# Can I drill a hole throu cast iron?



## Yamster (Jun 15, 2011)

Hello,

I have a Delta table saw 36-979. Well, maybe i should call it 36-980 since I have T30 fence installed on it as well (even though I bought it separately).

Anyway, I am thinking about attaching a outfeed table to it. I've checked out some plans that are available on the internet, and I am going to incorporate some of the cool ideas and nice designs when I build one myself.

I am going to make it a "fold-down" type - I can fold the extension down when I am not using it for easier storing. However, there still will be a permenant/fixed section, which will be above the area where the motor sticks out (so it's wasted space anyway when I store away the saw against the wall).

I am thinking about cutting the extra bed frames, which I have no use for, and use them as L angled bars to attach the fixed portion of the outfeeed table. So... these L bars will be bolted to both side of the table top, extended out to the back (outfeed side), and some MDF or plywood board will be bolted between those L bars. Hm.. Not sure if I am doing a good job describing it, but I guess it's a very common way of attaching the outfeed table to the table top.

Anyway, I think I may be able to use the existing holes on the bed frame (it's a type that can be used for different size mattress, so there are holes already). Even if I still need to drill some holes on the bed frame, I guess I can handle that - I will need to get some special drill bit.

However, I wonder if I would be able to make holes on the side of the table top... It's made of cast iron. Isn't cast iron harder than steel? Would I be able to drill a hole using conventional metal drill bits? Also, isn't cast iron more brittle than steel, meaning I may end up shattering or the table top or create a crack?

I wish I knew how to weld or had a friend who knows how with all the welding tools - then I can just ask him to weld the frames to the table top... Maybe I should take on welding as another hobby. I will have to sleep on the couch for many night, but I am pretty sure my wife will eventually forgive me. LOL

Seriously, any advice or tips or recommendations or encouragement (or discouragement - if what I am about to do is really stupid) will be greatly appreciated.

Thanks!


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## firemedic (Dec 26, 2010)

Don't try to weld mild steel to cast iron... 

On the other hand cast iron drills very very well. Start with a smaller hole and step up to the size you need for a clean hole. It's drills far easier than mild steel.

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...


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## woodnthings (Jan 24, 2009)

*Bed frames vs Cast iron*

Some of the older bed frames are super "hard" steel and don't drill easily. On the other hand cast iron is softer than steel, but brittle as you said, and drills easily. In either case use a pilot drill 1/3 smaller than the hole you want. Smaller drills need to spin faster than larger drills. So for example for a 3/8" hole use a 1/8" pilot bit.

Welding is a great capability and I have welded a bunch of mobile tool bases, farm implements and tool stands. You can also fill a hole that was drilled in the wrong place...BTDT! :laughing: 

An industrial grade MIG welder will be over $1000 but others can be had for under $500. Mine was about $1600 if I recall. The difference is in the "duty cycle" or how long you can hold the gun down and run a continuous bead in seconds or % of minutes.

Keep us "posted" on what you are doing.  bill


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## Yamster (Jun 15, 2011)

Thank you for your quick and informative responses!

You guys are awsome. I will be off to the hardware store to get some drill bits later tonight. I wonder if I should go to HF. I only need to make 4-6 holes, and by the next time I need to drill holes on metal, I am pretty sure I won't be able to find these bits... :laughing: So, maybe I should get cheap bits?


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## mickit (Oct 5, 2009)

Yamster said:


> Thank you for your quick and informative responses!
> 
> You guys are awsome. I will be off to the hardware store to get some drill bits later tonight. I wonder if I should go to HF. I only need to make 4-6 holes, and by the next time I need to drill holes on metal, I am pretty sure I won't be able to find these bits... :laughing: So, maybe I should get cheap bits?


If you only need 4-6 holes, and you're goin' to HF, then you only need 4-6 bits:laughing:
Kidding of course...the HF bit's should be fine, but mind the advice above about RPMs. The bedframe material, as noted, may be some really tough stuff. I use it a lot and generally it's harder than 'normal' steel. Before you drill, do a 'scratch test" if you cannot make a decent scratch with the bit you want to drill with you're gonna need a harder bit. HSS should cover anything you're gonna encounter, and is not that expensive('specially for a small set).


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## BWSmith (Aug 24, 2010)

Very good advice above.....so this post will overlap some/all.


Welding CI is such a deep subject that books have literally been written on the topic.It/we only resort to it as a last ditch effort....maybe the broken pce isn't availible?Its off the chart expensive?Stuff like that.It does however drill and tap real easy.The dust from any machining is....uhhh,real nasty.So clean up well.

Bed frames,also known as mystery metal.But with a twist(ha)....it is,more often than not...extremely hard.And lots of times it has some real nasty inclusion "stuff".Think drilling concrete and hitting aggregate(rocks)...its almost exactly like that.Cutting it ain't much better.When we use it(rare),we'll try to use abrasive chop saw....trashing a bandsaw blade ain't worth it.Good luck with your build,BW


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## cabinetman (Jul 5, 2007)

I would pick up a few bits for each size you start with and increment to. Use drops of cutting oil as you drill.












 







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## Porphyre (Jan 5, 2011)

.....


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## Yamster (Jun 15, 2011)

mickit said:


> ... HSS should cover anything you're gonna encounter, and is not that expensive('specially for a small set).


Thank you for the tips. By the way, what is HSS?


