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Old 04-07-2011, 12:02 AM #1
hansolo8221
 
 
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QCTP question

So, I have a question for all of you machinists out there. I am setting up a QCTP on my lathe and was wondering what the optimal height for it is. I have a mill/lathe combo machine (don't hate me, please ) similar to a Grizzly G4015Z. I've been doing some modifications to make it, well, less sucky, which currently means putting on a QCTP.

So here's the question. If you look at the G4015Z, you'll notice that there is a riser block between the compound and the tool post itself. When I was preparing to install it I measured everything and figured I'd just put the QCTP on top of the riser block as well. Well, after modifying everything to work (which involved some cutting, grinding, turning, drilling, tapping, etc), I put it all together, dropped a cutting tool in a holder and centered it, and as it turns out I have to drop the tool holder almost all the way to the bottom of the post. Here's a couple pics (sorry for the crappy quality, I had my video camera handy because I was shooting video, and apparently it takes really lousy still pictures ):



(You can make out the nice big CHINA on the side, though )

The other tool holders, like the knurling and boring tools, end up about the same height as well. So, the question is, ideally, where do you want the tool holder to sit? I would assume that you want it about midway, so you have room to adjust up and down if necessary. Right now the top of the holder is about 3/4" down from the top of the post, so my plan is to shave the riser block down about 3/8", which should bring the holder to about center. It's perfectly usable as-is, and since this is with a 1/2" tool, which is the largest it can hold, I can't imagine needing to drop the holder down further; if anything, using a smaller tool would mean bringing the holder up. Still, I'll have more peace of mind knowing I have room to adjust it later should the need arise.

Before I do any more cutting on it, what are your opinions?
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Old 04-07-2011, 08:15 AM #2
y0da900
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Make sure you check a parting tool, the one that came with my QCTP is held up at a slight angle. As long as the largest tools your system can hold are where they need to be, there doesn't seem to be any need to make changes. If you upgrade from those brazed carbide tool bits, you might want to consider getting 1/4" or 3/8" tooling, which would improve your adjustment range a bit.

You can always shave it down if you run into a tool that is problematic, but it is rather difficult to put back if for some reason you ever wished it was there. I'd leave it until necessary to shave it.
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Old 04-13-2011, 12:47 PM #3
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Is this a post or wedge style QCTP? if it's a wedge you'll be fine, but if it's a post i would consider making a new riser plate that will put the majority of your tools on center with the post.

also, I really hope your not centering your tools off the tail stock unless your tail stock is perfectly on center at every point along it's travel.
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Old 04-14-2011, 12:53 PM #4
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Quote:
Originally Posted by y0da900 View Post
Make sure you check a parting tool, the one that came with my QCTP is held up at a slight angle. As long as the largest tools your system can hold are where they need to be, there doesn't seem to be any need to make changes. If you upgrade from those brazed carbide tool bits, you might want to consider getting 1/4" or 3/8" tooling, which would improve your adjustment range a bit.

You can always shave it down if you run into a tool that is problematic, but it is rather difficult to put back if for some reason you ever wished it was there. I'd leave it until necessary to shave it.
Good call on the parting tool holder, I forgot to check that one because it didn't come with a blade. I have a couple on the way now, but it looks like it should work fine at this height.

I looked at indexable tooling, but ended up going with a set of the standard tools because it was cheaper for a wider variety of cutters. I don't do enough cutting that I am going to wear them out very quickly, which is where the indexable tools would come in handy; I am more likely to do a few of a wider variety of cuts, rather than a large number of the same cuts over and over.

Also, I went with the full 1/2" tools for the rigidity (they were also pretty much centered automatically in the stock tool post). Is there a particular benefit in downsizing to smaller tooling?

Quote:
Originally Posted by cs900 View Post
Is this a post or wedge style QCTP? if it's a wedge you'll be fine, but if it's a post i would consider making a new riser plate that will put the majority of your tools on center with the post.

also, I really hope your not centering your tools off the tail stock unless your tail stock is perfectly on center at every point along it's travel.
It is a wedge type.

I usually center off the tail stock. I don't have any formal machinist training, I've picked up most of what I know online, and I've seen a few videos and guides that recommended doing it that way. I've also heard the method of facing a piece and adjusting tool height until the face is even. My question on that method, though, is what do you do for boring bars, parting tools, or any other cutter that is not intended for facing?


I've used my lathe for a couple parts now with my new QCTP. First is a custom shortened piston housing for a Tippmann A-5 Cyclone feed system:



The right is the stock aluminum housing, which I shortened for a custom modification (which I really need to get around to making a separate thread about), the center piece is the front section that I hacked off. I did this job years ago when pretty much my only tool was a Dremel; you can see my hack job of reproducing the groove. On the left is my new one cut from black Delrin.

I'm also working on a custom poppet valve, for ICD markers at the moment, though it could easily work for a variety of other poppet markers. I'm going with a ramped valve face, similar to the zenitram valve. What tool do you recommend for an internal chamfer like that? This is the setup I used for now, though I could not get a very smooth surface finish from it:



I used the boring bar because I had to grind the face of the tool at a sharper angle, otherwise the lower edge of the tool would drag against the surface. Viewed from the top the tool bit is square across the front, and I came in perpendicularly to the angle of the chamfer. I needed the length of the tool to get the reach inside the valve body at that angle. Is there a better method than this?

Thank you guys for all your help and input.
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Old 05-25-2011, 10:23 PM #5
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I think you pretty much need a CNC rig to do a Zenitram valve.

As to centering your quick change tool post, as metioned earlier use the cut off tool as you'll notice right away if your height is off. The other option is as set of rockers for your QCTP so you just set it and forget it.

I am in the same predicament as I just got myself a 9 X 20 Lathe.



^^ There's a CAD version of a Zeni I did.
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Old 05-26-2011, 07:24 PM #6
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If the inlet is actually curved, you can get a concave radius cutter that should do it, but you are stuck with what radii are available. If you are doing it in a softer metal or plastic, you can make your own radius cutter by drilling into steel with the appropriately sized drill and removing 3 of the 4 quadrants. Difficult to create a tool this way that has much rake, but that isn't an issue for brass or plastics.

If you just want it conical, I just made a tool with an HSS blank at the angle that I wanted and feed it in slowly. Works great, it's how I did the Leprechaun Nelson valves on MCB.

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Old 05-26-2011, 07:54 PM #7
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Shiny.

The Zenitram valve actually has two radii. I assumed when I drew it up that it was a large radii curve and then a simple mating fillet.

The stem however is a single radius piece.

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