Pattern Making

[seacoastartillery]

     We thought it might be interesting to see if you folks who have done some sand casting or lost-wax casting or maybe some lost foam casting can inform us a bit on the topic of basic pattern making.  What are the design elements you have to consider, what materials do you normally use for the pattern and what methods do you use to form the pattern?

     Mike and I have never done this before, so this is a request for information type post.  We have only one photo to post, so maybe the people engaged in this endeavor can show us a few more.

Always willing to learn,

Mike and Tracy


Ah, ah, ah Gary.  I'll get in trouble for revealing this fact, but what the heck!  The very first thing an inspector is taught is:  "Never scale the drawing!"  Guess what Gary is doing here?  He, he, he, he  To further incur his rath, I will also ask Spuddy, "That doesn't look like your 1838 6 pounder, now does it Spuddy?  Mike showed him how to adjust the taper attachment, so I guess we participated in this further departure from 'The Schedule'.  Sorry 'bout that.  How did you design that pattern, Gary?  What is that wood you are using?

[KABAR2]

That looks like a DAN type drawing     or is it a Gary original?

I guess Gary will have his done long before I start mine....

[GGaskill]

What are the design elements you have to consider, what materials do you normally use for the pattern and what methods do you use to form the pattern?

One thing to consider is what process of mould making you will use.  Investment casting allows you to do almost anything as you don't have to worry about undercuts that cannot be pulled from the mould like with a sand casting.  The pattern can be made from almost anything with a modicum of strength; usually the choice is made based on the number of moulds to be made, so something like white pine is OK for a few moulds, but for many moulds, a metal pattern would be preferred since it will withstand use better.  For small pieces, I would use aluminum until the expense gets too great.

Sizing the pattern requires knowledge of the shrinkage factor for the metal to be cast as well as allowance for any post-casting external machining.  If the outside is going to be machined, you need enough to guarantee that you can machine the whole surface.  The following is copied from my One of my half scale mountain howitzers thread of 2005:

"When you make a casting pattern, you have to make two enlargements (called allowances)--one for shrinkage and one for machining.  The shrinkage factor you look up in Machinery's Handbook (different for each metal); the machining allowance primarily compensates for distortion in casting.  I increased the length from a finished 18.6" to 19.27" and the diameter from a finished 3.8" to 3.94".   For aluminum, I am guessing you should about double those numbers."

There are some photos of the pattern, matchplate and flasks in that thread also.  If you are going to use a matchplate, the pattern should be split along the center line so that the pieces can be put on opposite sides.  It should be screwed together while turning.  You don't want to have to saw it in half because you will lose the thickness of the saw kerf that way.

[Spuddy]

     We thought it might be interesting to see if you folks who have done some sand casting or lost-wax casting or maybe some lost foam casting can inform us a bit on the topic of basic pattern making.  What are the design elements you have to consider, what materials do you normally use for the pattern and what methods do you use to form the pattern?

     Mike and I have never done this before, so this is a request for information type post.  We have only one photo to post, so maybe the people engaged in this endeavor can show us a few more.

Always willing to learn,

Mike and Tracy


Ah, ah, ah Gary.  I'll get in trouble for revealing this fact, but what the heck!  The very first thing an inspector is taught is:  "Never scale the drawing!"  Guess what Gary is doing here?  He, he, he, he  To further incur his rath, I will also ask Spuddy, "That doesn't look like your 1838 6 pounder, now does it Spuddy?  Mike showed him how to adjust the taper attachment, so I guess we participated in this further departure from 'The Schedule'.  Sorry 'bout that.  How did you design that pattern, Gary?  What is that wood you are using?

I like it

[smokemjoe]

You have to make a pattern oversize as the metal will shrink, make out of wood or plastic, have one then made out of alloy, cut in half and fit to a cope and drag mold .

