Milling a T-slot with light machine?

[TTD]

Seeing as I hardly ever use the compound rest on my little 7x12 except for the odd time I do short tapers, I’m getting ready to make a simple T-slot rest to take its place. Nothing fancy, just a single T-slot down the center of some 1.75” thick x 2” wide x 6” long CR1018 flat bar. T-nut will be for a 3/8-16 bolt as it’s pretty darn close to the M10 stud used for the factory compound (stud measures .386” o/d)

Here is my issue….I don’t have a proper milling machine yet so I’ll be doing all of this on my little 1/2hp lathe with milling attachment. Yeah, I know…I need bigger, more powerful/rigid machines. Hopefully someday, but this is all I have for now.

Anyways, after milling the initial center slot to correct depth/width, do you think a measly 1/2hp could handle the T-slot cutter itself? I’d be taking a cut .328” deep x .334” (.167” each side of center slot). My gut feeling is “probably not“, but I honestly don’t know & wanted to ask first before ordering the cutter. I don’t mind buying the cutter if I can do it, but also don’t want to spend good $$$ only to find out that I bought an overpriced paper weight.

Thanks for looking & any tips you may have!

 

[rgray]

I have cut a few T-slots , but with a mill. I was surprised how little effort it took. I like you was intimidated and thought it would cut really hard.
Keeping the chips out is a big thing, so an air hose or coolant is nice.
Most of my worry probably came from using dovetail cutters for one side or both, they don't cut near as well as the T-slot cutters I've used.

 

[BaronJ]

Hi Todd,

Assuming that you are talking about holding the cutter in the lathe three jaw and milling out the center of the slot first and then changing cutters to do the "T" if you go steady and feed to work into the cutter from the operator side so that you are not climb milling, with plenty of coolant, you should be OK.

But that six inches is a long cut and unless you have it secured as rigidly as possible there is always the risk of chatter and jamming the cutter.

 

[JimDawson]

As long as the setup is pretty ridgid you should be fine. The lathe should have plenty of power to turn the cutter.

 

[TTD]

Thanks for the reassurance, guys.

Never tried cutting a T-slot before so I suppose the only way I will know for sure is to just buy the cutter & give it a whirl…I really need to stop second-guessing myself all of the time! I’ll add the cutter back onto the list when I place my next order.

@rgray - Yep, that was exactly my thought/worry, too. Glad to hear the T-cutter cut easier than you thought it would. I’ve cut a few dovetails now & didn’t find it too bad at all, but to be fair they were only small 3/8” rails for scope mounts.
I’ve had the lathe & milling attachment long enough now (I think) to learn most of its limitations/shortcomings & what it does & doesn’t like. Most of you fellas here with real machinery will giggle at me for saying this, but taking a .328” DOC x .781” o/d seems (at least to me) quite substantial for the little guy …inexperience shining through at its finest! lol

@BaronJ - Yes sir, that’s precisely how I planned on doing it. As for the 6” length, I can’t do the entire slot in one go anyways. My crosslide only moves a paltry 2.75” & my vice is 2” wide, so I would only have around 3/8”- 1/2” either side of vice unsupported at a time. Yes, it’s a time-consuming royal PITA to make a cut, shut lathe down to reposition the work, verify everything is still running true/parallel & then make the next pass. Repeat as many times as necessary to reach the other end! I’ve done that routine so many times now on other projects that I’m pretty much oblivious to it….it’s just another step needed to get the job done.

@JimDawson - Thanks Jim, that’s just what I wanted (hoped) to hear . When I first got the lathe a few years ago, I unknowingly, yet quickly, perfected the art of frequently stalling the small motor out mid-cut with either too heavy a cut, too much feed rate or (most likely) a combination of the two. No doubt that there was a poorly ground cutter mixed into those equations also.

I’m still no machinist by any means, far from it, but now that I at least have a better understanding of speeds/feeds & (still learning) how to let the lathe tell me what it wants, I’m pretty confident I’ll get it done with minimal issues. Just wasn’t sure if the puny motor would be biting off more than it can chew. Thanks for putting my mind at ease!

