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How To Drill Lug Holes

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Since I couldn't persuade Ziggy to do it for me, I have been slowly working thru my Rollie collection, changing all the spring bars to the correct size. It's something of a chore as I have a bunch of them.

The watches that I have to change are two catagories - the classic watches with MBW/TW Best cases, lug holes and sapphire crystals

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The vintage watches that are becoming my new obsession. I have several new MBWs since this picture was taken.

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I started with some Chinese vintage cases that Josh and Andrew sent me to practice on. Now that I have it down to a science, I am zipping thru the "Perfect" watches I got from them and my MBWs.

Here are the watches I did this evening, an MBW Milgauss, an MBW DRSD, and a . . . [drum roll] . . . very rare MBW cased GMT II with 2893 movement.

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Here is the objective. We want to take these nasty little pins out of our watches and replace them with the correct pins that are larger and much stouter.

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First, you NEED a drill press. If you don't have a drill press, you should task the job to someone who does.

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Although mine is a free standing model with twin laser guides, you don't need any of that - any table top drill press will work just fine.

This is NOT a drill press and it will not work worth spit for this.

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A dremel is a fabulous tool, the press stand makes it even more useful, and mine gets a world of use, but it absolutely is not the right way to drill lugs. When it comes to polishing a watch, it's great.

Drilling lugs is all about set up, tool speed, set up, cobalt wire drills, set up, plenty of lights, set up, cutting oil, set up, a vice with rubber jaws, and did I mention set up? As with most tool and die work, it's all about how you set it up.

I set mine up using a fine wire drill that I can run thru the upper and lower lug, allowing me to adjust it such that the centerline of the hole is concentric with the centerline of the drill. The drill in this picture is for illustration - it's actually the drill I use to chamfer the holes.

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As you can see above, a case that might appear to be properly positioned is actually a little crooked. Positioning the wire drill thru the lugs makes the invisible become readily apparent.

Once you have evrything lined up correctly, a good quality cobalt bit will do a half a dozen cases. The key is a slow, steady advance of the drill thru the work piece and plenty of oil - regular, household 3-in-1 oil is fine. If you see smoke, you are going to fast. I haven't timed it, but I would thing ot takes about 15 seconds to go thru each lug at 3000 rpm.

Do not "choke up" on the drill by putting most of it up in the chuck. While it is true that a short, stubby drill is less likely to break than a long one, you are also much more likely to touch your watch case with a spinng chuck which can ruin a very nice case in a skinny instant.

Once you drill all your holes with a size 55 cobalt drill, you chamfer the holes with a larger drill (I use a 3/32). Note that the set up is dramatically different.

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To drill thru the lug, you want the centerline of the existing hole to be concentril with the centerline of the drill, you want the point of the drill to go straight down the existing hole.

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Chamfering is different. This isn't like "frenching" a car antenna (for those into custom body work), you want the edge of the larger drill to uniformly widen the RIM of the existing hole VERY slightly. That requires even contact all the way around and to do that the surface of the lug must be perpendicular to the axis of the drill. Remember, this is a very, VERY slight touch - if you see shavings, you have gone WAY to far.

post-223-1164094220_thumb.jpg The DRSD (Case scratches are from daily wear)

post-223-1164094241_thumb.jpg A pic of the GMT II

post-223-1164094277_thumb.jpg Another of the GMT II

post-223-1164094254_thumb.jpg A pic of the Milgauss

post-223-1164094304_thumb.jpg Another of the Milgauss

I took the pics before cleaning the watches up so you could see that there is no reason to scratch a case during this process. Next, I will take a little jewelers rouge and polish the watch cases with the dremel and them hand buff them with a little Flitz.

I hope you found this to be helpful.

Bill

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Hi Bill.

Now this was nice!!! Hope everything is good with you and your famely, give them my best bro...Cheers...

//robi

Hi Robi,

I hope all is well with you and yours -- you gearing up for Thanksgiving? I need to stop eating now! I always eat til I am sick on Thanksgiving and this year I will have all five kids home with me since the oldest is home from the Navy. It will be the baby's first Turkey Day!

I saw your post earlier wanting to see the difference in springbars so I decided to put together a long reply with all kinds of pics. I was going to send you the link but I see you beat me to it.

Cheers

Bill

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Excellent write up Bill!

Could I make a couple of observations that others may find useful if attempting this kind of work...you really should wear safety glasses/goggle when doing any kind of drilling work like this to protect your precious peepers (eyes) also keep any loose hair / clothing tied back out of the way so it can't get caught in the drill and the drill press should have a guard around it as a secondary measure...

Secondly, you went to all the trouble of good setup but did not use a countersink bit to finish the holes! As you say the drill only needs a very light touch, over do it and you've ruined the lug hole. A chamfer bit is more progressing and controllable than a drill plus it puts the correct 45deg angle on the hole edges.....

