dubwarrior2
Part of things
"Open up, its the filth"
Posts: 576
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Sept 6, 2017 17:05:24 GMT
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Decided to snap the anti-rool bar bolt on my mk4 golf today. Decided against the nightmare of changing the wishbone so attempted to drill the rest of the bolt out..... took over 2 hrs using a mixture of HSS bits and carbide bits in a demel.
What I want is to just put a drill bit through the centre of the bolt and increase the sizes.
Hss bits lasted seconds!!!
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droopsnoot
Posted a lot
Posts: 1,438
Member is Online
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Sept 6, 2017 17:32:40 GMT
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Normally the thing that blunts HSS bits is running them too quickly. I've bought some in the past that show the optimum rotation speed on the packet, but I can't remember what make they were, and it seems to vary depending on the type of material, not just the diameter of the drill. www.vikingdrill.com/viking-Drill-FeedandSpeed.php
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Sept 6, 2017 17:48:51 GMT
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As a rough rule you need a slower bit speed the harder the material your drilling. Is your drill multi speed? If it's just a fixed fast speed you'll just blunt all your bits straight away, unless you are drilling wood or something soft like that.
If I'm drilling out bolts I'll start slow and increase the speed until I get some big bits of swarf coming away and then hold that speed, if the bit squeals then it's too fast. If you have a bench grinder you can re-sharpen your HSS bits, watch some youtube vids for instructions and you'll get the knack of it eventually!
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dubwarrior2
Part of things
"Open up, its the filth"
Posts: 576
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Sept 6, 2017 17:52:49 GMT
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I did whack the speed right down. Even dipped the tips in grease but just useless.
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Sept 6, 2017 19:52:04 GMT
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Try some decent cobalt steel bits, got me out of many a mess
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Last Edit: Sept 6, 2017 19:52:52 GMT by fordperv
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fad
Posted a lot
Posts: 1,781
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Sept 6, 2017 20:33:19 GMT
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Does depend on just how hard the snapped bolt is too. Some steel is just too damned hard.
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Sept 7, 2017 16:53:46 GMT
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Does depend on just how hard the snapped bolt is too. Some steel is just too damned hard. And the more inaccessible the bolt,the harder the steel .....
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fad
Posted a lot
Posts: 1,781
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Sept 7, 2017 17:06:13 GMT
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Standard law, that.
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Sept 7, 2017 17:47:12 GMT
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Titanium bits seem really good - used one when I had to drill out a stud in an alternator the other day.
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Sept 8, 2017 15:25:01 GMT
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I bought five Bosch Ines for 12 quid - they wore out eventually. I just keep sharpening them with the angle grinder.
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Sept 8, 2017 15:26:35 GMT
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If you're drilling out pressed studs from the balljoint, flatten the top with and grinder and then hammer them out.
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Last Edit: Sept 8, 2017 15:27:16 GMT by DavidB
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Sept 8, 2017 17:29:08 GMT
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When I have a difficult job I just ring Dormer they tell me the best drill to use I buy it and hey Presto out it comes
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It will come in handy even if you never use it
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You will be doing two things wrong with your HSS drills as they will do the job. Too fast rotation and not enough force applied.
For speed, simple thing to remember for HSS into steel is 10,000 divided by drill diameter.
However thats a good approximation of speed in perfect conditions in a pillar drill or lathe with cooling, for jobs like you are doing you cant cool or lubricate enough and cant control feedrate well and the bolt material will be harder so just aim for about half of that.
Lets say you were going to drill first at 4mm diameter to put a pilot hole through, thats what I would do. 10,000/4 = 2500 / 2 = 1250rpm max. You can see that depending on your bolt size the final drill might be going very slowly ideally, a 10mm drill will only need about 500rpm for example. If in doubt go too slow, it will work better than too fast.
The more important thing is feedrate, which on a machine is no problem to control but for a hand help drill all you can control is force applied. The key point here is that the drill must cut, you need to see swarf, if its not cutting its rubbing and will blunt very quickly as you have found.
The problem you might have now is that once you spend a time just rubbing and creating heat the bolt material can harden due to working, now you may need to get through that hard surface to make good progess again.
On the whole the things to remember are less speed and more force / pressure / feedrate to make sure you get cutting not rubbing and not much heat. Pressing hard enough to cut will create far less heat than being gentle.
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Last Edit: Sept 9, 2017 8:07:40 GMT by chris y
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Sept 14, 2017 8:34:16 GMT
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When I have a difficult job I just ring Dormer they tell me the best drill to use I buy it and hey Presto out it comes bahahahaha I see what you did there....
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Take the Next slot right coming up on the left.
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muffy
Part of things
Posts: 78
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Sept 14, 2017 19:26:44 GMT
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Hss bits are perfect for drilling out the bolt. But they need to be good quality set like sherwood etc. You do get what you pay for. Learn how to sharpen them and you will not need to buy new drills for years. As for coatings like titanium they are pointless for a home gamer.
Ben
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Sept 14, 2017 21:05:49 GMT
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When I have a difficult job I just ring Dormer they tell me the best drill to use I buy it and hey Presto out it comes bahahahaha I see what you did there.... Thanks I was half way through the post when I realised. For those who don't know Dorma and Presto are two of the best manufacturers of drill bits
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It will come in handy even if you never use it
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Sept 15, 2017 4:13:12 GMT
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Hss bits are perfect for drilling out the bolt. But they need to be good quality set NOT like sherwood etc. You do get what you pay for. Learn how to sharpen them and you will not need to buy new drills for years. As for coatings like titanium they are pointless for a home gamer. Ben Fixed that for you...😂😂😂 Sherwood and Wurth both use the same cheese for their drills, good enough for plastic,wood etc,but you can see by the sparks when you resharpen them, that they are soft.
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Sept 15, 2017 4:22:41 GMT
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Buy a decent,variable speed drill , a decent centre punch and a tub of cutting compound and you will be amazed at the results that are possible with good quality hss drill bits when your speeds ,feeds and cooling/ lubrication is correct. My years of experience of having to rectify the results of people trying to drill out bolts,making a hash of it,and then expecting minor miracles to sort it out,show that 95% of the time the speed was way too high. Enough pressure wasn't applied and,no matter what drillbit you use,if you start off by drilling it off centre,it's not going to miraculously find its way back into centre....😂
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Sept 15, 2017 8:43:50 GMT
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Sharp bits and less speed, watch the swarf or lack of it as it will give you a clue if the drill is sharp or the speed is wrong, try stop start the drill with pressure, if it's a small drill you cant go mad on it or it will bend or break.
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dubwarrior2
Part of things
"Open up, its the filth"
Posts: 576
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Thanks guys.
Interesting replies with regards to pressure.
I'm a strong believer in putting firm pressure on a drill to get it to cut and, as somebody else stated, prevent it from just "rubbing"
However
Having come from various engineering backgrounds, I was always told the opposite. That a sharp drill bit should do its own work and require very little pressure.
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