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Hello:
Two things that would help when you drill holes:
1) clamp the work piece so it doesn't move.
2) put a piece of scrap under the work piece so there is less breakout.
Plus the melted chip suggest the drill bit was turning too fast. Cut slower or add a coolant.
Carl.
Hello, thanks for responding.Quote:
Originally Posted by carl blum
1) yep, that helps with all drilling, but I don't think it's important in this scenario. Or, at least I don't think it would help.
2) Actually, I would definitely not suggest doing this. When you drill, you build up heat and you want a clean cut out on the bottom. Because plastic cracks with pressure, putting pressure on the outward side actually cracks the plastic as you push down. I've had far less cracking when done this way.
The lesson I've been telling everyone when they buy a drill press is to use the slowest speed...all the time. Metal, wood, plastic, there is NEVER a good reason to use a bit fast. I have a cheap 150 piece set of brad point bits I bought 20 years ago for $30 that I still use. I do not throw away drill bits because you do very little damage to them if you're running slow and cool. Twist bits with metal is a different story, but brad point bits will last you many many many years if you abide by this rule.
Here's a video I made a few years ago showing my testing fast vs slow with the drill press: https://youtu.be/syvr608UPs0
This is NOT and never will be a BRAD POINT bit. It could be facetiously referred to as a 'nail point' bit. These are pretend brad point bits. In some cases as you found the hole edge is really a mess due to the 'scraping' action of the outer cutting edge.Quote:
Originally Posted by Make Things
A TRUE brad point bit has a very small point, like a brad! The true brad point bit has cutting 'spurs' at the outer end of its cutting edge. Normally the brad point bit has a flat cutting edge, as the outer perimiter of the hole is already cut by the spur. This results in a flat bottomed hole, very useful in some circumstances.
I had this discussion with the manager of a huge tool store in Perth. He argued with me that the Sutton drills I purchased WERE brad point bits. He'd been in the business 'for years' and knew what he was talkng about (he didn't). I needed to drill some precise CLEAN edge holes and though knowing the drills were NOT brad point bits I took a chance that being brand new the drill would provide a clean edge hole. They didn't.
The manager would not give me a refeund for the drill I used, the drill that PROVED they did not cut a clean hole. He needed the ok from Sutton [the Austalian manufacturer of the dril bit] So a quick call to Sutton and advising Sutton they were NOT real Brad point bits, they agreed with me and authorised the refund. Hopefully the manager is now wiser about brad point drill bits :-)
The attached images show proper brad point drilled holes, including a 32mm brad point bit. These holes were drilled with a Blum hinge drilling machine, used to drill the mounting holes for Blum hinges. These hinges require a flat bottom hole to endable correct ftting. The brad point bits do this. The drill bit used for this example have already drilled hundreds of holes in MDF and STILL produce clean holes in plastic/perspex.
When drilling perspex drill speed and cooling are important as the perspex does melt easily.
The drill bits you have are just ground with an inverted angle, instead of the 118 deg included angle.
You can improve the cutting action for clean edged holes by SLIGHTLY rounding the very outer edge/corner of the cutting edge with a honing/sharpening stone. This will help prevent/reduce material tearout.
Best wishes in your endeavours
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The bit that I bought was labeled as a COLT TwinLand Brad Point Wood Drilling Bit. I'm going by what the manufacture labeled it as. If they called it a chicken-do-little bit, I would have called it that in my video.Quote:
Originally Posted by Peter Sanders
Thanks for responding
HiQuote:
Originally Posted by Make Things
Please understand my response was not a criticism of your post, but a criticism of the invalid labelling by suppliers of what 'they' refer to aa brad point bits and to assist you and others of this misleading naming and what a true brad point looks like and how well it can cut.
Best wishes :-)
Peter
No, I totally understand. There's just so many different types of tools/fasteners/bits/etc it would be nice if there was a common consensus, but there's often times all sorts of mislabeling that goes on. There was another one...I can't remember what it was...that was similar to this.
Again, I love getting any sort of responses, even just for clarity ;)
