JV Puleo

My 1910 Mitchell "parts car" project

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Mike... where do you get dental burrs? I've never seen one that I noticed. I'd ask my dentist if I had one.

courl you take a picture of one so I have an idea what to look for?

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Ebay should have them.  They look like a dremel bit but have a small ball at the end that has little cutting blades.  They are not a standard diameter shaft so you would need a tool that has an expanding collet that can clamp down on it.  Used them all the time when I was a machinist for the military. 

Wave-Dental-Operative-Bur-Tungsten-Carbide-HP-Round-Straight-Taper-Fissure thumbnail 6

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These are the ones I 'scrounged' off my dentist. They fit in one of the collets that came with my Clarke 'Dremel' tool.

 

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These I bought at the same time I bought my engraver. I think they are diamond coated. I have not tried them yet. These came from Amazon.

 

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Sorry about the photo quality. In the lid of my small grinding wheel box you can see some small milling type cutters that fit into the Dremel type tools. I hope the above is of help.

 

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Good. My Dremel tool has the collets. I'll see what I can find. This is a job for a day when I'm feeling relaxed. I think it will be fussy to do but may well come out very nice.

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From memory the hardest part was holding the Dremel tool firmly so the tool did not skid off onto the good part. One thing I forgot to mention was; because of the inclusions in the welded 'old aluminium' metal I used low melting point aluminium with a brazing torch to fill in any 'dents and pits'.

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I'm not familiar with "low melting point aluminum". I'll have to look for it but I don't think I'm gong to have much in the way of inclusions since all this was new 6061.

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Posted (edited)

Thanks Mike. I will file that away for future reference. How did it work? I read some not very complimentary reviews on the web but I am often skeptical of those. People who don't read the directions, or attempt repairs that are unrealistic often run to the internet to complain so I always take comments with a grain of salt.

 

I've ordered some round grinding stones and, as Laughing Coyote suggested, a couple of HSS cutters. I'll probably tackle the welds while the impeller is being cast.

 

 

Edited by JV Puleo (see edit history)
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It was a few years ago that I used it last. I remember that I first bought some special aluminium filler that worked fine, (I think it was resin and aluminium powder) , apart from the colour being different to the aluminium, that I was trying to fill. I wasn't looking for strength, just to fill a few small divots for aesthetics. It was then that I found out about low temperature repair rods at a vintage motorcycle show. There was a guy doing a demo with the 'stuff' and I was impressed with what he was achieving with it, so I bought some.

 

I used my brazing hearth and was surprised how much heat was needed to get the aluminium up to temperature before the rods melted into the 'divots'. As you say - many don't RTFI (read the f***ing instructions) and practise on a bit of scrap alloy first.

 

Looking at the photos of the welding I must admit I was expecting it to look better than it does. It maybe the thickness of the material that was the problem. As I have only done a tiny bit of aluminium, gas and TIG welding, many years ago, and only on thin sheet aluminium of the same thickness, I am not qualified to criticise.

 

Below is a photo of the special aluminium filler after polishing. You can see what I mean about the colour.

 

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The welds are thicker than I'd expected too but (to put the best possible twist to this) there is now material to make a real fillet. I was resolved to live with the welding bead if it was small although it wouldn't look right. Cleaning up the weld, if it goes well, will look much better. Also, the weld now obscures a gouge from the near disaster that I couldn't get out completely so if all goes well it will be that much better a job.

 

I've tried gas welding aluminum, not very successfully so I'm not prepared to second guess the man who did it. I'd thought of making the entire pump out of bronze, in which case I could have soldered all the joints but the cost of materials - for a part I don't even know if it will work - was prohibitive. Maybe some time in the future I'll make another one but I'm going to see this one through to the end in any case. I'm learning stuff as I go here so even an error isn't wasted.

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Posted (edited)

I started boring the center of the pump yesterday morning and only finished it about 3:00 PM today. Of course, no sooner was I half done I though of a better way to do it. But, by then it was set up and working so I kept on with it. I was getting a vibration in the table of the mill I didn't like so I ended up taking small cuts which really drew the job out. Were it not that I've so much work in this one piece, I might have taken a chance and been more aggressive but I tend to come down on the side of "it's working no matter how long it takes." Here's the hole taken out to round...

 

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And after hours tending the machine, about as big as I dare make it. I completely failed to calculate the maximum size I could bore so all the time I was doing this I was worried that I'd have to improvise another boring bar to finish. In the end, that wasn't necessary but you can see how extended the boring head is.

 

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Aside from a nasty burr on the back side, it came out fine.

