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23rd Jan 2020, 07:52 PM #1
Norman Patent tool post. Advice needed please
Inspired by Barron John's build of the Norman Patent QCTP, I have commenced a build of my own.
Because my lathe has a rather large distance between the top of the cross slide and the centreline of the lathe, I need to build a pretty solid rigid post.
Just happened to have laying around the w'shop a piece that might lend itself nicely.
It is a piece of steel shaft 45mm diam. with what appears to be a pressed on flange which is welded in a machined cavity under the flange. The flange is 15mm thick, 85mm diam.
Question 1. Will that likely be rigid enough, or do I need a thicker base/flange?
Question 2. If the above will be adequate, I am thinking of turning the bottom of the flange out to a depth of about 0.25mm, to about 5mm from the outer edge, so that when the flange/base sits on the cross slide, it will be only contact on the outer 5mm.
The shaft/post will be bored out for a centre bolt, into a "T" nut which will fit the cross slide "T" slot. Tool positioning will be achieved by rotation of the whole unit when the centre bolt is loosened.
I hope that all makes sense. Cheers.
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23rd Jan 2020, 08:12 PM #2Most Valued Member
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Depending on how you are holding it down and on how flat your compound is you met be better with full contact rather than a ring, you will lose some rigidity with point contact. (Defining how much, or how susceptible to harmonics it will be required more brain than I have)
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23rd Jan 2020, 08:59 PM #3
Hi Phill, Guys,
You don't need the flange ! Once the post is securely fastened to the top slide it doesn't need to move, ever !
All the hight and rotation is done using the tool holder. About a quarter of a turn on the securing bolt that is pulling the split collet together will lock the tool block solid.
My post is 32 mm diameter ! Obviously you need to scale things up or down to suit your lathe. A 45 mm post will be like the rock of Gibraltar.
Original post.
https://metalworkforums.com/f303/t20...orman+ToolpostBest Regards:
Baron J.
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23rd Jan 2020, 09:27 PM #4
I need the new tool post to have a large footprint, similar to the original in area, because it cannot be fixed to the cross slide due to the fact that I need to be able to turn from the rear (in reverse) and from the front. This lathe has much more room and travel to turn large parts behind the spindle.
The green tool post shown here has a 90mm X 90mm footprint to give the rigidity needed because it is so tall.
The flange on the proposed new one (in the chuck) is a bit smaller in area, which is my main concern.
IMG_20200123_181529.jpg
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24th Jan 2020, 01:17 AM #5
Hi Phill,
Thankyou for the picture ! You know, thousand words...
I would be using the "T" slot right at the front of the cross slide. I would also put a peg in the bottom of the post to engage with the cross slot. No way it can turn then when tightening the post down. The down side is of course that you won't be able to just loosen the securing bolt and slide the post out.
If you do use the flange, make the face flat and if desired cut it down so that it doesn't foul the feed handle.
Now since you don't have a top slide it might be prudent to make a second tool block or just a thick ring that you can use to set the hight from.
On my rear tool post I just use a piece of scrap that I put on the cross slide and under the block to set the hight and then remove it till the next time.Best Regards:
Baron J.
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24th Jan 2020, 01:49 AM #6
John, the existing tool post T nut sits up above the top face of the cross slide, by about 5mm, and the buttom of the tool post has a slot cut in the left and right bottom edge into which the T nut fits to prevent rotation of the post. (The T nut is 90mm long)
That should work for the base of the new post also?? I was going to try to use the existing T nut and post centre bolt if possible, so that I have the option of using the original setup if required.
I still haven't got my brain around that split collet on your tool holders yet.
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24th Jan 2020, 06:30 AM #7
Hi Phill,
John, the existing tool post T nut sits up above the top face of the cross slide, by about 5mm, and the buttom of the tool post has a slot cut in the left and right bottom edge into which the T nut fits to prevent rotation of the post. (The T nut is 90mm long) That should work for the base of the new post also??
I was going to try to use the existing T nut and post centre bolt if possible, so that I have the option of using the original setup if required.
I still haven't got my brain around that split collet on your tool holders yet.Best Regards:
Baron J.
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24th Jan 2020, 12:57 PM #8
This is the setup, and the post & nut I hope to use.
IMG_20200124_094018.jpgIMG_20200124_093750.jpg
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24th Jan 2020, 09:17 PM #9
Hi Phill,
No problem, just bore your post to fit the existing stud. Make your tool block to suit the new post.
Make sure that you have enough material to hold the tool size you want to use between the tool and post, and thick enough not to distort when tightening the nip screws onto the tool.
My tool holders are 1" inch thick with a cutout to hold a 1/2" tool (13 mm).
I've just looked at my pictures and realised that I've not rounded off the back edge of the rear tool blockBest Regards:
Baron J.
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