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drilling big holes


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i really don't fancy your chances with a hole saw but give it a go


personnely i would take the lump of steel to a engineering firm


If lump of steel was unmoveable then i would chain drill it.


Center punch the center of the hole then mark a circle the size of final hole. Now get about a 6 mm drill bit then mark a hole half a drill diameter smaller then you large hole (43mm large hole-3mm[6mm/2)=40mm) now center punch round this at about 6.5mm distances then drill out each of the center dabs until you get a chain of holes then a big hit with a hammer and the center should fall out then clean it up with a file and you have your hole.


If going for the hole saw make some coolant get some oil and mix it with water and detergent until you end up with something close to milk and then use it in a sqeezy bottle to flood the area once in a while to move away cutting and cool the teeth of the saw. I would also advise a wee bit of above mixture while chain drilling don't use pure oil as its cooling propertys are sh*t and it just smokes and slows cutting.


Sod the heater wheres my shades

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If you want a smooth hole, find a local fabricator with a rotorbroach. If you want a pretty good but not perfect hole then have it profiled (flame cut) which can be done by hand reasonably well or by CNC profiler very accurately. It'll be a tricky "home" job on 10mm plate.




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It depends on the finish and dimesional accuracy you desire.


1st option - center pop it drill small hole (12mm) to take metal out on middle to make it easier for following drills. go up in size to 43mm and drill..............Obviously you need a 43mm drill bit and a powerful drill press etc


2nd option as suggested chain drill it (lots of small holes drilled around the desired diameter of finished hole. You can then either try a hole saw (doubt it would work on steel) or axesaw the holes together to free up the inner scrap section. You could then file the half circle left from original drilling to a smooth finish.sadly NOT very accurate


3rd option iis to get the item flame cut at a fabricators..bit rough


4th option is to get it plasma cut...lot better finish and more accurate


5th option is to get it EDM'd (Electrical discharge machine) by a good Engineering company, commonly known as wire cutting...this will be the most accurate hole available and will run at approx 4-6mm per minute....expect to pay approx £45/hr for the service and allow for programing time on top


6th option is to get it jig bored at Engineering company.................possibly more expensive than EDM nowdays


Basically what do you need the hole for...........how urgent is it?...........where are you based?


I could get the work done for you FOC 😬

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Oopp's forgot........... 😳

Laser cutting.....very good option as suggested, but buy beer also as suggested due to cost for programing and cutting time will not come cheap if you walk off the street......................find a source and play dumb..............smile a lot and look lost. you may get the vote!


Us Engineers like to feel important and special......................... 😬 Problem is England refuse to reflect it in wages.. *thumbdown*

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No no no 😳


I'll try to explain, type of hole "cutter" you need it has two parts,


Front part, a round cutter (in fact a punch). The back part which is a tube that punch pushes into


First drill a pilot hole say 1/4" or what ever, you then with a bolt secure the punch one side and back tube on the other, slowly tighten the two together


Out pop a neat hole


Try here


On the other hand 10mm thick !! *mad*


R300 NUT



Edited by - Bafty Crastard on 27 Jun 2004 00:00:42

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Then again you could set it up in either a 4jaw chuck or on a face plate of a lathe and turn it out....this should only be tried by a person that know's wht they are doing with lathes..........!


Basically there are dozen's of ways to put 43mm hole through 10mm steel.


Wht you need to decide is how accurate you need it to be, the finish required and if you want to spend money to achieve it. List below goes from cheap to expensive, funny thing is that the quality, accuracy and finish follow suit to.


Cheapest - Chain drill and file

Cheap - Flame cut

Cheap to Medium - Drilling

Expensive - Milling

Quite expensive EDM, Laser, Plasma


If I can help then please call me at home 01952 240730

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Thank you very much Rob

I'm buiding my own exhaust manifold. I had the tube bend in shape, i am now complenting how i am going to attached them to the engine.

The idea is to recreate the plate which is welded to the pipes.

I don't believe this plate is available on the market, this is why i'm trying to make one.

But maybe I'm wrong *confused*




Emily, The Very Yellow 21

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in that case 10mm seems a bit thick for a car engine.


But get a gasket and wander down to a nice machining place and they more then likely be able to cut you out the same shape from sheet steel. if you are willing to do some cleaning up go to a welders or fabricators and get one of the old boys to cut it out using a gas torch If have worked with some of these old guys and some of them are amasing i have seen one guy burn nuts off and leave the bolt undamaged. *eek*


Sod the heater wheres my shades

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I have just Contacted Demon Tweeks and they have one left for a 1.4 1.6 K serie.


My engine beeing a VVC I am not sure if the flange for the smaller engine will fit on a VVC.

Can someone tell me please 😬




Emily, The Very Yellow 21

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Can't help you with the manifold sizes, but if DT can't help, try ringing Powerspeed in Kent or any other custom exhaust place which regularly makes K-series manifolds. When the GF and I were considering making up our own exhaust for her CBR1000 powered Ginetta, Powerspeed were more than happy to supply the collectors and manifold pipes for us to use to make up the exhaust ourselves.






p.s. in the end we bottled it, and got one made professionally...

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