Steam Tractor 3/4" (Rudy K)

[Don1966]

Like Bill I think the annealing will help with your drilling. You might also consider using cobolt bits, they stay sharp longer and a little more expensive. Your doing fine Kim just keep at it.

Don

[Kim]

Thanks Don,
I might have to look for some cobalt bits.  I did get Titanium coated bits for this and that seemed to work OK (at least before!).  But I might try getting some Cobalt and see if that helps too.
Thanks for the help!
Kim

[zeeprogrammer]

I have no doubt success is around the corner.

Been following.

[Dave Otto]

Hey Kim

Sorry to hear about your troubles; at least you are able (so far) to repair and move forward.

I was going to ask about your procedure and type of bits? DOM should be a pretty easy task to drill and I doubt there is enough carbon to surface harden by quenching; but annealing cant hurt.

I'm with Don the cobalt drill bits can stand a lot more abuse than HSS; are you using lube? If you are not already I would consider trying some 135 degree split point screw machine length drills from a well known manufacture. Something on the order of Chicago Latrobe or Precision Twist Drill.

My guess is that you are probably pushing the drill too hard, it binds in the hole and breaks. Do you have a depth stop on your mill that you can peck down against. lower the stop say .05" drill up to the stop; retract, clear the chips add oil, lower the stop another .05 and do it again. Please tell me that you are using a good quality cutting oil made for steel?

I'm sure that you can get over this little hump in the road and move on to more fun things.

Dave

[Kim]

Thanks for the detailed list of pointers Dave.  More very helpful input!

If you are not already I would consider trying some 135 degree split point screw machine length drills from a well known manufacture. Something on the order of Chicago Latrobe or Precision Twist Drill.

I'll look at that.  I've got inexpensive HSS Titanium coated bits that came in a 10 pack.  So likely not the highest quality, though it is exactly what I used to drill all the rivet holes in the wheels and in this part so far.  They do seem to dull after a few dozen holes though.

My guess is that you are probably pushing the drill too hard, it binds in the hole and breaks. Do you have a depth stop on your mill that you can peck down against. lower the stop say .05" drill up to the stop; retract, clear the chips add oil, lower the stop another .05 and do it again.

Well, this is pretty much what I'm doing.  The tube wall is only 5/32" (0.156") thick, and I'm doing it in 3-4 pecks about 50 thou each.

Please tell me that you are using a good quality cutting oil made for steel?

Another good question.  I'm using the lube I happen to have that has always seemed to work on steel - Tap Magic.  It lists lots of materials and then says "all cuts on all metals".  I've got A-9, but that's more for Aluminum. And Rapid Tap, and Grizzly's Viper Venom. But the Tap Magic is what I've been using on steel.

Thanks for the help Dave,
Kim

[Jasonb]

Kim, how are you starting the hole? spot drill, centre drill or just going straight at it with the drill?

[Kim]

Hi Jason,
I've done some of both.  Initially, I was religiously spotting every hole.  But sometimes that seemed to cause problems because the bit would grab the edge of the spot and go all wonky.  Or sometimes the spot would be off a little bit.  If I noticed (which means it was off by quite a bit) I would adjust the position so the bit was straight down.

After reading a different thread (fairly recent one) on drilling small holes, someone had suggested not spotting and just approaching the surface really slowly and letting the tip of the drill make the start.  So I tried that, and it seemed to work equally well.  So for these ones that have broken yesterday, no, I didn't spot them.

I don't think that's the problem.  but I could be wrong.  Something I don't understand is the problem for sure!
Kim

[Dave Otto]

Hi Kim

You should be able to drill 3X the drill diameter on the first peck but the way you are doing it should be fine. My guess is that the questionable quality of the drills is your main issue; the TIN coating probably  isn't buying you anything; I would just get the bright finish or steam oxide. I like I said before I would try the 135 degree split point drills in screw machine length. With the split point drill you wont need to spot the hole, although you will need to be careful starting on the round tubing.

I have sets of screw machine drills and find the they work for the vast majority of the work I do; it is very seldom that I reach for a jobber length drill.

