# How to make a cut off tool?



## jaded13640 (Feb 10, 2017)

I had to do a little project recently where I needed to make a "bushing" that was about .300 dia by about .300 thick. I had a much longer piece of steel stock, about 3 or 4 inches long, I could have cut a smaller piece on the abrasive cut off saw but, it was kind of a short piece and decided not to. But, of course that meant I had to face away ALL the stock I didn't need AND, had to hold that little tiny piece, that was the finished product, in the chuck. 

So, it took forever and was just a stupid little piece to tighten up the shifter rod on a truck where the plastic bushing had worn down to nothing. It was held on with a cotter pin and it broke, I was doing a whole different project on the truck when he mentioned he had to tied it back together with a jump rope. I didn't even notice it till he mentioned it and it had no way of getting the correct bushing that late at night but HAD to get the truck done that night, he had to drive it to work the next day.

What might have done better? 

I took the entire machine tool operations sequence in college to get my drafting and design degree years ago. The idea was that by having to actually make stuff we'd become better designers because we'd understand things like tolerances. For example, why you don't put a four place decimal on a drilled clearance hole, you really can't achieve that kind of accuracy with a drill. It all made sense than AND I learned I was actually pretty good at machining in the process. At one point when I got laid off from one design shop I worked as a machinist at a shop. It was great to have gotten that training that I never guessed I'd need. Now I have a small mill and lathe if I need to make something.

So how could I have made that simpler? What should I have done to cut the time? I don't have a good way of cutting stock, the only way I could have really done it better with what I have is to have put the stock in the vice and cut it off with a cut off wheel/die grinder. 

Maybe I could have turned the diameter and then used a cut off tool, but I don't know how to make one, I can't remember how we did that in school and never had to do it in the field.

Thanks in advance,

Wayne


----------



## mikey (Feb 10, 2017)

Wayne, it sounds like you have a definite need for a parting or cut off tool. What kind of lathe and tool holding system are you using? I ask because most of us use a parting blade held in a tool holder, held in a quick change tool post. We buy the tool; we don't make it (although you could if you've a mind to). There are HSS blades and inserted tip blades and brazed carbide blades but all are held in a tool holder. So, what do you have for a tool holder?


----------



## jaded13640 (Feb 10, 2017)

My tool holding system is just the simple, old screw in the top against the tool holder deal. It's got the rounded "keyway key" and cup deal at the bottom and you have to set it up every time, no quick release.


----------



## stupoty (Feb 10, 2017)

If your parting off small diameter parts (or thin wall) I find a  hss tool blank ground to a parting tool works well.

Stuart


----------



## mikey (Feb 10, 2017)

Are you talking about a lantern tool post? I know they had parting tool holders for those but cannot find a pic of one. If you have such a holder then you'll need to grind a tool for it. Or, you can switch to a more modern quick change tool post and avail yourself of the many choices for parting tools. Hopefully, a member who uses those lantern tool posts will chime in soon and be more helpful.


----------



## jaded13640 (Feb 10, 2017)

Yep, it looks like a lantern, must be the "lantern style". I do very little with this machine. Every once in a great while I need to make something totally different. I have what I have, I really can't see retooling with a quick release. I know there was a time where there was no such thing, I guess I'll have make one, if anyone can  help with that, I'd really appreciate it.

Wayne


----------



## tq60 (Feb 10, 2017)

In a jamb like this one just cut a small "v" where you need to cut and with lathe running slow just use a hack saw.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


----------



## jaded13640 (Feb 10, 2017)

Good idea, simple. Sometimes simple is best.

Wayne


----------



## David S (Feb 10, 2017)

If no parting tool, then I would have cut the rod off with a hacksaw to yield a piece about 0.5" long then face it off, turn it around and face it down to 0.3".

David


----------



## Wreck™Wreck (Feb 10, 2017)

No reason to make one as it is far less time consuming to buy it, you are after all concerned with machining time as you mentioned. Spending 2 hours grinding a tool for one 30 second operation on a handful of parts is not productive.


----------



## jaded13640 (Feb 10, 2017)

True wreck, but at the same time, as little as I'd use it, I'd only have to make it once. The hack saw trick sounds easiest, or buying one. But, if I have the tooling stock and the free time, it doesn't cost me anything and experience is most often a good thing. Your thoughts?

Wayne


----------



## royesses (Feb 10, 2017)

A 6" vise is overkill for a RF45 style mill. A 4" is more appropiate for that size mill & IMO 5" max. I have a 5" GMT vise on my PM45 & it's slightly too big. Not enough Y axis travel to make use of the 5" full capacity. Better to save your money rather than getting something too big & most importantly the weight. I take my vise of the table quite often, a 6" is still light enough for me to be carried by hand but I'm glad I have a 5". I also have a 4" vise as well. I prefer the 5" though.

But those GMT 6" Premium vises are pretty nice. I'd love to have one but don't need one on my current mill. But if you plan on upgrading to a full size knee mill in the future than the 6" will be perfect.


Here's what the 5" looks like on my mill.




I couldn't even complete this cut without my bellows & DRO scale getting in the way. Not enough Y travel & the 5" vise is not even maxed out.




Here's what a 6" vise looks like on another PM45 (gt40's)
View attachment 253544


----------



## jaded13640 (Feb 10, 2017)

Yep, that's my tool lantern, your holder is different than mine, mine only hold square tools, I do have one holder that is angled in like yours there but it also only holds square tooling stock. I didn't recall a cut off being that thin, It seems to me we were shown how to grind one out of square stock in school, but I don't remember if we actually did it or not. If this is too much trouble, I just cut a v and hack saw it or do it the way I have been but I like that, I only wish I had a tool holder like that. Not much point in buying a holder and tool for something I use so rarely. If I can make one out of square tool stock, I would be willing to do so, if someone has the dimensions. Or at least a picture, I could then decide if I want to bother. 

