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working with steel
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Glen
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working with steel

howdy all,

just been making kang for a while now which is an all steel bot with no armour. just uses cheap parts and the like but im mainly using it as a steel practice.

a few things id like clarified before i start on cobra.

- what drill speed should i use on mild steel? ive seen 3 numbers in 3 books and have nfi which one i should be using. at the moment im using 650rpm which drills well BUT ive got a drill bit that has literally twisted itself. ill get a photo but it looks like somebody has cut a drill bit in half and stuck it back together the wrong way round so the spirals are all wonky..

what type of lubricant should i use for drilling + cutting. im using silicon spray at the moment. nfi if its the right stuff to use.

speaking of cutting what TPI blade should i use in the jigsaw? its a 370w thing which i dont think has the power to do serious steel. ive got a 14tpi in there which seemed to do the trick, i tried a 32tpi and it just spun up and did nothing. i tried pulsing the power on and off but that didnt get me anywhere (one speed im afraid FULL POWER Razz )

i was thinking about buying one of those big horizontal reciprocating saws, they use to demolish walls and such. do you think it would be worth my while or should i just trade in my 370w b&d jigsaw for a decent variable speed one?

oh yeah and the last thing is, can i anodize my steel, and paint it with a clear coating to stop it rusting?

any help appreciated.
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Post Wed Oct 13, 2004 6:28 pm 
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Knightrous
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Okay, this is what I know.

Use trefolex for drill and cutting lubrication, it's magic!

A fine tooth blade cuts steel good, probably something like 25-30TPI for steel (Corrent me anyone)

Drilling speed is all dependant on what size drill. If you are using 2mm-4mm around 800rpm is good. 5mm-8mm 600rpm generally is good, 8-12mm 350-400RPM is a nice speed and anything larger, try using 200rpm or lower. Make sure you actually have a set of metal drills, not just wood drills! Cool

I'm not sure what is classed as "good" advice up there, but I hope it helps Wink
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Post Wed Oct 13, 2004 6:42 pm 
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Valen
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the drill rpm is based on the cutting speed
bigger drill the faster the outside of the drill is cutting
there will probbly be some tables around that will let you know what tool speed you want (usually given in feet per minute)

we have a drop saw that doubles as a band saw
was about $300 at hairy forbes does a good job and beats the crap outta a hacksaw for cutting off 100mm ali round ;->
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Post Wed Oct 13, 2004 6:45 pm 
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timmeh
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Drilling speed can allso depend on what typ of drill bits you use as i have high speed drill bits and i tend to drill at about 900rpm for larger size bits over 5mm and 1500rpm abouts for smaller size bits under 5mm i do have a list that tells me the correect speeds but i was bluntening them allot so i decided to go slower.

If you are going to be using a large drill bit about 9mm or more then first drill a pilot hole close to 25% of the large size drill bit as this helps the larger drill bit to drill more easily
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Last edited by timmeh on Wed Oct 13, 2004 7:52 pm; edited 1 time in total

Post Wed Oct 13, 2004 7:11 pm 
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Valen
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you sure they arent "high speed steel" bits?
just tells you the steel the bits are made out of.
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Post Wed Oct 13, 2004 7:17 pm 
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Totaly_Recycled
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Iff you drill bit has twisted its self then chances are that it was an el-cheapo made drill .All good quality drill bits are high carbon steel and wont straighten out but will break or shatter if they get bent or jambed. If you intend on doing a lot of drilling with the one sized drill then go to an engenering shop and invest in a good quality bit of the size you need make sure you use a lubricant and the right speed and dont force it and you will find it will last a long time usualy the slower the better for all cutting tools

P&N austraila make good drills

Sutton drills are my favorite but are one the more expensive brands.

Vikeing make a reasonable priced reasonable quality drill but the cuting edge has a wierd chamfer and they seem to cut more on one side than the other .

Expect to pay about $4to $6 for a drill about 3mm to about 8 mm then any thing from about $8 to $12 up to about $12 mm then any thing from $12 to $35 for a drill bit up to 16mm i havent bought any bigger ones than this but they would be expensive .

Post Wed Oct 13, 2004 7:36 pm 
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timmeh
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I have a set of sutton drills and i highly recomend them Very Happy

They are 1.0mm-10.0mmx0.5mm and if i remember correctly they costed me about $40
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Post Wed Oct 13, 2004 7:51 pm 
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Glen
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yeah my drills came in a pack of 50 for $20 so go figure.

i think a set of high quality 4mm, 6mm and 8mm bits are needed as ill be needing to do a few holes in some 6mm steel fairly soon Surprised
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Post Wed Oct 13, 2004 7:57 pm 
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timmeh
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Get one of those $10 drill bit sharpeners from bunnings that fit on the end of a power drill.

Dont buy the expensive $70 generic brand one as it dosent do any better.
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Post Wed Oct 13, 2004 7:59 pm 
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mytqik



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Glen,

Here are some engineering based answers.

