# Cutting a t-slot along a radius



## wrmiller (Jan 23, 2014)

Hey guys,

I want to make a t-slot in steel along a 1.5" radius or thereabouts in a complete circle. This will be the base for a radius turning tool and I want to be able to pivot a full 360.

Not having attempted something like this before, I thought I'd ask for suggestions regarding how and what I'd use to go about this. I figure to use a 6" rotary table to rotate the plate, but that's about as far as I've gotten.  

What kind of cutter would I use, and any particulars in it's setup?

EDIT: I screwed up. This probably needs to be in General. Somebody please move?

Bill


----------



## kd4gij (Jan 23, 2014)

I don't see how you could get a T slot cutter in what you discribed. You could make it in 2 piceses and bolt the center pice in.This is what is used for cutting T slots http://www.use-enco.com/CGI/INLMK3?PMK0NO=1473430


----------



## Tony Wells (Jan 23, 2014)

Bill, it's pretty normal to need tee nuts or something in that type of slot, so an opening must be created somewhere. It can be milled as a round opening the diameter of the major width of the slot, placed in a location where it will never need to hold a tee nut, or some have a hole drilled up from what will be the bottom, stopping shallow of breaking the plane that will be the upper side of the tee slot. 
In that case, you can insert the tee slot cutter from the bottom and into the collet. Either way, you will need to mill the minor slot width first, and it is recommended that you mill it about 0.030 deeper than you will run the tee slot cutter. They do better with that.


----------



## wrmiller (Jan 23, 2014)

kd4gij said:


> I don't see how you could get a T slot cutter in what you discribed. You could make it in 2 piceses and bolt the center pice in.This is what is used for cutting T slots http://www.use-enco.com/CGI/INLMK3?PMK0NO=1473430



Thanks, as I was pretty sure I couldn't get away with using my friend's woodrift(?) cutters.

I'll check these out at Shars. As for how, I was thinking that I'd use a center cutting end mill of slightly larger diameter than that of the t-slot cutter, and plunge to depth on the arc. Replace with t-slot cutter, plunge to same depth then 'slowly' rotate the handle on my rotary table 360 degrees. This oversized hole will be needed anyway to get the bolt heads into the t-slot.

Or am I dreaming?  

Bill

- - - Updated - - -



Tony Wells said:


> Bill, it's pretty normal to need tee nuts or something in that type of slot, so an opening must be created somewhere. It can be milled as a round opening the diameter of the major width of the slot, placed in a location where it will never need to hold a tee nut, or some have a hole drilled up from what will be the bottom, stopping shallow of breaking the plane that will be the upper side of the tee slot.
> In that case, you can insert the tee slot cutter from the bottom and into the collet. Either way, you will need to mill the minor slot width first, and it is recommended that you mill it about 0.030 deeper than you will run the tee slot cutter. They do better with that.



Thanks Tony!  You hadn't replied yet when I started typing. Nice to see I had 'some' idea of how to go about this. Didn't think of your second suggestion though!

Bill


----------



## elf (Jan 24, 2014)

Actually, you don't need to widen the slot just to insert the T-nuts/bolts.  Design the nut/bolt with a rectangular head that fits the slot. If you really want to be able to work through 360 degrees, you may also be able to cut the slot with smaller tools and eliminate widening the slot just to get the tool started.

p.s. Can you post a sketch or dxf file of your design?


----------



## wrmiller (Jan 24, 2014)

elf said:


> Actually, you don't need to widen the slot just to insert the T-nuts/bolts.  Design the nut/bolt with a rectangular head that fits the slot. If you really want to be able to work through 360 degrees, you may also be able to cut the slot with smaller tools and eliminate widening the slot just to get the tool started.
> 
> p.s. Can you post a sketch or dxf file of your design?



If I understand what you're saying, I'd need to keep the bolt/nut from twisting once installed right? So if I use nuts in the slot, I could also leave a raised squared area on one side of the nut, around the threaded hole that just clears the slot diameter. This would keep it from twisting. This raised area and the rectangular head have to be short enough height wise to go below the slot's minor diameter when installed, twisted 90 deg, then raised so that the squared/raised area fits into the slot and prevents twisting.

And sorry, other than writing down dimensional notes I work mostly from visualizations in my head. Even when I'm making stuff for my pistols and such. I don't have, nor know how to use a cad or drawing program. My machinist friend tried to teach me Autocad about 20 years or so ago but I wasn't very good at it as I kept visualizing 3 dimensional parts and putting them together but couldn't figure out how to do that on a computer program. :shrugs:

I did have two years of drafting in high school back in the day of t-squares, triangles, and french curves, so I have the general idea, but couldn't seem to get a handle on the new computer aided stuff. Probably a genetic defect or something... :LOL:

Oh, and I miss-spoke: this base is for a new compound for my lathe. The radius cutter base will just bolt to my t-sloted cross-slide and rotate through 360 deg around a bolt or stud sticking up from the base. Probably need a thrust washer/bearing to keep things smooth. Dunno yet.

I'm no machinist, I just make 'stuff'.  )

Bill


----------



## Holescreek (Jan 24, 2014)

Years ago I made an adapter to mount a J head on my M head Bridgeport. I used a "corn cob" roughing T-slot cutter for it.  All you need is an entry/exit hole to get it started.




Set your compound up on your rotary table and cut your center channel to depth first then set your T-slot cutter in the hole at the proper depth and crank away.


----------



## elf (Jan 24, 2014)

The t-bolt only rotates a few degrees.  Here's a drawing showing the cutter (top and left) and the t-bolt (right).  If you use t-nuts, then the diameter of the bolt will need to be smaller.




If you want more of a ledge, you can make a set of cutters with two flutes.   

I'm not saying that this is easier than just using a stock cutter, but it will give you the ability to safely clamp anywhere in the slot.


----------



## coyotejake (Feb 2, 2014)

Y'all might have to forgive me, but sometimes I like to take a sharp left turn in my brain.  Sooooo, have you thought of the possibility of chucking that into a lathe and face grooving the slot and then boring the key ways?  That way, no top entry hole to sooner or later 'land on' with a nut that you wont be able to tighten.  Just sayin'.


----------



## Tony Wells (Feb 2, 2014)

I thought about suggesting that, but since this is a lathe compound, it would take a fair sized lathe and did not know what was available to the OP. And still there is the issue of getting the tee nuts in, and that could be done one time, from the bottom.


----------

