Someone once said "the man who never made a mistake has never made anything" So well done for the effort and the vid, I will look forward to your solution to this hiccup.
It looks like the insert has to fit to the shoulder with absolutely zero clearance, or perhaps even a tiny bit of interference. It is noticeable that the commercial insert pockets have two locating faces. Cutting forces on the insert are going to be large and any clearance will allow the insert to move and loosen/ shear the fixing screw. You can’t win em all! Phil
That's what I thought too, and also the seating face needs to be either ground absolutely flat or even slightly concave to make sure there's no rocking forces exerted on the insert. In any transient mechanical load, even microns of movement or rocking will kill longevity. In a home shop I'd probably try concave (a few hundredths of a relief pocket that doesn't reach the insert outside pressure edge.
Likely because there is no pocket for the insert, to take the cutting force. So screw gets all the shearing force during cutting. A small pocket, maybe 1/3 width of insert, on top, to take the upwards cutting force would help a lot. I'd put some copper spaceholder into insert place and make a small pocket replacement with TIG welder, so insert could not move upwards any more.
A smaller depth of cut might have reduced the problem, but the trouble with a triangular insert means you have a very large cutter contact, don't forget the lower edge is in contact all the time. When I made one yesrs ago I angled the insert very slightly so the lower edge doesn't rub, but the problem is the dovetail isn't 60 and I couldn't be bothered to do the calculation for the offset to make it right. If you are making both male and female it doesn't matter about exact angle, but I can always use a proper dovetail cutter after bulk is removed.
@@chrisstephens6673 Tht is why the next one I make will used DCMT's. They are only 55° nose angle, so the bottom will have clearance, and also will make that cutter with proper pockets to support the insert on two sides.
If it were not for the fundamental sin of being 60°, I would have suggested to braze the insert on an intermediate (mobile) plate transferring the efforts into an ah-hoc pocket. As it is I agree that the only sane way is to change insert type. Thanks for showing me that it was a very good bad idea... (I thought to do the same) Jean
I know I have at least 6 tool holders. I found the deal of the century on a package that includes a Precision Matthews PM-1440E-L, a PM-940M-PDF mill that's been converted to CNC, MSC SGS-618M surface grinder, small tool grinder, and a granite plate. There are 7 jaws, at least 4 vises, a full 5C collet set, angle plates, an indexer, and both an imperial and metric butt load of end mill bits, side milling bits, and other stuff I haven't catalogued yet. Also about 200 pounds of aluminum plate, rod, and bar stock. Previous owner bought the lathe and mill new and it's very lightly used. He machined only aluminum, Delrin, and nylon. My effort now is finding a rigging company to move it. I'm super pumped about this :)
First question is easy to answer: i don't currently have a lathe, therefore i have no tool holders 😂😂 Edit: therefore the second question is also easy to answer: I have EXACTLY the number of tool holders I need. 😂😂
@@RotarySMPyou should have asked how many lathes we have ..... And how many are usable. I collect lathes. And they start out as barn finds mostly. Mostly. I have 7 projects, 5 working lathes, and 4 totally restored for a total of 16? Can't do the math. It's late and I'm sure I've forgotten a couple. My favorite is a Hendey 9" precision tool and gage lathe. The very last one EVER built. It needs A LOT of work.
@christopherleveck6835 I have 5 lathes, 2 function and 4 mills, 1 functions. 3 cnc are broken, the manual mill works! I use CXA holders for my 2 working lathe. They are in different states. I have about 10 holders each. I'm not happy with my tool selection. I always seem to have the wrong insert style , especially for threading. I have more tools than I have holders, and seems like fewer tools than I need to complete a job. Doesn't help having stuff in separate states. The tool I need is always in the other state
Hi Mark, almost success ! I "believe" that the guiding principal of indexable inserts is that the screw is there just to keep the insert from falling off when sitting on the shelf😉 , and that all of the cutting forces are absorbed by the pocket.
@@RotarySMP so something I saw when you were making the tool, and made a mental note of, was that you were using the screw to push the insert against the tool. (Maybe this has been said already) I'd make the next one centered. That's what caused your screws to break... well amongst other things I guess. But it certainly didn't help. On a different note, I don't suppose I could talk you in to doing a video on the process of machining with FreeCAD could I? Since you're designing a new tool and all....
woooh i am now a lathe owner. old harrison from the 40s. i have no quick change tool holders because i don't have a quick change tool post. but i do have a lathe. yahooo :D
I dont think improved fastening will be enough, as it does not address the fundamental design error of having only one edge to locate the insert, while having two edges in engagement.
