Drilling large holes

[firebird]

Hi

I have the need to make some holes in 1/2 steel plate ranging in size from 5/8 up to possibly 1 inch. I have an x3 mill which should be powerful enough to handle the job. Would blacksmiths drills be ok or would I be better off buying a boring head.

Cheers

Rich

 

[joeby]

I am not familiar with the x3 mills, but it takes a good bit of torque to run a 1" drill in steel. Then you also have the problem of "daylight" - do you have enough room to fit a 1" drill?

If you haven't an immediate need for a boring head, how about drilling the holes 1/2" or so, and using a four or six flute end mill to finish them?

Kevin

 

[stevehuckss396]

Take a look at some hole saws. If the hole doesn't need to be exact, use a 1 inch hole saw. It can be chucked in a 1/2 inch chuck. If hole placement and size are critical, try a 7/8 hole saw and finish with a boring head.

 

[Jasonb]

If you work up from 1/2" in 1/16" steps using blacksmiths drill then the X3 will be OK, I've done it on mine, just use a very slow speed as the size goes up. You may also want to lock the quill and feed the head down which reduces the chance of a snatch particularly once you get over 3/4"

There is still a fair bit of room under the head with a blacksmiths drill, not much less than if using a than a boringhead.

If the holes need to be accurate with a decent surface finish then a boring head is the better bet, with brazed carbide bits, I have a 2" one from Chronos. Or if the plate is not too big you could clamp it to a faceplate and bore in the lathe.

Jason

 

[Bluechip]

Hi Rich

I use these

http://www.axminster.co.uk/product-Axminster-TiN-Coated-Stepped-Bit-Set-20339.htm

Quite accurate, you can get the same sort of thing from other suppliers.

Dave

 

[firebird]

Hi

Dave, I have some step drills but each segment wont be big enough to go through 1/2 inch steel plate, its a good idea though. I could get somewhere near and then file out.

Jason, thanks for confirming the x3 will cope with blacksmiths drills. The part will be too big to fit in the lathe so I can't do it that way.

Steve, I have a set of hole saws that I have used on wood. Will they cut steel ok or is there a special type?????

Kev, another good Idea, I don't have any end mills larger than 1/2 inch though so I will have to look into the cost.

Cheers

Rich

 

[stevehuckss396]

Steve, I have a set of hole saws that I have used on wood. Will they cut steel ok or is there a special type?????

I have used my saws on mild steel up to 3/8 thick. Use cutting/tapping fluid and it will go well. For stainless steel we use saws with carbide teeth but they are very $$$$.

Medium speed, push medium hard, and lube often.

 

[Jasonb]

I have a set of hole saws that I have used on wood. Will they cut steel ok or is there a special type

As long as you don't use the really cheap ones you should be OK, I've used Starret, bosch and the red screwfix ones. Buy the Blacksmiths seem better.

The only problem with endmills/slot drills is you will need a MT3/R8 collet holder capable of taking the 1" shanks.

Jason

 

[Tin Falcon]

Just a note here for the state side folks the "Blacksmiths " drills are called reduced shank or silver and deming drills on this side of the pond.
As far as the hole saws I think I would lean toward bimetal type of blade.
Tin

 

[firebird]

Hi

Thanks for all the info. At this point I think I'm leaning towards a boring head. More expensive but I think will be more useful in the long run. Probably a daft question here but can a boring head be used as a fly cutter.

Cheers

Rich

 

[Tin Falcon]

can a boring head be used as a fly cutter?

My answer would be yes but why. IMHO it would put un needed wear and tear on the boring head.
Fly cutters can be had for a fraction of the cost of a boring head. Or can be made .there are threads here where guys have made fly cutters and IIRC boring heads although a boring head is more work.
I have used a fly cutter as a boring head as well ,that is if the dimension is not real critical. Remember to watch the tail end of the cutting tool it may do funny things if it touches the work.
Tin

 

[firebird]

Hi Tin

I have one of those cheap fly cutters but didn't get on too well with it, although thats probably pilot errror. I just wondered, as you do on sunny Sunday afternoon.

Cheers

Rich

 

[itowbig]

in believe rake60 post some plans for a fly cuter here. i made one very easy to make. if i can find it ill post back.

 

[itowbig]

here ya go fly cutter

 

[firebird]

Hi

Cheers Sid

Rich

 

[Bluechip]

Hi

Dave, I have some step drills but each segment wont be big enough to go through 1/2 inch steel plate, its a good idea though. I could get somewhere near and then file out.

Jason, thanks for confirming the x3 will cope with blacksmiths drills. The part will be too big to fit in the lathe so I can't do it that way.