Just my 2c worth....

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i have three drill presses and one similar to yours but now i have a jewelers press which i showed over a year ago on how to do this, it was a great job of showing how but one thingi do different is i use a diamond point to bevel the edges it seems to not dig but only sand the edges for me, but like u say it is all about setup and for me it is a feel thing as well, but like i posted before , it is a much better way without screwing up like many have by using a hand drill

good job

joe

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i have three drill presses and one similar to yours but now i have a jewelers press which i showed over a year ago on how to do this, it was a great job of showing how but one thingi do different is i use a diamond point to bevel the edges it seems to not dig but only sand the edges for me, but like u say it is all about setup and for me it is a feel thing as well, but like i posted before , it is a much better way without screwing up like many have by using a hand drill

good job

joe

I'd like to see the difference between the chamfer bit previously mentioned and the diamond you mention.

Also, is there a tool for removing the crystal retaining ring like on a Milgauss MBW. I have tried everything that always works with MBWs, but the Milgauss retaining ring is made differently and I cannot get under it, even by tapping a razor blade (that always starts a crack on everything else).

These Milgauss watches grow on you. I have two MBW Milgauss 6541s (one stingray strap, other rivet bracelet) and I find myself liking them better and better. I just need to be able to change the crystals.

Bill

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Excellent write up Bill!

Could I make a couple of observations that others may find useful if attempting this kind of work...you really should wear safety glasses/goggle when doing any kind of drilling work like this to protect your precious peepers (eyes) also keep any loose hair / clothing tied back out of the way so it can't get caught in the drill and the drill press should have a guard around it as a secondary measure...

Secondly, you went to all the trouble of good setup but did not use a chamfer bit to finish the holes! As you say the drill only needs a very light touch, over do it and you've ruined the lug hole. A chamfer bit is more progressing and controllable than a drill plus it puts the correct 45deg angle on the hole edges.....

Just my 2c worth....

Very Good - and I cannot believe I neglected to mention that, especially with five kids of my own. I beat that into them unmercifully and Lord help the one I find risking their running lights!

I personally like jewelers glasses. They aren't quite as good a protection as goggles, but they do pretty well and they make it easier to see clearly what you are doing.

Bill

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This is all very good information and most helpful. In changing straps on my reps, the screws are so easily stripped that makes it a little disappointing. It seems that poor quality lug screws is a fact of life in collecting reps and that drilling new holes for spring bars is to be expected. I don't have the drilling equipment or the expertise in this kind of work , but do have a good watchsmith who will work with me. Thanks again for the excellent post.

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Fantastic post, well done, well written, clear and detailed, and thought out to consider all the problems.

The only thing that makes me nervous is clamping the watch in the vise with the crystal still attached...especailly on the Tropic ones, easy to damage...

I am so glad you posted this, this is by far the best How-To for drilling lug holes that we have had, detailed, considers the fact that alignment is critical, shows step by step what to do in clear english, and shows how to overcome all these problems, and do it the right way. Simply putting the case in a vise without considering the issues you raise, is not the way to do this job.

Thank you for taking the time to do such a detailed post. Well done Bill, excellent job.

Should be pinned as a How-To Drill Lug holes.

RG

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Great setup! This is what i have. From your pictures, i also see that you get the "bunching" or extra material around the edge. I have not figured out how to finish the hole perfectly yet - can you also provide some suggestions on how you polish them at the end? Counter sinking, etc.

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Bill,

Write ups don't get much better than this! An excellent job, along with clear, concise pics (as with all of your posts).

Well done!

:)

Cheers,

R

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Fantastic post, well done, well written, clear and detailed, and thought out to consider all the problems.

The only thing that makes me nervous is clamping the watch in the vise with the crystal still attached...especailly on the Tropic ones, easy to damage...

I am so glad you posted this, this is by far the best How-To for drilling lug holes that we have had, detailed, considers the fact that alignment is critical, shows step by step what to do in clear english, and shows how to overcome all these problems, and do it the right way. Simply putting the case in a vise without considering the issues you raise, is not the way to do this job.

Thank you for taking the time to do such a detailed post. Well done Bill, excellent job.

Should be pinned as a How-To Drill Lug holes.

RG

Hi Ziggy,

Hi praise indeed coming from you.

I neglected to mention that the vise I use is made by Dremel -- it has hard rubber jaws. That is a real benefit for a couple of reasons. First, the rubber doesn't damage the crystal or case back, yet grips the watch tightly, and Second, the rubber allows some slight amount of flex and I suspect (no way to see it) that the flex allows the watch to adjust ever so slightly as the drill tries to pass thru the existing hole.