 

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There is enough room on this side to use an O-ring as a gasket if I want to. I'll have to test it and see what works best.

 

 

Edited by JV Puleo (see edit history)
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Having decided that my wooden impeller pattern wouldn't do, I started making an aluminum one. This has the advantage of being much more precise...it's more work but I'm not really equipped for fussy woodworking and find I'm more comfortable with metal. The first step was the "base plate". In this case, the diameter is too big because that was the only piece of suitable metal available.

 

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Bored to the hole size for a 1-1/4-20 thread.

 

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And tapped. This is the tap I bought to make the water fittings so it's come in handy.

 

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Then the hub of the impeller...bored and reamed to 3/4"

 

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Then turned down to 1-1/2 with the end turned for the 1-1/4 thread.

 

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After threading, the base plate screwed on.

 

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Since it was nice and secure on the mandrel, I turned it down to 4-1/8"

 

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Then put it in the chuck to reduce the thickness.

 

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It's now about 1/2" thick. Finished size is 3/8" but now I will cut the slots for the vanes. I'll cut them on the side facing out, then unscrew the piece and turn it around.

 

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Posted (edited)

Work continued today on the impeller pattern.  I set the piece up in the mil to cut slots for the blades. Obviously they go on the other side of this piece but the idea is to use the center to hold it and to turn the piece over when it's done.

 

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With that done, I made a second slotted plate. This will serve as a clamp to hold the blades securely while I turn the OD down. The piece is something I made as a fixture - and at this point I can't even remember what it was for.

 

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Here it is screwed onto the hub the correct way. I had to turn down one end so the clamp would slip on - the projection it makes will serve to help indicate the casting.

 

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The next step is cut corresponding slots in the hub so the blades are held on 3 sides when I turn it.

The additional holes are for the 3 bolts that will clamp everything together. I'll have to fill the holes in the pattern after this is done.

Edited by JV Puleo (see edit history)
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Putting slots in the hub of the impeller. These are needed because I want the blades to be perfectly straight.I haven't quite figured out how to put any draft (i.e. taper) on the blades which  you would want to do to make it easier to pull the pattern out of the sand. I'm hoping that they can mold it without the draft but that requires that the blades be perfectly straight and it will still be tricky getting it out of the sand. They have done something like this for me before so It's likely possible if finicky.

 

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They are very close but not absolutely perfect... it will require hand fitting the blades.

 

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I cut those from a piece of 3/16 x 1-1/2 aluminum flat stock and milled one edge square.

 

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And also discovered that while the stock is a nominal 3/16 it is actually a bit thicker. Not much and it would make no difference in most circumstances but fitting them into the slots requires I thin each one down. I did the first one rubbing it on a piece of 100 grit sandpaper. It worked but it's very time consuming. Tomorrow I'll get so 60 grit to see if I can't hurry it along.

 

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when I get it close I finish up with 220. Whatever scratches there are will have no effect on the casting, especially if I paint it when done. I also bought some Bondo to make the fillets. Real pattern makers use wax but I don't have any and don't feel like waiting to get some - that is if the Bondo works. If it doesn't, I'll have to go for the wax. I also got the Dremel cutters I ordered to clean up the welds but that can wait until I send this out.

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I fit the other blades today. This took a little doing because the slots don't line up exactly but, since this is a pattern rather than the finished part it wasn't a deal breaker. Then I set it up in the lathe with the clamp attached. This is to keep the blades straight, and make sure they don't come out, when turning it.

 

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four of the blades are actually a press fit. Two of them were a little loose so I glued them in.

 

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Now I have to fill the hole in the center and provide a way to pull it out of the sand. Not having a piece of 3/4 aluminum rod, I turned one down from 1"

 

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With some luck, I may actually finish this tomorrow.

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Those vanes look to be about twice the height of those on my 1930 Dodge Brothers impeller. You should have pretty good circulation!

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The vanes are going to be quite tall but everything here is oversize. They'll be shorter, and the diameter smaller, when the casting is machined.

 

 

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Posted (edited)

 

I finished the plug by putting a 3/8-16 threaded hole in one end. This is for the screw that will be used to pull the pattern out of the sand.

 

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The plug pressed in...

 

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And then the whole piece faced off again to get it flat. It's still about 1/8" thick but that is to allow for machining the casting.

 

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Next I tried to make the fillets at the base of the blades. I bought some Bondo for this - I've used it before on wooden pattern - and made a filleting tool by gluing a ball bearing to a piece of aluminum rod.

 

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It didn't work. The Bondo is too soft and hardens too fast. Lacking a better way to proceed, I decided to make the upper water connection. First I drilled and reamed a piece of hexagonal brass bar.

