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Thread: Norman patent rear tool post.
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9th Jul 2019, 07:25 AM #1
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.
07-07-2019-004.jpg 07-07-2019-003.jpg
These are the parting blades that I bought. 200 mm long, 2 mm thick and 12 mm wide HSS.
07-07-2019-001.jpg 07-07-2019-005.jpg
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.
07-07-2019-006.jpg 07-07-2019-015.JPG 07-07-2019-002.jpg
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.
07-07-2019-011.JPG 07-07-2019-007.JPG 07-07-2019-008.jpg 07-07-2019-009.JPG
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.
07-07-2019-010.JPG
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.
08-07-2019-004.JPG 08-07-2019-005.jpg 08-07-2019-006.JPG
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.
08-07-2019-007.JPG 08-07-2019-008.JPG
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.
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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.Best Regards:
Baron J.
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9th Jul 2019, 08:04 AM #2Most Valued Member
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Nice work. I’ve never thought to rough out a hole with a hole saw. Good idea.
Chris
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9th Jul 2019, 09:04 AM #3Most Valued Member
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In regards to the pockets you have cut for the clamp plates is there any reason why you didn't use a smaller diameter end mill/slot drill to finish the pocket reducing the size of your radius.
If you had used a smaller tool piece you could of almost had it flat at the rear, and if practical you could of machined the rear/back edge slightly wider to give you a slight TEE shaper and your plates would fit with only a small radius possibly showing at the rear.
Nothing wrong with what you have done just another way to possibly make it look slightly neater.
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9th Jul 2019, 11:00 AM #4
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9th Jul 2019, 05:54 PM #5
Hi Guys,
Thank you for your comments ! If I'm completely honest, simply laziness Anyway at that point I had realised that I had measured from the wrong end and the screw holes were now offset.
FWIW, I'd had a visitor that brought me some goodies ! One of the things we talked about was filled epoxy putty and how good it was for filling voids and the like. So that is why I/we used some to fill the back of the slot. After about an hour you could file it flat, and then I used a wood chisel to get it flat to match the surface.Best Regards:
Baron J.
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9th Jul 2019, 07:09 PM #6
If you make up 2 new longer clamping plates and file them to the same shape, it will look like it was meant to be. Maybe it's just me but it would drive me crazy looking at it or the putty on a machine tool.
Talking about putty, I used to have some quick steel that came in a tube and you kneeded it together. I picked it up for someone's job on a car at the time from my local auto place.
The owner selling it to me who I had know for 30 years and used to be a fitter/turner told me his son was racing motorcross bikes and broke a lever, not having a spare on the day they used the quick steel to add to the bit left and make a new lever. He came home with it still working fine and it went into the spare parts.
Amazing how they have come up with such a product, I know the couple of times I used it that you could file/shape and drill it not long after being applied.
Nice work on the toolpost anyway, look forward to the updates.
I could do with a rear toolpost myself, but I am not going to pay $500 for another Dickson style one. Unlike yours mine is a bit more complicated, but it is possible.Using Tapatalk
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10th Jul 2019, 01:50 AM #7.
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Hi John,
Back in 2015 you showed us a very neat one piece rear toolpost you'd made that appeared extremely rigid. https://metalworkforums.com/f65/t196...06#post1878306
I'm keen to hear what advantages the Norman type post might have over its predecessor because I'm toying with the idea of making another rear post to accommodate tee section parting off blades.
Bob.
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10th Jul 2019, 05:43 AM #8
Hi Bob,
Good lord, I'd completely forgotten that I posted that ! Was it that long ago, 2015. Now that you have reminded me of it
I was actually thinking about using that big chunk of cast Iron to make the new post. Particularly since it has already been machined to fit the "T" slot. It just needs turning down to 35.2 mm diameter to suit the tool block.
The thoughts behind it was to be able to take advantage of the interchangeability of tool holders between the front and rear of the cross slide. For instance I tend to thread away from the chuck and it would be nice to be able to put the threading tool in the rear tool post.
