The Shop > Tools
Thick stubby drills
PekkaNF:
Finally I got my parcel....PostNord sat almost week atop of it. Express my hiney.
Anyway I got real brand name Rotabroaches, set of short 14-20 mm dia and extra 25mm OD. Rushed to make an MT3 minimum lengt adapter and plan was good, but the MT3 blanks that have been joy to work before turned me down. This one was made of mysterymetal and it was proverbial to work with.
It had a nice 40 mm ground outside, checked it and it was true, drilled and bored the 3/4 hole, with some difficulty, beacause the material was "sticky", got a little oversize hole (19,06 mm). Then I turned the oil grove (planned to place an angled hole from it to rear of the cutter recess. All well and original ground surface was saved for the cutting oil seal (Grub screws were M12*12 and could be shortened just a bit to clear Nylon or acetate bushing that plays the role of the seal....or that what I had in my dreams.
Went nearly acceptable, but when I threaded the M12, it raised the metal around the thread. Had to turn down the perimeter and now it is not anymore good enough finish for any kind of seal. Bugger.
Had no time to test. Hope it works. I would have liked the blank a tad longer (it is 30 mm long, dog ate 7 mm of it at the tail and web left behind of the weldon seat is thin. But that was only thick enough blank I had.
Well, I call it POC.
Pekka
PekkaNF:
Got parcel from Germany, same size/weight parcell ordered a little later 1/3 price of P&P and 1/20 of aggravation...looks like I'll be ordering more stuff from EU than from Brexit. :lol:
Anyways I declare this partial success. I was planning to use this one to check coolant feed troughh nylon bushing, but the MT3 blank does not finish easily to any kind sealing fit without resorting to grinder and that creates it's own set of problems....mainly the fact that I haven't used mine yet.
Got 30 mm ID 42 OD ball bearing and same size shaft seals, planning to make other adaptor for trough coolant feed.
Questions:
* How to produce good enough finish on shaft for lip seals on HMS? I have grinder, but never used it for a real work - to achieve certain shaft roughness. What kind of grinding stone for normal hot rolled bar stock, drawn bright stock and tempering steel?
* How to grind it dry? I'll still need to order curtain and cobble up an shop vack adapter, because the cast iron fan I had was way too heavy.
If it turns out to be too hard, I'll probably put this project aside until I have the grinder all sorted out, might as well do the whole adaptor from bar stock MT and all.
Pekka
PekkaNF:
Just a little progress. Have to add reaction bar to hold the inducer. I don't want it to do flail imitations.
Not sure how well it will hold the coolat, but that piece was an off cut and it't the first try. No lipseals or such.
With third (coolant) hole it starts to look bit like a swiss cheese.
Pekka
sparky961:
--- Quote from: PekkaNF on September 16, 2016, 02:59:16 AM ---* How to produce good enough finish on shaft for lip seals on HMS? I have grinder, but never used it for a real work - to achieve certain shaft roughness. What kind of grinding stone for normal hot rolled bar stock, drawn bright stock and tempering steel?
* How to grind it dry? I'll still need to order curtain and cobble up an shop vack adapter, because the cast iron fan I had was way too heavy.
Pekka
--- End quote ---
Did you get the finish sorted out? I'm assuming by "HMS" you mean hot rolled mild steel. I find this easier to turn than CRS (cold rolled steel) but can still be tough to get a nice finish. In "my" CNC lathe at work, the solution is to CUT HARDER and CUT FASTER... seriously. If the chips aren't pinging off the inside of the enclosure and you can't hear the motor working, it isn't taking a big enough chip. Really nice surfaces this way too.
Unfortunately few on this forum have machines like this at home to work with (myself included), so the rest of the mere mortals need to resort to emery cloth, sandpaper, files, steel wool, and such. Sometimes, if you're really lucky, you can get an insanely sharp piece of HSS to do the trick. Put the carbide away unless you're going to be hogging away material.
Try to see what your machine is capable of. Set aside some of your tooling budget to break a few things while testing. Wear a full face shield and have the e-stop readily accessible. HOLD PARTS FIRMLY. Feed seems to give more favourable results than depth of cut, but you don't want to be just scratching off a few thousandths either. I suspect it's some sort of burnishing effect going on.
PekkaNF:
I used file + emery... not proud. It is nowhere any known even metric (or probably even fractional inch) dimenssion, just tried to keep the errors on right way...
I actually get pretty good finish on tempering steel when using sharp carbide tools and a lot of cutting speed, swarf must be hotter that violet. DOC is minimum recommended and feed just short of stalling the lathe. Then piece is true and finish is good.
Problem is that you have to sneak to diameter, because all finishing cuts must be about the same depth. I'll put TDI to cross slide, mike diameter and try to fine adjust the cutting depth (e.g. recommended minumum is 0,3 mm DOC, I'll play something like 0,3 - 0,5 mm) to hit final diameter in three or four successive cuts, trying to keep the DOC as constant as possible, but may need to adjust each cut to make last cut same DOC as previous. Some can count on cross slide dial, mine is not that great somewhat between metric and imperial....close to both, but not close enough.
I never had predictable results with hobby type finishing "shaving" cuts for last few "thou". Although I have learned a lot of sharpening HSS and I see the benefit. maybe it works on free cutting steel?
I may need to learn my own MT3 tooling, including tapers and testing equipment.
Pekka
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