NCRich 13,791 Posted June 14, 2022 So I've got a JK 5517 and I want to install fixed bars. I'm no stranger to drilling these lugs, but I'm not quite sure of the size bit. I have some 2mm stainless rods and I would prefer a press fit. I'm not sure what size to drill the receiving holes. 2mm? 2.1mm? I think I could drill a 2mm hole then put the rod in the freezer and the case in the oven. Contraction and expansion would take place respectively and I could just insert the rod and wait for it to come to room temp. Then it would be snugged down. Anyone have any thoughts? Some on you pretengineers have any knowledge in this area? Thanks in advance. Share this post Link to post Share on other sites
als86 5,421 Posted June 14, 2022 Without going into too much detail I think that would work but it would be quite tight. 316SS(Or austenitic) has an expansion rate of 1.34mm/mm but if you exaggerate the upper and lower temps (so 300°C is nearly 5mm/m) i.e 280°C and -5°C it should make the tolerances bigger and 0.1mm should be suffice. So 2 mm bit. Thats my thoughts from an engineering background Note: I have zero expertise in modding watches this is purely the physics of it. 1 Share this post Link to post Share on other sites
NCRich 13,791 Posted June 14, 2022 13 minutes ago, als86 said: Without going into too much detail I think that would work but it would be quite tight. 316SS(Or austenitic) has an expansion rate of 1.34mm/mm but if you exaggerate the upper and lower temps (so 300°C is nearly 5mm/m) i.e 280°C and -5°C it should make the tolerances bigger and 0.1mm should be suffice. So 2 mm bit. Thats my thoughts from an engineering background Note: I have zero expertise in modding watches this is purely the physics of it. Thanks mate! Of course this will assume I can drill the hole straight (even with a drill press). I think I'll go with a 2mm bit and I can always size up to a 2.1 if need be. 1 Share this post Link to post Share on other sites
FudgyDocker 3,508 Posted June 14, 2022 I know you're old and getting a bit funny, so I'll just say "Wear an oven glove when taking the case out of the oven" You're welcome. You'll thank me for this sage advice, later. Share this post Link to post Share on other sites
Dr Fun Socks 76 Posted June 15, 2022 Id start small, obviously it’s easier to make a hole bigger than smaller. Maybe start with a 1.8 or 1.9mm drill bit and check to see if it slides in. Im sure you can get pins with knurling on one end so it grips when you push it in. Or just hit one end of you 2mm bar with a hammer to slightly ovalise it so it grips. Id say you have close to no chance or cryo fitting it in but i like the thought process. For what its worth im a tool maker but obviously just use whatever method your most happy with! Share this post Link to post Share on other sites
vmlopes 1 Posted June 15, 2022 Just get a 2mm reamer and stop guessing Share this post Link to post Share on other sites
deju 1,888 Posted June 15, 2022 When undertaking any project, always start by thinking what would @Popperini do. This is the perfect process of eliminatio . Now you know the wrong answers, your left with the correct way 1 Share this post Link to post Share on other sites
Popperini 17,966 Posted June 15, 2022 9 minutes ago, deju said: When undertaking any project, always start by thinking what would @Popperini do. This is the perfect process of eliminatio . Now you know the wrong answers, your left with the correct way That's really quite hurtful. True, but hurtful. Share this post Link to post Share on other sites
NCRich 13,791 Posted June 15, 2022 1 hour ago, Popperini said: That's really quite hurtful. True, but hurtful. 3 hours ago, vmlopes said: Just get a 2mm reamer and stop guessing Hmm..reaming.........what is the advantage of that over a drill bit in this application. I looked it up online but I'm not sure why it would be better. Share this post Link to post Share on other sites
narikaa 129 Posted June 15, 2022 (edited) A far simpler 'quick and easy' transformation is masking the existing spring bars with a tube. When reaffixed you have the appearance of a solid bar Edited June 15, 2022 by narikaa Share this post Link to post Share on other sites
Popperini 17,966 Posted June 15, 2022 BTW, I'm genuinely interested to hear how this one goes, as I've also got a length of 2mm stainless rod I bought with exactly the same project in mind. I was going to drill the lug holes out to 2mm - knowing that my abilities are so woeful that the holes would almost definitely end up a bit over-size anyway... Then use some JBWeld to hold the bars in. An interference fit (hot/cold as you described Rich) would be the ideal method. Share this post Link to post Share on other sites
Foxindebox 469 Posted June 15, 2022 11 minutes ago, Popperini said: BTW, I'm genuinely interested to hear how this one goes, as I've also got a length of 2mm stainless rod I bought with exactly the same project in mind. I was going to drill the lug holes out to 2mm - knowing that my abilities are so woeful that the holes would almost definitely end up a bit over-size anyway... Then use some JBWeld to hold the bars in. An interference fit (hot/cold as you described Rich) would be the ideal method. If you are planning to refinish the sides of the case afterward (Which I assume you would to clean up the ends of the rods), you can drop a bit of solder into the gaps (if any…). 2 Share this post Link to post Share on other sites
vmlopes 1 Posted June 15, 2022 2 hours ago, NCRich said: Hmm..reaming.........what is the advantage of that over a drill bit in this application. I looked it up online but I'm not sure why it would be better. Because it will be way more accurate and less chance of wondering Share this post Link to post Share on other sites
NCRich 13,791 Posted June 16, 2022 20 hours ago, vmlopes said: Because it will be way more accurate and less chance of wondering I'm still not sure I understand. I have a pilot hole already there in the case, all I have to do is enlarge it with progressively larger drill bits. I've done it a lot before and never had an issue with wandering. I can see this if no hole existed, but one does as a guide. Share this post Link to post Share on other sites
Popperini 17,966 Posted June 16, 2022 2 minutes ago, NCRich said: I'm still not sure I understand. I have a pilot hole already there in the case, all I have to do is enlarge it with progressively larger drill bits. I've done it a lot before and never had an issue with wandering. I can see this if no hole existed, but one does as a guide. I don't think vmlopes realised that the lugs are already drilled. As you say - there's bugger-all chance of any wandering happening when you're drilling through existing holes. Unless you're me, of course. 1 Share this post Link to post Share on other sites
NCRich 13,791 Posted June 16, 2022 9 minutes ago, Popperini said: I don't think vmlopes realised that the lugs are already drilled. As you say - there's bugger-all chance of any wandering happening when you're drilling through existing holes. Unless you're me, of course. Well I've got to wait for all the parts to come in, so lots of time to ponder before destruction. I think it will be 2.1mm in the end with a tiny bit of solder to finish it off. Maybe some JB weld. Have to see. 1 Share this post Link to post Share on other sites