If this isn't a machining man moment I don't know what is! My wife is out of the house for the next couple of days so I'm making hay while the sun shines (at least from another direction, it shines when she's here too)
I'm building a new lathe for myself and thought I share the project with you all. Now here's why this is a machining man moment, I was downstairs milling out the carriage for my lathe while at the same time breaking in the gear box on my new lathe. I've come up to take a break and check in here while while collecting my two ebay boxes from the front porch. I almost forgot...read my book on machine shop practice while waiting for the wife earlier! BTW, one of the ebay boxes has my new ultra cheapie digital camera for posting...I may be asking for a life line on this....I'm a digital virgin
If there is one thing that I've found consist in this hobby it's that every time you want to do something you have to make something first. Here and there in these posts I've mentioned that I want to build some very small hit and miss engines and with the size of components I want to make a small lathe is pretty much required. While I have a Sherline long bed there are a couple of things that weren't what I wanted right now....first I'm having some issues with the tail stock not lining up with the headstock (They're going to check this out for me) and the other thing is that I've wanted to make a truly small lathe for several years so things sort of came together for an idea. I've spent my lunches at work for the last 5 years reading books as there's nothing else to do so I decided I wanted to make a lathe that will be small enough to cart to work like a lunch pail.
I find it really interesting how things tend to come into galactic alignment for me every once in a while...seems like some things are just destined to happen. What are some of those things you may ask...
1. I realized that I have a short "bed casting" as it were from my Sherline mill head assembly that could be used for my new bed and it's quite compact by comparison (about half the lenght of my current lathe).
2. A few years ago I looked without succes for a dovetail cutter to make my parts, suddenly, recently I found a dovetail cutter on ebay that I could use to make my parts.
3. Was I going to reuse the existing headstock or make one? I decided to make one.
4. How was I going to make the spindle assembly? I'm not that confident as yet that I could get a level of accuracy that I'd find acceptable. In floats a Morse socket that is a 1" O.D. and has an MT1 interal taper.
5. I started looking for bearings and got some sticker shock. What did I find on ebay....Harley headstock tapered roller bearings $15.00 for a pair (I'll get back to you on the accuracy, but if nothing else they'll work for proto).
6. The real kicker was an aluminum extrustion I found on ebay from 80/20 (a great source of aluminum on many occasions) What do they have but what I'd have to call the PERFECT aluminum extrustion for making both the headstock (If I use smaller bearings) and the tail stock. It came like manna from heaven just as I was considering how to make a tailstock assmbly that didn't start out as a 4 lb block of aluminum. I thought I'd have to do a built up assembly and I wasn't all that keen on that. The nice thing is that it's also ideal for making the tailstock adjustable which is something that I really miss on the Sherline.
7. OK so here's the thing that I'm pretty sure that will get some heads shaking....I want to make it cordless. Before you think I've lost my mind tune in to this...the Sherline motor generates 10 oz inches of torque in standard application and up to 30 oz inches for spurts. Milwakee has just come out with a new brushless (wound stator) line of drills with a peak torque of 525 inch POUNDS of torque for the "plain drill" and 675 for the hammer drill. (At this point I'm thinking that may be overkill so I'm going to give a Ryobi Lithium drill I have already a shot). I plan to be doing light work so I give it a 50% chance of being "enough" for light tasking)
So here are some of the challenges I've run into already. I'm using a HF Central Machinery mill to do the job which takes MT2 Collets. I got a dovetail (60 degree) cutter for the carriage assembly only to find that it was a little smaller than I wanted for the job so I headed back to get the next size up and got a surprise (can somebody explain this please), the first one I got was a 3/8" shank with a 3/4" diameter... the very next size up is 1 3/8" which has a 5/8" shank! Guess how that worked out with my MT2 collets (I'm flexible if nothing else, I'm keeping the cutter and going to try to put a larger mill with it at some point in the next couple of years). At any rate back to the smaller cutter and was able to make my cut with all of about 0.010" to spare on the face length.
I'm now all happy because this piece has been sitting in the mill for about a week waiting for me to have a chance to make the part. My new 55 degree cutter came in and I went to work....correction, I tried to go to work. It turns out that well, some less than helpful decisions had been made on this cutter...turns out the guy got them made with a 12 millimeter shank...everybody know where that falls in a standard MT2 collet set? That's right folks....NOWHERE As if that's not enough to fry your bacon turns out that the bed angle is ACTUALLY 55 1/2 degrees. Now you know where my motto comes from (anything worth doing is going to be a pain in the butt). But in part this is one of the things that I like about machining, it requires you to build patience. One way or another I'll get this worked out...stay tuned to find out how.
I decided to check out the fit on my bearings to my new would be spindle. The holder is made to fit in a turret which means...it's undersized by 0.002 to make allowance for an easy fit. (I'm sure glad I got the soft one so I can knurl it to make up the difference).
The thing that has been pretty interesting so far is that I've had all the metal I've needed in my existing materials bin so that's been a real help. I was thinking about how I was going to get my saddle assembly true and the other day someone posted on facing a block of material in the lathe using a 4 jaw and I can honestly say that it wouldn't have occurred to me to do that so that was inspiring as I think the lathe could do it more accurately than my mill as the part is so relatively large.
Seeing as I couldn't work on the carriage today (the dovetail issue) I decided I'd start work on the saddle. The piece was extruded plate and varied about 0.0025" in thickness. I was going to mill it but wasn't sure it would be an improvement, then I thought about the lathe but it was still on the "spin cycle" for the gear box break in. I looked at the piece and my ego took over...even if I could live with the variance, when I anodize the part those streaks in the surface from the extrusion would be staring me in the face forever I just couldn't live with that. So I decided to have a go at lapping using sandpaper and my surface plate. Through imperical testing I can tell you that you can get a pretty nice finish on both sides of a 3" x 5" block of aluminum in about 1 hour and 38 minutes (provided your arm doesn't fall off :-)). Now it looks better and it's only got a variance of 0.0015" which I'm prepared to live with for now.
The new lathe finished it's break in and I decided it was time to call it an night and report in. All things being equal I hope to get some photo's to you in the next few days.
Stand by for further developments.