Primitive Machining Project for the Skill-Deficient
June 9th, 2009Tool Holders!
I have learned something about machining. You can’t just buy a quick change tool post set and be happy. The set will only have two holders for turning tools. Once you start grinding tools, you’ll end up with a variety. In other words, more than two. So when you want to change tools, you’ll find yourself moving tools in and out of the tool holders.
The upshot of all this is that you need more than two holders.
Some guy on the Chaski forum posted a photo. He has a collection of tool holders, from CDCO Tools. They sell cheap Chinese tooling. The photo showed dozens of these things in a drawer, set in rows. It was like a Communist-bloc tank display. He has a library of tools he has already made, and they’re sitting in their holders ready to go.
Another guy says you have to have at least 10 in order to be happy. And someone said he makes his own.
That got me thinking. This should be an easy project for me, once I have a mill. You buy cold-rolled steel, cut it in suitable chunks, make them pretty with a fly cutter, tap a few holes, cut a few grooves, and you’re done. I doubt I can do it for less than the $9 cost of a CDCO tool holder, but that’s not really relevant. If I wanted to have everything done for me, I wouldn’t be buying machine tools.
I suppose you could make them from aluminum. Tool holders are pretty beefy. I don’t think aluminum ones would be flimsy enough to flex. The threads might be a problem, though. I guess you would have to worry about them holding up.
My set came with two holders suitable for turning and facing. One has a groove in the bottom of the tool slot, to support a boring bar. The other doesn’t. I assume the grooved type must have some disadvantages, because if it didn’t, there would be no reason to manufacture holders without grooves. I have to figure that out. I don’t think I’ll ever want to use this kind of holder for boring, since I have a holder designed especially for boring bars. But versatility is good.
I also want to make some brass knobs for a bathroom cabinet. I realize they probably won’t be as cute as the ones at Home Depot, but it’s an irresistible project.
I have to get some tapping tools. It’s an essential I somehow overlooked.
June 9th, 2009 at 10:27 AM
Practice on aluminum. make real ones out of steel. The clamp on the toolholder has more than enough strength to bend the aluminum. Threads are actually a non issue, you just put in steel inserts.
the reason holders aren’t all manufactured with grooves is it’s another machining step. it costs a few cents more. The Chinese don’t make this stuff cheap by throwing in extra machining for free.
ten is probably a good number. Buy barstock to size, cut it to length, and machine it. Get a LOT of #7 drills. Buy at least two packages of ten. High speed steel is plenty good. And a handful of taps: Spiral flute, plug type, fast spiral, GH3, steam oxide.
You’ll also need a walton tapper.
http://www.wttool.com/product-exec/product_id/26695/nm/Piloted_Spindle_Tapper_Walton_
This will allow you to drill a hole, then take the head out of gear so it freely spins, remove the drill bit, and put in the tap handle. The tap still gets turned by hand, but the machine holds it perfectly perpendicular AND in exactly the right location so the tapped hole is flawless every time.
You will eventually learn to run the tap in the threads with the mill on low speed, sensing when it’s overloading, but for now, the walton tapwrench is the best bet.
June 9th, 2009 at 10:51 AM
Seems to me that I recall mentioning a few months ago the set of “taps and dies” you would soon need because the only thing efficiently done on a lathe is an ACME thread and other things larger than 3/4″ or 1″.
Like drill bits the Craftsman and Harbor Freight sets are nice but taps & dies wear out and break so a half dozen 1/4-20 and some 3/16″ and 1/8″ sized suff in course and fine thread will usually do the trick. As a home handy man/amateur car mechanic/model airplane hobbyist I rarely use anything over 5/16″ or 3/8″ although I have $600 worth of Craftsman stuff in plastic boxes that’s 15 years old–most never used.
It’s your design and you’re the machinist so why use 1/64″ or 1/32″ increments when standard bolt sizes will do for most applications unless you’re building a steam turbine or space shuttle?
June 9th, 2009 at 10:58 AM
I was figuring on getting some stuff I could use by hand, since there aren’t many holes to tap, and they’re fairly shallow.
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I don’t think it makes sense to get a huge set. I can get a small set of HSS taps and dies without breaking the bank.
June 9th, 2009 at 11:18 AM
Ahhhh. Taps and dies. Tapping by hand. Yes. Isn’t that where you carefully measure, drill, start your threads and then move everything over an inch because it’s impossible to remove the broken end of the tap from the hole.
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Maybe I was doing something wrong.
June 9th, 2009 at 11:58 AM
Leo…the correct sized drill goes a long way toward minimizing tap breakage…then you should also not try to tap holes 2″ deep by hand–use an over sized counter bore with threads in the last 3/18″ to 1/2″ or so. Or pre threaded inserts like og mentioned
June 9th, 2009 at 12:54 PM
I’d get 10-24,1/4-20, 3/8″-16, and 1/2- 13 in inch, and 4mm, 5mm, 6mm, 8mm in metric. Get spiral flute H3 taps in black steam oxide if you can, or bright if you can’t. Taper taps are for tapping a hole that goes all the way through. Plug taps are tapered a bit less and allow you to put in a liquid tight plug, if the hole is blind. Bottoming taps allow you to thread all the way to the bottom of a blind hole. Plug taps are the best overall compromise, IMO.