Drill rpm = ( cutting speed (feet/min) x 4 ) / Drill Diametre.

For mild steel, a typical cutting speed = 100 feet/min. Therefore for a 1/4" drill in mild steel =

drill rpm = 100 x 4 / 0.25 = 1600rpm.

Thats my imperial "rule of thumb"

Here is my metric one (its a bit easier, but less accurate)

Drill rpm = 9000 / drill diametre. therefore for the above question:

drill rpm = 9000 / 6.35 = 1417 rpm.

The imperial one is the more technically correct. For harder materials, the cutting speed should be reduced to around 80.

As for a lubricant, this term is not techniacally correct. It should be "coolant" as you do not want to lubricate the drill bit, you want the drill bit to be cooled. This is to ensure it does over heat, which will anneal the drill bit & it will loose all of its mechanical properties & easily become blunt.

A good rule of thumb, is, if your swarf (the metal shavings the drill is cutting) are coming off blue, is it getting too hot & therefore requires a coolant. Therefore you can use any oil available for a coolant. Chainsaw bar oil, motor bike chain oil or even brake fluid. Just be sure to throughly clean the oil from the metal, especially the brake fluid, as it will prevent paint from sticking in the future.

For stainless steel, kerosene is a good choice.

Next for the jigsaw blade, another rule of thumb is that 3 teeth should always be engaged at any one time. IE the thinner the metal, the high TPI (teeth per inch) required.

I would recomend you save your money & buy the best quality Jiwsaw you can. I personally buy Metabo tools, but these are expensive as they are imported from Germany.

(i just paid over $300 for a 5" grinder, compared to $19 I can pay at supercheap. However Metabo have a 3yr trade warranty & guarentee that you can push in the spindle lock while the grinder is going flat chat. Try doing that with a $19 grinder & it will end in tears.)

As for anodising steel. No can do. Anodising is limited to Titanium & Aluminium. Annodising is the process of deliberatly forming a protective oxide layer on a metal. Aluminium forms an oxide layer which seals the aluminium from the atmosphere. Unfortunately steel does not. The oxide layer we call rust doesn't do this & allows the atmosphere to continue to rust the material.

To anodise aluminium, the existing oxide is removed with an acid, then the aluminium is placed in a acidic solution with a die. This die is obviously the same as the final colout required. Then a huge amount of electricity is passed from an inert anode, through the coloured soltioun to the part to be anodise (the cathode). This forces the oxide layer to build up quickly & to take on the colour of the solution.

As a footnote, Jewellers use lemonade when doing this to jewellery.

You can however sand/polish/strip/blast steel down to its natural state & then cover it with a clear coating. Just be aware that if you get a nick/scratch in the clear coating, the parent steel will rust.

Hope this answers your questions.

Post Thu Oct 14, 2004 12:09 pm 
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andrew



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Well in my cases in drilling steel. Is to use lots of lubricant. I use this valvoline stuff similar to wd40. WIth drilling my weopon bar i started mega small and worked my way up wither 2-5 drill sizes at a time always relubrication both the drill bit and the area being drilled. This worked very well with my 78$ ryobi drill press on the lowest speed possible. Also when feeding the drill bit into the work do not force it in hard but VERY SLOWLY ease it in.

With cutting lubrication is also good and using the right tools as in a cd thickness cutting disc or the coreect jigsaw blade.

Thats what i have learnt anyway's.
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Post Thu Oct 14, 2004 12:15 pm 
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timmeh
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I got the ryobi drill and i took it back cos the damn chuck and handles kept falling off allsoo its a lot harder to adjust things so i got the gmc one and axtra $40 i think and it was heeps better to adjust and was a more solid desighn.

Only prob i have with those cheaper drill presses is the bench flexes downward when you press down firm with the drill bit while drilling steel.
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Post Thu Oct 14, 2004 10:43 pm 
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3Faze



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I just use a big f-off pillar drill from the early 70's on middle and feed down slowly, using as little pressure as possible. Works beautifully for almost everything.

But then it is about 2-4kW Shocked

Post Fri Oct 15, 2004 2:18 am 
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Nick
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@ Mytqik - what's your take on feed rate for drilling steel? I used to go with a slow feed rate like the other guys mention, but recently I decided that for larger drills (over about 6-8mm) it was better to use lower speeds and the most agressive feed rate my drill press was capable of. The reasoning was that the high feed rate generated less friction and extended the drill life. So far, I have seen good results, but I would like an expert sanity check on that...
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Post Fri Oct 15, 2004 8:45 pm 
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chrisjon65
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well i suggest 2 things ........use coolant as already suggested ....and the second thing is make sure your drill bit is SHARP all the time
if you dont have a bench grinder 'get one ' a drill press 'get one ' Very Happy
xmas is getting close and both items can be picked pretty cheap
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Post Sat Oct 16, 2004 8:34 am 
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