Cuttting 4.75" diameter hole in lead

TimH · Jan 27, 2016

I have to cut a 4.750" diameter hole through a 4" thick piece of lead. Thinking of using a hole saw but thought someone here might have a better idea. I have a feeling the holes will have binding problems.

yardbird · Jan 27, 2016

Not only that but it seems like a hole saw would load up like crazy.

I can see the shit being like cuttin play dough?

If you have radial arm post drill? Poke a pilot then try trepanning it? Might be able to get away with babying it on a BP for a one time deal? Maybe not?

Brent

magneticanomaly · Jan 27, 2016

I think the key will be not to go crazy with feed just because the lead is so soft that you can. A hole-saw will work, with light feed and frequent pecking and flushing out the chips. So would the biggest twist drill yo have for a pilot, then bore to size. Make sure the work does not squish out of your fixturing....another reason to feed lightly.

crossthread · Jan 27, 2016

Tim if you have to do this often and the rest of the lead is not a complicated shape, it would be a whole lot faster to recast the lead and machine to size.

jscpm · Jan 27, 2016

Using a hole saw is probably a reasonable idea, but you may have to clear chips frequently.

An annular cutter will clear chips better, but is much more expensive.

Conrad Hoffman · Jan 27, 2016

I wonder if a Forstner bit would work? Not sure if they come that big!

CalG · Jan 27, 2016

Depending on a lot of details, this might be a job for a short length of pipe and a hydraulic press.

Chip Chester · Jan 27, 2016

There are large Milwaukee hex-drive bits that are much like Forstner bits, but they have teeth around the edge too, in addition to the blade. They have a stout screw point as a center locator, and are self-feeding in wood. If you have the horsepower and workholding, you might experiment with one of those.

If I had to do it, and only the one, I would chain-drill the perimeter, then saw the webs to get rid of the center. Then, I'd go back with a boring head and widen it out to spec. But that's only for one...

For many, I'd come up with a heated core stamp that melts its way in, at least for roughing.

Chip

HuFlungDung · Jan 27, 2016

Waterjet maybe? I've heard they can cut cheese with those

MCritchley · Jan 27, 2016

I have heard freezing the material helps. It stiffens it up and allows you to cut not deform.

Limy Sami · Jan 27, 2016

Been here done this -for a 1 off the easiest way is to chain drill and press a piece of sharpened tube through to size the hole ............ or if it's close tolerance, a boring head of some description.

Speed needs to be very low for boring, tools need to be sharp zero of negative rake to stop dig ins and coolant or oil, for chain drilling dub the drill as you would for brass.

adama · Jan 27, 2016

You need to go carefull melting it, if its for certain scientific uses melting it can contaminate it enough with things in the atmosphere to bugger it up for certain radiological uses.

onecut · Jan 27, 2016

Try a hole saw swipe the point of teeth with a stone to flatten the point use coolant liquid soap will do run slow-apparently it works

Illinoyance · Jan 27, 2016

If using a hole saw. drill several holes just inside the final diameter to allow chips to clear.

Metalcutter · Jan 27, 2016

Carefully handle the chunk. Setting the part down even with a little drop will change the dimensions. When you start milling watch out for the bullets. Two hundred rpm to start and do it in the middle where you have space to practice.

Regards,

Stan-

rcoope · Jan 27, 2016

HuFlungDung said:
Waterjet maybe? I've heard they can cut cheese with those

You can't practically waterjet it because it will turn the contents of your waterjet tank from benign waste into toxic waste that will cost many thousands to dispose of.

Interesting suggestions here. The forester style bit seems like a good choice but the biggest I saw was McMaster 2890A51 is $306 and it's only 4". Boring would seem more viable at 4" thick but I'd vote for re-casting it if you had to do any number.

PeteM · Jan 27, 2016

Recollection is that a hole saw made of Kryptonite will work.

More seriously, a hole in the periphery and a very coarse tooth band saw (brazing or welding the blade) could work. If accuracy is needed, it could likely be bored to final size with a sharp positive rake cutter. Lube the teeth so they don't load and end up half cutting and half melting the work.

Don't know the safety implications of this. Given the problems of lead poisoning, especially with young kids around in a machinist's family, you sure don't want to make anything but large chips and then clean them up thoroughly. Small particles caught up in the air, clothing, exhausted through a vac, etc. could be a problem both in a commercial shop (think OSHA) and a home shop (think kids).

paracongo308 · Jan 27, 2016

Take a piece tubing, turn the outside to 4.75 put a knife edge rake on the inside diameter and cookie press it out in one of those cheap hydraulic presses.

PeteM · Jan 27, 2016

paracongo308 said:
Take a piece tubing, turn the outside to 4.75 put a knife edge rake on the inside diameter and cookie press it out in one of those cheap hydraulic presses.

4" deep? Personally have no experience punching a hole lead sheet that thick.

TimH · Jan 27, 2016

The piece of equipment we are working on weighs well over a ton. The cavity the hole is in is about 18" deep. It already has a 3 1/2" hole in it. So I plan on making a plug with a pilot hole then hole saw it out. Not sure how well my idea will work

yardbird said:
Not only that but it seems like a hole saw would load up like crazy.

I can see the shit being like cuttin play dough?

If you have radial arm post drill? Poke a pilot then try trepanning it? Might be able to get away with babying it on a BP for a one time deal? Maybe not?

Brent

Cuttting 4.75" diameter hole in lead

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