# Slotted holes



## marcros (19 Mar 2014)

How do I produce slotted holed in 3mm mild steel. Is there an alternative to drill a hole and extend it with a file?

I don't have any specialist metalworking tools. I don't want to spend a fortune on tools- if the answer it to take the items somewhere, so be it. 

What drill size will provide clearance for an m6 bolt shank to pass through?


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## Spindle (19 Mar 2014)

Hi

The 'engineering' way is to mill the slot - otherwise I'm afraid it's two holes joined by sawing with a piercing saw, or a series of holes joined, and filed to shape.

A 6mm hole will allow a 6mm bolt to enter, anything larger is the clearance which will be determined on the circumstance of it's use.

Regards Mick


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## spinks (19 Mar 2014)

you could have it punched in an engineering shop....but that may give a slight bowing to the material...otherwise its drill and file!! And I would go 6.5 for a 6mm bolt


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## marcros (19 Mar 2014)

Drill and file it likely is then. I had better buy myself a file. I assume that it is a round one I need?


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## Spindle (19 Mar 2014)

Hi

No, a flat file, the rounded ends will be produced by the drill.

Regards Mick

Edited to add: Join the holes with a jig saw and metal cutting blade.


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## seaco (19 Mar 2014)

6mm bolt 6mm hole...


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## -Matt- (20 Mar 2014)

6mm hole tends to bind on an M6 thread. Wants to be clearance ideally and therefore 6.5 or so or if not available, 6mm hole and a round file to just open it up enough.

How big is the slot Marcros? At a guess (and probably wrong but will do for an example anyway) you might be making something for the bolt to slide along, to adjust its travel?
If it were me, I'd scribe up the slot, mark and punch the centres at each end then drill the holes. You'd only need two because the middley bit can easily bit nipped out with a cutting disk on the grinder and 3mm material will be through in no time. 
Even up the flats to your markings with a flat file and take the corners out with a square one. At 3mm thickness, you should be able to do the above in about 15 mins if that.


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## marcros (20 Mar 2014)

It is a slot to allow a little bit of adjustment when levelling out and setting some fence rails on a table saw. It is easier to measure as carefully as possible and then to adjust than to guarantee that it is perfect before drilling. As for length- it shouldn't need to be a huge slot- probably just enough so that the holes do not overlap. 

I do have a die grinder which I had forgotten about. A carbide burr in that should make short work of the connecting piece. 

I have a few metal drill bits. I can easily get a 6.something mm one to give a tiny bit of clearance. I need to get the burr anyway. Failing that a file.


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## Spindle (20 Mar 2014)

Hi

I'd use a 6mm drill, twist drills normally drill slightly oversize and if you're finishing with a burr then that will be good for adding clearance if required.

An M6 x 1 thread has a major diameter, (from the tops of the threads) of 5.79 - 5.97 mm

Regards Mick


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## MMUK (21 Mar 2014)

3mm slot? Pick up a milling bit with a 1/4" shank and fit it into your router on the lowest speed setting and use plenty of cutting fluid.


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