Today I started a new pattern to make a metrology parallel/level

I have been itching to make a new pattern to cast a machinists cast iron parallel that will accomodate a level. So far as I know, such a tool has not previously been made. It will be 18 inches in length. If it is well received, it may later be joined by 24" and 36" parallels of similar design. I am old-school in pattern making as I work in wood and glue rather than 3-D printing them.

This pattern is composed of Baltic birch plywood, yellow cedar, and basswood so far. I will post some photos below which are largely self-explanatory.



Making a 1/4" steel template for routing oval windows in pattern. Using the belt grinder made quick work of the grinding. I cut out most of the waste milling freehand. But finishing it on the er was like sanding wood. The grinder is amazing.


Template in use.


Template after I welded the two halves back together after grinding the inside.


Mocking up the web on the flange of the pattern

The pattern glued up but needing fillets and outside corners eased. There is also some modification for the middle window to allow mounting a 10-arc sec vial

Gluing up the flanges and trying to keep them good and square. This method worked pretty well.

You can see the 3 deg of draft I cut into the inside surfaces of the flanges. It is a lot easier to cut the draft first and then glue though keeping the flanges square vertically has to be set up solidly.

Next up is adding inside fillets with epoxy and rounding over all outside corners and then priming and painting.

My overall plan is to use the resulting pattern as a master from which I will cast Freeman's Repro One working patterns using POP as the mold making material for the working patterns. This will be my first attempt with the Repro. It is supposed to have minimal shrinkage and deformation. Let's hope so. Anyonew with any helpful hints on its use please speak up.

Denis

 

This morning I set the pattern up on the mill to true up all edges and flange surfaces. Because I want the web to be accurately located on center and parallel to the flanges, I fixtured it with the web located on 1-2-3 blocks. Then I used a nice new 3/4 carbide end mill to trim the flange faces and sides. This was important on this pattern as users will be location mounting holes based on those surfaces and it would be aggravating if some distortion of the casting caused them to make an error. Of course, the casting will distort slightly, but this design should not bow or twist to any noticeable degree given it symmetry. Inspecting the pattern now shows everything to be within a few thou of “plumb and true.”


Prior to bolting down


Overview


Side view showing pattern suspended on blocks.



Next up is rounding outside corners over and then installing ribs, center window build-out, and fillets for inside corners.

Denis

 

Very nice Denis. It makes my patterns look like kindergarten art projects hung on the refrigerator...
In the second picture, the belt sander, is that something you made?

 

Thanks, Tops! Yes, i did make it from plans sold by a young man on Etsy. It is an amazingly useful and versatile tool, I think the designer, Jer Schmidt, must be a genius. He is only in his early 20’s, yet his design is better than any commercial belt grinder I know of. I use this tool usually many times daily most days of the week. It has a flat platen, small contact wheels, large contact wheels and can be oriented vertically and horizontally. The real amazing part of the design is that it can be changed from one setup to another without tools and very quickly—-in less than 30 secs. So, the user ends up actually using all the various options. I find it to be extremely useful in both casting fettling, metal fabrication, and wood working. And my grandson and I just started a knife-making reject based on the Ruana Knives design (cast aluminum handle).

I did tweak the building plans in a couple important ways and would discuss that with anyone who decides to build one. One piece of advice I will suggest right now is to do as Jer suggests and use a 1.5 to 2 HP 3-phase motor with a VFD. Do not cheap out and use a treadmill motor. I tried that initially as suggested by a few people on YouTube. I could make the device run (sort of) on the TM motor, but the performance difference with the real motor is simply orders of magnitude better. Making the grinder is not cheap. I think I have about 1500 to 2K in it. Wish i could have done it 30 years ago.

https://www.etsy.com/listing/969297...query=jeremy+schmidt&ref=sr_gallery-1-1&bes=1




Denis

 

I have (finally) decided how to handle the build out of the middle window to accommodate level vials. Numerous options were considered some of which were ugly or awkward or too flimsy. I wanted to not interrupt the curve of the middle window unduly and still offer a mount surface that would work for a variety of vial lengths and would be very solid and easy to use.

My plan is to add columns to the middle window each column being 1/2" front to back. Along the length of the window the column will be a halfi inch in width being .625" from center to center of a solid shape which would be described by taking a 3/4" high 1/2" diameter rod and moving it along the long axis of the window .625 inches. So, it will be a sort of hybrid rectangular solid with semicircular ends. It will straddle the web. It will allow vials of about 2.75 to 4.5 inches in length to be attached securely to the level. With some modifications sizes outside this range could also be used.

I had a couple hours in the shop today and used the time to make a die in which to cast Freeman Supply's Repro polyurethane 2-part plastic. The repro is new to me and this will allow a small-scale trial of its use. Later on I plan to cast my wood pattern in Repro to make working patterns. This will save wear and tear on the master pattern and allow me to have more than one pattern for use which should speed production.

Here are a couple of pics of the "die' which is quite crude by die making standards but which should serve the purpose. It was made by tack welding two pieces of hot-rolled 3/8" bar together and then milling out a pocket which is stretched fore and aft 1/8" to allow for the kerf to be made when the pattern is split along it long axis.while it is standing on one of tits flanges. After the pocket was milled, I drilled and reamed 1/4" holes and then milled away the tacks. I did a little polishing of the interior and then fitted pins which will align the two halves. (Yes, I could have just milled solid columns rather than making the die. But, I'll never learn anything new if I keep on doing things the way I have previously done them. ;-) )

Here is the tacked-up block milled out 3/4 deep and 5/8" wide.



Drilling and reaming the alignment pin holes.



Pins in and halves separated



Partially closed. The short round cuts on the four corners of the seam are where the tack were milled away to allow the block to be split.