Sometimes, not knowing what to expect when doing an operation for the first time is actually worse than the job itself

 

[mikey]

Hey Todd,
It sounds like you're making a plinth for your lathe - good idea. I was just wondering why you need a T-slot unless you plan to do more with it than just hold a QCTP with the bolt. If its only to hold the QCTP, wouldn't it be simpler to just find a way to fix the stud?

 

[TTD]

Hi Mike

Thank you for the suggestion, I appreciate it. 100% correct also!

Actually, at first I did think of just simply drilling/tapping a hole in the new block to fix the stud & call it a day. In fact, I’m still thinking of doing it anyways to hold my regular tool holders, regardless of the T-slot. I do plan on making/using a rear-mounted parting tool holder after seeing how you built yours & even thinking of maybe trying single point threading from the rear also…I like the idea of chips just falling off directly into chip tray instead of building up on top of cutter bit/work piece before finding its way down.

I suppose I don’t really need a T-slot for the rear mounted holders either, I could just fix a separate stud for them also. I just figured if I was already going through the trouble of making a new tool rest anyways, I would add a T-slot for versatility if nothing else. Kind of a “Better to have it & not need it rather than need it & not have it” sorta thing.

Besides, I still consider myself green as grass regarding machining so I’m always eager to learn how to do different operations. As trivial as it may seem to most (and it really is), cutting a simple, functional T-slot to use at this point is more of a confidence-builder than anything that I can add to my small but growing list of “fledgling” accomplishments.

Thanks again!

 

[mikey]

Sucks that most little asian lathes don't have T-slotted cross slides. That would make life a whole lot simpler.

If it was my lathe, I would make a stud in the plinth and also drill/tap a hole in the rear of the cross slide for accessories like a rear mounted parting tool. There is much to be said for a ledge on the bottom of a tool holder that bears on the front edge of the cross slide; it locates the tool quickly and accurately so it is perpendicular to the spindle, while a single screw will lock it solidly to the cross slide so that it absolutely cannot turn in use.

I rear mount my parting tool and knurling tool back there. Eliminates chatter, increases rigidity and like you said, the chips fall in the right direction.

By the way, I have cut T-slots in steel with my little Sherline mill. Not the same as trying to cut it with a milling attachment but that little Sherline motor is only 60 Watts and handled it with no problems so a 1/2 HP lathe should handle it easily provided you rough out the slot first. I prefer Keo cutters for this kind of thing. If you're lucky, you may find one for a good price on ebay. T-slot and Woodruff key cutters do not tolerate run out so are best held in a collet, not your lathe chuck.

 

[MSD0]

Hi Mike

Thank you for the suggestion, I appreciate it. 100% correct also!

Actually, at first I did think of just simply drilling/tapping a hole in the new block to fix the stud & call it a day. In fact, I’m still thinking of doing it anyways to hold my regular tool holders, regardless of the T-slot. I do plan on making/using a rear-mounted parting tool holder after seeing how you built yours & even thinking of maybe trying single point threading from the rear also…I like the idea of chips just falling off directly into chip tray instead of building up on top of cutter bit/work piece before finding its way down.

I suppose I don’t really need a T-slot for the rear mounted holders either, I could just fix a separate stud for them also. I just figured if I was already going through the trouble of making a new tool rest anyways, I would add a T-slot for versatility if nothing else. Kind of a “Better to have it & not need it rather than need it & not have it” sorta thing.

Besides, I still consider myself green as grass regarding machining so I’m always eager to learn how to do different operations. As trivial as it may seem to most (and it really is), cutting a simple, functional T-slot to use at this point is more of a confidence-builder than anything that I can add to my small but growing list of “fledgling” accomplishments.

Thanks again!

You’ll probably find parting much easier without the compound and won’t need the rear mounted parting tool holder.

 

[markba633csi]

In any case, you'll need a sharp new cutter, plenty of cutting fluid and some patience
mark