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dalee100
04-13-2015, 05:46 PM
Hi,

I want to say thanks to those who commented on my question the cut off tool holder. Sadly, due to the size of the holder, I had to stay with a 0 rake. Just have to grind the rake I need.

But on the upside, I have all but a boring bar holder for my new tool post. I don't have a suitable piece of steel yet, got to get to scrounging. I did take a few photos to share of the machining.

I've been using a Norman style post on my 8x14 lathe for about 5 years. It's been a solid and easy setup to use and make. But I really miss the quick and easy 90deg indexing of a square dovetail type. When I came across photos of this post, I thought I would make one for myself. I've had the photos for a while, but finally got around to making it.

Squaring up the post
http://i.imgur.com/8fimdz5.jpg

Machining the hex on the tool post nut
http://i.imgur.com/m35Hzbr.jpg

Cutting dovetails on a slab of future tool holders
http://i.imgur.com/ITfUOx9.jpg

4 general holders and a cut off tool holder
http://i.imgur.com/1DZEtd0.jpg

Thanks for looking!
Dalee

dalee100
04-13-2015, 05:48 PM
Added two more photos

Close up of tool holder mounted
http://i.imgur.com/jpuQRbB.jpg

Close up of tool post
http://i.imgur.com/hef4JkC.jpg

Paul Alciatore
04-13-2015, 11:43 PM
Looks like a nice job. Enjoy your new post.

Doozer
04-14-2015, 12:02 AM
http://www.penturners.org/forum/attachments/f30/70736d1329705727-quick-change-tool-post-dsc_0058.jpg

Looks a bit like the Hardinge toolpost system.

-D

otherworlds
04-14-2015, 01:04 AM
Nice work!
I'm curious how you made the two long, deep slits in the tool post? i.e. big slitting saw, bandsaw, other?

Forrest Addy
04-14-2015, 01:43 AM
I like it. Sensible design, especially the flex feature on the dovetail (note the saw cut and the relief hole). Saves making parts and makes for very rigid tool holder grip - possibly equal to the gib style aloris. Tighten the side bolt and the whole side of the tool post squeezes the holder with a stiff, hefty hunk of the tool post mass as a deflection hinge.

I'm not thrilled with the giant corner relief holes at the corners of the post dovetails. True, you need corner relief to mitigate stress concentration but a circumscribed hole removes less material than a dovetail apex centered relief. More bearing and less wear on the dovetail.

What material? 1018? A36? Alloy steel? HT?

Anyway nice job, and excellent concept. Fewer parts is always a good design goal.

ammcoman2
04-14-2015, 09:07 AM
Hey, I have a patent on that!!!! Actually I copied mine from the Stevenson design and added the second dovetail for boring etc.

http://i56.photobucket.com/albums/g189/ammcoman2/P1030024_zpsee70f0f1.jpg (http://s56.photobucket.com/user/ammcoman2/media/P1030024_zpsee70f0f1.jpg.html)

Nice job. You can never have too many holders though.

Consider making the extended tool holder to clear the tailstock and also the adjustable handles (Fastenal et al)

Geoff

Doozer
04-14-2015, 10:14 AM
Consider with the Hardinge design, the cutting forces are directed
to the stationary (non-clamping) side of the dovetail. In the designs
pictured, the cutting forces are directed to the flexure part of the
dovetail. This makes the Hardinge design stronger and positionally
repeatable. It is also very easy to make, as instead of a flexure,
it utilizes a dovetailed nut and a drawbolt to facilitate clamping.

-Doozer

outback
04-14-2015, 01:29 PM
Nice job and nice design. Curious what material you used.
Jim

dalee100
04-14-2015, 11:44 PM
Hi,

Thanks for the compliments! The little bit of use so far has shown it to be very solid and easy to use. And it was fun to make. To answer the questions.

I used a piece of scrap AISI-633 for the tool post. The tool holders are A36 hot rolled. Nothing is, of course heat treated. The steels used should be quite tough and wear well in this application.

Otherworlds, I did think about using a slitting saw and the mill to cut the slots. They would have looked very nice that way. But, I was lazy and used a band saw to cut them.

Mr. Addy, When I came across the photos of this tool post, I too was impressed by the simplicity. And for all the same reasons as you. The corner relief holes should have been a bit closer together. The dovetail should have taken out half the hole. A bit of mis-calculation on my part. Hey, it looked good on paper!:p I didn't put the holes there for stress relief though. I drilled them to make manufacture of the tool holders easier. If I make a set of holders a bit over sized on the dovetail or the angle is slightly off, the holes should give the them some free space to run. At least that's my theory.

Geoff, Rats! Busted! :D Honestly, I can't remember where or when I came across this design. But I know I'm not the first to think of it or make it. I think I will be stealing your handles on the draw bolts. I like wrench-less tool changes. I do have a set of prints from John Stevenson for a tool post. But it uses a cam to lock the holders in. An nice design also. I might make an extended tool holder like that. I do have a couple similar extended holders for the Norman style post.

Doozer, It's kind of similar to the Hardinge with the dovetails being reversed. And I probably agree that the Hardinge is a bit stronger, but I don't think it's enough to matter in the real world. Kind of a "How good does good enough need to be?" situation. This should be more than satisfactory for a bench lathe.

Dalee

ammcoman2
04-15-2015, 08:48 AM
Dalee, I was indeed wrong about my reference to the Stevenson design other than the dovetail clamping arrangement. After I rearranged my brain's recall facility, I'm pretty sure I copied the design shown on the Hemingway website: http://www.hemingwaykits.com/acatalog/Quick_Change_Tool_Holder.html

I added the second dovetail since I figured the handle would get in the way on the original design when in boring mode.

Geoff

J Tiers
04-15-2015, 08:59 AM
http://www.penturners.org/forum/attachments/f30/70736d1329705727-quick-change-tool-post-dsc_0058.jpg

Looks a bit like the Hardinge toolpost system.

-D

Mebbe I'm dense, but I don't see what moves in the Hardinge post. And what do the pins do?

Doozer
04-15-2015, 10:36 AM
Looking straight on, you see a triangular shaped nut
that clamps both dovetail slots simultaneously.
In the center you can see the hole for the draw stud
with threads in it, which is connected to the clamp
handle on the opposite back corner. (background
in the picture presented). The triangular nut does
look like part of the main block, must be some
grease or grunge, giving the look of a fillet.
That makes it confusing to discern for sure.
http://www.practicalmachinist.com/vb/attachments/f33/95845d1388872406-fs-hardinge-dovetail-quick-change-tool-holders-img_7467.jpg
The pins are for the height adjustment screws to bear on.

-Doozer

dalee100
04-15-2015, 11:33 AM
Dalee, I was indeed wrong about my reference to the Stevenson design other than the dovetail clamping arrangement. After I rearranged my brain's recall facility, I'm pretty sure I copied the design shown on the Hemingway website: http://www.hemingwaykits.com/acatalog/Quick_Change_Tool_Holder.html

I added the second dovetail since I figured the handle would get in the way on the original design when in boring mode.

Geoff


It's hard to keep track of all the things Sir John has done. I didn't know Hemingway offered a kit. Though it shouldn't surprise me. But the single position baffles me. Why wouldn't you want two holder positions? Facing and boring are two common operations and being able to switch between facing and turning without effort is nice.

Dalee

otherworlds
04-15-2015, 03:32 PM
Otherworlds, I did think about using a slitting saw and the mill to cut the slots. They would have looked very nice that way. But, I was lazy and used a band saw to cut them.No need to apologize! The slot looks very straight and even; that's why I asked. :)