Restoring an old Camelback drillpress

Since some of you guys wanted to hear more about my restoration of an camelback drillpress from around 1900 here is my progress so far and the plans for casting some parts of the drivetrain assembly.


All that was left from the drillpress was the upper halft with the table. I had to build a new foot for it from welded plate and a thick steel pipe filled with concrete. The extended flat steel at the top of the steel pipe is the mount for the "headstock".


This is the headstock model Iam going to cast in aluminum. The 2 blocks supporting the bearings are detachable from the bottom half to part the mould.

The motor will be mounted on the extended end of the foot. Going with a double V-belt from a 63mm pulley to a 280mm pulley at the end of the headstock spindle. Inside the headstock will be a stepped flat belt pulley i need to cast. The belt than goes up to the drill press spindle on another stepped pulley I need to cast.

I hope you can follow my clumsy explanations. I can post some better pictures of the wooden headstock model this weekend.

Tim

 

Wow! When you said drivetrain I was thinking pulleys and shaft. This will be quite a project.

Pete

 

Here's about a 1940's vintage design which is more or less complete if that's any help describing pulleys and parts.

 

Thanks. Thats about how I plan to do it. In my design the motor will sit unter the lower stepped flat belt pulley.


Thats the finished headstock model for the lower pulley. Iam going to cast it in aluminum.

 

Comments:
1). I would suggest softening the pattern’s transition from the grey vertical component to the red flat portion for two reasons—-the sand doesn’t like sharp edges and will crack off there. And the aluminum does not like sharp corners, particularly inside corners. I can see a fat shrink defect developing there at about the midpoint of that inside corner.

2). For those reasons I would glue the three pattern pieces together, generously soften (radius) all outside corners and add a very generous (1/2” radius or so) fillet to all inside corners.

3). Have all of the modified pattern in the cheek of a 3-part flask with the vertical pieces pointing down.

4). Put 1.5” dia by 1.5” high risers over each of the vertical areas but located in the cope.

5). Fill it via runner and gates in the drag. Gate into both vertical parts.

The other option would be to cast it on its side and part midway on the pattern, but that would require completely changing the draft of all parts. Radiusing would still be needed. As would risers.

I am suggesting the above as if I knew those changes are required and would result in a good sound casting. I don’t. But I do think they are a good idea.

Denis

 

Thanks for the advice Denis,

Iam going to modify the pattern with a radius as you suggested. I planned to round off the inside corners in the mould. You suggest to glue the pattern together. Wouldnt this make pulling the pattern from the mould much more difficult?

I noticed another porblem...my casting capacity. I'd need to melt several batches of aluminum in my A10 crucible, transferring it to a bigger steel crucible and keeping it liquid until i reach the needed amount.

Tim

 

That casting will be more than 10 pounds?! I would not have guessed it. How much volume is it?

So far, I don’t recall anyone trying to accumulate multiple melts in a holding vessel and then pouring. That seems like a big technical hurdle.

A pattern combining the the three pattern pieces into a single pattern piece should not be particularly difficult to draw out of the sand. It may not pull cleanly the first time you try as sand has a way of revealing small errors made in fabrication that might otherwise escape inspection. But a little sand paper and Bondo can usually iron those problems out nicely over the course of a few trial packs ad draws. I think waxing the pattern with paste wax and buffing it out helps me and I also like to then apply some graphite which I rub into the surface with very black fingers. A final dusting with common talc purchased cheap at a pottery shop near you and then a blow off of excess talc and you should be ready to pack.And I would also suggest using a simple muslin parts bag for dusting talc and graphite. HT1 has long espoused them here for good reason. They are cheap but lay down a nice uniform parting layer.

Denis

 

The pattern weights around 2kg. Its made from pinewood/woodscraps and bondo. I assume a density of around 0,6 g/cm3. This ist around 3333 cm3 total for the pattern. With a density of aluminum of 2,7 g/cm3 I need ca. 9kg for the part plus gating/risers.

Tim

 

Put the part on a diet ;-). That would be much easier than using some scheme to combine melts for a single pour.

The base would be easiest to reduce by simply cutting out a very generous rectangle. There is probably no need for it to be a solid block. The vertical sides need not be flat-sided rectangles either. Route/sand generous coves into the inside and outside surfaces. Now the part will weigh 5.5 pounds and look 1930’s Art Deco. Ribs on the sides for better art critic reviews and “extra credit.” Or make sides hollow using green sand and gaggers or silicate-bound sand cores. Easier to cove them externally.

Denis

 

Alright I'll get rid of that extra material
I made it thicker because I was concerned it will warp when I bolt the bearing blocks on top of the raised sides and put some tension on the belt.

