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Post by mahking51 on Feb 10, 2008 18:30:28 GMT
Hi All,
I just wondered if anyone can point me in the right direction to get a METAL CUTTING 90 degree Countersink bit that will go in my pillar drill?
I need to c/sink some slotted screw heads flush into a piece of 3mm guage plate and have bodged it so far with a woodworking bit which justs gets hot and 'smears' the steel giving a raised lip which has to then be removed. I'm also probably using too high a speed. Said bit is then totally burned and u/s.
When done the screws have a small groove around the heads as the c/sink is larger than needed, looks terrible!
Any thoughts welcome please.
Regards,
Martin
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Post by engineerone on Feb 10, 2008 18:44:48 GMT
martin, metal screws are not 90 degrees on the head. actual angle is 60 degrees included. basically try a screw supplier. depending on where you are, actually check out the post from dom in relation to eye bolts, and then check some of the suppliers mentioned there. paul  |
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Post by andy on Feb 10, 2008 18:48:01 GMT
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Post by johnboy on Feb 11, 2008 6:33:58 GMT
Don't know where Paul gets the 60deg included angle from but according to DIN 963 for slotted c'sk screws an M6 screw has a head dia of 11mm x 3mm high which gives an included angle of just under 80 degrees. You need a proper metal cutting countersink from someone like Buck and Hickman (easy to find on google). Gauge plate is pretty tough to machine even before heat treatment, use a slow speed and plenty of cutting fluid.
John
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Post by mahking51 on Feb 11, 2008 8:15:09 GMT
Many thanks guys, just ordered a set. Re the srews they are wood screws holding the guage plate to a piece of walnut hence the 90 deg angle.
Cheers,
martin
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Post by engineerone on Feb 11, 2008 10:49:15 GMT
johnboy, it's in the name, engineer  old english pan heads were neither 90, nor i think 80 degrees. they were much nearer the thread angle for whitworth standard threads. anyway always happy to update my knowledge. paul |
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Post by engineerone on Feb 14, 2008 22:30:45 GMT
well i finally looked at one of my machinery handbooks sorry for the delay  however it was not as helpful as i wanted, since it is an american one dated 1934, it only shows the head details of american standard threads both metal and wood. however, the included angle of the countersunk head on an american standard wood screw is max 82 degrees , min 80, which i must say surprised me. but of course what that means is that from the horizontal upwards, the angle is 49 degrees, which is a little more confusing than i first thought. so i too have learnt more, must read more often and more quickly ;D paul |
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Post by wrongnail on Mar 17, 2008 11:23:10 GMT
If the screw heads are similar in shape to the head of the screw on a Stanley cap-iron, then I would think you need to mill the recess for the head. You might manage this if you have a 4-jaw chuck to fit your lathe head, an appropriate size of 'end-mill' and some means of presenting the work to the cutter. I'm no expert at metal cutting, so maybe your drill will have a suitable speed for this function. In which case all you need is a HSS end mill of the right diameter. (These metal cutting, end-mills cut super-clean motrtices in most hardwoods by the way.) You might also need to drill a 'dimple' to guide you for the hole which you are going to drill to take the thread. So it means changing bits for each hole, to be accurate.
Hope you can follow my jumbled reasoning..
Best of luck.
John
PS. It occurred to me, the screws you have might be countersunk. So I have checked the threaded, metal screws on my guillotine. The angle of the countersink, is the same as a wood-screw in this case. I believe they might be equivalent to a No 16 woodscrew, but I have no means of checking this accurately.
So if your screw/bolts are c/sunk wouldn't a normal metal cutting countersink bit do the job?
John
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