Dave

[Kim]

Thanks everyone for the many helpful suggestions and tips.

I spent a long afternoon in the shop and made some good (if somewhat glacial) progress.  I started by finding my sharpest center.  Turns out my spotters jumped around a lot - they were all single flute and didn't have much of a point. So I found a nice sharp center and used that to spot all the holes around the circumfrence.


I setup a fence at the back of the tube to get all the holes at the correct longitudinal spot, so all I had to worry about was positioning them rotationally.  The location isn't that critical - these rivets are just for looks.  But I do want them to look nice, straight, and regularly spaced.  This picture shows the makeshift fence I used the centering and drilling operations.


Next I got a new drill and looked at it. It was a 135 degree bit, and it looked 'pretty' sharp.  So I used that.  I took the hole very slowly.  I was drilling scared.  It took me a while but I got one hole done, without breaking anything. Then another one. And another one.  By the 4th hole, I was starting to think I might be possible.  This is where I started to think I might finish this project someday. The hole circled in red is one with the bit broken inside it.  The 4 circled in green are the ones I just did!


And about 2 1/2 hours later, I had all 25 of the remaining holes complete.  All with that one bit!  This is my victory shot after I broke through that last hole


In the end, I'm not sure the annealing really did much. It was still hard stuff to drill.  So I think you were right on this Dave.

So what did I do differently? Mainly, I just took things really slowly and carefully.  And I listened...

I still did 50 thou pecks, clearing chips & lubing in between. The last 50-60 thou was always the scariest (third peck). This is where the bits broke each time before.  It seems like the steel is a little harder close to the ID, though I have no clue why.  Things sounded different when I got to this point, so I always went VERY slowly here.  And when they sounded 'different' I'd back out and clear chips & lube again.

I think the listen part was very important. I could hear a different sound when the going got hard - when it started to break chips that were too big, or too hard, or something.  I don't really know what I was hearing. But it sounded different. So I slowed down and I cleared chips more often. And it seemed to help.

And if I was getting that sound too much, I would take out the bit and try and hone it a little. This really helped too!  I didn't use any sharpening jig, the bit was just too small, I just did it by hand on a diamond stone.  I did this 3-4 times during the 25 holes.  One time my 'shapening' made it worse - oops! - but it didn't break.  It just 'felt' like it wasn't working as well as it should.  So I took it out and tried sharpening it again.  Then it worked great.

I could tell a big difference after sharpening.  The chips would come out nicer and it would cut faster.  But I always went slow and listened carefully to the drill.

One more victory shot, just because I can!


Now I just have to go drill out and plug that hole with the broken bit in it, and I think I'll be able to move on!  (I'm sure you'll all be thrilled not to hear me whining about these holes for a while!  )

I still really don't know why things went south when I started doing this set of rivet holes.  I probably just started to get too confident or something.  But wow! this really taught me to slow down and LISTEN to the drill. I think that is what made all the difference.

Thank you all for your help in getting me past yet another hurdle in my machining apprenticeship
Kim

[Steamer5]

Hi Kim,
 Keep at it...you'll beat the  !!

Been enjoying posts, had a thought when I read your wheel sager, on the front wheels instead of  adding the grippers(?) to the OD, how about starting with a heavier wall tube & turning it down & adding the rivets for decoration. Didn't bother suggesting it earlier as you had done it, & looked like you were having fun!

Cheers Kerrin

[10KPete]

Well, I think it's safe to say that now you are tuned in to drilling holes. Same stuff applies to larger holes also!

 

Pete

[zeeprogrammer]

 

Awesome.

And a great post.

[Kim]

Thanks Kerrin, Pete & Zee!

Kerrin, that's an interesting idea about carving the grouters out of the wheel rim itself. I'd have to think about how to do that.  Don't know if I could come up with an easier way to do that, but its in interesting thought!

Kim

[b.lindsey]

Well done Kim, we knew you would prevail

Bill

[Don1966]

Well done Kim on the project and learning Process..........

Don