Jump to content
  • Current Donation Goals

How To Drill Lug Holes


TJGladeRaider
 Share

Recommended Posts

Just to clarify the calculations...

HSS Twist Drill Recommended Speeds and Point Angles

Type of Steel.............Point Angle.........SFM

Steel < 180 HB..........118....................80-110

Steel 180-280 HB.......118....................45-70

Steel 280-380 HB.......135-140.............30-45

Steel >380 HB...........135-140..............15-25

Stainless Steels..........................Point Angle...........SFM

Stainless steel 200-300 series......135-140...............20-40

Stainless steel 400 series and PH..118.....................30-60

RPM =

SFM x (12/pi)

Diameter of drill bit

In my example I chose this, Stainless 300 series, and I chose the high end value of 40 SFM

Drill bit #55 is 0.0520" diameter

Plugging the variables into the formula

40 X (12/3.14)

0.052

40 X 3.82

0.052

152.8

0.052

= 2938 RPM

Me thinks were onto something now, and will get good results...

Bill shamed me into going to get myself a small drill press and start offering this service, although I have been doing some research for a few weeks with that idea in mind, he gave me the push I needed to do it. I dont' believe in half jobs, or guessing at this stuff, with this data it should be easy to do...

RG

Link to comment
Share on other sites

Me thinks were onto something now, and will get good results...

Bill shamed me into going to get myself a small drill press and start offering this service, although I have been doing some research for a few weeks with that idea in mind, he gave me the push I needed to do it. I dont' believe in half jobs, or guessing at this stuff, with this data it should be easy to do...

RG

Awesome Rob!! I'd be proud to send you a guinea pig.

Link to comment
Share on other sites

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

You are correct. The smaller the bit size the higher the RPM's.

I was thinking on my current 110 TON Chilled Water Air Conditioning project. We use bigger size drill bits every day not this tiny ones. I need to separate my job from my hobby, two completely different fields. Now you know why my username is vaccum....NO it is not misspelled....vaccum is the rep for vacuum.

Cheers, vaccum

Link to comment
Share on other sites

wow!!!! i'm speechless.

i decided to do some last minute reading on lug hole drilling before tackling my wm 1680 and cam across this thread.

bill, chief, and rob.....you guys are an amazing wealth of information. i think i will put my lug drilling on hold for now. i'm especially glad i didn't attempt to try the lughole re-bias project first.

the craft has come along way from just punching through the lug holes with a dremel or a hand-held drill. my hats off to you guys. :thumbs:

Link to comment
Share on other sites

  • 1 year later...
  • 8 months later...
  • 1 year later...
  • 1 year later...

To add to an old thread (because I just finished up mine on my 5512) - I don't have a proper drill press so I was a bit nervous about chamfering the holes afterward.

One thing I tried on my practice case before "going live" was an old hand crank drill. Yep, straight from my grandfathers toolbox.

I just rested the bit on the case at the proper angle and cranked the handle letting just the minute weight of the drill put the pressure. About 6 or 7 cranks did the trick perfectly! It really let me control the process too!

So if you don't have the proper set-up - or are afraid of going too far, this is just the trick!

Link to comment
Share on other sites

  • 1 year later...

That's how I did my seadweller and. Submariner no problem at all very simple to do , now getting strap to fit pins ( SEL ) end links was another matter then getting it to fit watch was a night mare all sorted in the end though .

Link to comment
Share on other sites

  • 1 year later...

I know this is an old thread, but I was wondering if anyone knows the answer to these questions below, as I have the same question.

What is the correct method for drilling lug holes from the inside, on watches which aren't drilled right through?

 

 

Is this drilling doable just from the inside??

 

Anyone know please?  Is it done with a tiny angled drill such as a dentist type drill?

Edited by SSTEEL
Link to comment
Share on other sites

I know this is an old thread, but I was wondering if anyone knows the answer to these questions below, as I have the same question.

Anyone know please? Is it done with a tiny angled drill such as a dentist type drill?

+1 to this question. I've been wondering the same thing myself.

Any ideas would be great.

SSteel, I'm hoping to get a drill press within the next few weeks and will try a few things to see if I can drill the lug holes on these types of "half-drilled" lugs.

I'll report back back with any progress I make.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...