View Full Version : Make a dovetail tool for therapy.

02-23-2008, 08:23 PM
In the spirit of all the trick-cyclists (psychiatrists) on the forum discussing depression in the workshop, I was determined to try the old “If it feels good, do it” therapy today. Instead of committing monkey grass decapitation, crepe myrtle murder, leaf raking and other yard chores that were depressing the pi$$ outta me, I decided to hibernate in the shop & make something. Whew, that was close.

The original project was to emulate John Moran’s tangential toolholder for square HSS bits but got sidetracked ‘cuz my normal method of building up aluminum dovetail QC holders from separate pieces wouldn’t work. S-o-o-o, now we gotta make a dovetail cutter using a carbide insert as the prolific Mr. Moran and Bob Warfield show on their websites.

I figgered a chunk of the 1” 4140 pre-hard I bought for the disc sander motor hub adapter would work well. 4 insert corners and a ton of blue chips later I had the thing started.


Once the pocket was cut for the TCMT insert, I tacked it place with super glue and lined up the mill with a #34 bit installed backward in a collet, then drilled & tapped for a 4-40 socket head screw.


I had trouble drawing the insert in CAD and must have missed a little because the pocket ended up being a little to deep. Had to shim it out a little with brass shim stock…works OK so who cares.


I ran a test on a scrap of 6061 and it worked really well. My X3 seemed happiest at .030” DOC until it got in deep and I had to back off to .015”. The finish is very slick. I feel great and didn't have to take any medication! Gotta go now, my home-town Tigers are playing the Volunteers on ESPN.


02-23-2008, 08:35 PM
I like the idea of supergluing the insert so you get the hole in the right place, ill be adding that one to the list of good tips!:D

How does it perform in steel?

Your Old Dog
02-23-2008, 08:38 PM
Nicely done! Thanks a lot for the pics, they're always appreciated.

02-23-2008, 08:39 PM
Haven't tried any steel so far. I'm saving that for later when I can handle the possibility of failure better. I don't think I can take Sir John callin' me a clumsy bastid just yet.;)

02-23-2008, 08:39 PM
Fantastic project!!! I also like the glue trick..

Neil??? Projects Group???? JRouche

02-23-2008, 08:51 PM
awww surely john wouldnt be *that* mean again would he?:D

its turned out really well, didnt think of using an inverted drill to locate the hole either, simple but effective!.

02-23-2008, 10:40 PM
Nice work, What insert was that ?
Errr :D --- Hate to say it-- Go Vols


02-23-2008, 10:42 PM
I saw that it was a TMCT in your post

02-23-2008, 11:06 PM
great job, have to make me one. Oh, if you increase the feed on the lathe you will get less hay and more little chips that get under your collar and in your boots. but you don't need a hayfork to clean the lathe. Have some 4340, will start one tomorrow if I'm not stuck in the kitchen. Peter

02-24-2008, 12:09 AM
Nice work DICKEYBIRD, the cut looks great.

Yes on the super glue, I often forget about it when/where it would be useful that the times I do remember it seems like a new trick to me, thanks for the reminder.



02-24-2008, 12:16 AM
Errr :D --- Hate to say it-- Go VolsGee Ted, thanks. It musta been you that kept that last second 3 from goin' in.:(

(And all those missed free throws and yada, yada, yada.) Good game but we beat ourselves.

Peter, I tried several different speeds & feeds but it kept "making hay" with the cheapo CDCO inserts I have. The chip breakers work on aluminum and mild steel but not on the "hard stuff." When these are gone I'm going to shop for some good ones and see how they do. I suspect it's a totally different experience.

My lathe is only an old Taiwanese 8X16 and .030" is about as deep as I dare cut in steel. I like doing the harder materials once in a while though....I get to hear the motor get down & grunt. The original POS motor was replaced years ago with a genuine Wisconsin-built Marathon 1/2 hp motor that most times just loafs along with the little stuff I make.

02-24-2008, 12:27 AM
Is that a slip of yellow paper I see between the insert and the holder? Gary P. Hansen

A.K. Boomer
02-24-2008, 12:47 AM
That could come in handy, nice work.

02-24-2008, 12:54 AM
Nope, yellow brass shim stock as mentioned earlier in the post.

My Jethro Bodine cipher'n skills failed me and I made a .006" error in either the CAD drawing or handle twistin'. I turned a taper on the back side of the 4-40 screw and slid in shims until the insert was tight when the screw was fully tightened. I'll have to keep a close eye on it and replace the shims when the insert frets through the brass and gets loose. Apparently I can't machine ANYTHING perfectly yet.

(OK John, your "Clumsy Bastid" goes right about HERE.) :)

02-24-2008, 01:10 AM
Go here and scroll down to the dovetail cutter - then don't repeat my boof! :(


My calculations were off on the tool diameter and it got tossed into the scrap bin. It's still there, come to think of it.

John Stevenson
02-24-2008, 05:43 AM
Nice job, must get round to doing a couple on of these days.

One point when drilling the mounting holes for inserts.

Do as Dicky did and find the center then move about 10 thou to the BACK edge then drill.

The idea is that the hole is off center so when it's tightened it pushes the insert into the pocket.

It also pays to step the back face slightly so top edge of the insert at the back isn't touching the body but the support is just below the top edge.
Same at the corners, take care to see they are clear.

The reason for this, especially on an interrupted cut is that the unused corners and edges take a beating and when you come to use them they have fine chips and flaking on them.

Ideally it's best to use a tapered cutter equal to the angle of the insert and pocket out to just less than the insert hight.
J&L sell these cutters but for a one off in the home shop it is a bit over the top, unless you fancy making more cutters of various types later ?


02-24-2008, 01:36 PM
Well, the darn thing works great! Much better than the operator.

I carefully measured an AXA holder, hogged a chunk of aluminum to the correct depth and width with a 3/4" 2-flute endmill then chucked up the new dovetail cutter to finish up. When I got down to the final cut...lessee, 2 guzinta 6....4 + 7, carry the 1, yup, .011" will do it with a couple left over just in case. Man that final cut is pretty! Take it outta the vise, throw it triumphantly onto the QCTP; WHAT THE...the handle comes around a 1/4 turn too far! Musta been my cypher'n again. Oh well, a .006" brass shim makes it n-i-c-e. Thank heavens for super glue & shim stock.

I think I'll go murder some crepe myrtles, I need some therapy.;)