Model Engine Maker

Help! => Mistakes, muckups, and dangerous behaviour => Topic started by: Sky King on March 31, 2019, 03:51:38 PM

Title: Dreaded "tink" sound!
Post by: Sky King on March 31, 2019, 03:51:38 PM
In the process of building Elmer's #29 Mine Engine and had gotten down to the cylinder and  drilling all of the 19 holes required.
Well, all went just fine until the last hole,one of the steam passages, had only a few thou to go and "ting"!!! @#%^&%#@ bit broke!!  Tried every trick in the book and never could get it to budge. Beat it up so bad I just threw it in the mistake drawer and started a new one. This time I drilled the passage holes first!!
Yes I was "peck" drilling,,only about 20-25 thou at a time...
Title: Re: Dreaded "tink" sound!
Post by: kvom on March 31, 2019, 03:55:55 PM
Did you spot drill?
Title: Re: Dreaded "tink" sound!
Post by: Sky King on March 31, 2019, 04:01:22 PM
Yep, and even milled a 1/16" starter hole about .125" deep to keep bit from wondering out due to the angle.
It was very close to being all the way thru when it broke.  Left about 3/32" piece..
Title: Re: Dreaded "tink" sound!
Post by: AOG on March 31, 2019, 04:14:13 PM
What were you making the cylinder out of?

Tony
Title: Re: Dreaded "tink" sound!
Post by: crueby on March 31, 2019, 05:11:57 PM
Adding oil between 'pecks' helps.  Might just have been a dull bit?
Title: Re: Dreaded "tink" sound!
Post by: b.lindsey on March 31, 2019, 05:22:19 PM
It always seems to be that LAST hole. One of Murphy's corolaries no doubt.

Bill
Title: Re: Dreaded "tink" sound!
Post by: Sky King on March 31, 2019, 05:59:47 PM
Aluminum

Bit could have been dull
Been around a while
Title: Re: Dreaded "tink" sound!
Post by: AOG on March 31, 2019, 06:23:22 PM
For me it usually starts with a dull bit. Since itís dull it tends to wander. When the wander gets big enough the side loads cause the bit to go tink. Itís amazing how well you can diagnose it after it happens but never see the signs when your actually working on the part.

Tony
Title: Re: Dreaded "tink" sound!
Post by: cnr6400 on March 31, 2019, 06:30:33 PM
Drop of cutting oil, especially for deep holes, and frequent pull-outs to clear ALL chips and brush on a little more oil, makes a big difference. Sharp drills are always better, of course.
Title: Re: Dreaded "tink" sound!
Post by: mklotz on March 31, 2019, 06:33:05 PM
If the cylinder is aluminum (or other non-ferrous material), you can use a saturated alum solution to dissolve the broken drill fragment.
Title: Re: Dreaded "tink" sound!
Post by: Kim on March 31, 2019, 06:38:46 PM
Sorry to hear about the broken bit.  I can relate to the "last hole" thing...   :(
Kim
Title: Re: Dreaded "tink" sound!
Post by: Sky King on March 31, 2019, 06:41:02 PM
Actually that is the first bit I have broken in a really long time,,
Canít say that for taps!!!

Never thought of the alum,, will give it a try and might be able to salvage something for another day
Title: Re: Dreaded "tink" sound!
Post by: jadge on March 31, 2019, 08:06:42 PM
Been there done that, more than once.  :-[

When drilling and milling aluminium alloys I use a squirt of WD40. It stops the chips "welding" to the cutting edges but allows the chips to be thrown clear of the flutes when the tool is retracted. The trouble with oil is that it is sticky so the chips tend to remain in the flutes. Was it a quality drill? You can bend a HSS drill a fair way before it breaks. I didn't extract a drill properly on the CNC mill before the table set off to the next hole. The drill must have bent at least 20į but it didn't break. Carbide is different, a bit off and it snaps.

Andrew
Title: Re: Dreaded "tink" sound!
Post by: Sky King on March 31, 2019, 11:33:40 PM
I don't think it broke due to side load or bending. I think it seized and twisted into,,,just guessing~!!!
But I will use every one of everyond's suggestions in the future!!!!