Thankyou for reminding me.Best Regards:
Baron J.
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10th Jul 2019, 10:13 AM #9Most Valued Member
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That will certainly be handy John, but it will also allow for quick and easy sharpening of the parting tool blade. In my experience having a sharp blade does more to alleviate parting problems than any other remedy. The next best “fix” I think is having some back rake built into the holder. If you have that, sharpening simply involves a quick touch of the face of the blade against the side of the grinding wheel.
Chris
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10th Jul 2019, 06:57 PM #10
Hi Chris,
Just loosening two screws will allow the blade to be removed and sharpened, and just loosening the Allen screw will allow the whole tool block to be removed, so you wouldn't always need to remove the blade.
Just a quick note for others reading these posts.
The blades that I have bought are 2 mm thick and 12 mm wide. They are a rectangular cross section and are not tapered. The tool block uses a simple groove with clamp plates that grip the blade by compression between the top of the blade and the bottom of the groove.Best Regards:
Baron J.
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11th Jul 2019, 02:47 AM #11
Hi Guys,
I mentioned back in post No: 5 that I had a visitor, and we had talked about "Epoxy Putties" well here are the pictures of the goodies I got given to me
10-07-2019_001.jpg 10-07-2019_003.jpg 10-07-2019_002.jpg
It helps to get to know the company rep
10-07-2019_004.jpg
This is the epoxy putty that was used !Best Regards:
Baron J.
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11th Jul 2019, 08:38 AM #12Most Valued Member
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- melbourne australia
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Good score. It would be a very expensive to buy all those items in Oz.
Chris
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11th Jul 2019, 11:38 PM #13
Toolpost column.
Hi Guys,
Took the wife out shopping today, so not got a lot done.
11-07-2019-002.jpg 11-07-2019-001.JPG
I found a suitable M6 cap screw for the split clamp. It needs about three or four extra threads on it to get the length right. This is how it looks both inside and outside the tool holder block.
11-07-2019-004.jpg 11-07-2019-003.jpg
I had toyed with the idea of using the existing cast iron parting tool holder, you can see it in the second picture at the back, but since I had a suitable length of 40 mm diameter round BMS bar I decided to use it. Also it would mean that I had a parting tool that I could use whilst I finish the new one.
Now I've always made the assumption that BMS bar is reasonably round ! I stuffed it into the four jaw and clocked it up, and put a centre in it. Then I turned it around and checked that it was still true. No way ! it bounced up and down around 25 thou. So to double check I turned it back around and clocked it again. It was way out of true. In fact even rotating the piece there was only one spot where it still clocked true.
So I turned it around again and re-clocked it true and put in a centre. After taking the chuck off and putting a hard centre in the spindle and a live centre in the tail stock, I re-clocked the piece of bar only to discover that it was a bit like a five lobed corkscrew. Only a few thou variations but it did surprise me.
So I set it up in the lathe between centres. I couldn't lay my hands on either the lathe dog or the catch pin, so I had to improvise with a bit of 10 mm stud bar and two nuts and washers. I drilled and tapped M6 in the worst reading end to be able to use a short M6 cap screw as a catch pin.
After setting it all up, it took a 10 thou cut to get the piece of bar truly round and parallel.
So that is as far as I've got at the moment. Next job is to turn it to size.
Thanks for your comments.Best Regards:
Baron J.
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11th Jul 2019, 11:57 PM #14Golden Member
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I've got the impression that if you look very carefully, things that are assumed to be round like bars and drill holes can be a bit like UK 50 pence pieces. Articles pop up in the ME and MEW magazines now and then discussing this. Something to do with the centreless grinding process and reuleaux triangles but I dont really know what I'm talking about here just vague memories.
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12th Jul 2019, 12:06 AM #15
Hi Bill,
Yes I'm slowly starting to discover strange things like that ! I've always assumed that a drilled hole will be round, and it is ! That is until you start to ream it and find that you get that slip stick behaviour.
All part of the learning curveBest Regards:
Baron J.
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