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View Full Version : Micrometer carriage 'stop'



Michael G
10th Sep 2016, 04:59 PM
My lathe is one of those that could be optioned up and/ or accessorised to the hilt. One of the accessories available was a carriage stop. Literally many years ago I'd started making one but stopped for more urgent things and didn't return to it. However, the other day I realised that it would come in handy for a couple of things so decided to continue.
The stop consists of a bracket (which I had) and a dial indicator case, located on a dovetail on the carriage. I did manage to find a couple of pictures of the complete item as well as some more detailed pics of the indicator case on ebay - it went for silly money but the pictures were good enough to scale from.
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The first attempt I made I didn't get the side radii right, so I had a clash with the bracket holding the micrometer. I initially tried linishing Al off but there was a fair bit to come off hence leaving it.

Today I set it up on a face plate and had another go. To do that I used a subplate with some holes tapped so that a neat fitting plug bolted on and held the top of the case. The bottom just bolted on and away I went. I blued the sides with texta so I could see what cleanup I was getting. First two photos are of the general set up, the third is of the assembly after 1 pass and the last photo of the other side. The traces of blue left after the passes show how imprecise linishing can be for uniform stock removal. It took another 15 thou DOC to get rid of those marks.
The radius is 116mm. To get that I had to reverse the tool post and after putting in the boring bar holder, remove the locking handle. The tool is a LH boring bar, bought precisely for jobs like this. The lathe is meant to have 12" swing but I think to get that you have to do things like this. Speed was only 115rpm. With potential for clamps to fly off I keep the speed down and don't stand in line with the faceplate. If doing a batch I imagine you would make up a fixture that would hold 2 or even 4 with proper mounting and get away from that issue.

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While it looks complicated, the part is actually very simple in application and a version could be made to suit just about any lathe.
To secure the indicator, there are two grubscrews that come in around the 4 and 8 o'clock positions. Once those are done up the top piece secures with 4 screws from underneath. There is a round glass and circlip to be fitted to protect the indicator but I won't fit those until I've painted it. Looking at the photo above and comparing I need to round off the top around the dial too. Not difficult - a ball nose cutter and rotary table will do it, or as the front face is angled, mount in a lathe fixture perhaps.

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The mount is just a dovetail attached to the carriage which secures with a knurled screw and is height adjusted with the grubscrew and nut arrangement.
The micrometer head is just that although strictly according to the photo of the original item it should be a LH one and (I think) read in reverse like a depth mic (another job - put on the engravings). A solid rod could be used although the adjustment would not be there.There is also a turret version with 6 threaded stops which would be useful for runs of parts.
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The indicator is not a standard sized one but the next size down (42mm diameter). I could only find a tenths version. Probably one graduated in 5/10ths would be better as even on a slowish feed it whips around faster than my reflexes can handle.

Of course, you could just use a DRO...

Michael