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## Yamster (Jun 15, 2011)

BWSmith said:


> ...Cutting it ain't much better.When we use it(rare),we'll try to use abrasive chop saw....trashing a bandsaw blade ain't worth it.Good luck with your build,BW


Hmm.. kinda scary. :shifty: What about using a reciprocating saw with a blade for metal? Or.. should I get a abraisve disc for my chop saw? Wait... the idea of using the bed frame was to save the cost... If I end up buying some special blade or disc... should I just buy some L bars made of "regular" steel (or even aluminum?), and use the saw/blade I already have?


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## Yamster (Jun 15, 2011)

Porphyre said:


> Wait a second.
> 
> Are you drilling through holes in the top? IE, you're going to have a bolt and nut holding the bedframe / bracket on?
> 
> ...


Hmm.. what exactly is "tapping"? Are you refering to enlarging a hole which already exists? Well, I am planning on drilling holes through the side of the table saw top and use bolts and nuts to attach the bed frame bar.


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## woodnthings (Jan 24, 2009)

*I've done exactly what you want to do*



Yamster said:


> Hmm.. what exactly is "tapping"? Are you referring to enlarging a hole which already exists? Well, I am planning on drilling holes through the side of the table saw top and use bolts and nuts to attach the bed frame bar.



When I made the out feed table for the Triple 12" saws I had to drill a few new holes in the back edge of the saws to accept the 1 1/2" angle it rests on. 
Mark, punch, pilot drill, then drill final size one size 1/32nd, larger than the bolt diameter. 
Tapping is the process of cutting threads in a hole. It can be wood, aluminum, steel, or cast iron. There is a specific size drill for each size bolt, you need a tap drill chart to determine which one and usually a set of drills in 1/64 th increments and or number drills. This process is a little advanced for a beginner. Sometimes it's almost impossible to get a nut on behind so a threaded hole is best.  bill


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## firemedic (Dec 26, 2010)

Yam... I built this side ext for $20... I already had bolts, ply and melamine. The angle and flat bar was only $20. I dont think it's worth hacking up bed frames. Just one man opinion though.

Oh, and I got it from a steel yard, not a box store... MUCH CHEAPER and they cut it to my specs for free and only charged me for what I went home with.

Ps, pay no attention to the filthy shop, :no: I took some inspiration from Kenbo and got it all neat n tidy since then! :yes:

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...


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## dodgeboy77 (Mar 18, 2009)

HSS is High Speed Steel. Drill bits made of it will be marked HS or HSS. Not all HSS is equal. I have had bad experiences with some Harbor Fright bits because they were so brittle they break off in the hole, requiring cussing. Go with a name brand HSS twist bit for drilling iron and steel.

Incidentally, cast iron is one of the few materials that should be drilled dry. Using a lubricant to tap it is kind of optional. This page has a decent chart if you scroll down: http://its.fvtc.edu/machshop1/coolant/cutfluids.htm Actually, for steel I usually use whatever I have handy - 3 in 1 oil works well.

Yamster - Tapping is making threads inside a hole using a tool called a tap (If the tap breaks off in the hole it is called other things). To thread the outside of a shaft you use a die. Search the web for details.

Bill


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## Wrangler02 (Apr 15, 2011)

It's been a lot of years; but if my memory serves me correctly I was told that for drilling cast iron you should use kerosene rather than cutting oil.


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## Zircon (Aug 1, 2009)

I thought it was just me that couldn't drill thru bedframes. I ended up cutting a slot with an angle grinder and using a bolt with a washer.


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## Brink (Nov 22, 2010)

Wrangler said:


> It's been a lot of years; but if my memory serves me correctly I was told that for drilling cast iron you should use kerosene rather than cutting oil.


Cast iron is drilled dry. The embedded graphite lubes the cut.

Aluminum and brass gets kerosene

Steel gets oil.


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## woodnthings (Jan 24, 2009)

*+1*

I find Thread Cutting oil works best for mild steel. Stainless and other harder steel require specialized lubricants.
They do 2 things, keeps the bit lubed as well as cool. A correctly sharpened bit will produce a continuous curl, but I find it best to relieve the downfeed for an instant and start a new curl. The long ones get all wrapped around the bit and then ride up and they are dangerous to remove while spinning. They will catch your hand or glove and cut it....DAMHIKT :furious: I use cardboard box halves to surround the work when possible to capture the chips/curls on a drill press. A magnet suspended close by the chuck will also catch the curls, but put it in a plastic bag, then to release the chips pull the bag inside out and pull it off the magnet. All the chips will be inside....DAMHIKT :thumbsup:

I've drilled about as many hole in steel as wood. This truck had 3 entirely different bodies over it's lifespan. It was assembled entirely with 1/4" stove bolts on the body panels every 4". Stainless running boards and windscreen frame.
Handmade eggcrate grill. Headlamps off a '39 White garbage truck...


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## Wrangler02 (Apr 15, 2011)

Brink said:


> Cast iron is drilled dry. The embedded graphite lubes the cut.
> 
> Aluminum and brass gets kerosene
> 
> Steel gets oil.


I stand corrected. You are correct. The memory is not as good as it used to be


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## CNYCarl (Apr 16, 2011)

Porphyre said:


> Cast Iron is not going to give you a continuous swarf; it just chips out. Apply enough pressure to get regular sized, shaped, and interval on the chips coming out.
> 
> Use Cutting oil. Especially if you think your drill speed is a little high, it's hard to use too much.


NO, NO, NO. NEVER LUBRICATE CAST IRON WHEN DRILLING OR TAPPING!

Cast iron has lots of free graphite in it that when drilled or tapped with oil will clump together in a paste that will wedge the cutting tool tight, causing the tool to break.

Drill or tap cast iron dry or flood with light tool coolant, never oil!


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