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Raj1 1st January 2003 08:27 PM

drilling holes in chassis
 
Hi,
any tips on getting a good shape hole in a 2mm thick sheet of steel with a drill, the hole needs to be neat to allow mounting of a mosfet!



Thanks
Raj

Mark A. Gulbrandsen 1st January 2003 08:53 PM

Raj,
There are a number of ways to drill it but you will most likely end up with at least some burr on the exit side of the hole after drilling through. Also, there may be a smaller burr typr ridge around the side that you are drilling from. The causes for this can be drill running at the wrong speed, wrong rake angle to the drill itself, and too much pressure on the drill bit. A proper cutting drill bit will give out a continous spiral chip that does not end till you are all the way through the plate. De-burring the hole is a very common thing to do and although there are drilling jigs available for hand drills to keep the drill sauare with the plate....thats all it guarantees. You would get the best results with even a small drill press as the speed can at least be set to near what it should be, although feed is still manually controled. Also drilling at a very high speed with the bit will only burn it up in a hurry!! Especially if you are drilling through steel. Proper bit speeds and proper feed are imperitive to drilling excellent holes. Get a copy of "Machinery's Handbook" at your nearest library and you will find all this pertinent data in there...plus so much else that it may leave you in a state of bewilderment for a while.....
Mark

haldor 1st January 2003 09:41 PM

2 mm thick is basically sheet metal. You will get much cleaner results with less distortion if you use a hand punch. You don't say what diameter hole you need but a Whitney handpunch should be able to handle it.

http://www.vansantent.com/Hand_punch.htm

If a punch won't do what you need (because the hole is too far from an edge) then the best results will come from clamping the sheet metal between two pieces of wood and drilling through the stack. This way the sheet metal will be supported from above and below. This will greatly reduce distortion in the sheet metal from drilling.

Phil

Raj1 1st January 2003 09:45 PM

phil
 
The hole needs to be big enough to pass a m3 screw thru it.

Thanks
Raj

Bobken 2nd January 2003 12:23 AM

Re: phil
 
Quote:

Originally posted by Raj1
The hole needs to be big enough to pass a m3 screw thru it.

Thanks
Raj

Hi Raj,

Not much use for this particular job, unfortunately, but for any larger holes in future, a stepped cone drill is excellent in use, I have found.

Regrettably, the smallest size hole mine will drill is 4mm, but it will go up to 20mm with the same drill, in 2mm 'steps'. I know that larger ones are available, but I don't know if any smaller ones are.

Because of their unique construction, they are much sturdier than most drills and will cut a far more accurate and clean hole.

Usually, you will find that with a conventional twist drill, the hole will 'triangulate' to some extent in sheet metal, even if it is used in a pillar drill, due to vibration and the long unsupported length.

If you feed it carefully, you can use the shoulder on the start of the next size up to remove the burr on the 'feed' side (it is intended for this) and then by turning the work over and lightly drilling from the other side, you can remove the burr from that side too.

I bought mine a few years ago, but didn't use it until recently, as I have good sets of 'proper' drills, and I initially thought that using this stepped one was rather amateurish and naff!

However, having tried it for chassis cutouts in some 1.5 mm stainless steel (which is very hard and gritty to machine) to my surprise and pleasure it really does work well, and it retains its 'edge' too.

Also available, but I have not tried one as the resultant hole sides are slightly tapered (which for an engineer, is just not on, but for most electronic purposes it would probably be quite OK), is a similar tapered cone drill (with no steps) which will give an infinite number of sizes between the smallest and largest.

I hope this is of some help to you in future.

Regards,

Raj1 2nd January 2003 08:44 AM

Thanks Guys!
 
Thanks guys for your response, Happy New Year!!!!


Raj

mjounot 3rd January 2003 07:56 PM

I use Black +Decker "Bullet" drill bits . They make nice round holes.I think they are called pilot point bits. Mike


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