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T-Slot Cutters


Well-Known Member
Premium Member
How about, "Were you really that unclear, or were you playing me for your own entertainment?"

Like I said earlier, I didn't think I was cryptic or unclear, and your continued line of questions about stuff I did not actually say, lead me to think that either you were doing one or being the other.

There are enough things that amount to being truly terrible information, taken as fact in the hobby side, without putting in effort to make that worse, I figure.

And Modulus isn't all that is in play, so no, not that either.


Ultra Member
Premium Member
I really was unclear, sorry you took it personally. All good. It was the combination of "matches the width of the slot" & "support' that threw me. You did say "support to the cutter" which I missed.
And I guess I should have said 'all other things equal' a larger diameter section deflects less 'in cantilever loading'.
One key point in this; this “tee slot” is not a standard size. I’ll look again, but I could not find a tee cutter that matched the dimensions of the tee slot in the tool rest of my lathe (see the drawing I attached in the original post). All the t-slot cutters I found had either a too small aspect ratio (bottom of the tee would be too narrow), or the width of the cutter face (and hence the height of the tee channel) severely exceeds the space available.
A tee cutter for 1/2” bolt gives a large enough aspect ratio, but the cutter face width (height) is 25/64ths. I only have room for 7/32nds.
I bought a key cutter that should work, dimensionally anyway. I’m hoping I can make it work if I’m very gentle & patient and do as much pre-work with the end mill before loading the key cutter - as per Dusty’s post).
I need to find some 1” plate and then I should be able to give this a go. (I prepared a piece of 3/4” plate, but measuring it, it’s ends up a little less than 0.750” thick. Even at 0.750”, it’s really tight - hence the reason for needing to replace it in the first place. The ‘floor’ of the tee channel ends up only 0.079” due to the vee channel that runs perpendicular below it . Not much material for a cast iron piece! I could make the whole thing thicker, but tool height quickly becomes a problem.)
Last edited:


Ultra Member
@FatherWes had to read your first post and look at the drawing.

Couple of comments.

Warranty on a cutter, unless its flawed when you get it, there is none. The moment you use it returning it is almost impossible.

In which case, modify away. The big thing is as long as the under cut depth is enough, the depth vertically can made deeper by extending the shank dia reduction for clearance.

Just remember, anything that cuts is a consumable, sometimes and expensive ones.

Learning to solve problems is part of being a machinist, don't over think things just do to get the results you want.