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Old 03-21-2014, 07:53 PM
burdickjp burdickjp is offline
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Default trying for an elegant and effective quick change tool post

I'm looking to put together a simple quick change tool post with emphasis on ease of manufacture and positional accuracy. I'm not much worried about being able to change tools one-handed, or in record times. I want to be able to spend time setting up my tools and know they're in the same spot when I change them out.

I came across Lew Harstwick's awesome design here at homemadetools.net. I like the idea of ground rods and V grooves.

In trying to fit it with my wants I've decided to tackle it a bit differently, shown below:


This is a top view. The tool holder is on the left. The two ground rods and related hardware are roughly center. The tool post is on the right. My Sieg C2 uses a 10mm stud to mount the tool post, so there's a through-hole centered on the tool post to accommodate it.

To pull the tool holder against the post I'm looking at using a regular T-slot and T-slot nut engaged by a 10mm socket-head cap screw. This is the horizontal screw in the drawing. You can see that it is offset vertically to clear the tool post stud. You can see a similar through hole for mounting a tool holder parallel to the axis of the lathe, which is similarly offset.
I'm thinking about changing the design to have the through-studs centered between the ground rods, which would put the tool post stud offset from the body of the tool post.
One issue I'm foreseeing is that t-slot nuts are relatively short, which means they'd only work for a small vertical range of tool holder positions. To increase travel I'd either have to make one as tall as the tool post, which wouldn't be hard, or bore the block in several places to allow me to put the nut in a few different vertical places, depending on the desired height of the tool.

What are your thoughts on this idea? What do you think of the through-studs, the regular T-slot nut, and the positional accuracy of the ground rod on v-slot design?

Thanks!
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Last edited by cutter; 03-21-2014 at 09:35 PM.
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  #2  
Old 03-21-2014, 09:36 PM
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Scotts Scotts is offline
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Welcome to our place on the web. We are glad you are here. An excellent picture and drawing by the way. It would be a shame to see it go away.

Please read here we enjoy pictures so much we would like them to remain for as long as each thread is accessible.

Someone will be along more knowledgeable than I about your project.

Thanks again for participating and adding to the discussion here.

Scott

I see I was typing and it was being fixed.
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Old 03-21-2014, 09:42 PM
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Welcome, Mr. Burdick.

We do not use embedded images or offsite hosting on our website.
I realize that this is quite different from most other sites but you can read the reasoning behind it in this part of our FAQ.

However, you have provided an additional reason; I could not read your post without scrolling side to side on a 21 inch monitor and we're not really enthusiastic about side scrolling.

I have removed your embedded image and uploaded your drawing as an attachment..
If you click the thumbnail of the drawing it will open in a reduced size. then if you click it again it will open full size in a new tab.
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Old 03-21-2014, 09:45 PM
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Not to be a wet blanket or anything but why re-invent the wheel? There are a number of good quick change toolposts on the market already. Not sure what you'll gain by making your own...
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Old 03-21-2014, 11:10 PM
burdickjp burdickjp is offline
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Quote:
Originally Posted by LKeithR View Post
There are a number of good quick change toolposts on the market already. Not sure what you'll gain by making your own...
That's not something I'd expect to read on a forum about fabrication...


I finished out my initial idea.
Things changed: perpendicular and parallel through screws are now centered and intersect, so you get one or the other, but not both. This puts the t-slot nut centered between the two rods. The tool post stud is offset. There's a screw and two thumb nuts to locate the tool holder vertically. The vertical locating screw is M6. The screws holding the rods to the tool post are M4. The through screw is M10. It'd be nice to reduce the tooling requirement to as few tools as possible.
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Old 03-21-2014, 11:51 PM
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GWIZ GWIZ is offline
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Welcome to the Site.


The picture is a side view (without the rods shown).
Too keep the clamping bolt in the center I would try adding a center stud that is threaded from both ends that will allow you too drill a hole thru its center.

As to the T-nut, you want too keep it from flopping around you can add a dowel pin or cut a slot in the post so the T-nut can track, extend into.
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Old 03-22-2014, 12:06 AM
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RancherBill RancherBill is offline
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I am not a machinist.

I thought I had seen one like this before. It is very similar to the Dickson Tool Post. If you can believe the write up, it is one of the best designs in the world along with Aloris, Multifix, Tripan and Multiquick.

I look forward to your build.

Welcome.
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Old 03-22-2014, 01:54 AM
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Quote:
Originally Posted by burdickjp View Post
That's not something I'd expect to read on a forum about fabrication...
I guess it depends on your point of view. Some of us have the time and inclination to make our own tools; some of us don't. Since I'm still working I want to maximize the time I spend making saleable chips. I get more than enough "project" work making specialty jigs, fixtures and tools; I don't have time to make "basic" tools that are readily available over the counter...
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Old 03-22-2014, 08:01 AM
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Roundrocktom Roundrocktom is offline
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Welcome to the site.

I like your tool post! Nothing wrong at all, simple easy design.

GWIZ pointed out how to keep the T-nut from flopping around.

I have a Aloris tool post on my lathe. I've made my own holders for it, but what a pain! I suspect the first builders used shapers to cut out one long dovetail, thin sliced off blocks to machine into tool holders. With a slot cutter, and using simple dowels, that design is easier to make.

Lew's "wedge cam" is very neat. When I've need a quick "eccentric" on a shaft, I've opened up my three jaw, slipped in some 1/4" shim, clamp down and machine lightly. No, tail stock doesn't line up, but is fast as simple.

While I can buy most fixtures I need, half the fun is making something. I'm in the shop for pleasure work. Not my daily job, but something I enjoy.

Last edited by Roundrocktom; 03-22-2014 at 08:07 AM.
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Old 03-22-2014, 09:15 AM
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Quote:
Originally Posted by LKeithR View Post
I guess it depends on your point of view. Some of us have the time and inclination to make our own tools; some of us don't. Since I'm still working I want to maximize the time I spend making saleable chips. I get more than enough "project" work making specialty jigs, fixtures and tools; I don't have time to make "basic" tools that are readily available over the counter...
yep!!
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