Thanks. It's Schaublin - that chamfer is probably there for a reason... we just haven't it out yet. Randy Richards (in the Shop, on YT) made his dovetail cutters with a single 60 degree insert. Only 25% of the hassle and you always know which insert is doing the cutting :) Homework problems: 1: 6 tool holders, 2: more than 6.
I’m envious of your collection. I’ve just got one of the standard 4 tool fixed height jobbies. I keep telling myself I need to upgrade it, but I never get around to it. I would like to have maybe 6-7 tool holders minimum.
The answer is, if you have N toolholders, then you always need N+1. Because you can guarantee that whichever tool you take out to put in a tool for a specific job, that will be the tool you need for the very next operation. Currently I have 13 Multifix size A holders.
Got 11 holder for my late asian lathe (multifix clone), but only 6 or 7 for my good old euro one, not enough. The downside of DCMT cutter is the large diameter needed and low cut height (
Yep, the insert screw should be pushing the insert into the pocket. And the cutting forces should be in the same direction, into the pocket. Bought a used LS Okuma, it come with a QC tool post and one holder, purchased 2 more holders. No matter how many, i will likely always need more.
Hi. On one lathe I have like 13 tool holders and it’s ok. On another lathe I have like 20 , and it’s not enough. And on my cnc lathe 8 post turret seems enough. Most tools for one job was 8 tools on a manual lathe, all saved in the DRO . More is definitely better not to always change them around
Hi Emil, I also want to have all the standard tools loaded, with thier offsets in the tool table, and then a few spares for special tools which get loaded for single jobs.
Your main problem is most likely not the threads coming loose but the screws stretching - hence why they break so often. All the cutting forces are taking up by the screw, scince the cutting only happens at one side of the triangle, shifting the inserts over to the center of the cutter (and down - did you check if the dovetail became lower when the inserts loosened up?) I think the Cutter would work if you brazed the inserts on - or you design one as shown with s pocket that contains the insert on two edges 😅 Thanks for sharing though, takes some courage to share the fails too! Looking forward to the next one!
@@RotarySMP Fairly often, you can never have enough tool holders. I cope by planning the tools I need and setting them up before a project so I'm not swapping mid-project.
@@RotarySMP Depends on the project. Like most people I keep the most popular ones in the holders and swap out the special ones as needed. You can never have too many tool holders!
Hello Mark, Good days, bad days in the workshop... We all enjoy the good days and learn from the bad days... See you on the next one... Take care. Paul,,
I only have 6 CXAs so far for my old Harrison. My solution for the inserts will be to use my little Elliott shaper. More toolholders are on the to do list 😀
@@RotarySMP ah so many choices, I would love to find a space for a surface grinder but that would probably mean giving up a motorbike, which is too high a price. 🤔
5 and 3 Morse taper ones. 4 more in the mail, 2 Dickson I need to modify and a chunk of steel I need to turn into more. I think so where in the realms of 40 tool holders would suffice, until I need 50.
"Suck it and see" engineering usually generates the most interesting results and the most lessons. Those lessons and results often lead to less suck and see.
Without being to difficult the problem is the screws are taking the cutting load. They should only ever hold the tool down never in. The screws stretch after a while and even in a proper tool holder they should be replaced after every tip change. Thats anything with a 2.3 ~2.7 mm thread. You could save it by using a dowel in place of the screw and a clamp style on the back. Alternatively in the past when new cutters were not available I have converted to a 3mm standard cap screw and a machined bush to fit over the screw and into its screw seat area. The bigger screws hold up remarkably well and whilst they still stretch lasted longer than the 2.5. These were used in high volume production machinery that often had to deal with inconsistent cuts and chunks of metal floating around the tool. If you make a new tool it might be worth considering changing the tip style from a TCMT style to a VNMG style. It would cut the 60 deg when set to the correct angle and because it would use a sweeping cut at the end of the tip to cut a flat bottom. A VNMG would be well supported and would comfortably get by with the standard screw for attachment. You could just copy the nest from a turning tool. Another option could be add some support for the top edge of the tips in the cutter. A few blobs of weld or braze and machine just to give some support in a third axis. You would loose a little cutting depth but it would work. You could even get cheeky and drill and tap for a screw and have its head supporting the third axis of load. Good Luck Cheers
Well right now I don't have tool holders. Haven't made the upgrade yet on my little lathe. Guess this week was for learning! I'm sure you'll get this dovetail business sorted soon.
