Bi-Metal hole saws

They'll do a great job as long as the material is not too thick. I have used them on 1/2" CRS with good results.

Lewis.

They work great for stuff that isn't too thick. They don't eject the chips like a twist drill does, so you need to flush them out occasionally. A thin aerosol penetrating lube works good for that, with a tube nozzle and is also a good coolant. Grey cast iron is self-lubricating, but you'll need to clean out the dust. They need a lot of pressure to cut well--hopefully, you'll be using a drill press?

Ken Grunke

Read the other responses. Right on...

However, depending on the material and thickness, check out the Hougen self-ejecting plug hole saws. Especially if you are doing this on a drill press.

If you think you are going to drill those holes by hand, get a gym membership and an expensive drill at least 6 months ahead of time. :)

Cool :)

AJS

Low pressure air blown constantly into the cut area to cool the saw and extract the cuttings works wery well in cast iron. I hole-sawed several hundred 4-1/4" holes through 1-1/4" thick cast iron using this method and a magnetic drill on a vertical surface.

RJ

thanks guys. It will be drill press for the mild steel and unfortunately hand for the cast iron block. It's a tight space so I may have to get an air drill or something down there. I was asking a few tool shops and they said it couldn't be done with these :) Clearly it can. (as I thought)

AJS

One thing I didn't see mentioned is that all bimetal hole saws are not the same. If you're buying just a couple for specific jobs it's worth buying good ones. The best I've used are Lenox, Sandvik are a close second, and Starrett are typical of what I'd consider barely acceptable. If you're looking at other brands a couple features that the better tools seem to have are variable pitch teeth and a solid, rather than stamped and formed, back.

The tip on drilling a couple 1/4" tangential holes is a winner. The difference it makes is amazing. Instead of churning the chips around in the saw kerf, they end up in little sand castles on the drill press table right under the 1/4" holes.

Ned Simmons

Another consideration -- don't expect a *pretty* hole, such as you would get with a boring head in a milling machine (and lots of passes). This will be rough -- *far* from the kind of hole you would want to run a piston in, for example.

You didn't say what function the holes in the cast iron will serve, nor how deep the holes would have to be.

Good Luck, DoN.

Well I am in Australia so my choice will be finding the best of what we have available. I will look for the solid back Etc :)

Cool.

AJS

It will be an inch to an inch and a half deep I think. I am hoping to thread the hole. It will be for an oil return line. Low pressure. It's either drill the block at this location or drill the sump and feed to there. I would like to thread the return point and the sump is quite thin.

AJS

If this is a car or truck engine block, beware of hidden oil or water passages, or destroying the structural integrity of the block. One little stress riser, and that crack is off to the races... :-(

Given the same choice of drilling on the cast iron block or the oil pan, I'd pick the pan every time. You can make or buy a simple "floor flange" adapter to thread your return line fittings into, and clamp it to the pan with a hand-cut gasket and some RTV FIPG, and an easy to make backing plate for even clamping pressure.

Or machine a simple flange adapter and weld or braze it to the pan.

Hell, if it's low stress, I'd try something quick cheap and dirty like a Myers Hub. (Clamp-on hub for NPT threaded electrical conduits, seals to the flat surface with an O-ring. If the O-ring is compatible with the oil, you're done in seconds.)

Best part is, if you drill the engine block and something goes seriously wrong, you are royally screwed - the engine block is now trash. But if you screw up a stamped steel oil pan, they can be welded and patched easily, or worst case trashed and (fairly easily in comparison) replaced.

-->--

Starrett hole saws are available here in Australia from J.Blackwood and Son. They have branches in all capital cities and in the larger country towns.

You've already gotten another followup from this which tells you why drilling the engine block is such a bad idea.

Aside from that -- look at the side walls of the hole saws you are contemplating. They need to be at least as tall as the thickness which you intend to drill through. And usually there is a bit of projection of the arbor into the saw which might hit the cast iron before you got that deep.

And if you are planning on tapping it -- remember what I said about it not being a pretty hole. It may be too rough to tap cleanly enough for the threads to seal.

To do this right, I would suggest mounting it on a milling machine and using a boring head to sneak up on the desired size, which would give you a much better finish -- if the block did not develop a stress riser as described in the other followup.

The fitting of a flange to the oil pan is a *lot* better idea in terms of how to recover if (when) something goes wrong.

Good Luck, DoN.

The block is used for turbo and non turbo application so there is a marked area when the turbo engines are drilled. That's where I would go into. I am still deciding between the two. I would prefer the block but I will probably go for the pan.

AJS

It's the factory location for the oil return. I might be better getting an appropriate sized drill bit for this job. The advantage of doing it this way is not taking the motor out. Once the motor comes out I have far to many other jobs that I will need to do in there. Hoping to delay them until later. Looks like I might go for the pan. Get a spare one and do that first then the swap over will be much faster.

thanks

AJS