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Can you make a parting tool using HSS blanks?

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Pcmaker

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#1
I don't have a parting tool, but I have some 1/4" blanks. These specific ones:

https://www.amazon.com/gp/product/B0131IRHLM/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

Can you make a parting tool using one of these? I figure it's hard because it's gotta be absolutely parallel.

Also, my carriage is smooth to turn on the chuck side and as I move towards the tailstock, it gets tougher to turn the carriage wheel. Any tips? I've played with the bolts holding the carriage wheel, but can never get it right. That and as I adjust the bolts, I gotta keep in mind the thread dial indicator to keep it working.
 

dtsh

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#2
First off, wow that's expensive for plain old 1/4" HSS, those should be no more than perhaps $2 each. I would check with Shars, CDCO, or the usual suspects in the future.

As for the utility, I don't see any reason you *can't* use one. You will need to grind relief angles on the nose and the sides, but otherwise it should work OK. The only real disadvantage as I see it is you'll lose 1/4" of material with every parting cut...which may or may not matter to you.
 

Pcmaker

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#3
I meant grinding it down to where it's thinner. Maybe to 1/16th of an inch. The problem is getting to 1/16 and having it perfectly cut.
 

francist

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#4
You can absolutely do that -- it's the only type of parting/grooving tool I use.

You are limited somewhat to the depth though. After about 5/8" or so it gets hard to keep things consistent in the grind, but up to that is pretty easy. The trick is not to keep it parallel, but to make the top edge slightly wider and also keep the leading end slightly thicker. That way there is no drag on the sides. I'm not talking much here -- a couple of degrees if that. I use a grinding wheel and rest, I would not recommend trying to do it "freehand" although I suppose it could be done.

Mine is presently ground out of 5/16" square HSS, and the width is about 0.068" ( so just around 1/16" thick). Not the greatest photo, but here it is being used


-frank
 

Pcmaker

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#5
How else would you grind it down with a benchgrinder,if not free hand, though?
 

WesPete66

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#6
This is from a rookie, but I was struggling with a job needing parted. My parting tool was flexing like crazy. I happened to have such a ground tool in my box of goodies, and it worked great when I tried it. But yes, it's limited as to depth of cut.
As for the difference of movement, could it be wear of the bed/ways when closer to the headstock since it sees more use over there?
 
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benmychree

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#7
Obviously, the thing to do is buy a real parting tool and holder; if you intend to part off small delicate things in soft metals, you may get away with 1/16" wide tools, but bear in mind that they WILL break easily, and will tend to wander sideways in the cut, and not cut off squarely. Better use a minimum 3/32" wide tool, of the standard type, or even "T" type, but they will also wander if the cut is very deep. A 1/4" tool bit would have very little strength in the vertical plane, especially when ground on the sides to a narrow width, with tapered clearance vertically, and consequently break easily. Typically, small lathes do not seem to be particularly good at parting in the first place, even with proper tools.
One thing that I have noticed is that especially when using a QCTP, if the post is not positioned towards the center of the cross slide, instead of overhanging the cross slide, as they are often positioned, the holder with the parting tool tends to tip towards the chuck, putting the parting tool into a bind that can cause breakage of the tool.
 

Pcmaker

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#8
I have a parting tool and parting tool holder, but it won't stick in my QCTP well. I got the blade at least. I just need to find a way for it to stay in the QCTP and stay parallel to the chuck.
 

francist

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#9
How else would you grind it down with a benchgrinder,if not free hand, though?
Some people use the rest for supporting the hands and hold the tool being ground higher up on the wheel. That's what I was referring to as "freehand", as opposed to resting the tool solidly on the rest while grinding.

-frank
 

pontiac428

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#10
A parting tool holder for your QCTP is around $20 from Shars. Good parting cutter blanks are around $5 in various thicknesses and tool steels. Much easier to work with, even though a ground square blank will do the job in many cases.
 

mikey

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#11
I have a parting tool and parting tool holder, but it won't stick in my QCTP well. I got the blade at least. I just need to find a way for it to stay in the QCTP and stay parallel to the chuck.
You can grind parting tools from square blanks but it is a lot of work. You need about 5 degrees of relief on both sides and 5-10 degrees of front relief. Best way is to rough it out with a tool grinder and then use a fixture to accurately grind the side relief with a surface grinder. Assuming you don't have the equipment to do this, using the parting tool you say you have is probably the best bet.

I am unclear as to what you mean by "... it won't stick in my QCTP well." Perhaps you can clarify what kind of tool you have and what your problem is in more detail. Seems to me that sorting this one out will be easier than grinding a tool from a blank.

Just an aside but if you are not using a P-type parting blade, you should try it. I use a P1-N mounted upside down in a rear mounted parting tool holder on my Sherline lathe to part stock up to 2" OD at high speeds with no chatter or dig ins. This P1-N blade is only 0.040" thick and I've never broken or bent one. It has parted everything from Delrin to 4140 to O-1 steel without a whimper. I use a P1 or P2 on my larger Emco lathe and part from the front, again without issues, so I happen to favor these kinds of blades. I also have an Aloris inserted carbide parting tool that works well but it has a 1/8" thick insert - wastes a lot of material.
 

pdentrem

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#12
There is uneven wear on the ways. The majority of the wear is usually in the first 6-10” closest to the chuck plus the width of the carriage. If one adjusts the gibs to tighten at the chuck end the tail stock end ends up being tighter to too tight. Have to compromise on the gib settings.

As for making parting tool, if only using HSS blank, I would use a 1/2” blank not a small 1/4” one.
Post a picture of your tool post set up please.
Pierre
 

bfd

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#13
you don't need to grind the sides perfectly parallel in fact you need to add some clearance on the sides front to back and clearance on the sides top to bottom but this tool will have limited depth of cut. I have seen some parting tools on this website made from cutting up an old woodsaw blade ( like a table saw blade this gives you a carbide tipped parting tool worth a try I have never done it. looked interesting bill
 

Asm109

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#14
You grind with a bit of relief so the tip is the widest part of the cutter.. If you are parting off the exact width of the cut is irrelevant. Free handing is plenty accurate.
If you are trying to cut a groove for an oring where width is important you do one of two things.
Make cutter narrow, plunge then move the carriage over and plunge again OR
grind the cutter slowly and measure the width frequently with a micrometer. grinding is slow and it is easy to just take a thou or two at a time.
 

royesses

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#15
I have a parting tool and parting tool holder, but it won't stick in my QCTP well. I got the blade at least. I just need to find a way for it to stay in the QCTP and stay parallel to the chuck.
does your parting tool holder look like this?


This is the parting blade I use $7.95 from LMS. It works fine.


That hoder is flat from top to bottom and the P1X blade it a t shape so the blad only makes contact with the holder at the top of the tee. When tightened up it will stay in place. You can also shim up the bottom so it will stay at the proper distance from the holder. I milled a groove in my holders so the whole blade sits flat against the holder and the T sits in the groove. I had to use a carbide end mill since the LMS holders are hardened. It burned up a HSS end mill.

Roy
 
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