Tool Post Grinder -Making a new one...

[dave2176]

Ray,
I'm really enjoying this thread. All the great guys on the forum have got me adding to my to do list like crazy. Thanks for taking the time to share.

Dave

 

[Ray C]

Thank you, Dave. It's nice to hear -and I'm glad you're enjoying it.

It also goes to show that you don't need ultra fancy equipment to turn-out decent parts. This is all done with modern production machines that didn't break the bank. The lathe is a Precision Matthews 1236 that's a couple years old now and the mill is a PM-45 ...which is about 5 years old and I haven't had the need to tram it yet. I use the machines a LOT but, the fundamentals are always cared for -and there's no sign of wear whatsoever...

One of these days, I'd like to show folks how to "sneak up" on a precision lathe cut. I've taken my time on these parts (because I've got a long stretch of time off work) and all the dimensions within 2 tenths of where I wanted them -and all are within the tolerances I established. It can be done and anyone can do it... but, you need to track previous cuts and watch the dials very, very closely. Also need to watch temperatures and corresponding expansion coefficients.

The main shaft for this item is fairly complex and has 4 zones and 3 diameters and all but one are critical. I'll make a point to show how to nail a diameter. Heads up, it will be a long post... hopefully I'll get to it tomorrow.

Ray

Ray,
I'm really enjoying this thread. All the great guys on the forum have got me adding to my to do list like crazy. Thanks for taking the time to share.

Dave

 

[Bill Gruby]

Which of these are you actually using Ray?

http://hubbardspring.com/subcategory.php/category/48/Spring Washers

"Billy G"

 

[Ray C]

Looks like we'll get to the shaft early today. The boss doesn't have anything planned for me today.

I'd swear I had some previously hardened shafts around but, no dice. Right now, the shaft is in the oven. It's 1045 material about 15/16" diameter that we'll heat treat to RC42. According to the book, at this hardness level and diameter being under 1.25", it will harden all the way through uniformly if a water/brine quench is used (not so for oil quench). RC42 is chosen because it's still easily cut with carbide. Once you get beyond 45, I use ceramic inserts.

The shaft needs some hardness mainly because of the small section that rides in the radial roller bearing. Soft metal would deform in fairly short order. Also, hard metal cuts with a smoother finish (at the expense of requiring more cutting pressure).

Here's what it looks like -and unfortunately, the piece is a little more complicated that I'd prefer. The extra diameters are driven by the bearing I happen to have on hand. BTW, I'm treating two pieces of stock. This piece has several critical dimensions. So far, I've have good fortune and haven't blown any pieces yet -but now isn't the time to get cocky. This is going to give me a run for my money because it's thin, will require slightly higher cutting pressures -and I'm shooting for -0.0000, +0.0002" tolerances (translated: it's diameter cannot be under spec and is allowed to go over by 2 tenths). If I get in a pinch, I will resort to using grinding compound to get the critical parts in spec.




OK, see you in a couple hours when the stock is done cooking.

Ray

 

[Ray C]

Hi Bill... G'morning....


I settled on these. Same ones you found...

http://www.amazon.com/gp/product/B0085ZO75G/ref=oh_details_o00_s01_i00?ie=UTF8&psc=1


BTW: We're delayed a bit this morning... Went to check the oven and it was going the wrong way (cooling down). The heating element wire came loose. -Lot's of expansion/contraction and a screw loosened up. We're back and running now.



Ray

Which of these are you actually using Ray?

http://hubbardspring.com/subcategory.php/category/48/Spring Washers

"Billy G"

 

[Senna]

Looks like we'll get to the shaft early today. The boss doesn't have anything planned for me today.

I'd swear I had some previously hardened shafts around but, no dice. Right now, the shaft is in the oven. It's 1045 material about 15/16" diameter that we'll heat treat to RC42. According to the book, at this hardness level and diameter being under 1.25", it will harden all the way through uniformly if a water/brine quench is used (not so for oil quench). RC42 is chosen because it's still easily cut with carbide. Once you get beyond 45, I use ceramic inserts.

The shaft needs some hardness mainly because of the small section that rides in the radial roller bearing. Soft metal would deform in fairly short order. Also, hard metal cuts with a smoother finish (at the expense of requiring more cutting pressure).