I’m in the same boat as you’re are with tool holders. I keep buying them in packs of four. I have about the same number you have. People question me why, when I can change tools in them. But I hate doing that. So every new tool I get gets its own tool holder. Same thing for my mill and ER and DA collets. I’ve got around 100 collets and a bunch of collet chucks plus at least eight drill chucks. Same thing in lathe collets a full set of 64 5C collets. Jacob’s rubber flex collets and chuck, etc. Yeah, you can never have enough tool holders, collets, chucks, etc. I also just buy all my tooling. It really doesn’t pay to make my own. I don’t see the point. I’ve tried a number of Chinese versions and the better ones work just fine, if someone shies away from buying high quality brands. Though, used ones come on the market and are almost always just fine.
threaded fastener clamo force is related to bolt stretch. i'd counter bore the bolt hole and maybe redesign the cutter to add threads thar are bored away. we used to use a min 1.5x bolt diam for min thread length,
@@RotarySMP most bolt failures that I've seen are around the first thread above the nut threads. I think that is where the cyclic stresses are greatest.
Maybe try reducing the feed rate? Try reducing the d.o.c , too. Each tooth would take a smaller bight and therefore reduce the loadings. This may, or may not work, but it's worth a try.
@RotarySMP fair enough. It was just a thought. The problem seems to overloading the fixing screws. So, what's the simplest way to address that. Maybe you're hitting the job too hard on each pass with the dovetail cutter. What would be the downside of giving it a try? Nothing to stop you making a different cutter if that doesn't work or if you have to go painfully slowly with the current cutter.
@@uncleheavy6819 I suspect that slowing down, means more vibration cycles, as it take longer to cut the dovetail. I really think this design is a failure.
Try using the grease that comes with some toolholder on the screw threads. This will help you apply much more torque to the insert screws in the dovetail cutter. This is the purpose of supplying the small tubes of grease with some new insert tooling.
@@RotarySMP have a look at the bike sauce channel . he did a test of a few torqkey bike t-handle fixed torque drivers turns out that even the very inexpensive ones are very repeatable and accurate to the set point. might be one suitable for your needed torque
Its not a problem to use loctite on the little screws in if your cutter. If you want to change the inserts just heat up the tool to 150 to 200 celsius and the loctite will disintegrate . This temperature will have no effect on your tool. I have done this many times in my 25 years of machinist work. The best is Offcoarse to make a new cutter and use a correct size tap for the screws. When you made the cutter and you pre drill the holes for the threads you probably used a wrong drill or a dull drill and the hole for cutting the thread ended up to large. And now you have loose threads because of this. Specially for these small threads it can be tricky to end up with a correct size hole after pre drilling. For the smaller threads i drill the holes slightly under the recommended pre drill size and use a watchmaker hand reamer to sneak up on the smallest hole size that allows you to cut the threads. And this way end up with "tight " thread that is less likely to come loose when vibrating under cuts 😀
I did use the correct 2.1mm drill for M2.5 and it was new, but you are right that tolerances get pretty tight down there. But the real root cause is having the insert engaging on two sides, with only support on one. My version 2 cutter will include all the lessons learned.
