# Cutting a long slot in a fairly thick mild steel plate.



## Tony Bird (Feb 17, 2015)

Hi,

Yesterday I had to cut a 9 long slot in a ¼ thick mild steel plate unfortunately it was way beyond the sensible capabilities of my light Milling machine.  So I decided to remove the metal from the slot by chain drilling and filing. 

This is the system I learnt when I was an apprentice the day before yesterday or so it seems.  The bit that has to be right is the marking out and centre punching; also sharp drills and a good file are required.  The idea of chain drilling is to drill holes in a straight line with centres that when drilled the holes almost to join up.  It is also necessary that the holes drilled are square to the surface of the plate as it helps when filling the slot square.  The more accurate the holes are positioned the less work is required when filling the slot.  For drilling the holes it is a good idea to screw the plate to some flat wood.

First a length of steel plate was cut; this is about the limit that my mechanical hacksaw will manage. 





Then the position of the holes was accurately marked out centre punched and spot drilled.  Then every other hole was drilled a little undersized. 





Then the holes between were drilled slightly undersized.





The holes were then drilled to size,





A file was used to connect three of the holes.





A hacksaw blade was inserted and all the holes were joined.





A piercing saw was used for the short section.





Section removed.





Starting to file long run.





Long run filed and both of the short ones.  Time for tea!





Close up of long run.





After tea finished.





Regards Tony.


----------



## portlandron (Feb 17, 2015)

Thanks for posting how you did it. I have used this method in the past but never thought to first drill the holes undersize, nice trick.


----------



## RichD (Feb 17, 2015)

The hole pattern came out perfect! Good job.

That's how I cut the arc/slot on the far end of my taper attachment. It was only a single row of holes, but it came out well as did yours. 

Probably almost as fast as milling considering the setup time to cut an arc of 28.648" radius ~11.5" long.

Rich


----------



## tornitore45 (Feb 17, 2015)

Came out better than milled with sharp corners. Obviously you have skills with a file.
Back in middle school shop we did lots of that followed by interminable filing.


----------



## bazmak (Feb 17, 2015)

A good informative thread with good engineering skills.All you missed out
on was the blood,sweat and tears.Well done regards barry


----------



## Tony Bird (Feb 18, 2015)

Hi Barry,

*All you missed out on was the blood,sweat and tears.*

My wife says its good for me?

I decided against using the plate as a letter box.

Regards Tony.


----------



## Blogwitch (Feb 18, 2015)

Very nice indeed Tony, very well done and explained.

It would pay you, if you had any more to do like this, to get hold of a die filing machine, they really do make jobs like this very easy.
It is like having a third never tiring hand for sawing and filing.

John


----------



## windy (Feb 18, 2015)

Good to see basic metalworking skills being used they solved problems for those of us who do not have large machines available plus it keeps you fit.


----------



## gus (Feb 18, 2015)

Blogwitch said:


> Very nice indeed Tony, very well done and explained.
> 
> It would pay you, if you had any more to do like this, to get hold of a die filing machine, they really do make jobs like this very easy.
> It is like having a third never tiring hand for sawing and filing.
> ...




Hi John,

During my trade school days, I was dreaming of making a filing machine.I hate sawing and filing. But I did complete some student projects done w/o machining. I did ask our instructor about the existence of such a machine. Way back in 1961 Singapore Workshop Technology was so primitive. Dreaming of DIY same machine. SOS SOS.


----------



## Tony Bird (Feb 18, 2015)

Hi John,

*It would pay you, if you had any more to do like this, to get hold of a die filing machine, they really do make jobs like this very easy.  It is like having a third never tiring hand for sawing and filing.*

Yes it would have been useful, I had a filling machine for many years but sold it as it wasn't used often and took up space in the workshop.  In fact this is the first slot that I have cut by hand in a very long time; mostly I can use my small mill but this job was too too large.

Regards Tony.


----------



## Blogwitch (Feb 18, 2015)

It is always the same Tony. But I use mine a lot, mainly as a vertical hacksaw as I find I can't saw or file with one arm.

John


----------



## MachineTom (Feb 18, 2015)

A 1/4 EM run around the perimeter in 3 passes, should have been attainable with a light milling machine. Or use it instead of the saw and file, end result stil the same just less time spent on hand work.


----------



## gus (Feb 18, 2015)

Drilling holes in between is a great idea . Have drilled same size and getting into trouble.
Thank You Maestro Tony. Much as I dread,there are occasions when this drill/cut/file method is best alternative when milling and shaping not possible.My trade school instructors was not the best we had in the 60s. Many were tradesmen with City&Guilds Certificates and not highy skilled fitters and machinists as Singapore's main industries was Entreport Trade with Malaya.Indonesia and Philippines. Manufacturing Industries were very basic. But we were taught basic skills well and up to us to develop and excel. Our foundries were pouring very low quality Cast Iron using C.I. scraps. Buying castings to meet B.S. or ASTM or JIS was then  impossible.


----------