Here's what it looks like -and unfortunately, the piece is a little more complicated that I'd prefer. The extra diameters are driven by the bearing I happen to have on hand. BTW, I'm treating two pieces of stock. This piece has several critical dimensions. So far, I've have good fortune and haven't blown any pieces yet -but now isn't the time to get cocky. This is going to give me a run for my money because it's thin, will require slightly higher cutting pressures -and I'm shooting for -0.0000, +0.0002" tolerances (translated: it's diameter cannot be under spec and is allowed to go over by 2 tenths). If I get in a pinch, I will resort to using grinding compound to get the critical parts in spec.


View attachment 66675

OK, see you in a couple hours when the stock is done cooking.

Ray

That part would be an ideal candidate for a good cylindrical grinder. Turn everything .001-.002" large and then spin it between centers on the cylindrical.
It could also then be turned in the soft state, heat treated to the ideal hardness without regard to cutting suitability, and ground for size and finish.
I'm sure a machinist of your caliber will do fantastically, perfectly well on your lathe but a cylindrical grinder is a pretty neat tool to have.
You should be on the lookout for a good B&S 13 or Cincinnati #2 in the future.
Super versatile machines and I believe you'd use the snot out of one if you had it.

 

[Ray C]

You're absolutely right! I'm doing a compromise for a few reasons though. Ideally, I'd turn it slightly oversize with some normalized soft metal then take it down with the TPG or better yet, a cylindrical grinder. Being the kinda guy I am, I used the old TPG for parts as, it was way too big and heavy. Also, even if I had a cylindrical grinder A) I'm completely out of room in the shop and B) I'd have to teach myself how to use it first .

Also, I'd prefer this piece to be about RC 50 but low 40's will have to do. I've already thought of re-making the part the right way once I get this TPG in a functional state then, swap-out the original one. We'll see how this goes...

Ray

BTW: Hmmm, "machinist"... -not so sure about that title yet...

That part would be an ideal candidate for a good cylindrical grinder. Turn everything .001-.002" large and then spin it between centers on the cylindrical.
It could also then be turned in the soft state, heat treated to the ideal hardness without regard to cutting suitability, and ground for size and finish.
I'm sure a machinist of your caliber will do fantastically, perfectly well on your lathe but a cylindrical grinder is a pretty neat tool to have.
You should be on the lookout for a good B&S 13 or Cincinnati #2 in the future.
Super versatile machines and I believe you'd use the snot out of one if you had it.

 

[Senna]

You're absolutely right! I'm doing a compromise for a few reasons though. Ideally, I'd turn it slightly oversize with some normalized soft metal then take it down with the TPG or better yet, a cylindrical grinder. Being the kinda guy I am, I used the old TPG for parts as, it was way too big and heavy. Also, even if I had a cylindrical grinder A) I'm completely out of room in the shop and B) I'd have to teach myself how to use it first .

Also, I'd prefer this piece to be about RC 50 but low 40's will have to do. I've already thought of re-making the part the right way once I get this TPG in a functional state then, swap-out the original one. We'll see how this goes...

Ray

BTW: Hmmm, "machinist"... -not so sure about that title yet...

I'm completely convinced that title fits you. In fact, having seen some of your work, Master could precede that title.

 

[Ray C]

Here are the shafts still in the quench bath. I wasn't worried about decarburizing so, they sat in the oven naked. The scraps on the bottom prevent the hot pieces from melting thru the aluminum pan. It started-out with 3 gallons of cool brine water and the parts went in at 1550F (soaked for 40 minutes) and cooled off in about 20 seconds. The water temp is now 170F. I'll let the parts sit in the warm water about 30 mins until the oven cools to the desired tempering temperature of 700F. With a 1 hour tempering, followed by an open air cool-down, the parts should be about RC 42.

In their current hardened state, these parts should be approximately RC 55 -which is about as hard as 1045 can get. Metal in the post-hardened condition is highly unstable, subject to easy fracture and is considered dangerous to machine. If I threw them on the ground, they'd probably fracture. Right now, they are basically "metal glass" and if tapped together, ring like a bell. The tempering process is critical...



Ray

PS: As predicted, the shop is nice and warm now . Nothing better than heat treating on a cold day.

 

[mattthemuppet2]

I'm completely convinced that title fits you. In fact, having seen some of your work, Master could precede that title.

I agree, although I think Craftsman is more suitable than Machinist. It's always a pleasure to watch and learn from Ray's project threads, even if I'm not always sure what's going on