3" holes in 2.5 thick A-36

MwTech Inc · Dec 3, 2020

I have not worked with this sized material before. It's a in-shop project. Job requires 6 holes with a finish size of 3" 0.000/+.005

Plate is 24x54 , the only machine it will fit on is our #4 vertical mill. This mill does not have a quill.

Mill in good condition, table feeds do work, 17x84 table so there is room to move around.

Assume.....after some research.......use a spade drill 2 15/16 then bore to finish??

Is there any other method I'm missing??? We don't have a selection of drills to work from small to large

Would have to purchase a spade bit holder/blade...........so asking for advice before the purchase.

Currently the plate OD will be cut by our steel supplier, didn't ask about roughing out the holes, concerned about a hardened/oblong surface to deal with on our end.

The plate will be cut with an oxy setup per Steel Co info

Blazemaster · Dec 3, 2020

If you dont want to order a tool, drill a hole pattern so a slug falls out, then bore to size.

g-coder05 · Dec 3, 2020

Check out Superdrill from Showa. You could go 75MM and dial in the boring head to bring to size in one pass. They hold size near dead on, I use a 250MM in Ductile 10" deep for asphalt plant trunnions stub shafts and size is consistent and insert hold up to serious abuse.

https://www.showatool.com/product/up_img/1523931538-289680.pdf

snowman · Dec 3, 2020

depending on the service center supplying the steel, they may be able to quote it with the holes already in it if they are putting it on a plate handler.

Limy Sami · Dec 3, 2020

First Q (and IMO the biggie)

How many of these plates have you got to do?

rbent · Dec 3, 2020

Ask if they can mill the plate for you instead of oxy fuel cut. Steel fab house we use for big stuff can mill on their plate machine and could mill the hole to close size so you could finish bore it.

memphisjed · Dec 3, 2020

A hougen cutter in the mill should get you there with no second boring or reaming. 3" is big.

Mud · Dec 3, 2020

MwTech Inc said:
Currently the plate OD will be cut by our steel supplier, didn't ask about roughing out the holes, concerned about a hardened/oblong surface to deal with on our end.

The plate will be cut with an oxy setup per Steel Co info

I used to do the torch shape cutting for local shops before the steel suppliers had that capability, up to 12" thick. A36 doesn't get real hard. It will get a surface scale from the cut that will wear a notch in your boring tool insert, so use 2 boring tools, one to rough and one to finish.

Dan from Oakland · Dec 3, 2020

All else fails- have the holes burned undersize and finish bore- its A36 not 4140. Use a crude flycutter with a brazed carbide tool bit for the roughing and get under the scale.

SShep71 · Dec 3, 2020

An annular cutter may be the best bet, most have a 3/4" Weldon shank which is just a straight 3/4" diam shaft with flats on at least two of the sides.

Bherzog · Dec 3, 2020

If you use a spade drill, make sure the mill have enough torque at the rpm required for the drill.

Bruce

gbent · Dec 3, 2020

IME, don't be scared of burnouts in A-36.

Phil in Montana · Dec 3, 2020

By the time you buy all the tooling to do this job it might be better to sub it out to a shop with a hbm (the right machine for the job)...Phil

eKretz · Dec 3, 2020

Have the holes burned to 1/4" under size and bore them. As the others have already mentioned, A-36 doesn't harden appreciably when it's O/A burned. It's basically about the equivalent of 1020. If it's just the one part I wouldn't even bother using two tools, just take one and whack it through leaving enough for a small finish cut - any notching that may occur will be nowhere near where the finish cut is contacting the insert.

EmGo · Dec 3, 2020

memphisjed said:
A hougen cutter in the mill should get you there with no second boring or reaming. 3" is big.

I'd be scared doing that with just a table feed ... sounds like he doesn't even have one of those hand-crank verticals ? Rotabroaches cost a lot and they are a little fragile.

Limy Sami · Dec 4, 2020

SShep71 said:
An annular cutter may be the best bet, most have a 3/4" Weldon shank which is just a straight 3/4" diam shaft with flats on at least two of the sides.

I looked that idea up, ....big$$ ?

dian · Dec 4, 2020

there are trepanning cutters that go 50 mm deep. can you flip the plate? (or find some that go deeper.)

snowman · Dec 4, 2020

Dan from Oakland said:
All else fails- have the holes burned undersize and finish bore- its A36 not 4140. Use a crude flycutter with a brazed carbide tool bit for the roughing and get under the scale.

If they are doing burnouts in 4140, they also have the ability to normalize it post cut.

A 3" annular cutter of that depth is going to have a 1 1/4" shank.

Limy Sami · Dec 4, 2020

dian said:
there are trepanning cutters that go 50 mm deep. can you flip the plate? (or find some that go deeper.)

That plate weighs in excess of 900lb and flipping plates ain't like flipping burgers.

snowman · Dec 4, 2020

Limy Sami said:
That plate weighs in excess of 900lb and flipping plates ain't like flipping burgers.

Sure it is, you just have to attach your spatula to a forklift!

3" holes in 2.5 thick A-36

Titanium

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