Quick change tool post (QCTP) dismantling modification and reassembly (Season 3 Episode 5 )
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- Опубліковано 12 тра 2020
- I have a quick-change tool post with a set of tool holders that are mounted with dove-tail slots which are held in place by sliding wedges. This was malfunctioning and I dismantled it showing what is inside. It appeared to be a minor manufacturing problem. The brand is Bostar size 250-111 AXA. I found a minor defect in its manufacture and corrected it.
This is a very handy accessory for the lathe. I bought it mainly because it is more rigid than the standard South-Bend/Boxford half-moon or lantern style tool posts. It also automatically keeps the tool centered each time you change tools. I have 7 tool holders that fit the tool post and wish I had 10. Several are dedicated to certain types of tool: knurling tool, parting tool, and boring tool, leaving 4 general purpose holders. Often kits come with only 5 in total.
The standard old Boxford tool holders for High Speed Steel do not fit these tool holders - even the 250-111-XL size. So I spent hours on the bench grinder making them fit. I ground off the bottom, rather than the top, because they can be difficult to get low enough to center. I never use the half-moon tool post any more.
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Season 3 Episode 5 of the playlist
"How to use a general engineering lathe" by Evan Lewis (evan-e-cent now evanecent).
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Thank you sir!
I have the same Bostar tool post and have had to do quite a bit of work on mine too...
My biggest beef with it is that they surface ground every externally visible part to a beautiful finish - which makes it look like a high quality tool. On the other hand, every single mating/moving part on the inside that should have been precision ground was rough machined - at best - and the threads on the wedges look like raw castings!! On top of that, the wedges and tripple-start screw are dead soft and immediately started eating into each other. I've cleaned up the thread damage with small files and a dremel and spent several hours filing and stoning the surfaces where the wedges slide up and down within the main block. I don't have the equipment to do a proper grinding job, but at least they're relatively smooth now.
I'm going to try to quench harden and temper the moving pieces before reassembly. (Hopefully they're not just mild steel!)
I just found your video, but the reason I tore into my Bostar was that I saw another video by a guy who had similar problems with his: m.ua-cam.com/video/3zBlI4fuQJM/v-deo.html
Happy machining to you sir!
Thanks for your reply. Apparently I got lucky. I think you can get the idea from my video that the parts look reasonably well machined and after a couple of years of use they are not showing any sign of wear. With the amount of variability of quality you are describing it looks as though they have several factories making them with zero quality control standards.
You Simply! Bought ! The WRONG ! TOOL ! POST !
The top hex nut should have serrations on the bottom to keep the center hub from backing out and creeping around to the adjustment screw.
Helpful vid. Thanks
I watched this a couple of times and I'm not sure exactly what you did or where the washer (good job on the washer) went. I can see the center tube turning was an issue and I was worried about the small thread on the bottom of it. I have one of these tool posts also and went thru some changes to get the handle to come out right also but can't remember what it was. Perhaps you could explain exactly what you did to adjust yours. Thumbs up for the video.
By memory, I believe I placed the shim/washer over the fine thread where I showed the measurements: 19mm inside diameter and 25mm outside diameter. This allowed the big "screwdriver slot" in the central column to screw down tightly against the washer, while allowing the spiral mechanism enough room to operate smoothly. Otherwise it would lock down onto the triple start spiral and prevent it from turning. Consequently the column had to be left loose to allow the spiral to turn, but then it would become progressively looser and would not stay adjusted. With the shim in place the central column could be tightened down firmly and would not move. I hope that makes sense. It is a bit difficult to explain.
I have found that items from China seem to be machined well from good materials in most cases, but the final quality control leaves a lot to be desired. Fortunately the defects I have found have all been fairly easy to fix. Apparently if you buy a Chinese lathe you should strip it down completely and look for problems as you rebuild it. It is commonly reported that they still contain casting sand, often with paint over the sand. Can't be good for wear and tear on parts like bearings and gears.
It kinda makes you want to clean all the parts, put dykem where they touch, operate it and get a good look at the fit. One video I watched measured about 0.025" slop end to end between the center tube and the center acme spindle (the spindle with the handle could be lifted up and down 0.025"). He added a washer under the large head around the tube that left about .003" clearance. I also noticed that one of the wedge jaws have a set screw on the bottom on some brands and not on others. I wonder what that's for. I seems like it would bottom at the same time the wedge jaw is dropping to tighten on the holder. That doesn't make sense to me unless it has something to do with operating it without a holder attached.
