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How to modify Proxxon MB 140 drill stand to act as mill

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I was thinking about how to modify my Proxxon MB 140 drill stand to have a reasonably accurate vertical feed so I could use it as a mill. So I did a web search on 'Proxxon stand modification' and after several pages of results I came across this modification by a guy called Stu who posted it in a Railway Modellers' forum. I asked him for the details, and he very kindly provided the following plan:




He made his block out of Perspex, but I have never worked with Perspex before, so I thought I'd try it with an old piece of pine that was lying around. This wood one works fine and I thought I'd share the results with the forum because there has been such a lot of interest in mills. However, I have ordered a block of 100mm square Perspex to make another one because I have a feeling the screw threads will last longer.


The following is a picture of the original stand before modification:




The following are the tools I used together with the block of wood ready cut (the very cheap drill stand I used to cut the 20mm and other holes with my large drill is not shown):




As you will note, this is not an expensive modification once you have the drill stand, tap wrench and spade bit -- all of which would be useful for many other jobs.


There are a couple of changes I made to Stu's original plan:


1. The tightening bolt at the back is not threaded into the block. Instead I drilled a 6mm hole and it closes with a simple wing nut.


2. Rather than driving the 'height' bolt directly on to the top of the stand, I cut off the tip of an old chopstick, put a layer of CA glue on the end to stop it fragmenting when the bolt comes into contact, and use it as a plug in the M5 hole left by the depth stop screw (which is removed when the stand is used as a mill).




As you will find out when you try this, the dimensions are not critical.


The stand's post is 19.8mm, and because the diameter of the flat bit was 20mm, a good slit is needed in the block to give enough clearance for the sides to flex. 2mm is just fine when you put a 6mm hole across it for the M6 bolt with the wing nut. You'll note that the slit I made on the other side of the hole for the stand looks as though it reaches into the hole for the depth bolt. This is actually the bottom end of the circular saw cut, which is much shallower on the other side of the block. When I make the next one out of Perspex I'll file it out instead.


I did also buy a shielded ball bearing for the bamboo plug but it works so well without the ball bearing that I'll leave it out until it proves necessary.


In practice it seems accurate. One turn of the knob gives a 1mm change in height because the M6 bolt has a thread spacing of 1mm -- so that suits the knob I bought from Maplin very nicely indeed!





I hope this is as useful for others as it has been for me. Once I receive my Perspex block I'll post pictures of that as well.







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