Tomorrow I will mix up a little repro and cast the columns. I'll remove the Repro after it is semi-solid. That way it should not stick too tightly to the mold even though the mold is by no means polished. To install the column, I'll cut a 1/4" wide slot it in so it can straddle the web.

[Credit due to Forrest Addy who patiently listened and helped me decide on which design option to chose for the columns.]

Denis

 

Good thoughts, Kelly. I think I will put a little time into polishing the interior of the mold.
I have PVA, past waxes, and slicone rubber mix and spray. I thought I'd get my feet wet on a small scale with this little post project.

Concerning "nasty" ingredients: yes, one of the components contains cyanoacrylate. So, good ventilation is needed for mixing.

I talked to the customer rep at Freeman and considered the Repro NS Fast-Cast Polyurethane. He did not push it that much. Still wondering if I should have gone that direction....

Denis

 

I followed Kelly's hint about polishing the mold. I simply used my band saw to split a piece of wood doweling and inserted a flap of first 120, then 200, then 600 Si-C paper to work a s flap sander. Worked pretty well. Then I waxed the mold 3 times and poured the Repro. One hour later---voila! Its perfect for my purposes. Demolded very easily and cleanly. I am both pleased and relieved as I anticipated more problems than that. No bubbles. Very fine mold seam. Granted, larger and more complex patterns may present more challenges. But this seems very promising


The dimple in the middle of the mold is due to my screwing around with the Repro while it was gelling.


Denis

 

And here are the columns/bolsters in place. This material machines beautifully. There was not a single included bubble.

Here is the slot cut into the bolster so it can stradle the web.


Bolsters glued into place.


Now on to fillets and putting draft on the outside of the flanges. I'll be using epoxy for fillets.

Denis

 

In the middle of the night I heard a grinding sound in my head, then a couple of clunks and a scraping sound and then finally some whirring....;-) It was then that the idea of using the Fast Cast Repro for fillets rather than using epoxy, as I have done previously, finally occurred to me. The epoxy did a fine job of fillet-making. But it took at least 6 to 8 hours in a warm shop to cure enough so that I could reposition the pattern and do another set of fillets. I incline the pattern about 30 to 45 degrees perpendicular to the fillet line I am filling to allow the viscous liquid to self-level and then cure. I'll do the same with Repro, but the gel time is 6 or 8 minutes and it is fully set in an hour. Chances are I can do a new set only a half hour after starting the first set. Since most patterns require at least 8 sets, using the Repro will greatly shorten the time span needed for getting all the fillets done.

The viscosity of the Repro is quite similar to that of the West System epoxy I have used in the past. The Repro, however, has no tendency to produce bubbles. So, I don't need to pop bubbles with the Mapp torch like I did with the epoxy. That's no big deal as the torch step was easy and kinda fun, actually. But it is just one less thing to think about.

Here is an end-cap fillet with the pattern leaning away from the viewer 45 deg.


Denis

 

I made 8 "sets" of Repro in inside corners today. (I could have done more but was feeling a bit under the weather due to my 2nd Covid booster yesterday which "kicked in" last night. I am OK again this eve.) The material had gelled enough in 30 mins to allow repositioning without risk of the most recent fillet sagging. I mixed about 4 cc at a time and carefully placed it in the corners using a 10cc syringe. I was able to use the syringe over and over by shooting silicone into it prior to drawing up mixed Repro.

https://www.youtube.com/shorts/4AgojLQHwi0

For some reason I can not embed a video using the button in the task bar, so I just pasted the address.

Denis

 

Nice pattern making.

 

Thank you. For such a small mass of material, patterns seem to require a lot of hours.
[QUOTE="Tobho Mott, post: 45667, member: 4”]

Vertical format videos under 1 minute long are being turned into "shorts" which work a little differently than regular YT videos and apparently won't embed. I don't know if there is any workaround other than either shooting horizontal or recording for a bit longer.

Jeff[/QUOTE]
Thanks for explaining that, Jeff. I’ll avoid vertical formats in the future. I kind of like short videos.

Denis

 

Duplicate post

 

Today I cut the draft onto the outsides of the pattern and started putting on some high-build primer. The primer reveals all the little ditzels that will need to be filled/sanded etc. The primer, recommended to me by DavidF a while back, is amazing stuff. It covers a lot of "sins" and is ready to sand 2 hours after application. Not cheap, but worth it.

Here is the general setup I used to get my best possible cut. The red circle highlights the clamp mod I made to my Grizzly fence many years ago. For fussy stuff, it helps as pressure from the spring-wheel does deflect the fence a few thou. Generally that does not matter. But in this case it does.

The dial indicator helps in repositioning the fence in 4-5 thou increments.


After making the cuts. About 2 degrees of draft is present. As a final step after painting, I will split the pattern cutting at the crown for its length.


Putting on the first primer coat. Then I'll get out the Bondo and fill the various negative defects and sand off the areas that are proud. The primer sands beautifully without loading sand paper.


Denis

 

Another fine looking pattern Looks fantastic!

 

I put some lacquer on the pattern today. It is not perfect, but I think good enough to pull cleanly from the sand. Tomorrow morning, after two cups of coffee and installing a newly sharpened blade in my table saw, I will set it up on the 1.375" face and split it down the middle. I'll first drill 3/16 registration pin holes in each end cap. Then the halves will go onto a match plate and some fairing and narrow filleting will be done. Then the real fun begins. Will it pull cleanly? Will it cast truly? Lots of unanswered questions.



The lacquer highlights each and every tiny imperfection---frustrating but helpful to me when tuning up a pattern in preparation for molding.


Keep your fingers crossed!

Denis

 

Looking forward to hearing of your success Denis!

 

I love match plates. It's the only way to go on frequently cast patterns.
I have no doubt that you'll have great success.