Wayne


----------



## Wreck™Wreck (Feb 10, 2017)

A 6" vise is overkill for a RF45 style mill. A 4" is more appropiate for that size mill & IMO 5" max. I have a 5" GMT vise on my PM45 & it's slightly too big. Not enough Y axis travel to make use of the 5" full capacity. Better to save your money rather than getting something too big & most importantly the weight. I take my vise of the table quite often, a 6" is still light enough for me to be carried by hand but I'm glad I have a 5". I also have a 4" vise as well. I prefer the 5" though.

But those GMT 6" Premium vises are pretty nice. I'd love to have one but don't need one on my current mill. But if you plan on upgrading to a full size knee mill in the future than the 6" will be perfect.


Here's what the 5" looks like on my mill.




I couldn't even complete this cut without my bellows & DRO scale getting in the way. Not enough Y travel & the 5" vise is not even maxed out.




Here's what a 6" vise looks like on another PM45 (gt40's)
View attachment 253544


----------



## Chuck K (Feb 10, 2017)

Wayne, you can grind the parting tool to any thickness you wish.  Just grind a couple degrees of relief on the sides and a chip breaker on top and you're good to go.  You can search the Internet for a pic of a hss parting tool.


----------



## royesses (Feb 10, 2017)

Here is an ebay search with a bunch of parting tool holders many starting at $1.00 bid with no bids so far.  The photo is not my post, just a reference for you to look at. I have a mini lathe with QCTP. Just trying to help you out.
http://www.ebay.com/sch/i.html?_fro...nkw=lantern+post+parting+tool+holder&_sacat=0
Roy


----------



## pstemari (Feb 11, 2017)

Also, if you don't want to go the parting blade route, you can always grind a regular tool bit into a parting tool. Just grind a notch in the corner until you get a long, narrow tongue sticking out, length and width depending on your requirements.  Add clearance on both sides and the end, grind in some top rake and a chip breaker, and you're good to go.

Say for example you're working with a 1/2" square tool bit.  Grind a square notch 3/8"-7/16" wide and 1/2"-3/4" long out of the front right corner. That will leave you a 1/16"-1/8" wide, 1/2"-3/4" long, and 1/2" tall cutting tip.  Grind about 5-10 degrees relief on both sides, 8-10 degrees top rake, and give it a try. It's a tedious exercise; softer grades of grinding wheels will cut faster on tool steel. I like the white Norton wheels.


----------



## kwoodhands (Feb 11, 2017)

jaded13640 said:


> I had to do a little project recently where I needed to make a "bushing" that was about .300 dia by about .300 thick. I had a much longer piece of steel stock, about 3 or 4 inches long, I could have cut a smaller piece on the abrasive cut off saw but, it was kind of a short piece and decided not to. But, of course that meant I had to face away ALL the stock I didn't need AND, had to hold that little tiny piece, that was the finished product, in the chuck.
> 
> So, it took forever and was just a stupid little piece to tighten up the shifter rod on a truck where the plastic bushing had worn down to nothing. It was held on with a cotter pin and it broke, I was doing a whole different project on the truck when he mentioned he had to tied it back together with a jump rope. I didn't even notice it till he mentioned it and it had no way of getting the correct bushing that late at night but HAD to get the truck done that night, he had to drive it to work the next day.
> 
> ...



Wayne, you can buy parting tools in a T configuration. The T is made so all you have to do is grind the front relief.
The sides are narrower than then the top so no extra grinding necessary. These tools come in different thicknesses.
I have 3 thicknesses , 5/64" , 1/16" , and 5/32". You can make a holder that fits your tool post. Slot a piece of stock that allows the parting tool to slip in, then hold it tight with several set screws drilled and tapped into one side. Might be possible to eliminate the slot, just drill and tap a piece of square stock that will push against the T tool. The T sits tight against the back of the lantern and the square stock is held in the lantern and set screws push against the T.
mike
You could also use high speed steel blank cutter and grind it to the proper width . This takes a long time and proper relief must be ground on the front, sides and top. Much easier to buy a T type of tool.


----------



## jaded13640 (Feb 12, 2017)

I liked both of your comments. I like the ideas both presented. I do so little on that lathe, I can't see going to too much trouble. I remember learning about parting tools but I don't remember being taught how to use one or actually seeing one back in college. I can only assume that's why I seem so in the dark about this. It turns out, it seems, that it's more trouble than it's worth. It's looking like, in my case anyway, it would be way easier to be wasteful, leave it long and just machine more away than going to all the effort to make a tool, or the expense to buy a tool. When I realized what was really involved, I realized it probably wasn't going to be worth it when I only roll the machine out and do something with it once or twice, three at the most times a year. Many of those times a cut off tool wouldn't even be needed. It's looking like it would be easier for me to cut my stock off, leave a little long and just clean it up face it to size. That just seems like the smartest way for MY situation. It would be different if I were using it once a week and wasting a bunch of stock. I've only actually had to buy any stock a couple of times, I've just gathered pieces of scrap here and there which is mostly all I need.


----------



## Chuck K (Feb 12, 2017)

OK...Lets talk about single point threading....LOL


----------



## jaded13640 (Feb 13, 2017)

Oh man Chuck, I'm screwed dude! I've cut threads once and that was for my "no twist clamp" assignment in college. That was roughly 22 years ago...sooo...yea....screwed. 

Wayne


----------