It is a cool project for sure but I haven't had much luck with insert dovetail cutters (even with special inserts). I would suggest either solid carbide or brazed carbide cutters. (even the Chinese one seems to work ok) Having more cutting edges also really seems to help everything run smoothly. You might need a shaper or if you can lock the you could use the mill as a shaper. then you could have a CNC shaper (or I guess maybe planer depending on how you set it up)
Good point Luke. Do you mean like these ones? www.amazon.de/Rankomu-Schwalbenschwanzfr%C3%A4ser-60-Grad-Schwalbenschwanzfr%C3%A4ser-6-schneidiger-Hartmetall-Schlitzfr%C3%A4ser/dp/B0BGLCB6VL/ref=sr_1_5?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=1DSLARWXG8CNA&dib=eyJ2IjoiMSJ9.8WzPYC3r7G6O8gFi_ke5i5Fj599SnibgzCk_aT0SXgzFuMsFnPfydojVE9eI4LnSSB5nhy7BZNQz55KUSfAQWEkTIlBZ_cjvMst5XbiTjJwlR-27T-kFFx0tSDMJZ4t3Trtei9EBQpXwAl9kiyMAR0gRoJCBrPpGJpdc0UTL6v30i7H6JNUHK7WQr_EkLC2vB9WL-WWc7s4o2RXC-nXfXvDSpCCzDz4zHGjxtp6QK_wjiWDSisTgD8F3JbloJSF_Km1NDNQf2tQPDu556OK4-33uX5PGtanVhXLJl0GuQo0.Gp76sz4RLngJhN9Tp5YkVxUBteYzYpxrAO61qPzugfY&dib_tag=se&keywords=hartmetall+dovetail+cutter&qid=1713947713&s=industrial&sprefix=hartmetal+dovetail+cutt%2Cindustrial%2C145&sr=1-5 It looks terrible, but I guess i could tune it up on the Clarkson before use. I even have the shaping head for the Maho, and have almost never used it.
I think the screws loosen prematurely because the insert is mostly held in place by the screw. On most other tooling, the insert is also held by a groove, etc., and in some cases the force of the screw is even amplified by acting on a ramp, that then clamps the insert.
Well done Mark, we have all learned today and he world is a better place for it. Sorry your dovetail tool holder prototype doesn't yet meet industry standards, but it took Sandvik a few goes too and they started a bit earlier than you did. For my lathe, an 8mm Lorch that I try to learn watchmaking on, I have one tool holder: Me! I'm the tool holder. For the tiny forces involved in making watch parts we often use a hand held graver on a tool rest. I have got a cross slide for it but no tool post, so it's a really cool paper weight for the moment.
Hi Michel, I think the single guiding surface at the back, combined with the insert cutting on two edges, or at least rubbing on one, makes is vibrate back and forth along that rear edge, loosening it.
I have made the same style cutter years ago never had any problem with it. But I never made so agressive cuts with it like you. You even made a wave like finish, indicating of flexing. 60 m/m and 0.03 mm per tooth sounds reasonable.
I found the insert edges didn't really cut unless I used closer to 0.1mm/rev. I made a bunch of small error on this one which added up. The next one will be better.
I had a similar issue with a homemade cutter where screws were getting loose. I realized that it is due to using 2 surfaces of carbide insert getting irregular contact for cutting. Your dovetail cutter is always under pressure on the bottom end while surfacing. Sides of the carbide gets in contact for a short time when the carbide hits to side profiling while spinning. So bottom pressure and side pressure is not constant on the carbide bit and it wiggles the screw. I really needed to seat the carbide like the one you show on 14:42 of your video. Fyi😊
Make to mounting systems for the inserts. Leave the screw in the middle and add a clamp to the back of the insert. This will reduce the lever on the screw and make it only guide de insert laterally
The root cause of the inserts coming loose is that the side of the insert seat was cut at 90deg instead of 97 deg. At 90 there is only a very small contact point between the insert and the side seat. After a while the hard edge of the insert touching the cutter body will wear out the holder and come loose. Commercial cutters always have the side of the seat cut to match the insert angle.
I currently have 7 tool holders for my lathe, but it is not nearly enough.. I tend to buy a additional tool holder every time I order tooling for the lathe from a certain supplier I use.
NEVER enough tool holders... lol... but I also never have enough tools in general. It looks like you have a direction for the future, but I do agree with the consensus here. Still, it was great that you brought back all that treasure from Malta! what will you make with all the tool holders? more toolholders? How's the bandsaw going?
Hi Mike, the band saw works well enough to not be my most urgent job, but jumps out of gear often enough to drive me nuts :) I will try to have all my standard roughing and finishing tools, threading and cut off tools loaded and dialed in on the tool table, so I dont have to keep touching them off.
@@RotarySMP thx for the videos. I could offer all kinds of suggestions, but nothing I've tried... the closest I will get to this is a reverse chamfer and then finishing by hand with a file. =D
I've got exactly 0 of those tools. saying that - I have 6 sash clamps for wood and bought 8 more pipe clamps. It's very unhealthy for your state of mind to have less of whatever. Great job as ever
Hi, i own 11 tool holders (Dixon Style) for my old lathe. 5 of them i build my own with my Klopp shaper. If you had one, the dove tail would have been easy (just a joke)
One thing that could be an issue is the number of the cutting edges. With 4 cutters sympathetic vibrations could be set up in the cutter, loosening the screws. I suppose you could go with a prime number of cutting faces such as 3 or 5 but that would be harder to machine.
