Saving the hole.

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dgoddard
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Joined: Fri Jul 07, 2006 10:29 pm
Location: Lebanon MO

Saving the hole.

Post by dgoddard »

I have a project that would make better use of material If I could cut a hole through a piece of 1018 CR half inch plate and save most of the material that formerly filled filled the hole. The hole I need to make would be somewhere around 2 inches in diameter and the "1/2 x 2" (roughly) piece (the "puck") could be used to make another part of the assembly.

Essentially this would be a trepanning cut. I have no such expensive tool but I am wondering if there is a way to accomplish this cut on a lathe or milling machine that would be fairly efficient, and not require expensive tooling.

If I could make a 1/8 inch circular kerf for a depth of 1/2 inch so that I end up with a plate with a hole through it and get to keep the "puck" It would be nice. and both time and material efficient. I have considered some of the "cup" type hole saws, as some of them are reputed to cut mild steel but I do not know if I have to provide special cooling. My Lagun FTV2 10x54 millling machine has water based flood cooling and might be the better choice for cooling the tool as my lathe 12x36 lathe only is set up for manually applied cutting oil.

I do have the ability to grind a tool somewhat like a parting tool from a brazed carbide insert tool bit to "single point" through a half inch plate but I am not sure how well that would work or what details of the tool would make the difference between success and failure if that would be a viable option.

If I were to use the "cup" type hole saw, I am wondering if making the cut with or without the pilot drill in the mandrel would be necessary or desirable. Such a pilot hole is not necessarily a problem. Then there are the issues of chip clearance, feeds and speeds with such a cup type hole saw.

So that is the problem and my initial thoughts on solving it:

I figured I would seek the advice of wiser more experienced heads in this matter. (wild innovations also appreciated, but I imagine this is something that others have done before.) Surface finish is not a particular problem as the next step would be welding the puck to another piece followed by more machining to final dimensions and concentricity.

I am aware that If I obtained some bar stock of adequate size or heavy wall tube of adequate size I could just "saw off"some "pucks" but at the present I have much plate and the heavy bar stock would be an additional cost.

Suggestions please.
I never met anybody that I couldn't learn something from.
LIALLEGHENY
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Joined: Sat Jan 11, 2014 12:36 am
Location: Bohemia, NY

Re: Saving the hole.

Post by LIALLEGHENY »

Use a good Bimetal hole saw. Run the spindle as slow as it will go. Plenty of coolant and continually clear the chips. You'll cut right through without any problem. I do this all the time with all materials including stainless up tp 1" thick.

Nyle
chief
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Joined: Sat Jan 04, 2003 5:51 pm

Re: Saving the hole.

Post by chief »

+1 on the hole saw. It has the added advantage of not having the loose puck in the hole causing problems when it comes free from the plate. Also using a mill with a secure setup means you can do it without the pilot drill on the hole saw, if you prefer not having a hole in the puck.

Terry
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rudd
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Location: savannah ga.

Re: Saving the hole.

Post by rudd »

I think your are going to have a dickens of a time clearing the chips in the circular slot. Grind a trepanning tool out HSS and do it in a four jaw. I've done this with 1/2" structural plate and had no issues. The tool is going to have to be ground to the curve of the cut. Do it at slow speed with plenty of cutting oil. You'll want some back rake on the tip of your tool, should generate a healthy curled chip that will fall out on its own. Tool should be square on the end and taper back some in width so it doesn't rub as you go deeper in the cut.

Edit, if you do attempt the holesaw, drilling some small holes though the cut zone will give the chips a place to go. Get the plate up on some blocks so the chips can go on through.
johnfreese
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Re: Saving the hole.

Post by johnfreese »

Check out annular cutters like Rotabroach.
ccfl
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Re: Saving the hole.

Post by ccfl »

I'm cheap; here's what I did before I had a lathe or rotary table. Get a piece of plywood or MDF, cut a 1" hole in it. Wood only has to be bigger than the disk you want to make. Super-glue a 1" OD puck of whatever scrap metal to the backside of your 1018 plate. Clamp the wood to the table, set the plate-with-locating-puck into the wood, and cut your circle with a 1/8" endmill. Drill all the way through for a short length of cut (1/2" or so), this gives a safe place to start/stop/increase Z depth. Take shallow cuts and turn the plate by hand.
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tornitore45
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Location: USA Texas, Austin

Re: Saving the hole.

Post by tornitore45 »

What rudd said.
Keep track of your depth and when you are withing 10-15 thousand of coming through hammer it out. Alternatively have a wood plate behind and at before it fall free put pressure with the tailstock.
If you are lucky the piece cut through partially and that is the sign to stop.

No need to go buy a hole $aw or take a mortgage for an annular cutter.
Mauro Gaetano
in Austin TX
whateg0
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Location: Wichita, KS

Re: Saving the hole.

Post by whateg0 »

I do this with a holesaw frequently because I, too, am cheap. Drill a small hole, maybe 1/4" diameter, centered 1/8" from the OD of the hole to be cut. This gives the chips a place to get out of the kerf. Then slow and lots of oil. To keep the "puck" from getting stuck in the holesaw, if you can stand the holes not being perfectly lined up, flip the work for the last 1/16" or so.

If you do want to try trepanning, Tom Lipton did a video recently on grinding the tool.

https://www.youtube.com/watch?v=6PcEBaset1I

I think Joe Pieczynski did one, too, but I can't stand his "my way is the only way that works" attitude.

Dave

(edit: I just realized that Rudd suggested the same thing. Sorry.)
spro
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Re: Saving the hole.

Post by spro »

Good tips and I'll watch a video about trepanning very soon. I have used hole saws for various depths and find, at some point, the drill is no longer a pilot. The hole is already through the material and the drill pilot is acting like a router. So it is useful to have a sized arbor replacing the drill and lubing it. It is also much more stout.
whateg0
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Location: Wichita, KS

Re: Saving the hole.

Post by whateg0 »

I've never replaced the drill with a straight arbor. My thought was that the hole was just for bulk removal and it wasn't worth my time. I might try it, though, on the next hole to see if it makes that much of a difference.
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SteveHGraham
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Re: Saving the hole.

Post by SteveHGraham »

Plasma cutter or cutting torch.
Every hard-fried egg began life sunny-side up.
Magicniner
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Re: Saving the hole.

Post by Magicniner »

SteveHGraham wrote:Plasma cutter or cutting torch.
+1
That's how I'd do it if the scrap lump was worth a chunk of money, though other than Titanium I can't think of a material I work with regularly that would be worth enough not to just take the quickest route and bore it!
Of course if you don't have a plasma cutter there is the purchase cost to consider :D
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