Steve, I have a set of hole saws that I have used on wood. Will they cut steel ok or is there a special type?????

Kev, another good Idea, I don't have any end mills larger than 1/2 inch though so I will have to look into the cost.

Cheers

Rich

Rich,
Sorry, did not fully explain. I did several 1" holes in 12mm steel last year. Run the drill in till it runs out of step length. I then had a 1" dia hole half way thro. with a 7/8" 'pilot' as it were. Then reverse the job. You may just be able to do 1/2" thick. I admit it will depend on the step drill. See if it will work for you. Reasonably accurate.
I have used Bosch hole saws on thick steel (3/8") OK. It is possible to tweak the cutting diameter a bit by bending (alternate) teeth out with snipe nose pliers, not too much though. You get a wider kerf, so you need to slow the machine up a bit. It doesn't work with cheapo saws, I guess they are 'all hard'. The teeth break off.
Brain Fag !! Caused by changing the wretched clocks again. My mate has the right set up, he has two clocks in his lounge, one on GMT, t'other on BST. He just changes the one he looks at. ;D ;D
Dave

 

[shred]

You can use a flycutter as a quick-n-dirty boring head as well-- regrind the cutting bit to cut a hole instead of a flat and away you go, much like a circle-cutter. Officially it might then be called a 'trepanning tool' or some such, but the concept is the same.

 

[joeby]

Trepanning a hole 1" in diameter through 1/2" material could prove to be a chore, and a 5/8" hole . Usually, trepanning is used on much larger holes and thinner material, or for situations where saving the material from the center of the hole is necessary. Perhaps the center cut-out is actually going to be your part. That's something to keep in mind for flywheel material. Trepanning tools are much like parting tools, and sometimes they can be hard on the nerves.

Hole saws will do the job if hole size isn't going to be an issue, as they may cut oversize a fair amount. They are also useful for material savings if you can live with the pilot hole. Use cutting oil and stop often to clear the chips, and they will go through some pretty thick material, especially if you can attack it from both sides. The problem with hole saws is the lack of chip clearance, hence the need to back out and clean the kerf often.

End mills are easy enough to get with a reduced shank. I have 1" and larger end mills with a 3/4" shank. You could also use a Roto-broach, but they aren't exactly cheap.

Your situation may make a boring head a worthwhile purchase, as you won't be limited to one size. Your drill selection doesn't need to be much larger than 5/8" either, because you can bore from there. If you need to go really big, you can lay out your hole diameter and cut out the center with an end mill, just "eyeballing" close to the layout line, then finish by boring.

Kevin

 

[firebird]

Hi

Thankyou all for the info

Cheers

Rich

 

[BobWarfield]

Big holes are painful!

Some thoughts in my own (personal) order of preference:

- The lathe does them best for me, but that's not an option here because the part is too big.

- If you had CNC, you can interpolate the hole. This is where a small endmill cuts out a circular slug (or you can convert the whole hole to chips). The manual alternative is to put the workpiece on a rotary table and let the smaller endmill make a bigger hole.

- Next up are those pesky Blacksmith drills, which I agree, we prefer to call Silver and Deming. These work really well for me, but I have a big mill. Still, even my crappy import drill press does ok with them, so maybe it's alright. I just have a cheap import set, but I do find touching them up in my Drill Doctor helps a lot.

Past this point, we're into shear desperation. None of these is fun, but they all will work reasonably well given patience:

- I have a trepanning cutter. It cost something like $30 from one of the big houses. It works pretty well. Surprisingly well. But I've only ever used it on sheet metal. I shiver a bit at the idea of 1/2" steel plate.

- Hole saws. Once again, this has all been done on sheet metal in my shop, so I can't say how well it works.

- For larger holes, my plasma cutter works pretty nice, but it's likely a bit much for only a 1" hole.

If 'twere me, I'd invest in the Silver and Deming set. You'll use them more than you'd think.

But what about the boring head? Man, that is a real slow job on a mill. Of course an automatic head is really pretty nice, but they're so expensive I've been afraid to even try the Wohlhaupter I got a deal on. Crank through whatever depth of cut you can get, haul it out of the hole, loosen gib screws, change diameter with the dial, tighten gib screws, go through another cutting cycle. Man, life is short at 0.020 or 0.040 or whatever. BTW, it is really painful if you have the cheap import boring bars as well. At least get one good boring bar to fit your boring head!

I believe in boring heads strictly to make a finish pass to clean up and accurize these days, though I have made bigger holes with one at times.

Cheers,

BW