Installing a QC tool holder?

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littlejack

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Hey guys:
Another elementary question for you all.
I have a quick change tool post that I want to use on my lathe. I am wondering what is the usual method of fitting it to compound?
I am putting it on my QC 10" 54" Atlas. The milled flat area that the original tool holder (lantern) sits on, is not big enough. That is to say
that when turning the QC tool holder in position, the corners of said holder ride up onto the top of the compound casting.
Now for the question:
Is the proper way to fit the QC holder, to mill enough of the of casting off to allow the corners to clear?
The other option, would be to remove material from each corner of the QC tool holder, so that the corners clear the top of the compound
casting.
What is the proper procedure?
Jack
 
I think most people machine the compound casting. Whether on the Bridgeport or with a file, any method will do. I brought mine to my local job shop and they milled the casting and made a T nut for me.
 
When I put mine on you need everything off the compound so all that is there is a t slot. If you have a t nut with a screw hole in it you can use it to hold the Qctp down or make a t nut to fit then just tighten it directly on top of the compound. I've never touched the compound to machine it, to me it weak on it's own I've seen one snapped off.

Todd

I can send a pic of my set up if it will help you.
 
I have seen some compounds that had some of the hump milled off a bit to clear the QCTP, but you can put a shim under the QCTP to raise it up enough to clear the hump at the top of the compound. Because the level of the cutting tool is adjustable this should not be a problem.
 
Either remove the little bit of the hump to clear the tool post corner or fit a spacer underneath to lift it up will work. The compound usually breaks at the T-slot, as this is the thinnest thus weakest point. Mine was repaired prior to my getting the lathe. I made a new compound to replace the original when I bought a QCTP set. It is a topic posted here a while back.
Pierre
 
The bar that fits in the slot of the compound should be slightly thinner than the slot and either the bolt that is threaded into it is short enough to not penetrate that bar or the bottom of the bar has been dimpled such that the bolt cannot penetrate it.

This is not unlike Tee nuts for a Tee-nut slotted table. The Tee nuts should be dimpled on the bottom so the bolt can't penetrate them. Allowing a bolt penetrate the Tee nut - or similarly the bar used to secure the QCTP - is what breaks the top part of the slot in the compound, or breaks a chunk out of the Tee-slotted table.
 
Last edited by a moderator:
Thanks guys for all of your input.
After reading the first three replies, I decided to remove the hump on the casting with my "Chinese" drill press.
I realize, and have read that a drill press is NOT the proper machine to use as a mill, as the spindle bearings are not for side thrust.
I have used this one a couple of other times for light jobs, so I knew it would work.
I have a cheap "Shop Fox" X and Y drill vice and locked the compound in. I fed the compound back and forth (with the drill off) and
adjusted the level of the drill press table to get it flat.
I used a new 3/8" end mill to do the milling. I went slow, and only took off a few thousands off per pass. It came out perfect.
The QC tool post, fit real nice.
As for the T-nut, I made it a couple weeks ago. I used a piece of 5/16" cr flat bar. I drilled and countersunk a hole to take a 5/16"
nf counter sunk bolt. When the top nut is tightened to lock the QC down, the flat bar and the bottom of the QC tool post sandwich the
top of the T-slot in the compound and there is no worries about the casting being broken. The head of the 5/16" bolt does not push on the
bottom of the T-slot and try to push the T-nut up and break the casting.
Again, thanks guys. Much appreciated.
Jack
 
littlejack said:
Thanks guys for all of your input.
After reading the first three replies, I decided to remove the hump on the casting with my "Chinese" drill press.
I realize, and have read that a drill press is NOT the proper machine to use as a mill, as the spindle bearings are not for side thrust.
I have used this one a couple of other times for light jobs, so I knew it would work.
.....<snip>....Again, thanks guys. Much appreciated.
Jack
Click to expand...

I am glad it came out good.

The biggest problem with using a drill press as a mill is the way the chuck is held in the bottom of the spindle inside the quill. The chuck is usually mounted on a JT to MT adapter without benefit of a draw bar to secure it from the top. The side forces generated while milling can cause the taper to let go of the chuck mount and it will come flying out of the spindle at warp speed.

Be safe!
 
S_C:
I did not realize that about the chuck mounting. Thanks for the tip.
Jack
 
Some (but not many) drill press spindles have a threaded nose that the chuck screws onto. Some have a JT (Jacobs Taper) nose. I think the majority of the Chinese made ones have a 2MT or 3MT spindle nose. The chuck won't come loose on the threaded nose ones (but a drill chuck isn't a good way to hold a milling cutter as both the cutter and the chuck jaws are hardened). The main danger with either of the taper mounts (assuming that the spindle is not extended much) is to the workpiece, not the operator. When the taper arbor lets go in the spindle, the cutter will chew up the workpiece surface. Especially if the arbor is the tanged type (which most seem to be).

However, you got it done without that happening. :))


Robert D.
 
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