Then, the dovetail cutter is used to cut the sloped section of the dovetail. With the cutter stopped I lowered it to touch the bottom of the large slot, then raised the cutter 5 thousandths. Subsequent passes removed 20 thousandths until full depth was achieved. This dovetail cutter is a type of flycutter and makes the same noise as it operates so I arrived at the above settings based on the sound of the cutter. I tried various other approaches with poor results YMMV.
Attempting to cut the complete dovetail depth in one pass seemed to go fine slightly slower feed required but part way through the tool was pulled down and began to mill the center area in addition to the dovetail; thinking something wasn't tight enough I tried this a second time with the same result -- your tool might work better From the carbide insert's perspective, this dovetail flycutter provides one long interrupted cut.
I didn't expect the insert to last long in this application but it survives reasonably well at rpm -- I was able to complete 2 toolholders before I had to rotate the insert. Running the cutter at rpm caused the insert to chip rapidly, failing to complete one pass. When the cutter chipped it caused rapid galling of the sloped area because the insert wasn't removing the material so it rubbed the cutter -- it pays to watch for this to avoid damaging the tool irreparably should an insert fail.
Operating at rpm might increase insert life considerably at some loss in feed rate. The dovetail cutter can also be used as a facemill of sorts. When facing, the cutter has a wide contact area so it is wise to take shallow cuts to avoid chatter; I took 5 mils out of the large slot on one tool holder as an experiment and it worked nicely. Avoid facing while cutting the dovetail, this would make it hard to tell if the cutter moved downward, as happened when I tried to cut a full dovetail in one pass.
The raw material for my toolholders was 3 pieces of steel from a local machine shop which was kind enough to cut it to length and throw in a chunk of scrap aluminum. The AXA type toolholders are 3x1. The length and thickness of the raw material required adjustment, done with the big face mill included with the milling machine.
The ends were squared and all were within a couple of thousandths in size, simplifying measurements and clamping during following operations. This was slow but left a nice finish in the tool slot for the tool to sit on; I made one slot with an endmill but the finish wasn't as good.
Cutting dovetails was interesting because the width is more critical than I expected. I had read about HSM's making a precise dovetail test gauge to verify the size but didn't appreciate what they were dealing with until I tried it. I came up with a crude scheme which works for making a small number of dovetails. I placed a Phase II toolholder in the mill's vise and positioned the stopped dovetail cutter so it touched one side of the dovetail, then set the mill's horizontal stop for this point and similarly for the other side of the dovetail.
The dovetails were then cut using the stops to get close to the correct size; the width was a few thousandths under because of the method used to set the stops. Then, the dovetail was tried on the toolpost and widened 3 thousandths at a time until it fit. File the corners as needed if they interfere with the fit; I found that looking along the length of the dovetail with a light at the opposite side helped to detect any interference.
The mill's vise is precise, allowing this trial-fit technique to work nicely; of course, the holder being machined was re-installed in the vise with the same orientation each time. An obvious alternative which wasn't so obvious at the time is to remove the toolpost from the lathe and use it to test the holders without removing them from the vise Matching metric setscrews were used to hold the tool bits in place, allowing one hex key to work for both purchased and home brew toolholders.
The long metric setscrews for setting height weren't available locally so for now and perhaps always I'm using bolts. I don't have a way of bluing the holders so they will stay as machined. The DTI holder is higher than the toolholders and has a fixed pin to set the height above the tool post because this needn't be adjusted in use. The clamp was copied from a nifty Starrett design and works better than the clamp on the inexpensive magnetic holder I purchased -- as usual, I copy only the very best A tangential toolholder was on my list of things to try for a while but I procrastinated because I didn't want to lose the convenience of my QCTP: the ease of adjusting tool height plus the ability to instantly change tools is very hard to give up.
The picture shows my attempt to have my cake and eat it too ;-. There seem to be two common designs for tangential tool holders, the Freeby and the Burke. As best I can tell from the pictures, the Freeby is side-tangential while the Burke is corner-tangential.
The Freeby design has been used and documented by Ralph Patterson and Richard Hagenbuch passed away Dec , both of whom provided information and advice during construction of my version of the Freeby design. Both Ralph and Richard used aluminum for their tool holders so I did likewise, mainly because it is so much easier to work than steel. The concept of Freeby Berger's design is to tip the bit forward and left by 12 degrees and slope the top of the bit opposite to these tilts at 30 degrees in a diagonal direction the interaction of these angles is hard to visualize without the tool to look at.
The result is the side or the front of the bit cuts with relief provided by the mounting angle of the tool and rake provided by the angle ground into the end of the tool. Unlike regular tools used in the QCTP, the Freeby tangential setup can do both turning and facing without moving the position of the toolholder to another face of the QCTP. Of course there are some limitations to this tangential arrangement: cutoff isn't handled, boring isn't handled, threading requires some contortions and a special tool, left to right cutting requires adding a bit to the other end of the toolholder and perhaps some rotation of the QCTP depending on the task.
The QCTP provides the missing capabilities nicely using conventional toolholders. A 3x1. After the dovetail was cut, the outer side was milled at a 12 degree angle such that the bottom one inch is angled.
The centermost edge of the slot intersects the top of the angled side 1 inch up from the bottom - another view. Experience showed that it was difficult to see the bit in use so the area above the bit was milled away to improve visibility this could be done more elegantly with a tilting vise.
John Gedde built an AXA holder from my description and shared his drawing pdf. Interesting build method here. A major convenience with the Freeby design is the ease of constructing and using a sharpening fixture.
I used a scrap of aluminum, angling it at 30 degrees and then adding a V to the 30 degree face. The bottom was milled to leave a shoulder along the rear edge; this slides along the grinder's guide to allow moving the bit across the wheel - the dimensions are specific to the grinder so adjust as needed.
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Thread starter pdentrem Start date Jun 11, Joined Jan 28, Messages 2, What you receive are excellent drawings plus the article originally done by the designer G. Thomas, and all the blank steel components as well as the screws, drill blanks for pins etc.
Naturally the screws are British thread, not Imperial nor Metric. Since I do not have the taps to thread for these, I replaced them with regular 6x32, 8x32, and 10x24 hardware.
I used a knob and handle shaft that I had on hand, instead of cutting a steel ball for the knob. Total time to finish the build was about 10 hrs.
I have included some pics of the completed holder, before I do the metal treatment to complete the job. This website or its third-party tools process personal data e. To learn more, please refer to the cookie policy. In case of sale of your personal information, you may opt out by sending us an email via our Contact Us page. To find out more about the categories of personal information collected and the purposes for which such information will be used, please refer to our privacy policy.
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Results 1 to 7 of 7. Thread Tools Show Printable Version. Pics would be great as well as experience as to how well it works. Thanks Dennis. Hi Dennis, I've never built one of the quick-retracting toolposts, but it seems like it would really be a handy tool, especially for threading. I'm planning to get one eventually. Mike O'Connor liked this post.
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