole.



Used a small hole gauge (I don't have a set of gauge pins, yet) to measure the 11/64" drilled hole.  Came up with 0.1734" or a little over-sized.  With the 20% material thickness punch/die clearance, my target for the punch would be 0.170".



Turned the punch and missed my target by a little; hit 0.1688" to a target of 0.170".  Hopefully, close enough!



My punch (foreground) and die (background).  Note that I made the punch longer than a standard as I'm punching through a 1/4" aluminum plate guide, plus the 0.015-0.018" stock.  Standard punch length on my RW #XX punches is about 1/4".  I made it at 3/8".



Into the Thermolyne furnace for hardening, then tempered back to straw.



New, improved fixture and the 11/64" punch/die in the RW #XX.



It took me around 4 hours to extend the punch fixture and make the punch/die. I timed myself out at 14 minutes to punch the holes/slots in 10 blanks, a time savings of around 12 minutes to make a set of eleven parts. In retrospect, probably a bit of a waste of time with my mods, but it was more shop time!

Wish me luck on eBay! Few more parts to throw in the set then off to the auction site.

Thanks for looking,

Bruce


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## markba633csi (Aug 30, 2022)

Only her hairdresser knows for sure- that it's a reproduction Erector set part


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## BGHansen (Aug 30, 2022)

At one time I put "manufacturing marks" on parts (discrete file marks) and heavily advertised what to look for. We had a guy in the collecting club with questionable character who was putting my repro parts into sets and passing them off as originals. He was a good customer,  but I wanted no part of what he was up to.  I polish the brass up, but you can quickly add an aged patina with a propane torch.

The marks took time, so I started using a UV marker. They sell them on eBay for a few bucks. They come with a black light that lights up the dye. I didn't advertise it at all and waited for a large show to spill the beans. Imagine the look on his face when folks started calling him out for his "thievery"! It cost me a customer, but it was worth it. No way, no how would I put my reputation at risk; that's not the way I was raised! The guy has since passed away, so no dye on parts or file marks anymore.

Bruce


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