It could have an effect, but there are bigger problems with this design that I need to address. I'll make a new one and try to address all the good inputs people have given.
I also made a tcmt dovetail insert holder a few years ago and had problems with it. My cutter was a single insert one. At first the screw also got loose but at the same time I realised that the thread I cut was stripping due to weak steel selection. I made another one from 1.6582 HT aka 4340, which is plenty strong and hard at HRC 48ish. Then I notic3d that the surface finish was not good and traced it to the trailing edge of the insert rubbing. I guess I chose a small outside diameter for the cutter which combined with the small 7° rake of the insert caused it to rub. So not having any TPG* inserts which have 11° rake and would clear I just lapped a small secondary clearance angle on the slow turning diamond lap I have for scraping inserts. And it worked. Now I don't know if it would survive cnc use and climp cutting cuts. I only have used it in a manual mill with conventional cuts, taking small depth cuts so my experience and lessons may be very different from other people. My advice would be to use a higher rake angle insert regardless of whether you go with an 60degree, or 55degree. Instead of TCMT go with TPG* or TPM*, instead of DCMT choose a DP**
I already order DCMT. I am pretty sure I have back clearance on this one (35mm dimater), but will increase the diameter on the next one to about 40mm , so I am not too concerned with back clearance. If necessary, I could tweak that on the T&C grinder. This was some pretty tough steel. 6150 iirr.
My Grizly G0602 came with about 4 AXA holders. I ordered 20 more import ones from ebay that should be delivered in a couple of days. If I had a functional mill, I'd consider making some, but my mill is still torn apart.
To your credit, there are indexable dovetail cutters, but they all use TDEW or TDEX inserts, not TCMT. I have to look up how those geometries actually differ.
Australian here - the real question is WHY are those inserts coming lose. If you think about the actual loads they are being pushed (like all inserts) into the tool holder, but in your insert you don't have that angled back edge to the seat. So the contact of that back edge of the insert is tiny compared to most insert tools. I wonder if NOT having that angled back edge to the tool seat allows the insert to move just enough to eventually come loose while machining.
Yeah, I screwed up the 7° grind on the tool cutting that back edge. I will make a new cutter for DCMT inserts, and try to address all the various failings of the current design.
I have many days like that in the shop... I would locktite them and use a little heat when removing them. That's what I did to the cheapie lathe tools we ended up letting the kids use on the lathe at the highschool. Those things had junk screws in them that broke like glass. You should see the tools I (hacked up) made to pull my well pump out of the ground. The upper end clamps failed and the pipe was about 2' down the hole hanging on the power wire. Made a grabber for it and an attachment for the casing so I could pull the pump out with the mower. I didn't film it as the better half was sort of helping etc. Last time I pulled the pump I pulled it by hand. It's 100' down. So 30 pounds of pump and 100' of poly pipe full of water and a brass check valve. I can't pull that up by hand anymore... I have made many one time tools that are just good enough for one job and after that I don't care. And the better half is wanting to go back to Naxos this year since I took mom last year... She has me watching ticket prices which are much lower this year as our flights are already full for september since there aren't many flights so no non revving. I see they started fixing the part of the harbor wall that collapsed just a couple days after I was there last year. I guess it couldn't take my weight... It's the exact spot that we were standing at as the webcam is pointed at that spot.
I handn't heard that Naxos lost part of the harbour wall or breakwater. We will be there for a couple of weeks in July this years. My ground water pump is in my garage, but only has to lift max 7m, mostly less, as our house is built on the Danube flood plane (What could possibly go wrong?).
@@RotarySMP Yeah as you get off the ferry and take the right turn onto the sidewalk that whole area up to the corner where the little island church is slipped down. It was just after I was there that it happened. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-bWqcE3e9vEQ.htmlsi=J1c-pGoZTpHtgRIQ Fares have been lower than I have ever seen for peak season. I could have gotten tickets for july for under $700 round trip which are usually a 2K ticket. As usual we are planning on late september as less people nicer weather etc. Yeah not a fan of being that close to the Danube... My well is 100' and the typical static level is 50' but this year it's only 35' down since this spring has been basically normal and it's been raining. I only cut the grass (weeds) one time last year and I have done it 5 times so far.