June 9th, 2009 at 1:59 PM
Grizzly sells a big set of HSS taps and dies for $85. I’m thinking I should get that and then replace them with better ones as needed.
June 9th, 2009 at 2:31 PM
Bad tools cause you to learn bad habits at the minimum. At the maximum they can hurt you.
Taps and dies can be the most frustrating and aggravating things in the arsenal, with the increased aggravation going in an inverse exponential with value (not always price). The Sears Craftsman set I once had was junk, pure and simple. They were dull, and the plating (whatever it was) they put on to make them look pretty was an anti-lubricant. It was a huge relief when enough of them got broken to make it necessary to buy a new set of black oxide ones.
Hearty endorsement of og’s suggestion — buy fewer but better quality, and when you need another one, buy them one at a time. You won’t spend any less money in the long run, but most people can more easily accommodate a slow drip, drip than a huge expenditure all at once.
The Walton tapper is a marvelous gadget. Getting the tap or die started straight is three-quarters of the battle. For little taps (1/4″ and smaller) I use a chunk of 2″x4″ aluminum bar stock with holes drilled through it that just clear the threads. Get a few threads started, take the block away, and put the tap back in the hole. It isn’t perfect, but it’s better than judging by eye.
Regards,
Ric
June 9th, 2009 at 2:41 PM
Drill with precision, cut clean threads, and buy grade 5 or A-325 galvanized bolts as a minimum and 316 stainless (allen head, star point, or hex head cap screws) when you can afford it and use flat and lock washers and your bolted joints will be a thing of beauty and strong to boot.
Stainless or galvanized allthread rod cleaned up with a file after cutting to length makes nice studs you can seat in a non-thru hole wtih loctite and make simple clamps and jigs and “manual vices” using the nuts turned on the studs to hold down a piece of bar stock with a workpiece sandwiched in the middle.
There’s endless possibilities when you can do something besides chop and hack at metal.
June 9th, 2009 at 4:50 PM
Steve, the problem with not using the “better ones” to start with is that you end up in the situation the Leo describes.
I’d follow Og’s advice, but I’m surprised he didn’t recommend TIN coating, and I’m not sure you need the metric immediately. I only use them on metric devices I’m altering. Dies in those fractional sizes (with a “stock” to hold them) would be handy.
Something I find handy is a tap and drill index that pairs the correct drill with the correct tap.
June 9th, 2009 at 6:10 PM
From an email to Og:
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“I doubt I’ll need a lot of inch taps for the Harley. It’s a 2001. Half of the damn thing is Japanese. I should polish it with soy sauce.”
June 9th, 2009 at 6:40 PM
Whatever you do, a full set or bits & pieces, do buy quality.
Besides drilling the correct-sized hole, the next most important thing is to drill and tap straight. Anymore, I do my drilling in the mill, and just follow the drill with the tap, usually under power. I’ve broken maybe 2 taps in the past 4 years: one was because I grabbed the wrong drill for the 0-80 tap, the other was a 2-56 that I went a bit too far with on a blind hole.
And I’ve tapped a bunch of holes. 🙂
June 10th, 2009 at 1:48 AM
Buy a nice set of 135º split point drills in cobalt steel ($130) or HSS ($70). I would get a numbers set (it has all of the tap drills up to 1/4-20) and then maybe a fractions set. Later get the letters set. Greenfield, Chicago-Latrobe, Cleveland Drill are good brands. Stay away from hardware store drills. You’ll want a carbide spotting drill for your mill, as well. Og’s tap recommendations are good ones. I recommend the Greenfield brand. Don’t buy Hanson taps or Craftsman taps or hardware store taps. I use mostly bright finish spiral point taps, as I do lot of aluminum. I keep plug taps and bottoming taps on had as well, but will always use the spiral point when I can. I tap on my mill, after I have spotted and then drilled all of the holes. I used to use a spring loaded center in the chuck and a tap wrench, which worked like the Walton wrench. Lately I have just chucked the tap up in the Albrecht chuck and switched into low gear, about 70 rpm, and power tapped. Works great. The tap slips in the chuck it if binds up. Reverse to extract the tap. This is in aluminum; steel might require too much torque. Remember that taps are consumables, and get dull. They can be resharpened with a Dremel tool. Or buy a new one. Keep a good supply on hand. For hand tapping you will want a tapping block. You can make it or buy it:
http://WWW.OMWCORP.COM/prod_tb.shtml
June 15th, 2009 at 11:35 AM
I agree with Og’s idea of practicing on ali or some other material. When I was learning CNC milling we learnt on foam.
10 holders sounds excessive but given that I shim all of my tools manually I’m probably not the best person to ask. However I agree it’s a good little project but possibly not that simple as a starter one. Time will tell…
The trick on the bathroom knobs will be getting them to look the same. You should be able to do it without a specialist ball turning tool. Draw yourself out a large version on some squared paper. You can then approximate the shape with straight cuts. See http://1.bp.blogspot.com/_LA1ir3SXLqw/R-L6czC5eFI/AAAAAAAAAFM/SG6KA-J5UEs/s1600-h/P3200090s.jpg sorry I could not find an example in metal but the principle is the same.