Source for QCTP parting holder screws

ericc

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Hi. I have a parting blade holder that is fine except for the head of the wedge screw. It got wallowed out, as the import screws tend to do. For some reason, it is hard to find a replacement. I looked at the screw carefully, and it looks hard to make. It has a right hand thread on one end, a left hand thread on the other, and a set screw allen drive. This is a funny screw, and I don't think that Home Depot would carry it. Is there a ready source, or does this mean buying a new 207 holder? "Make do" is not a decent answer since insufficient tightening of the screw can allow the blade to creep out while cutting, leading to a lathe crash. This is not hypothetical. They did not blame me, since they said it is understandable that a beginner would make the wrong (easy) choice when put in this situation. Also, there is a huge temptation for the makerspace management to "make do" a little while longer before biting the bullet and replacing the whole tool holder only to get the screw wallowed out again.
 
If I understand correctly you should be able to source from MSC or Fastenal. Search STC-20 (common size we use around here in our shop) and you should be able to find a standard size to fit your tool holder.
 
Is it possible to drill a hole through the current damaged wedge screw itself and then tap some new threads for a secondary bolt or to drill out the current threads in the holder body and retap that to a more common screw/bolt?
 
The function of the parting tool holder requires the differential screw. It is possible to make a differential screw out of a right and left hand screw welded together. That is probably the cleanest way to do it. I searched STC-20. This is the correct kind of screw, but wrong length and thread.

The ghetto solution is to TIG weld in a new screw head. It is OK if it protrudes, but it cannot be too fat, else it won't thread in to be installed. I'd rather not do this, since it is a pain, and the head would almost certainly have to be heat treated again, unless it was a long extension.
 
The function of the parting tool holder requires the differential screw. It is possible to make a differential screw out of a right and left hand screw welded together. That is probably the cleanest way to do it. I searched STC-20. This is the correct kind of screw, but wrong length and thread.

The ghetto solution is to TIG weld in a new screw head. It is OK if it protrudes, but it cannot be too fat, else it won't thread in to be installed. I'd rather not do this, since it is a pain, and the head would almost certainly have to be heat treated again, unless it was a long extension.
The stc-20 bit was only meant to be a lead for you to follow. There are other sizes available( e.g. stc-4) that may meet your needs.
 
The screws like the STC-20 that bakrch gave as an example is the right type of screw as said but since the OP mentioned 207 holder I'm assuming it's an import. I've never seen this type of screw offered in metric or even a replacement for that parting holder.

Might have to make one. If broaching the hex socket is not an option could make it longer & stick out to machine a hex head on it.

Maybe email Shars to see if they can provide a replacement? If not, buy a new one unfortuantely, they don't cost much. I have one of these & never use it. I personally would get a different style holder. Or if the OP prefers this style, might be worth investing in a genuine Aloris one.
 
you may need to forget the fancy double pitches on the screw.

if you were so inclined, drill out the female threads in the toolholder and drill clearance for an long M5 bolt, or long M5 socket head screw
use the longer bolt to capture the wedge and draw the wedge to the tool
 
I was hoping there was an answer to this as mine has gone the same way.
I was thinking of just a bolt as a replacement but havnt dont it yet.
 
Hi. Drilling out the threads sounds like a great idea. That means that I'll be able to use a readily available right hand screw.

The comment about preferring a different tool holder are right on. I prefer using something else, but this is for someone I am helping out.
 
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