Saturday, 4 April 2020

Fixing (two) Mini Drills

Here I'm trying to keep busy during the lockdown.

I've got a couple of mini drills. These are very useful for grinding small items especially where access is tricky. The problem is that both are broken.

Firstly a Minicraft. This is a corded tool that has operates at 12v through a transformer. I'm sure that my brother gave this to me as a Christmas present many years ago. I've used it on lots of projects. 

The drill uses a keyless check that consists of a ring to hold the spindle while the chuck is turned to tighten on the drill bit etc. This isn't a great design. It's not possible to get enough force using your fingers to tighten this sufficiently. I usually have to use two pairs of pliers.

The chuck has fallen apart with the ring detaching itself.   

When sourcing a replacement the first thing to do is establish the thread holding the chuck. I measured the diameter at 8mm. The thread pitch was more tricky. I don't have a set of thread gauges so I took a macro photograph with the thread against a ruler. The pitch looks like 0.75mm.   

The standard ISO metric thread in 8mm comes in 0.75mm pitch so this seems ok.    

The new chuck

An issue is that there is no way to tighten the chuck. This chuck lacks the ring the original had. Some drills have a spindle lock to allow tightening but the Minicraft doesn't. It might seem rough but I filed two flats in the spindle to allow it to be held with a 7mm scanner.  

And it all works fine!
The next drill is a cordless one from Lidl under the Parkside name. It uses a collet rather than a chuck. The nut is aluminium and the thread has stripped. A chuck might be more useful so I looked for one of these.    

According to a YouTube video the Parkside tool uses the same thread as Dremel ie 9/32" x 40 ME (Model Engineer) I measured the thread pitch it does seem to be 40 tpi (thread per inch) 
"A commercial use of this standard does not exist" - you think?

Will it fit? Will it work? - I'll know then the chuck wings its way to me from China.

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