That would help, but doesn't address that you dont really want the tool engaging on two edges, which is required with a 60° insert for a 60° dovetail. I have odered DCMT' (55°) and will make a new cutter with a proper pocket to support them on two edges.
always clean where the inserts go in so there is absolutly nothing in then ( not even a speck of dust ( same goes for the back on the insert as well ) and always use a torkrench ( most is good at about 2.5 newton meter in my experience though some you need 9 newton meter ) since if its not torked down propperly the screw start to vibrate lose and then the insert starts moveing ang banging around witch can easily snap a tiny screw like that. but to much tork just destroy the screw head seat and the tool used to screw it in i know garant make make some pretty nice tork handels for a okay price also that with where it was 33.30 and you then moved it 0.14 and it hit 33.61 is the tool beding slightly sideways under the cutting pressure and deflect and then after you compensated there is less pressure so the tool dont deflect less as well and make it bigger . that why we always do a spring pass or two before the compensate ( and the roughing and finishing by themself so if we only need to run the finishing part we go straight to that ) but if we need to make more then one part we note the missing amout down and compensating in before we run the secend one so it comes out to spec from the start ( aka. you make the first one first run. note down the missing about. finish the first one. move back what you compensated to finish the first part. then compensate with the number you noted down first and it should be to speck or at least super close ) also personally for roughing out that big pocket i would use a ramp toolpath instead of a dynamic/optirough ( dynamic might have slightly less cutting force on the tool but it wear out the ways and screw of the machine way faster. and most of the time the ramp toolpath is faster also saw that your dovetail cutter only have one register side face so it can move up and down way to much ( unlike on the picture you showed in the video and even your high feed cutter that you used witch both have to sides that it register the insert up agenst) if you dont need the whole length then make so it also regiser up around the top of the insert. maybe even use bigger inserts so its possible ( maybe even do big insert with dual side register with screw and a small clamp down arm so we really can't move at all )
@@RotarySMP thats what i like to see. are you also gonna get a torque handle so you dont over or under tighten the screws ? most of the manifacturs for the insert screws also say on there website how much torque you should use on that model of screw
Maybe tighter threads would help. The screws probably broke after they loosened. How hot was your cutter getting? Heat may have compromised the Locktite. Also, I like the threaded hole drilled all the way through. It make it a lot easier to clean out chips and may make it easier to remove a broken screw. Thanks for the video.
I don't think better fastening would be enough to address the basic design failure of only supporting the insert along one edge, while two edges are engaged.
My understanding of threaded fasteners is that a rough rule of thumb is that any threads behind the 6th thread bear no load. In this case the thread didn't fail, the shaft fatiqued. Their is a number of problems with this cutter design. I have ordered DCMT inserts and will try to design and make the replacement cutter correctly.
I checked your “dovetail cutter making” video just to confirm that you did not cut the inside of the seat with 7 degree cutter to match the insert. The commercial indexable dovetail cutters have the side of the seat cut or ground to match the insert angle and the screw is located in such way that the cone of the screw head will push the insert towards that angled edge of the seat, wedging the insert tight in place, with the entire side of the insert in contact with the side of the seat. The way your cutter is made, only the very cutting edge is in contact with the side of the seat. Even if the screw is in perfect position, the narrow contact edge will wear out the holder at the contact point, come loose and the cutting forces are then transferred onto the screw rather than onto the cutter body. The DCMT insert will not solve the problem, you have to match the side of the seat to the shape / angle of the insert for the screw to wedge the inset to the side tightly. Your other option is to use TNMG insert and grind back relief on the edge engaged in cutting. Still, the screw must push the insert to the side.
Good point. My laziness was a major contributor. I have ordered DCMT, and will rough out the pockets with an endmill, but the plan is to grind up a D-bit with the 7° to profile the walls.
Grate work on the tool holders! That steal is quite tough to machine but should make decent tool holders :) Why not try brazing the inserts in now as it is still not any good at the moment? Hope its not a competition but just counted my tool holders I have 40, 23of them have my most used tools
@@LCalleja I'll probably make a video on paint drying first :) That cutter can be retired, or kept as a emergency flycutter dovetail cutter for aluminium.
