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Die grinder: How much air?
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=13500		 Page 1 of 1
Author:  ColinML [ Mon Sep 03, 2007 12:47 pm ]
Post subject: 

I know that John Hall says in the description for his (really nifty looking) die grinder tool that it needs 90 psi at 2 cfm, but even some small compressors for pin nailers are rated for this.  What is a realistic minimum HP/tank size to be able to work at inlay without constantly waiting for the compressor to catch up?


 


Thanks,


Colin
Author:  Bob Garrish [ Mon Sep 03, 2007 2:14 pm ]
Post subject: 
CFM ratings for tools are at a 25% duty cycle. If you want to run it full time you need an 8CFM compressor. If you're going to run for a length of time but intermittently, then you can use something with a big tank that'll get to 100PSI.

HP ratings on compressors are essentially useless unless you're dealing with a company that makes industrial compressors. I doubt you're going to buy a DevAir just to run a die grinder, so just look at the tank size and CFM ratings.
Author:  David Collins [ Mon Sep 03, 2007 2:17 pm ]
Post subject: 
I don't know which die grinder he recommended, but most really eat up the
air. They are often rated at "average cfm" which involves some formula
assuming short second bursts over some time span. Many cfm ratings are
not written for constant use, but rather some anticipated average use. An
average size die grinder can easily pull 15-20 cfm under full load at
constant use.

If you're talking about inlay work is this a pencil grinder or something like a
dental drill? When you say die grinder I think of a standard metal shop die
grinder with a 1/4" collet, like you would use with a cutoff wheel. Those big
clunky things are not something I would think too appealing for inlay work.
Author:  David Collins [ Mon Sep 03, 2007 2:20 pm ]
Post subject: 
Okay, I guess Bob already had a better answer than I did. I knew it was
some seconds per minute average, but didn't know exactly what. 25%, good
to remember. Thanks Bob.
Author:  crazymanmichael [ Mon Sep 03, 2007 3:22 pm ]
Post subject: 
are you thionking of getting a comprewssor to run just the little mini die grinder for inlay, or one for the general shop usage? remember you will probably want to spray finishes, and perhaps run vacuum clamps, perhaps even a ros.

it seems to be almost axiomatic that like clamps, you can;t have too much compressed air.
Author:  MikeP [ Mon Sep 03, 2007 3:55 pm ]
Post subject: 
do NOT buy a compressor with the name DeWalt on it..they are complete cr@p, and don't trust the manufacturer's ratings as they are almost always overrated. The bigger the tank the better for spray work, and make sure to do research on how to set up proper lines for water removal and oil extraction (that is if you get an oil lubricated compressor).  I take the extra step of putting a little filter with quick connect fittings right at the spray gun. 


Author:  Louis Freilicher [ Mon Sep 03, 2007 4:50 pm ]
Post subject: 
Here's a great article on compressors from The Practical Machinist Forum.

link


Louis
Author:  ColinML [ Mon Sep 03, 2007 5:15 pm ]
Post subject: 

Thanks for the helpful answers.  The article was especially helpful, Louis.


Yes, the idea was that I was considering buying a compressor to run the little die-grinder inlay tool that John Hall sells.  I really wish I had just taken the plunge years ago and purchased a large compressor.  Instead, I invested in electric sanders, an HVLP system, etc.  Now I can't justify the expense since I already have capable tools. 


All is not lost, however.  Tonight I took my first stab at inlaying a signature logo I got from Bob Garrish (Thanks Bob.  They look great!), and the olde Dremel seemed to do fine. 


Thanks again.  Appreciate the help.


Colin
Author:  Michael Dale Payne [ Tue Sep 04, 2007 12:25 am ]
Post subject: 
high speed pneumatic vein type motors eat air like crazy. You need near 6cmf @ 90 to be anywhere near full duty depending on the grinder
Author:  ballbanjos [ Tue Sep 04, 2007 2:09 am ]
Post subject: 
I have a 7HP stationary vertical compressor with an 80 gallon tank.  I don't remember what the cfm rating is, but at 90 psi, it's about 12 cfm as I recall.  At any rate, when using a Dotco pencil grinder as a router, the compressor runs a lot.  It keeps up with the grinder, but the compressor kicks in very frequently.  I wouldn't recommend trying it with a small compressor for inlay routing where it's on a good part of the time.

I've recently replaced my Dotco grinder with a very high speed dental handpiece--somewhere around 300K RPM.  Mine is an NSK.  It has ceramic bearings, uses no oil at all, runs at 30 PSI and takes only a fraction of the CFM required by regular die grinders.  It has air exhaust coming out of the nose (with no oil in the air) that keeps the routed cavity clean.  It's also very quiet--you can easily talk above the sound of the unit, so hearing protection isn't needed.  It's a great tool, and was easy to mount in a Stew Mac router base.  The compressor still fires up occasionally, but not frequently.

The two downsides:  They're pricey.  $350 or so plus the price of a foot control and filter/regulator.  The second is that they will only accept 1/16" shaft cutters.  You have to select your cutters from standard dental catalogs.  This turns out to not be much of a negative, but the standard 1/8" carbide mills won't fit.

Dave
Author:  Bob Garrish [ Tue Sep 04, 2007 2:39 am ]
Post subject: 
[QUOTE=ColinML]

All is not lost, however. Tonight I took my first stab at inlaying a signature logo I got from Bob Garrish (Thanks Bob. They look great!), and the olde Dremel seemed to do fine.


Thanks again. Appreciate the help.


Colin

[/QUOTE]

Never even occurred to me that you were 'that' Colin. Now the ML in the username all makes sense. Glad you're happy with them, must be even more fun to inlay than they were to cut!

(For the spectators, Colin has a -very- long last name)
Author:  ColinML [ Tue Sep 04, 2007 4:38 am ]
Post subject: 

Todd:  Thanks for the clarification abobut 1/8th inch-vs-1/4 inch die grinders.  I guess this is doable after all.   Good news.


 


Bob:  Yes, it's me (Montoya-Lewis).  Honestly, I just about cried when I sat down to try to figure out how to inlay this signature.  Having never inlaid anything before, it seemed like I had bitten off more than I could chew.  But the headplate I'm using is that black fiber stuff from LMI, and it's very forgiving of indiscretions.  A handfull of fiber dust helped.  Doing a bunch of test cuts in scrap didn't hurt either.  The fiber stuff behaves oddly when routed.  It sort of pushes away from the cutter, rather than crumbling or turning to dust as wood might.  I discovered that making lots of tiny plunge cuts worked better than anything to get the majority.
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