Broken drill bits and stuff

[Leftkeys]

Gents, hi. I’m in the process of drilling out the wire wheel hubs on the MFH 1:12 Sharknose. First, I’m going through drill bits at an alarming rate, both regular twist bits and some tungsten Proxxon style bits. My “technique” is to carefully drill pilot holes at 0.3mm and then expand to 0.5mm. The spokes are quoted at 0.4mm, I’m afraid to do less than 0.5. Second, even so, I’ve had drill bits break off in the partially drilled holes. I have been using hand tools and I have tried a small electric drill, as well, once I have some pilot holes drilled. Progress is negligible...

Any suggestions on the first issue, how do I avoid using up bits (some of my twist drills last less than 5 holes). And second, any thoughts on how to extract or drill out the pieces of drill bit stuck in the hub?

Thanks!

Bill

[blakebirk]

That's a tough one, I feel for you. I've built a couple of kits with the wire wheels, I use the high speed tungsten bits in a pin vise. I don't believe I did a pilot hole, just used the final size I wanted. I do break a few but not like you are describing. All I can say is be patient and use a gentile touch, as soon as you feel the bit begin to bind back it out and go again with a smaller bite. That's what's worked for me. Good luck!

[fatfrog]

I've watching people using tungsten drill bit with hand tools. I've been wanting to tell people that tungsten drill bits are not for hand tools. They are super hard and sharp so they are brittle. Very easy to break. They are design for machines where the spindles are super steady. Human hands are never that steady. Use High Speed Steel (HSS) drill bits. They are not as hard and sharp but they are more elastic so more forgiving and they work fine with most materials you find in a kit these days. Don't try to drill a hole too fast and in one go. Even machines don't do that. Drill the hole bit by bit. The metal get hot as you drill so the drill bit will stuck and prom to breakage. Using lubricant can ease up the heat generated and also prolong the sharpness of the drill bit. I use WD40 as a lubricant but of course other lubrication oils will work too.

Just my three cents.

[notime4me]

Try keeping as little of the drill bit out of the chuck as possible. The longer it is the easier to break just like a pencil.

[daves]

I had the same challenge drilling the wire wheels on the MFH 250TR. I use a small Micro Mart drill press at medium speed. .5mm is the correct size. Went thru a few drills till I got my technique down. Hand held is almost guaranteed to break the bits.

Dave

[danibear]

I used Sherline vertical mill + sensitive drill attachment + tilting stand attachment to do the new drills on Aluminium and brass as small as 0.4mm ID hole and as deep as 5 mm depth, no issues.

If you just use your bare handle to hold the dill, as some guys mentioned in the above posts, it will surely break at certain point, the deeper you go the more easily it will break. Because human hands shake....

If you are extending the smaller holes to bigger holes, I suggest use CNC carbid drills. They cut soft metals like Aluminium and brass very very easily, so that you can cut using less effort so that can reduce hands shake due to less force applied on the drill bit. But CNC carbid drills are brittle, it's kind of trade off. I practiced a lot.

OK, finally, how to deal with break drill bit inside the unfinished holes, pray.... that it still leaves a little of its shank outside.....that's all I can say..... that's definitely the worst nightmare you can ever imagine when drilling....

[Leftkeys]

Thanks, guys. Dave hope you own stock in Micro-Mark. Inspired by Miko and VR2 I’ve got a lathe and mini mill in process. Guess the mini drill press has to be added as well...meanwhile, I’ll try a little lube and see if I can make some progress.

[ferrarissimus]

I built many wire wheels from MFH in 1/12 and never had this problem. I use a Proxxon drill machine and use only normal 0.5 mm drills. Not more than one or two drills for all four wheels. But I dip the drill in boring oil before every hole. At the end you have to wash the hub carefully. Don't use too high drill speed to prevent too much heat.
regards ferrarissimus

[bestbalsakits]

yes, use lubricant.
Aluminum sticks to the cutting tool more than iron/bronze etc.

Wim

[Leftkeys]

Thanks to all, and a couple of PMs plus ferrarissimus and Wim, too. Using some lube oil really helped (forehead slap ). And the good/bad news is that it’s going to be really easy to switch to HSS bits because I’ve broken almost all those really cool looking tungsten bits. I’m going to miss them, though, sorta like wanting carbon fiber mirrors on your car. And using a rotary tool versus being cautious and twisting by hand had me breaking fewer bits. I think a mini drill press might be worth checking out, too.

Once again, the forum comes through with great advice and helpful suggestions.

The drilling will continue until my mood improves!

Bill