Cast iron ate my drill

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Soot n' Cinders
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Cast iron ate my drill

Post by Soot n' Cinders » Mon Feb 05, 2018 4:58 pm

While trying to machine the door ring for my smokebox, I've run into an odd snag. The cast iron burned up a brand new #19 drill bit after taking a #2 HSS center drill with no problems whatsoever. my 1/8" endmill and a #3 center drill also went in with no problems but as soon as I tried the #19, it started sparking a little and burned the corners off the cutters in a hurry. I've now lost both of my 19s and my 18, so while I wait for replacements I need some help figuring what is going on.
-Tristan

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Pontiacguy1
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Re: Cast iron ate my drill

Post by Pontiacguy1 » Mon Feb 05, 2018 5:27 pm

You might need to just re-sharpen the drill. A lot of times that cast iron will have a really hard casting crust on the outside, which you have to break through in a hurry. Just re-sharpen your drill bit and try again, this time slow it down a little bit and force it through a little faster. Once it breaks through that without dulling, should be OK.

Also, sometimes cheap drills are just that... Cheap. I have one set of good ones, and one cheap set I got at one of these cheap tool places quite a number of years ago. The cheap ones looked good and were TiN coated. The steel or heat treatment of the steel wasn't done right, though, and once the coating wore off, the drills dulled very quickly. I would re-sharpen them and drill about 2 or 3 holes, and they would be dull again. I went and got the same drill size out of my other set of drills and drilled about 10 holes with it and the drill was still sharp. Went back to the other drill, same speed and feed, and it was again dull after 2 or 3 holes. Something just not right about those. Sometimes, you get what you pay for.

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Bill Shields
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Re: Cast iron ate my drill

Post by Bill Shields » Mon Feb 05, 2018 5:31 pm

OR - you have hit a hard spot in the casting and may need a carbide drill to get through it (and pray that you are not tapping the hole in the process.)

Soot n' Cinders
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Re: Cast iron ate my drill

Post by Soot n' Cinders » Mon Feb 05, 2018 7:46 pm

I’ll try my hand at resharpening the drill bit and going again. Just odd that the center drill went in like it was butter but the brand new drill bit burned up on the first try. Wasn’t a cheap bit either, I’ve stopped buying the cheapest stuff out there because stuff like this happens.
-Tristan

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-2.5" scale Class A 20 Ton Shay

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Bill Shields
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Re: Cast iron ate my drill

Post by Bill Shields » Mon Feb 05, 2018 9:44 pm

center might have missed the edge of the hard spot.

been there, done that...it happens

Soot n' Cinders
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Re: Cast iron ate my drill

Post by Soot n' Cinders » Mon Feb 05, 2018 11:33 pm

Yeah, one of those things with castings, especially thin ones. Anyway, resharpened my bit and managed to get the holes done. It made chips like ductile iron but Im pretty sure its gray, so couldve gotten chilled at the foundry. Hopefully the inner part of the ring isnt as hard because Ill need to tap that for the door dogs
-Tristan

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-2.5" scale Class A 20 Ton Shay

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Fred_V
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Re: Cast iron ate my drill

Post by Fred_V » Tue Feb 06, 2018 8:27 am

I have a drill sharpener by General. Cheap little thing but once I learned how to use it I really like it. Can't beat it for the price. I have a cheap set of those TIN coated drills. I use them only for brass and they work great. I have ground the cutting edge flat on almost all of them as I use them.
Fred V
Pensacola, Fl.

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SteveM
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Re: Cast iron ate my drill

Post by SteveM » Tue Feb 06, 2018 4:31 pm

Glad you got thru that. We had a HSS drill break off on a hard spot and it left a piece of HSS embedded. Any HSS drill that came in after that immediately had it's lip removed. Had to use a carbide drill to get it out.

I buy drills in lots at garage sales, flea markets and ebay so that I always have extras on hand. That way, I never run into a situation where the only one I have of that size is dull or broken.

Picked up a Drill Doctor cheap, and while it may not be perfect, it does a pretty good job of sharpening them.

I have the drills in Huot dispensers where I can have 5, 10 or even 20 of the same size.

If a drill gets dull, it goes in the "to sharpen" pile, and when I get some time, I sharpen them and put them back in the drawers.

Steve

Soot n' Cinders
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Re: Cast iron ate my drill

Post by Soot n' Cinders » Wed Feb 07, 2018 12:14 am

Behold, corner burner iron! The foundry that made these castings should patent it as a surefire way to destroy drill bits. I had to resharpen my long 1/8" drill about 12 times to get the hinge done. On the bright side, I have gotten pretty good at sharpening drill bits by hand.
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-Tristan

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-2.5" scale Class A 20 Ton Shay

rkcarguy
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Re: Cast iron ate my drill

Post by rkcarguy » Wed Feb 07, 2018 12:48 am

Cast iron has varying hardness and little chunks of stuff in it that seems to eat tools, most of my machinist experience with it wasn't so great.
For parts of any quantity, we threw carbide tooling at it and although it took the "new" edge off of it pretty quick, it held up for a lot of pieces after that point. I've found most center drills are of a harder, higher quality steel than drill bits, and in some cases I've just carved a little relief on a center drill and pushed it all the way through if it was the right diameter I needed and the material was being really stubborn.

Bastelmike
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Re: Cast iron ate my drill

Post by Bastelmike » Wed Feb 07, 2018 4:11 am

Soot n' Cinders wrote:
Mon Feb 05, 2018 11:33 pm
Hopefully the inner part of the ring isnt as hard because Ill need to tap that for the door dogs
Hi Tristan,

just Keep the tap away from the hard spot.

1. Machine a large chamfer at that hole, larger Diameter bigger than tap Diameter.

2. Or use an endmill or drill bit with Diameter larger than tap and machine a countersink/counterbore. Just important that Your tap has no contact with the surface layer of the casting.

These chilled areas at castings are usually not deep therefore its important to remove the surface crust before using delicate Tools like taps.
Usually I prefer carbide tools for first machining castings.

Mike

Soot n' Cinders
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Re: Cast iron ate my drill

Post by Soot n' Cinders » Wed Feb 07, 2018 11:34 am

Thanks for the tips! I'll get the skin off so the tap wont rub on it. I have no idea how hard the iron will be under the dogs so I guess I'll find out. Looking forward to being done with the smokebox door though, hopefully the firebox door iron is softer.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

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