Toolpost Needle Valve Grinder

[Brian Rupnow]

I have to create a tool to grind needle valves. I simply can not turn something as small as I need on my 10" lathe. All of these small engines I build call for a #2-56 threaded needle valve with a 30 degree included angle taper, and I have no way to make one. Necessity is the mother of invention, and although I wouldn't be so bold as to say I invented this, some of you may be interested enough to follow along. The tool in the picture is a Dremel "clone" sold by Canadian Tire in Canada. Its not a bad little grinder, but its only good for freehand work. I am going to build a mount to hold it securely in my quickchange toolpost. Its too light to do any serious work with, but I bet it will be just fine for grinding very small valve faces and needle points onto #2-56 bolts. The mounting bracket I design and build is going to be quick, and its going to be free. More tomorrow.

 

[Mike N]

I use my cordless drill to spin the needle stem against my 1" vertical belt sander. I also use this method to round off the corners of sharp pins & screws that I have cutoff.

 

[ShedBoy]

I made a similar thing to what you are making. Check the nose of that thing to see if the bit behind the chuck unscrews. The dremel has a thread under there and it is quite a simple process after that. You will find many uses for it once you do it. I wil be watching along.

Brock

 

[Brian Rupnow]

I'll start this out with a quick 3D model of the grinder I have. It is dimensionally correct, and as I have to do a small amount of layout work I will need this.

 

[Brian Rupnow]

We'll also need one of the tool holders from my quick change tool post.

 

[Brian Rupnow]

The next thing we do is take a peice of wood 1 1/2" thick---pine, spruce, or hardwood, doesn't really matter. We have to cut a hole in the center that exactly natches the profile of the die grinder. That will be the toughest part of this whole build. I got lucky---My die grinder is two half circles 1.95" in diameter seperated by a straight section 0.175" long, (as measured by my calipers) so it is an easy profile to recreate. If your tool has a more complex profile in the area to be clamped, you may have to use a glue gun and small bits of cardboard to copy te exact profile. (I can explain more about how to do that if you need it.) The block of wood will have a sawcut through one side, and be drilled through for a 3/8" clamp bolt. You can't see it, but I have put a counterbore in the far side of my wooden block so I can epoxy a 3/8" steel nut into it.

 

[johnmcc69]

Cool project Brian, do you think there may be a benefit in it to do I.D. (internal) grinding?

John

 

[Brian Rupnow]

Next up will be to make an aluminum part, which in my case turns out to be 1 1/2" x 3.45" x 3/8" thick. It is drilled and countersunk 8 places for woodscrews to go into the wooden block. From the other side, it has two counterborres holes thru on center for 1/4" shcs. It is screwed with #10 wood screws to the side of the wooden block opposite the sawcut. Keep the woodscrews just short enough that they don't breal thru into the cut out for the grinder. For a really strong connection, run the screws in, back them out and coat them with 2 part epoxy, then run them back in.

 

[Brian Rupnow]

The last piece to build will be made from mild steel. In my case it is 1/2" thick x 5/8" deep x 3" long. It has two 1/4"-20 unc holes tapped in it to line up with the c'bored holes in the piece screwed to the wood. I forgot to tell you---Its a trick!!! Bolt the steel and aluminum parts together BEFORE you screw the aluminum piece to the wood.

 

[Brian Rupnow]

Now, if you have lead a pure life like I have, and all your stars are aligned, it will fit into your tool holder like this, it will be height adjustable to be exactly on the horizontal center of your chuck (I checked on mine) and it will be adjustable to any angle. More after lunch!!!

 

[CNC-Joe]

Thanks for posting that, Brian.
- It's nice that you're posting your work so that everyone can benefit from it.

What CAD system are you using ?

Joe

 

[Brian Rupnow]

Solidworks.

 

[Brian Rupnow]

Cool project Brian, do you think there may be a benefit in it to do I.D. (internal) grinding?

John

No John---I repeat myself---This is not for any medium or heavy grinding jobs. It ONLY has any value for accurately grinding SMALL things. The motor simply doesn't have enough power to do much beyond carburetor needles and very small (as in 3/8" diameter) valve faces.----Brian

 

[Brian Rupnow]

Don't get the notion that I'm totally altruistic. I have to make these drawings so I can make the parts myself. Have fun. I'll post a pic and a review of how it worked (or didn't work) after I make it.---Brian

 

[Brian Rupnow]

I am editing my post to say that this great experiment didn't work worth poop!!! It seemed like a great idea, and my first results were promising, but there is simply too much flex and wobble in the set up to really do any worthwhile work. Sorry about the formerly positive comments. I was mistaken. Oh well, Nothing ventured, Nothing gained..---Brian

 

[Charles Lamont]

My version, for a die grinder, is at the foot of this page:

http://www.charleslamont.me.uk/iqc_toolpost4.htm

Your tool looks as though, like my Dremel, it has a threaded end with a cap/nut over it at the business end, behind the chuck.
To set this up for a grinding job, I bolted an angle plate to the cross-slide boring table, bolted a bit of 1/8" plate to that, and poked a hole in it to take the Dremel. 2nd photo
on this page:

http://www.charleslamont.me.uk/Seagull/drive_coupling.html

 

[Brian Rupnow]

Charles--Yours looks sturdier than mine. Mine is all made of plastic, even the screw on nose cone and threads. Now that I've had a chance to use mine a bit more, I'm not nearly as impressed with the results. I wouldn't really recomend anyone build this. It doesn't cost anything but your time, but sadly the results aren't as good as I had first thought.---Brian

 

[jixxerbill]

I have thought many times about trying to make a grinder like that Brian. But mounting it always seems to be what changes my mind.. I saw this last time i was at HF, I started to buy it but didnt.. I think it could be mounted alot easier, but requires air instead of electricity..Bill
http://www.harborfreight.com/1-8-eighth-inch-air-micro-die-grinder-47869.html

 

[petertha]

Brian, did you see this post?
http://modelenginenews.org/techniques/needles.html

I noticed you used a cylindrical grinder. Is it making continous contact on the taper & maybe why its bending back teh stock from pressure? Maybe it would be better to use a disk style grinder, lighter grit & finer feed. A disk would run along the taper & only cutting a smaller portion at a time so less bending force? Kind of like sharp lathe bit contact vs big flat cutting surface principle?

FWIW, my experience with grinding stones typically packaged in offshore moto-tool kits must be made from bits of sidewalk cement. They cut crappy, heat the material & seem to clog easy. I bought some good quality rotary stones from a jewely supply place & they were like night & day difference (on hardened pin shafts). Dont recall what they were but they come in an assortment of colors like grinding wheels. They didnt cost that much & offered dozens of styles to choose from.

Is there any way to support the end of the wire in a makeshift tailstock to stop flex? Even a block with a hole in it? Maybe you could grind the majority of taper in a mid section & then lop off the end so it stays supported as long as possible?

 

[Charles Lamont]

Yours looks sturdier than mine. Mine is all made of plastic, even the screw on nose cone and threads.

The Dremel is the same, and I was a bit concerned, but it turns out to be strong enough to make a perfectly adequate mounting.