|
Material suggestions?
|
04-01-2015, 06:10 PM
Honestly, 1020 is probably good enough -- it's tougher than cast, and easy to machine.
Since you're machining away all of the mill face with your ratchet notches, you don't need cold rolled. If you choose hardened, you'll need carbide tooling to cut it. 
04-01-2015, 06:16 PM
I would use the 4140 pre heat treated for the ratchet, without question. Highest tensile strength and wear resistance. And I'd remake the pawl and it's pivot pin in the same material to be sure they are of equal strength. It machines beautifully with carbide tooling.
04-01-2015, 06:54 PM
Not to hijack Willies thread but this is a question about 4140. I recently bought some material from speedymetals.com and got some material from their fire sale which was described as "7/8" Round 4140 HT Cold Roll 46.5" Randoms" so I bought two of them. Once they arrive I realized the "HT" probably meant heat treated. Is this going to be a problem to machine?
Ed 
04-01-2015, 08:14 PM
Shapiro has some A36 in 1/2" thick and 1" thick bars. 3 1/2" wide on the 1/2" thick and 4" wide on the 1" thick both under $19.00. While it is primarily a structural steel it should work well in this application.
http://www.shapirosupply.com/index.php?m...ts_id=9650 
04-01-2015, 08:55 PM
(04-01-2015, 06:54 PM)EdK Wrote: Not to hijack Willies thread but this is a question about 4140. I recently bought some material from speedymetals.com and got some material from their fire sale which was described as "7/8" Round 4140 HT Cold Roll 46.5" Randoms" so I bought two of them. Once they arrive I realized the "HT" probably meant heat treated. Is this going to be a problem to machine? Ed, according to Speedy's spec sheet it has been hardened to 27 to 32 Rockwell C. I am curious as well about machining it, since I don't have a lot of carbide tooling for my mill.  Quote:4142 CFHT can be used for as wide variety of applications where greater toughness and wear resistance is needed over lower carbon grades. Typical applications include ejectors, back up and support tooling, cams, drill collars, bolts, stubs, couplings, reamer bodies, axles, shafting, piston rods, rams, hydraulic machinery shafts, gears, sprockets, valves, chain links, spindles, tool bodies, tool holders, tie rods, boring bars, machinery parts and components, etc. This material roll threads, knurls, and may be plated.
Willie
Thanks given by: EdK
04-02-2015, 05:59 AM
(04-01-2015, 08:14 PM)Dr Stan Wrote: Shapiro has some A36 in 1/2" thick and 1" thick bars. 3 1/2" wide on the 1/2" thick and 4" wide on the 1" thick both under $19.00. While it is primarily a structural steel it should work well in this application. A36 is NOT a good material for that application. It's got a tensile strength of 36,000 psi, and is soft as puppy crap. Even the original part on a Chinese import arbor press would be stronger. Using 1018 CRS would be a better choice at nearly twice that strength. The structural steels are good in compression or when mass can make up for lower strength. The ratchet part is stressed in shear by the pawl. You want tensile strength. 4140 is 95Ksi. 
04-02-2015, 08:55 AM
Ken is going to tear me apart for this suggestion but one of these will remove a lot of tough material pretty economically.
![[Image: 6-901-510.jpg]](http://www.kbctools.com/contentonly.aspx?file=images/items/6-901-510.jpg) Takes inserts that I can get cheap even up here.
Free advice is worth exactly what you payed for it.
Greg
04-02-2015, 11:12 AM
(04-02-2015, 05:59 AM)PixMan Wrote: The ratchet part is stressed in shear by the pawl. You want tensile strength. 4140 is 95Ksi. You know Ken, all this time my concern was that the ratchet might crack in half at the voids someday. The possibility of the pawl shearing off teeth never even entered my mind!  Thanks for pointing that out. I think for now though, I'm just going to get a slug of 4140 cold worked in the annealed state and see how that goes. Surely that will be stronger than what is on the (yes, it's an import) press right now. The pawl and pin seem to be good and solid. Perhaps sometime down the road if/when I can acquire a nice carbide insert cutter of some sort for my mill I can revisit this and make another ratchet from PH material as a test run of the cutter. Although cutting the internal key way in hardened material would be another problem for me.  I think Greg nailed it though. No matter what I use, I probably won't be around long enough to wear it out.  
Willie
04-02-2015, 11:15 AM
(04-02-2015, 08:55 AM)f350ca Wrote: Ken is going to tear me apart for this suggestion but one of these will remove a lot of tough material pretty economically. Excellent point Greg. If you can't find inserts, all you have is an expensive paperweight.
Willie
|
|
« Next Oldest | Next Newest »
|