I just received a King Canada klm1620 combo lathe and mill after waiting for over 10 months. $4000.00 Canadian and I spent weeks fixing it before it was even usable. You'd cut yourself on any of the corners including the tool post. Nothing was chamfered. Vice was wedged in to the T slots on the cross slide. Ways aren't machined true the cross slide gets tighter on the ways as you get closer to the head stock making it damned difficult to NOT be doing tapers constantly. Even to change spindle speeds I had to hit the tightener slot with a file cause the idler pulley used to tighten the belt was oversize to the slot and was just wedged in. There is less than a quarter inch clearance between the largest pulley diameter and the wiring. so the belt has to be wedged past the wiring which is tight against the case to get the belt in that groove. Beyond that? Someone in China hit it with something. The lever to engage the 1/2 nut is bent. The lever to engage the lead screw was bent and the roll pin mashed making it loose like a sore tooth and the engage the lead screw assembly fell apart on the first day allowing a key to come out screwing up the shaft. I fixed all of that and a pin # 765 fell out of the half nut engage lever in the cross slide. However that pin doesn't engage with anything There is nothing around it at all and the collar is one piece. That pin falling out had no effect on anything nor does it affect anything from what I can see and according to the schematic. Even the MT3 taper in the mill spindle came with a 3/8 -16 draw bar when standard MT3 Taper from what I can see uses 1/2 or M12. So to buy a ER 32 collet holder alone that fit's the taper and the draw bar is special. $98.00 for a cheap Amazon one. Or you have to change the draw bar or modify the collet. I can go on and on and on. The mill has more issues than that. From what I can see to start with after a single use. When you lock the quill just before machining it jams to the extent you can't fine adjust for the next cut without first disengaging the fine adjust move away from the work and run the quill up and down to free it. The set it all up again for the next cut. Oh! And while I purposely searched for a lathe mill with power lead screw and power cross feed specifically for milling and threading you can't run any of it while milling. Milling is all manual and worse with the jamming quill lock. Also there is at least 3mm of backlash in the screws and dove tails relatingso coming out of a cut when climb milling is an instant end to of an end mill. Even to change the speeds on the mill you have to use a goose neck or pry bar to tension the belts. A drill press has a lever to push the motor to tighten the belt but a $4000 dollar mill requires a pry bar with not even a designated place to pry.
This was a brand new machine right out of the crate. Some folks will say I should have sent it back. Then what? Wait another 10 months and maybe get something worse? Another brand? When they are ALL MADE IN CHINA? Probably all different production runs from the same factory. How about we quit manufacturing garbage in China make it here and actually have some customer service. There is even dumber shit on this machine. The ways are flat top dove tails. How do I make a carriage stop to clamp to it without drilling the bed or making a dove tail attachment that goes right across the ways? The 1/2 nut is on the left side of the carriage. You have to wear a glove when turning or threading cause the few days of use show a 90% chance of being burnt by chips operating that handle cause the chips are all falling right where the 1/2 nut handle is. So now I'm Micheal Jackson when turning with the lead screw. One glove just in leather the sequins are metal filings falling on it.
Seriously! aren't people tired of buying junk new that you have to modify or fix? It's cheaper to manufacture in China cause WE ARE doing most of the damned work and there is no customer service. If I had returned this machine they would have smashed it and thrown it in a heap to be shipped to china as scrap cause it's not cost efficient to send it back 1/2 way around the world fix it and return it. This whole Manufacturing in China model is not cost efficient and it sure as hell isn't environment or energy friendly. I just bought to oil cans. Both cost $20 each. The one made in China is light and made cheap as hell while leaking all over the place. The one made in the US weighs more empty then the Chinese one weighs full and is solid. Even the action of the mechanism is solid and smooth in comparison SAME PRICE! They are manufacturing in China cause it's the customers that are stuck with the shit quality and excusing it cause the hassle to get a manufacturer to deal with it isn't worth not fixing it yourself and you can't go somewhere better cause it's ALL manufactured in China.
Look at this video. Only a few issues that rendered this quick change tool post a piece of junk but other than that? OH YA! Works great!?!?!?!? I can guarantee folks would never allow a national manufacturer to get away with that.
SOUNDS ABSOLUTELY ! Ready! for the ! METAL SHREADDER ! NOW !
@@davidwillard7334 fine! give me a guaranteed good solution. at least I am confident with the quality an resultant repeatable accuracy of the work I have done
@@RoughAndWretchedRAW YOU HAD ! TOO !.FIX ! UP ! YOUR ! JUNK !! HEY !!
Hi Evan,is this the 5" or 4 1/2" centre height
It's just a Lathe !
It happens to be 4.5" center height made in 1955. This is 9" swing to Americans. The 10" swing models came much later.
Why don’t you clean off all the little chips before you even start working on it,that all part of precision type machining,just a thought?
Fair comment! The tool holder that I grabbed to mount on the QCTP was especcially messy!