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| Another new project... a QCTP (Quick Change Toolpost) |
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| AdeV:
OK, a quick update now I'm in "sunny" Spain... Thanks for the thoughts on the tumble polishing.... I was running at 112rpm for the most part, basically, I just picked a speed where I could hear my nuts rattling around & left it at that. I will try some proper abrasive next time, I didn't have any to hand hence not including any... I've also turned a lump of 3.5" 303 stainless steel down to roughly the same diameter & depth as the hole. At the moment, I think it's a touch too tight to just slip smoothly in, so I may need to lose another couple of thou. Just out of interest, what sort of dimensional difference does one need to ensure a nice sliding fit that isn't so tight it jams up? |
| Brass_Machine:
--- Quote from: AdeV on August 16, 2010, 02:53:05 PM ---O...I just picked a speed where I could hear my nuts rattling around & left it at that... --- End quote --- Now I have to clean my keyboard. Soda everywhere! :lol: Enjoy Spain. Eric |
| Rob.Wilson:
--- Quote from: Brass_Machine on August 16, 2010, 04:17:48 PM --- --- Quote from: AdeV on August 16, 2010, 02:53:05 PM ---O...I just picked a speed where I could hear my nuts rattling around & left it at that... --- End quote --- Now I have to clean my keyboard. Soda everywhere! :lol: Enjoy Spain. Eric --- End quote --- :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :doh: Rob |
| AdeV:
Onwards! Unseen by you ('cos I didn't take any photos of it, oops), I had turned a length of 3.5" s/s bar down to the correct diameter (nearly - I was a couple of thou over) for the toolpost. On returning from my 'oliday, I ordered a fab new boring bar to replace the knackered one I've been using, and got on with finalising the diameter & drilling the centre hole as far as I could. Yesterday, the spiffing new boring bar turned up; but it needed quite a shim to fit in the existing toolholder.... it was a whopping 0.410" low (measuring from tip to dead centre)! So, I made a 0.405" "shim" from some scrap 1/2" steel - which, it turns out, is exactly the right height :thumbup: Here's the new toy: I took a couple of trial cuts through the drilled hole, got some chatter on the first pass, but second & subsequent passes were as smooth as you like. Spot the happy bunny :) So, after cleaning up the drilled bore a bit, I decided to clean up the shoulder: You can see the chatter marks (LHS shoulder, nearest the chuck); that's because, not having any tools which will cut to a shoulder just now, I used the boring bar. To make it work, I had to have the cutter behind the work piece, and run the lathe in reverse. Other than the slight chatter, it worked like a champ. The strange looking "shoulders" on the bottom (RHS) are to cope with the fact my old boring bar couldn't cut a clean bore to a shoulder, so there's a bit of excess material left in the main toolpost body. Those cuts clear that, so it goes and sits right at the bottom. Next jobs: Open the centre bore out a little further, then off-set the piece & cut the cam (I may need to grind a tool up for that, as it will be between two shoulders...), then finally turn it round & relieve the top, cut a nice taper on the "handle" section, drill & tap for the handle... I should probably do some proper measuring soon... Nah, what the heck. Keep on cuttin'! |
| AdeV:
So, today I wanted to finish off the cam lock bit. First job was to tidy up the main bore & open it out to 1.5". This done, the next job was to off-set the work to cut the actual cam part. This achieved, I also scrounged up some weird turning tool from the bottom of a drawer somewhere. I think it's a left-handed tool to cut to a shoulder, but ignorance is bliss so I gave it a quick whizz on the carbide grinder wheel, just to sharpen it up, lobbed it in the toolpost (fortunately, no faffing required, it went straight in at the right height), and got busy with the cutting: Yes, I know the tool looks like it's mounted on its side. I took me ages to work out which way up it went... One thing about this tool, it cuts a very nice surface on 303 Stainless. The entire piece was now turned around, re-centered, a few touches removed from the main diameter just to get it to run true; then I cut a 20 degree taper. This is where the handle will go, and matches the taper on my current toolpost. After a bit of faffing (including re-setting the piece, as it moved a smidge when the taper was being cut, somehow), everything was ship-shape. A quick file to take the burrs off, and a quick whizz with some oiled-up wet & dry paper made no impact on the machining marks. So I pretended it is a "brush finish" & left it at that... Next job, drill & tap the hole for the handle. First up, I needed to somehow mount it in the milling machine, at an angle of 20 degrees, straight & true... After some headscratching, some messing about with the sine bar & gauge blocks, and discovering that the only way I could fit it into a V-block & clamp would be if I drilled the wrong side of the piece for the handle.... I suddenly got some inspiration. Having just bought a digital angle gauge, why not simply clamp it between V-blocks in the vice, and manually tip it up until the correct angle appeared. A bit like this: Simples.... used an end mill to make a small flat, centre drill (at max RPMs) to make a wee guide for the twist drills, drilled 4mm, 6mm, 7.5mm, 8mm & 8.5mm ready for an M10 tap. Now.... as anyone who has read any of my stuff before will know, tapping is not something I enjoy. I'm still dissolving two taps I broke off... and that was in Aluminium; now I'm tapping in stainless steel! I've also found tapping to be an energy intensive operation, and bloody slow. So... while I was on holiday, I noticed an auto-reversing TapMatic on eBay. Actually, there were several (of various makes), all going for around the £100 mark; one was on Buy-it-now-or-best-offer, so a cheeky offer of £75 was, to my surprise, accepted promptly :headbang: I also bought some spiral point taps, which I believe are better for power use than regular hand taps. Anyhoo, pop the tapping head on the mill - it uses up all my headroom, I could only just fit everything on! :bugeye: So, here's how to tap in Stainless: Line everything up. Set speed to 115rpm. Hold quill handle with right hand, use left hand to release quill lock (oh for a working quill spring...). Hold torque lever with left hand. With other left hand, switch mill on, then apply a load of cutting oil. Pull quill handle down until tap engages & starts tapping. Keep gentle downward force on until tap comes out of the other end of the hole; then pull quill up. Tap reverses & drives itself out of the hole. From first pulling the handle down to the tap fully withdrawing - 10 seconds (approx). MILLIONS of times easier than farting around with the tap, tap handles, trying to make it all run true. Yada yada. I am SO going to love this tapping head, even if it is too deep for the mill. I can always use it on the pillar drill instead. Anyway, that's more or less where I left it. The cam piece is now finished, I have the main holding sleeve & bolt to make, the pistons to make, the body to finish off, and the base to make. Blimmin' eck! |
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