[RocklockI]

The only reason I scaled the drawings with that caliper is ,that is was using it as a divider ,as you have not seen fit to supply my machine shop with proper ones . we should address this shortly at the next investors meeting .

Nice to see you got my 'good side' in that photo . .

This is no 1838 ,it is the 'Louverens' gun from 1690 . It is a VOC gun and still in great condition .

Spuddy , despite what some say ,just to be fire ants when doing Leg Lifts and Mother Lovers, (they hurt like hell ,but in the end they are only bugs ) . I did not want to make a small and a large 1838 .  yours is still pending .

That is my drawing ,which i scaled from a Visser Collection from the Netherlands it's a 2.5 lber . I eyeballed it with a scale .
 Why didnt you show a decent picture .   is MIKE going to have to do everything ? silly quesion , I know ? but ......


This is my working print .


print and work .



wood only .

Gary

[dan610324]

wood is a easy material to work , but it must be painted before the rubber mold is made from it
I have always used some kind of plastic for my masters until the fire , nylon or teflon .
but from now I will make them in steel or any other metal only

[GGaskill]

... until the fire ...

Yes, that is a good reason to make steel patterns.  When the foundry burns down, the steel patterns will survive.  Which is a good thing since they represent so much work.

Foundries are kind of like airplanes with retractable landing gear; they either have landed with the gear up or are going to land with the gear up.

[dan610324]

this was just the mechanical part I had there , all casting I have always done at home just because of the dangerous with fire , I dont want to burn down someone elses place
but this time it was an pyromaniac
he (or she) started the fire in a hughe pile of scrap tires that was on the outside of the house
the heat blow the windows out and then it start on the inside also
but the worst was that my friend who owns the tire shop have his mother living at the upper floor

[gulfcoastblackpowder]

Was she ok?

Great looking cannon Gary!  Should be a beauty when she's cast!

[Zulu]

Gary!!!
Making wooden barrels!  Check you out!
Next it will be full scale!
Zulu

[KABAR2]

I was surprised to see a metal lathe being used for wood turning I know I have seen others here do it for sabots

but I was told long ago by an old machinist that it was frowned upon because the sawdust can get into the workings

where it can hold small bits of abrasive metal chips etc and work as a lapping compound - old wives tail?

[Soot]

I think if the metal chips can get into the machine workings along with saw dust, you already have problems. I just made new way wipers and covers for my lathe to keep all that out.

Here is a link to some people casting bronze cannons and some of the nasty problems they encountered. Here
I'm not sure how much of it applies to your situation, but it's more info.

[Max Caliber]

Here are some casting patterns I have made.  Most are made of wood - birch, basswood, poplar, walnut, wild cherry, and others.  Wood that makes good gun stocks and cabinets will make good patterns.  Barrel patterns I have made in recent years are made of straight grained poplar.  Poplar works well as long as you use sharp tools and it takes paint well but warps badly here in this humid climate unless you keep it in a dry place.  I also use thick sheet plastic, casting resin, gasket rubber, aluminum, and other metals and recently have had good results using plastic kitchen cutting boards from Walmart, which are cheap and come in several thicknesses.  I make patterns oversized to allow for shrinkage and finishing.

[seacoastartillery]

     We are learning a lot and we certainly appreciate the participation of everyone.  A special thank you goes out to George Gaskill for all that interesting information on sand casting.  I always wondered about the saw kerf reduction on the tube patterns for the cope and the drag.  Screw the material together, BEFORE turning!  DUH, wonder why I didn't see that.

     Interesting tips and observations from everyone else too.  Just a couple words of caution to Gary:  Don't bring the same old question to the next board meeting.  The is still NO!  We can't buy a corporate plane this year!  No way, No how.  We can invest in a 16 X 16 foot tarp and ten bags of play sand from Lowes, then begin bronze Morko production.  What say you?  Dan, I get it.  Wood + fire = ashes, but Steel + fire = Steel.  Logical and not expensive when you consider the possible consequences of going with wood.