You know what a pain this can be, but I have used one drill bit to drill as many as five cases, and my drill bits are nothing special - just cheap cobalt drills I bought on Amazon. If you spin them at 3000 rpm and use a few drops of oil, you won't smoke them. Careful set up and you'll never break one either.

Also, I use this particular vise and a slightly modified 1 1/8 socket (used a dremel to slightly round out the socket by grinding down and polishing the teeth) as a press to seat crystal retaining rings on vintage watches. Works like a charm.

Bill

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EXCELLENT post. Bravo!!

One question though.... Why 3000 RPM? I haven't done a lughole job yet myself, but my instinct would be to spin the drill much slower than that.

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EXCELLENT post. Bravo!!

One question though.... Why 3000 RPM? I haven't done a lughole job yet myself, but my instinct would be to spin the drill much slower than that.

And you would be quite right - but keep in mind we are using very small wire drills.

During my Senior Year in Mechanical Engineering I managed a machine shop and 3000 RPM was a pretty good speed for wire twist drills in steel - especially using a cobalt wire. If you use larger drills (like 1/4 inch) you would normally drop to about 1000 RPM, and run a large drill (say 5/8) at about 600.

As I said previously, I have done as many as five MBW/TWBest cases with one cobalt drill, so it seems to be working pretty well.

Bill

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As I said previously, I have done as many as five MBW/TWBest cases with one cobalt drill, so it seems to be working pretty well.

Bill

Do you hire out? I have a TW Best SD I am dying to have drilled :whistling:

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Do you hire out? I have a TW Best SD I am dying to have drilled :whistling:

Truly, for what I would charge to be responsible for your watch, you could buy your drill press. This really is not all that difficult.

Bill

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And you would be quite right - but keep in mind we are using very small wire drills.

During my Senior Year in Mechanical Engineering I managed a machine shop and 3000 RPM was a pretty good speed for wire twist drills in steel - especially using a cobalt wire. If you use larger drills (like 1/4 inch) you would normally drop to about 1000 RPM, and run a large drill (say 5/8) at about 600.

As I said previously, I have done as many as five MBW/TWBest cases with one cobalt drill, so it seems to be working pretty well.

Bill

Bill, based on what I see in your pictures, 3000 RPM is too fast. A good general rule of thumb for stainless steel should be 300-600 RPM in my opinion. But rules of thumb are not as important as the results, and you have nothing to lose by running slower than you might otherwise be able to. It will just take a little longer. The deformation of the exit hole, or "bunching" as we seem to be describing it, seen in your pics is caused by heat. The heat is caused by excessive drill bit speed which results in the removal of material too quickly. High speed (3000 RPM) drilling will pack the flutes and metal will be removed faster than it can be cleared, so you will see the exit hole become deformed because material has essentially forced its way out. Material can also be removed too quickly by trying to advance the bit rapidly or the bit may be deforming slightly with too much pressure (excessive feedrate). There is a balance between speed and feedrate. The best approach is to run at the lowest RPM possible, be very gradual about advancing the bit, and use plenty of lubrication. Also, the lugs are sufficiently thin so that you might be able to take the bit up and down to help clear it.

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Bill, based on what I see in your pictures, 3000 RPM is too fast. A good general rule of thumb for stainless steel should be 300-600 RPM in my opinion. But rules of thumb are not as important as the results, and you have nothing to lose by running slower than you might otherwise be able to. It will just take a little longer. The deformation of the exit hole, or "bunching" as we seem to be describing it, seen in your pics is caused by heat. The heat is caused by excessive drill bit speed which results in the removal of material too quickly. High speed (3000 RPM) drilling will pack the flutes and metal will be removed faster than it can be cleared, so you will see the exit hole become deformed because material has essentially forced its way out. Material can also be removed too quickly by trying to advance the bit rapidly or the bit may be deforming slightly with too much pressure (excessive feedrate). There is a balance between speed and feedrate. The best approach is to run at the lowest RPM possible, be very gradual about advancing the bit, and use plenty of lubrication. Also, the lugs are sufficiently thin so that you might be able to take the bit up and down to help clear it.

Okidoke . . . nothing to lose so I'll try it. I learn something every day, so maybe that's it for today. I'll report back in a bit.

Bill

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Okidoke . . . nothing to lose so I'll try it. I learn something every day, so maybe that's it for today. I'll report back in a bit.

Bill

I would also suggest using a fresh drill bit this time, otherwise we can't be certain the results will improve because there could be some deformation to the old drill bit (that you might not even see).

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Very good info here. :thumbsupsmileyanim:

I am not a metal expert but I have learned that when drilling hard metals like SS the best results are obtained when you run your drill at low speed, apply very little pressure and use cutting oil for lubrication and to keep temp low. This method will save your drill bits. Also at lower speed the bouncing will be reduced.

