Thread: Norman patent rear tool post.
9th Jul 2019, 08:20 AM #1Most Valued Member
- Join Date
- Aug 2015
Norman patent rear tool post.
Hi Guys, Warning very picture heavy. Two days worth of them.
One of the round toit's I have was to make a new rear tool post for my Myford lathe. Its been on the "to do" list for a while, then recently I spotted some quite cheap parting blades on "Aliexpress" at just under £5 for the pair.
They turned up the other day. That has spurred me to get on and make the tool holder, particularly as I had already acquired a suitable piece of steel.
These are the parting blades that I bought. 200 mm long, 2 mm thick and 12 mm wide HSS.
I decided to clamp the blade using two flat pieces of steel with M5 screws. In this picture I had already started machining the tool holder block.
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The block is made from a piece of 20 mm thick BMS plate off cut, approximately 50 mm by 60 mm. I first machined a 12 mm wide groove down one short edge and then marked and drilled a couple of holes 4.2 mm diameter tapping size for M5. After I milled one edge 15 mm wide in two places to allow the clamp plates to grip the edge of the parting blade. Yes I measured from the wrong edge, which is why the screw holes are slightly off set to one side. I then cut two grooves to allow the clamp plates to fit. They were clamped and spotted before the holes were tapped M5. I tried to use some epoxy filler to make the back of the slots square, but one of them came out when I was boring the centre hole.
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After marking for the centre hole the position of the split clamp was marked drilled and reamed 1/2". I used a short length of silver steel for the clamp pin cut to suit the width of the block.
After which I put it in the four jaw, centred it up and drilled it 5 mm tapping size for M6. Its drilled all the way through and then threaded from both ends. The threads do not meet in the middle, but that isn't a problem.
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The split clamp pin has to be secured in the block so that it cannot move whilst the hole for the post is been machined. I made two thick washers and use a pair of M6 cap screws, one in each end, to secure it.
08-07-2019-003.jpg 08-07-2019-001.jpg 08-07-2019-002.jpg
I then replaced the pin with the tool block material and centred it up using a dial gauge and a long thin probe located in the centre punch mark. As you can see even with the lathe running the gauge needle doesn't even move. This is the same technique I used when centring the pin for drilling through.
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The hole in the tool block was cut using a Starret 32 mm hole cutter, its a lot quicker than drilling a smaller hole and then using a boring bar, that last picture shows how rough the finish from the hole cutter was, but it left me with a couple of mm to clean up.
This is the boring bar setup. A 1/2" inch carbon steel boring boring bar, made and supplied by "Alfred Herbert" made many many years ago. I'm sure long before I was born. Anyway it does a suburb job.
Last but not least the inside of the bored hole and the pin that was cut at the same time.
That scallop will match the curve of the post when its split and a screw through it.
I now need to make a start on the post. I've a nice chunk of cast iron for this.
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