     KABAR2,   I have heard this cautionary story before and some truth may be in it, but just think about that scale which comes off a new piece of steel as you first turn it.  Talk about abrasive. That stuff is gritty and abrasive for sure.  So we take reasonable precautions to protect our equipment like keeping our Way Wipers in good condition as Soot said he was doing, and always lubricating the bearing surfaces with the proper oil before each use.  I took a photo just a few minutes ago to see if the wipers were doing their job.  They were.

     Thanks Max, that's pile of experience there and those more unusual materials were interesting to hear about.

Anybody else have any suggestions?

Tracy and Mike


Not a speck of dust beyond the rubber Way Wiper.




We use the proper grade and type of oil suggested by the lathe manufacturer.  Lubricating before each use of your lathe helps to keep abrasive contaminants out of critical areas too.

[GGaskill]

The problem with turning wood on a metal lathe that I am familiar with is the saw dust absorbs the way oil and you have to renew it more frequently than you would otherwise.  I always cover the lathe bed with a sheet of newspaper to get most of the dust and sometimes will set my shopvac alongside and suck up the dust as it comes off the tool.

[Zulu]

Max Caliber,
Nice collection of patterns.  Although I see a couple of things in there I'm not sure we want to know what they are.
Zulu

[Double D]

Schuetzen butt  plare adn trigger guards, Zulu! 

[GGaskill]

Maybe the schuetzen hook butt plates?

[Max Caliber]

Yeah, they are Schuetzen rifle butt plate patterns.

[RocklockI]

This gun is poplar laminated with 4 pieces . Today I got it very nice all astrigills ,fillegrees wedding bands ,and other assorted little cures and lines .

I think I will use a paste wax on it instead of paint .

Gary

[GGaskill]

Those "dolphins" look like horses.

[dan610324]

yes she was ok , just shocked
the police got her out of the appartment just min before the window broke to her bedroom

[Cat Whisperer]

I was surprised to see a metal lathe being used for wood turning I know I have seen others here do it for sabots

but I was told long ago by an old machinist that it was frowned upon because the sawdust can get into the workings

where it can hold small bits of abrasive metal chips etc and work as a lapping compound - old wives tail?

Wood is abrasive.  OK, plan for it.  Keep it out of places like bearings and lubrication systems.

I live near a number of furniture making plants - some use computer automated machining - much like CNC mills.  So, it is being done where it's needed, just adapted to the media.

[RocklockI]

Those "dolphins" look like horses.

not a good pic but I can take more .

eta , I can not make more pics ,Tracy has my book .



This thing is a steal ! good shape too ! Tracy .......You think you hate it now wait we get her in the air !

[GGaskill]

To be more precise, like horse head and neck.  It has ears and the turn up at the end of the mane.

[dan610324]

it would be very interesting to know why they looked as they did
and whatever they look like they still are called dolphines , anyone who knows why ??
when was the name dolphines invented ?? is it a modern name or was it used also 400 years back ??

[GGaskill]

They certainly were images of dolphins or other sea monsters originally, and they evolved into simple handles before disappearing completely.  I would imagine their actual shape was determined by the sculptor who made the patterns versus some bureaucrat writing a specification on an order sheet.

[RocklockI]

I'm almost sure I've seen them refered to as dolfins from old records ,but I do not remember where .

I have really studied these things and I believe they are impresions of the unknown ,horrors of the deep .

Sea monsters were thought to be real by some and IMHO they are to give a fearsome look to inspire .

Their own crews mostly ! Offering as much good JuJu as a sailor could believe in .

Faith in your weapon is and has always been a top priority ,the Britsh even added a wooden slab stock to their STEN guns just to inspire confidence in them .

Gary

[dan610324]

yeah , but how old records ??
100 , 200 or 500 years ago ??

in the late 15th and early 16th century they didnt exist yet as dolphines .
first they was just 4 lifting rings