Capitulating to oil cups

I don’t believe I’ve ever had so much difficulty drilling holes. Five #80 drill bits lined up like casualties of war (where are their flags?), and not one successful hole achieved.

#622 had oil cups mounted mid-way down the crosshead guides. They are quite prominent in the photos, and I would love to model them. I couldn’t include any mounting pin for them in the etch because of the way the guides fold, and I couldn’t etch holes for mounting pins because there simply isn’t enough metal to spare as it is. So, I had hoped to drill holes after the guides were assembled, and I spent a good portion of my day attempting this.

201607041729_0001
622 in earlier days. Note the oil cups in the middle of the crosshead guides; there also appears to be an oil cup on the side of the crosshead slide, which I decided to omit long ago.

Because of the shape of the crosshead guides, the holes need to be on a cusp, and finding this cusp with a #80 drill bit proved to be impossible. The bit wandered off to make a hole off to one side.

So then, I thought of a cunning plan to make a drill guide by centre-drilling a piece of hex stock and then filing it out to fit over the crosshead guide. For some reason, the hex defeated drill bit after drill bit, flicking their points into the ether with disdain. I then tried to drill into the side of a length of rod, and broke the fifth drill bit.

So, #622 is going to lack those oil cups. If I can’t get the holes in the right places, the oil cups will be misaligned and look terrible. If I can’t make them robust, odd ones will break off and look worse.

While the crosshead oil cups are a distinctive feature of this engine, they are beyond me at this point.

10 thoughts on “Capitulating to oil cups

    1. Hi Richard, No doubt there is someone else in the world with this skill. There are, after all, people who will write your name on a grain of rice lining the streets in some places. However, typically jewellers are actually dealing with larger details that don’t need to be aligned so precisely. You and Rob have, however, made me go back and look at the photo, and perhaps I can get away with a but joint if it is soldered. I’ll have one more go; wish me luck!

  1. 1. Did you inspect the drills to see if they had a properly split point?
    2. Can you remove the cusp?
    3. Did you centre drill or in this case touch the place the drill will land w/ a very small centre drill?
    4. Are you drilling them in a drill press?
    5. Is the piece properly supported?
    6. How far do you have to drill?
    7. Are you using magnification/ before you madeand used the bush could you see the chip form?
    8. If you are using magnification and assuming you don’t have a DTI, could you see the amount of runout?
    9. Is the drill grabbing on soft solder?Is there solder on the drill from previous work?

    A .013″ drill is easily over constrained so don’t use a guide bush. It’s very possible those drills aren’t up to the task. On the other the hand the end of an etch isn’t going to be drill friendly unless you give it somewhere to land. Drilling that small with a capstan without proper skills is also very difficult. If you do get the drill to start you’re likely to have it grab at some point.

    Ideally you would set it up on a fixture and drill under magnification using an axis with a leadscrew to control it. This could be a mill, a milling slide, a face plate, a tailstock drill pad with some way of holding the part or something similar mounted to the cross slide at the right height. On my first lathe I most often rigged something up on the side of a toolpost. Later on I made a little threaded plate w/ 4-40 holes to enable me to hold and position fixtures made of whatever would do the job. I still use that plate to this day.

    If you look up Jerry Kieffer and drilling he gives all of the info you’ll need. At shows I’ve watched him drill very small, straight holes without bother. He rails against capstan use on anything sub .03″. There are regular people who use capstans everyday (most watchmaking lathes have levers which present similar challenges) but the few good operators that exist got that way by observing their work very carefully and doing oodles of holes- no doubt practising before attacking expensive instrumentation . Kieffer is also an advocate of making and using larger Z axis handwheels to make feeding easier which sort of makes sense with the speeds he uses. He advises running at around 1000 rpm when manually feeding/retracting with small drills which is criminally slow but it does work.

    If you’re not going in very deep, another approach would be to make a cutting tool. In the olden days you used to make drills for this sort of work. .013″ isn’t that small and if you only needed to go 1-1.5xdiameter you might be able to make a single flute cutter. I’ve made rivet snaps for simulated .004″ rivet heads on a Taig. Made in O-1, it took several attempts but they do work. Heat treating was the most difficult part. If I had to do them over I would use A2 and make a stainless cap to go over the end of the shank where the cutting head is during heat treat. The failures were all down to poor tempering that led to the cutting end parting ways when cutting into unhardened O-1.

    1. Thanks for all the advice, Andrew. I’ll definitely look up Jerry Kieffer.
      I was using both the lathe and the drill press. The lathe seemed to snag on the inside of the centre drilled hole. It was my first time ever drilling with the press where the work was not held by hand, and I wonder if that could have caused the bit to break.

  2. Brass can sometimes be “challenging” to drill. I am currently trying to find someone to turn a few brass ‘drums’ for me for a project I am working on (an H0 model of a 1940s sheepsfoot tamping roller, i.e. a piece of construction equipment). After searching for a few weeks I finally found a ‘volunteer’ right in the next office who offered to turn or mill the drums for me. I gave him a design drawing of the part, which contains a deep 0.040″ hole. He thought about how to produce that part and than – after consulting with some specialists – he said that he would not dare to have his milling machine drill that hole in brass, even if it was shallow. Brass would often grab drills and snag them. I now have found some special drills that are recommended for brass and have ordered a few for my colleague. I have not received them yet but maybe these drills having only one straight flute would also work for you. These drills produced by EUREKA are available at FISCHER, a German jewellery supply house under the following link: https://www.goldschmiedebedarf.de/product_info.php?products_id=5269&language=en
    Sorry, I do not know the correct technical name for these drills. I expect that they are also sold by watch maker and jewellery suppliers in North America.
    Hope this helps!

    1. Thanks Andreas. I have drilled many holes in brass down to #80 (about .012”), but it does require care and lubrication. My understanding is that brass wants to pull the tool in, and so a different cutting angle is preferred. Good luck with your parts!

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