Making Minnie water gauge

[Mark BParticipant @markb43031]

I've had to walk away from my workshop having had 2 complete failures at making my water gauge fittings.

My problem is drilling the length of a round section of PB102 bronze. My drill bits suddenly grab and snap off leaving am impossible to remove bit of drill bit in my nicely machined part!

I'm being super careful in advancing my drill bits. I've even been modifying my drill bits to zero the rake angle which is a trick I use for working with brass which has the same issue, but this hasn't helped.

Is there a reliable technique for drilling bronze over a long length without ending up with a broken drill bit stuck in the middle of your work?

[Mark BParticipant @markb43031]

[SteviegtrParticipant @steviegtr]

In the past i have done what i call backing the the tip off. Not so much the rake , but blunting the tip. It ends up looking a bit like a Masonry drill.

Steve.

[JasonBModerator @jasonb]

You can try suds on the drill bit each time you back it out as small bits tend to get hot, don't put it on the bronze as it will contract.

The other option is to go say 8mm deep with a smaller drill then open up 4mm depth to finish size, back in with the smaller and go 4mm deeper then open up the next 4mm. This means you don't have much drill side in contact so less heating and binding. Comming in from both ends also helps

[Phil H1Participant @philh196021]

Mark,

I have recently had similar problems. I suspect half the problem was that I was treating the bronze like brass. Whether I tried old or new drills – no difference it was still really nasty.

What seemed to help in my case was to slow the machine right down and I used plenty of oil inside the hole and take it really easy in stages as Jason has said.

Phil H

[Grindstone CowboyParticipant @grindstonecowboy]

I have read – probably on here – that PB tends to close up around the bit, so Jason's suggestion would seem like a good approach.

Rob

[Mark BParticipant @markb43031]

Thanks for the replies. I've had another go and have managed to drill through a length of bronze. I think the comments from Jason about heat and Phil about slowing it down and hence generating less heat helped. I'd certainly noticed the bits getting hot on my failed attempts which resulted in grabbing / binding and breakage!

The bottom line is PB102 is horrible stuff to drill. I've managed it by slowing the lathe down to about 30rpm and super slowly advancing a drill bit in a small about, then enlarging it a couple of steps up. All with cutting fluid. It's taken ages to do but you just cant rush this stuff it would appear.

[Jeff DaymanParticipant @jeffdayman43397]

A spade drill (ancient design, nothing new) as shown in the link below can be easily made in the home shop by grinding a drill rod / tool steel blank to shape, or forging / grinding. They don't jam in brass or bronze as easily as twist drills. If they do break, pliers can be jammed beside the flat end to get them out, usually. Just food for thought.

https://www.grainger.ca/en/product/p/WWG10L356?gclid=CjwKCAiAjp6BBhAIEiwAkO9WuvL1MQ1H9SyDSaZkfLCqJkS0DipMtKoWm-4W3LFpEF6TNfTJjcvm0xoCxWIQAvD_BwE&cm_mmc=PPC:+Google+PLA&ef_id=CjwKCAiAjp6BBhAIEiwAkO9WuvL1MQ1H9SyDSaZkfLCqJkS0DipMtKoWm-4W3LFpEF6TNfTJjcvm0xoCxWIQAvD_BwE:G:s&s_kwcid=AL!3645!3!303439922840!!!g!597199332678!

[Nigel Graham 2Participant @nigelgraham2]

Oh, yes… I don't suppose there are many of us who have not encountered this.

If I read this right, as the drill heats up does it expands more than the bronze? This seems to happen with some plastics too.

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