 

I took another look at the pattern today. I plan to remove the shaded area on the baseplate and the sides. What do you think? Where can I remove more material without weaken the finshed casting too much?

 

Only guessing here, but I think the red piece will be fine cut out as diagramed. In my shop I’d use a big hole saw( 2 or 3” dia) to first radius the inside corners and then saw out the rest of the rectangle. Then I’d use a roundover bit to put a 1/4” radius on the cutout. Finish with some draft.

For the uprights I’m sure the cutout you show would have no effect on strength. In addition to that I’d put an abrasive disc on my angle grinder and have some fun putting a broad gentle cove in in each broad face leaving maybe the parts directly under the bearing contact points untouched. Now your pattern will way between 1/2 and 2/3 original weight. It will be extremely strong and will look good IMHO.

I am sure ten people would have ten different approaches most of which would be good. Just saying my take on it. Casting is nice because it does allow for some coloring outside the lines.

Denis

 

Okay so here is what I came up with. I also reduced the contact points to the mounting plate at the bottom of the flat part. Next step is to sand it smooth.

 

How much did you decrease the pattern weight with your modifications? Do you plan fillets at the junction of the red and silver pieces and to fillet inside corners in the parts shown? Looks strong enough for the intended purpose.

Denis

 

It weights now ca. 1450 grams. This is about 6,5kg of aluminum in the finished casting.
Adding sprue, gating and feeders its still too much für my A10 crucible. I already thought about cutting the top off of a empty 5kg gas bottle and using it as an steel crucible with some lining to prevent direct contact of the molten aluminum and the steel.

I planned to round the junction in the sandmould after pulling the pattern. Maybe this is an bad idea?

Thanks for being patient with me

Parallel to solving the problems with the headstock I started printing the first parts of the stepped flatbelt pulley pattern with my 3D printer.

Tim

 

Well, you have made a significant weight reduction and with a little more aggressive use of a saw, more could be pared off. But, that might only get the net casting just under your A10 limit. It sounds like your furnace could accommodate a larger crucible? If so, that seems like an option you are sure to want in the future. So, maybe now is the time for that move.

The other way to reduce the weight of the casting further would be to use cores to form the two uprights. With cores, you’d have a lot of flexility of form. I often admire old-school castings that used webs with flanges to maintain strength but reduce metal volume. That’s maybe more work and complexity than you want to invest in this “simple” project.

Regardless the ultimate configuration of your pattern, I think most folks would strongly recommend establishing your sand radii in the pattern rather than attempting to do a lot of hand work on the sand after packing the mold. For one thing, sand will pull cleanly from a radiused corner but will often crack irregularly from a sharp inside corner. Secondly, even a firmly packed green sand mold will be relatively weak and easy to damage with hand work as it takes such a light and precise touch to do it. From my personal perspective, I try to avoid hand working molds. Usually, I end up carving a pouring basin and don’t mind that as it is pretty much free-form and forgiving. And gates usually need a little radiusing done by hand. Otherwise, I am very happy if I have to do nothing else besides very lightly kissing the edges of cope and drag with a very soft long-bristled brush and carefully blowing out loose sand. Even over-vigorous blowing can easily dislodge sand.

Denis

 

So its been a while and I figured out, that casting the headstock is at the moment a bit beyond my capabilities regarding melt capacity. I saved the pattern for a later project and plan to build the headstock from welded steel. Anyway thanks a lot for the help on the headstock pattern!

However I still need the stepped flatbeld pulleys...My vintage lathe ist too small to make them from a big solid round bar, so I will cast them.
I 3D printed the pattern for the first pulley, as well as the corebox. The core will be made from resin bonded sand.
Currently Iam smoothing the pattern. The second half of the corebox isnt finished yet.

 

Good stuff. Subscribed. I'm doing a drill press restoration too but much less involved than casting new parts.

I'm interested to see how the parts turn out when finished.

 

So I finally figured out a way to make the Core for the pulley. The Core now consists of two halfes, glued together on a a piece of round steel. With the steel rod I can also precast the hole for the spindle. The steel rod was sooted to prevent the aluminum from sticking to it and make it removeable after the cast.
The picture shows yesterdays test mould with the core in place.
If I cast the pulley I will use a bigger flask

 

Lookin good.

One thing I recently learned concerning cores is that avoiding weight bearing by the core or its support right up to the edge of the cavity will help reduce sand breakout at the sharp corner where the core enters the cavity. I would suggest on this particular core that you wrap 1/2" wide (you have lots of room) electrical tape maybe 2 or 3 wraps around the pattern right where the core will enter the cavity. This will relieve the sand a bit there so it is not weight-bearing and make cracking of the sand less likely. In tighter circumstances even 1/8" wide tape would make a difference.

Denis