 

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Then turned one end down to 1-1/8".

 

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I have a 1-1/8 collet (an unusual size) that I used to hole the piece while I turned the other end to 1-3/8". then I knocked the corners off the hexagonal section...

 

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And soldered in a sort piece of copper tube.

 

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It went back in the lathe using the collet, and I bored it 1.080 for a 1-1/8-20 thread.

 

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Then threaded it with a tap.

 

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This worked fine but the threads on the water pump didn't quite match. They were too tight so I was compelled to lap the threads in. It was extra work but it fits just fine.

 

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Then, I decided to try something else with the impeller. I bought so JB Weld "Steel Stick" putty. This is the first time I've used one of their products. I have an  irrational dislike for JB Weld, probably brought on by the way it's so often used to make rubbish repairs, but I tried it in any case. It worked reasonably well...

 

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After letting it set, I sanded it. I'm not 100% thrilled with the result but when all the fillets are done I'll paint it with sanding primer and maybe even using some glazing putty on it. I realize this is a bit much for a water pump impeller that no one will ever see but this is more a matter of working out a good technique. I have a number of cast parts I intend to make and those will be visible so before I get to them I'd like to have an idea how to go about it.

 

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Edited by JV Puleo (see edit history)
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I filled the corners of the other 5 vanes today. The filler goop does not shape all that well but I used a polished piece of 1/2" aluminum rod to press in the fillet so it would be uniform. I had to spray a little WD40 on the rod to keep it from sticking to the goop. That seemed to work reasonably well.

 

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Then I sanded them to get them reasonably smooth and sprayed a little rattle-can sanding primer on them.

 

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Tomorrow I'll try some glazing putty to see if I can eliminate the edges. The foundry likes the patterns painted as they come out of the sand better so even though it's made of aluminum, it will be black when it's done.

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Posted (edited)

I worked on the pattern this weekend... not very successfully. The glazing putty was a poor idea. It took too long to dry because it was too thick. I did sand it down but ultimately used bondo to fill the flaws. That worked reasonably well. It is, after all, a pattern. I want it as smooth as I can get it but a glass-like finish isn't needed. I finished it up today and dropped it off at the foundry. They will spray it with lacquer to keep the sand from sticking to the bondo.

 

 

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I will say that making this pattern has been useful. I have other parts I'll have cast and I need to get better at pattern making.

I then decided to tackle the welds and see if I could improve them. It wasn't easy. Its very difficult to control the Dremel tool and I still haven't been able to find a cutter with the radius I want. That said, I don't think there is any question that it looks a lot better with the welds reduced to a fillet.

 

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The only problem is that this took most of the day. I'm going to see if I can find something more effective for grinding the fillets. The HSS burr I bought worked very well but it only has a 5/16 radius and I need closer to 1/2". 1/2" grinding stones clogged up almost immediately. In the end, I did all the finish work by had with 100 grit sandpaper. Tedious but it's hard to take off too much metal.

Edited by JV Puleo (see edit history)
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Hello Joe,

 

That looks great! Just remember even the best sand casting isn't perfect - there will be small pits etc.

Are you planning on painting it? If so bondo is your friend.

 

T

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Yes. I used Bondo and my foundry friend offered to paint it when he makes the mold.

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I've been plugging away at reducing the weld to a fillet, a job that is proving both difficult and very time consuming. The largest cutter I could find had a diameter of 5/16? which is too small a radius. I really need something with a 1/2" diameter but cant find anything to work with my Dremel tool. I bought a cheap set of rotary rasps at Harbor Freight but they have 1/4" shanks for a die grinder. I have a die grinder but my compressor is so anemic it's not worth bothering with. So, I made a little fixture to hold the ball rasp in the lathe and turned down the shank/

 

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This worked reasonably well but it leaves a rough finish and I'm trying hard to not gouge the metal on either side of the weld so while it puts a concave surface on it, I've been sanding it by hand with a variety of different papers. The result is OK but it takes hours to do even a small section.

 

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I spent most of today doing just the area from the center hub of the pump to the end of the inlet tube so I'm still looking for something better.

 

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The result is so much better than the weld that It is probably worth doing but I don't think I'll do this again.

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Joe, have you tried the Dremel sanding drum? I used mine many times to sand down aluminum and it cuts really fast. The drums hold up pretty good as long as you use the Dremel brand sleeves. The HF ones are junk. Maybe the drum is too large of diameter though but I think it’s around the 1/2” mark.

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I tried that yesterday and it did work better but I only had 1 of the sanding drums so I'm off this morning to see if I can get a few more.

 

jp

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