Waiting for TJG report.

vaccum

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Okidoke . . . nothing to lose so I'll try it. I learn something every day, so maybe that's it for today. I'll report back in a bit.

Bill

Well, I was not quite right - there was something to lose. My COMEX just ate two cobalt drills - I thought perhaps the first one broke because it was dull so I tried a new one.

At 620 RPM, that cobalt drill will not cut an MBW case, and pressing harder only served to twist the watch in the vice binding and breaking the bits. Heat generation was MUCH higher and drilling thru side to side (two holes at once isn't even possible because there was no way to cut the first hole straight enough.

Here's what the end result was with the COMEX - again, no clean up or polishing yet. They look much better once the polishing is all done.

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I dug thru and found my wall chart. As you can see, the smaller the drill, the higher the speed, and the harder the stock, the higher the speed.

post-223-1164158137_thumb.jpg

Oh well, it was an experiment.

Bill

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Pushing harder could have definitely effected the results. Whatever the case may be, there are some unknown variables in either your technique or your setup (or both) because the results are counterintuitive.

Here's a common speed chart and description of proper technique:

http://www.ultimatehandyman.co.uk/DIY_Meta...l_technique.htm

Ignore absolute numbers for now, and just notice the trend that as the metal goes from soft to hard (aluminum, then steel, then stainless steel) speeds get slower and slower. This is common sense and generally accepted. I can't explain what is happening to you, but I would definitely continue to experiment with and try to find proper technique at low speeds. Because although you're not breaking bits at 3000 RPM, the results aren't as good as the could be. Perhaps experimenting on something other than a watch will help to perfect the method.

Good stuff, TJ!! Keep at it and soon you'll have quite a skill to behold!

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Pushing harder could have definitely effected the results. Whatever the case may be, there are some unknown variables in either your technique or your setup (or both) because the results are counterintuitive.

Here's a common speed chart and description of proper technique:

http://www.ultimatehandyman.co.uk/DIY_Meta...l_technique.htm

Ignore absolute numbers for now, and just notice the trend that as the metal goes from soft to hard (aluminum, then steel, then stainless steel) speeds get slower and slower. This is common sense and generally accepted. I can't explain what is happening to you, but I would definitely continue to experiment with and try to find proper technique at low speeds. Because although you're not breaking bits at 3000 RPM, the results aren't as good as the could be. Perhaps experimenting on something other than a watch will help to perfect the method.

Good stuff, TJ!! Keep at it and soon you'll have quite a skill to behold!

We may be boring members to death, but I find this fascinating.

Looking at the charts, they say the same thing, but the Delta chart goes farther into fine wire drills. Notice that trend as you go smaller and consider how much smaller we are going. I suspect that the best solution might be at significantly higher RPM, but 3100 is all I can do.

For my next example, I am going to try doing a couple of cases at max speed, with progressive passes using a smaller drill first before the 1.3mm drill and I am going to chamfer the holes first, rather than afterward.

I'll report back with pics.

Bill

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I have been doing some reading as well...

Here is the formula for calculating drill bit speed...

For Stainless Steel, 200-300 series, drill bit point angle is 135-140 degrees, and speed is 20-40 SFM (Surface Feet per Minute)

For 400 series Stainless, point angle is 118 degrees, and SFM is 30-60

To convert SFM into something useful like RPM

RPM = SFM x (12/pi)

_________________

Diameter of drill bit

So for a #55 drill, 0.0520 inches, we get 2900 RPM for the drill bit speed...

If you used a 0.50 (1/2 inch drill) in the same formula, you get a speed of 300 RPM...

The smaller the bit, the faster the speed to achieve the same SFM.

The other interesting point, is that Stainless tends to "Case Harden" if drilled too SLOWLY...firm and steady cutting avoids this problem...

RG

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I have been doing some reading as well...

Here is the formula for calculating drill bit speed...

For Stainless Steel, 200-300 series, drill bit point angle is 135-140 degrees, and speed is 20-40 SFM (Surface Feet per Minute)

For 400 series Stainless, point angle is 118 degrees, and SFM is 30-60

To convert SFM into something useful like RPM

RPM = SFM x (12/pi)

_________________

Diameter of drill bit

So for a #55 drill, 0.0520 inches, we get 2900 RPM for the drill bit speed...

If you used a 0.50 (1/2 inch drill) in the same formula, you get a speed of 300 RPM...

The smaller the bit, the faster the speed to achieve the same SFM.

The other interesting point, is that Stainless tends to "Case Harden" if drilled too SLOWLY...firm and steady cutting avoids this problem...

RG

Hmm... this is indeed fascinating. I suppose the standard charts don't handle the pin hole sizes we're dealing with, and we do need to extrapolate like this. So it is very likely, then, that spinning too slowly is in fact causing most of the problems we've always seen with broken bits and case hardening... Very interesting and unexpected!!

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