Well I won't be copying that idea because I made mine before you. Only 2 insetrs though. It hasn't broken yet but it hasn't had much use. At least I will know that when it fails, I won't have to repair or re-make it ! I have 14 tool holders for the lather and it's not enough. I need at least 4 more. 🙄
1. abut 20 i woud say , 2. all of them - and as allready suggested,a hair of interference in the tool is probably the way here,give the insert zero chanse to wiggle itself free
@@hedning003 I think those screws came loose because the insert could slide up and down that single rear supporting edge. Locking the insert in between two edges means the screw only need to pull, there should be no side loads on it, and no motion.
I think the cutter concept is ok, but there is too much stress on the insert bolt because it's expected to hold the insert against cut loads. Hard to explain but I think if you can design the cutter with a tighter pocket contacting the other unused insert surfaces to take all the cutting loads instead of relying on the bolt then I believe it should work. The bolt should just be there to stop the insert falling out - i.e. if the bolt gets loose the insert should not move sideways at all. Tight fit. A triangle is probably too difficult to make a precision pocket for the insert.
Hi Anton, yep that is the problem in a nutshell. I have ordered DCMT inserts and will make a new tool holder with proper pockets to locate the insert on two sides.
What number and kind of Loctite did you use (green…290 wicking?)? Normally you should be able to remove even the strongest Loctite by heating the tip of the screwdriver (propane, &c.), so you shouldn't regard Loctite as preventing you from indexing the inserts. It seemed kind of like maybe you "glued" the inserts in with Loctite, rather than only on the threads? But also that the Loctite worked well (too well?) on the deepest screw threads, but not on the screw threads nearest the head…perhaps the hole was bell-mouthed before tapping? All this suggests changes to the screw could help a lot. Perhaps a stronger material (alloy steel?) and maybe a finer thread. Or greater % thread engagement (i.e. smaller tap drill). I'm not sure it's worth giving up on this and starting afresh, though, I would start with red loctite on the threads and maybe CA glue underneath the triangular insert. Drilling out the screw threads and putting in a helicoil or a steel pin to rethread a tighter pitch does seem like it might not be worth the effort, but I'd still watch a video about it! :)
But reading more comments, yeah, the fact that the screw was doing all the holding for the insert was the real problem, all the stuff above is just band-aids over that problem. Still, I'd be curious to see attempts to save this tool!
Hi Jasper. Root cause... poor design and laziness :) - 60° insert for 60° dovetail means two cutter edges are always engaged. - Insert only supported on rear edge, means load variation between the two engaged cutting edges, will have the insert sliding back and forth along that guiding edge. - Not cutting that guiding edge to the correct 7° angle means that the insert is poorly supported there. - reusing screws which had already been fatiqued by operating with loose inserts. I have ordered DCMT's and will make a new cutter hopefully addressing all my lessons learnt.
I have 4 and i need more. but i live in germany, and here the multifix system is widely used. i am going to switch to the american system so i can make my own toolholders..
Hi Questioning: Those toolholders dont look like made by Schaublin. I have a few of Tripan toolholders and a few Schaublin lathes. Why should toolmakes cut of an angle of a tool that should stand up? Makes no sense to me. But a diy guy cutting them of would make sense. Nice lathe
If they were shop made, they are surface ground all over. I just double checked the Schaublin 125-CNC manual, the picture of the standard tool holder in the parts catalog has that chamfer on the bottom, so it is a Schaublin design.
Thanks Ronnie. The threads didn't fail, the shaft fatiqued, so I stronger threads would not address the significant design failures in this one. I will make a new one, hopefully addressing al the good advice I have received.
I don't think it's the handed-ness of the threads causing the issue - I think it's the intermittent load on the inserts that's fatiguing the screw material. It's basically hammering itself to death
@@iNerdier The worst part of this design was that the insert only had one shoulder to locate against. But it engaged on both the cutting edge and the bottom, so the insert could get pushed back in forth along the shoulder. A better design has a pocket with two shoulders to locate off, like that DCMT cutter I put a picture of.
@@RotarySMP lol I remember trying to drill a scissor ✂️. My drill bit got red hot then I learned that the scissor is hardened steel. Now your only option is to use inserts that accept thicker screws
@@hamood1234fool :) stronger screws is not the main corrective action. My main design flaw was the TCMT 60° inserts. They engage on two sides, but are only located by a single rear edge, so changing load between the two surfaces leads ot the insert vibrating back and forth along that edge. I will make a new cutter using DCMT inserts.
