4 way tool post on 12x36 woes..

LEEQ said:
I just went to yahoo and typed in qctp. Qctp plans popped up as an option. I clicked it and all different kinds of plans popped up with a variety of difficulty. There is something out there just waiting for you to see and make your own. you might need to change scale of some parts, but no step for a stepper. I can't decide which one to do myself, when mill is finished I'll pick one and dive in. Good luck

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Something I noticed about prefab Chinese carbide bits, is they do not sit the same height from bit to bit. I have two sets and no two bits cut at the same height. If you don't grind bits or use qctp, shimming will be required. Something to consider when determining the depth of that facing cut. You will also probably lose the detents set at 90 degrees if you cut the bottom of the fourway.
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Great :) haven't had a chance to look yet, was in the garage mounting my spindle box. Now just have to save up for a R8 collet kit and I can finish the mill off.
 
Did some digging and found some nice looking units. Have a few questions about the quick change ones that use an off center round to hold the tool holders.

First, going to try to make one, but not sure about the eccentric post, specifically how "off center" to make it. Also, is there some form of "stop" so that when your tightening it it doesn't keep spinning round, or does it reach a point where you cant go any farther?. If this is the case, what stops it from turning back the other way when your cutting ?

Secondly, I notice that all the ones I see use brass rods to put pressure on the tool holder to lock it. I have never played with brass and have none, so what about steel ? Is there a specific reason for brass. (need some serious education on brass lol).
 
Brass is softer than steel but harder than lead. Using brass will not damage your tooling etc when you tighten down to lock in place. Lead is too soft under some applications as it will move and relax after a time or if there is a continuous vibration. Lead works nicely under a set screw when there is a thread that the set screw would damage if used alone.
Pierre
 
pdentrem said:
You can shim the 4-way tool post higher and use an endmill in the spindle to machine the bottom surface of the tool slot. That way you are lowering the tool slot as you feed the tool post across the front of the end mill. Feed from the back towards you that way the backlash is removed.
You will still have to shim no matter what you do. It is the nature of the beast.
The pictures shows the start position which is the tool post is behind the end mill further from you, and the second shows the finishing position with the tool post closer to you.
Pierre
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Just an update.

I ended up taking this route, but only did two sides of the four way (that way if I screwed it up, it wouldn't be totally useless). It seems to work ok, but I think I could use to take another .002" or maybe a bit more off. I didn't have tons of shims to play with. I ended up stacking some of my paralels on the cross slide, and placing the 4way on that. Sorry, I didn't get any pics! :-/


Anyway, It is much closer to center height now, and I think a BXA wedge type is in my future soon!
 
Good going.
To set you tool height with a 4-way or similar setups, use feeler gauges under the tool. They have multiple leaves of varying thicknesses and the sets are cheap and easy to find.

Using the parallels to lift up the post is a good way. I used a couple HSS tool blanks just to illustrate on how to it. Naturally using an end mill in the chuck and shims tends to limit what one can do without doing multiple setups to achieve the amount of metal one requires to remove. Better to remove a bit much and shim the tool back up to center line than have the tool still too high.

I have an AXA wedge on my new to me lathe. It was originally on my 10" Atlas and I now have it on this lathe.
Pierre

new-1440.jpg
 
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