Best Yet Knurling Tool

[Wawoodman]

(11-10-2012, 04:45 PM)TomG Wrote: Mike,

If the parts were soft, I'd use a .249 reamer, but since they are hard I would go with a .2495. If they are still too tight after hardening, you may need to lap them out a bit.

Tom

Then I'm missing something. I thought the pieces would be slotted, bored, and reamed before hardening. Then you would assemble them with the knurl and pin. No?

[DaveH]

I think for the home shop mild steel would suffice however the knurl pins need to be hard.

DaveH

[TomG]

(11-10-2012, 05:11 PM)Wawoodman Wrote:

(11-10-2012, 04:45 PM)TomG Wrote: Mike,

If the parts were soft, I'd use a .249 reamer, but since they are hard I would go with a .2495. If they are still too tight after hardening, you may need to lap them out a bit.

Tom

Then I'm missing something. I thought the pieces would be slotted, bored, and reamed before hardening. Then you would assemble them with the knurl and pin. No?

Mike: You would have a tough time pressing a hardened .250 dowel pin into a hardened .249" hole. It would almost certainly crack the part.

Dave: The locking screws would make a mess out of soft knurl holders, not a good thing if they are running in an aluminum slot. Also, the knurls would eat them up fairly quickly with the side loads generated by feeding the tool.

Tom

[dalee]

(11-10-2012, 05:14 PM)DaveH Wrote: I think for the home shop mild steel would suffice however the knurl pins need to be hard.

DaveH

Hi,

I would tend to agree, mild steel would probably be fine for home use. 4140 pre-hard @ 35Rc to 40Rc would also save the hassle of heat treatment and still be machinable for the home shop.

Thanks for the stock sizes Tom. That will make things so much easier. I guess it will be another trip to the big evil city to go to the steel store.

dalee

[EdK]

(11-10-2012, 10:06 PM)dalee Wrote: I guess it will be another trip to the big evil city to go to the steel store.

dalee

Where are you getting your steel from? Midway Steel in St. Cloud has much better prices than anything in the Twin Cities so if it's convenient you might want to check them out.

Ed

[PixMan]

The Hardinge, Accu-Trak, and Form Rol Die brand straddle and bump knurling tools that I've used in job shops over the years have all been unhardened bodies with HSS or carbide pins. I can't say for certain what materials they use for all the parts, but it seems like pre heat treated (28-32Rc) 4140 and.or 8620. Those are the two most common materials used in making toolholders.

I know the solid carbide pins really last longer than HSS in thos applications, and none of them are press fit. They slide in easily so that if you are using HSS pins and the pin gets buggered up from a smash, you still have a chance of getting it out. I've seen their solid carbide pins survive multiple crashes.

[TomG]

I'm sure SPI had their reasons for hardening the holders in this design. If they are left soft then a shallow groove for the locking screws to bear on would be in order, so when they get chewed up they don't mess up the aluminum slots.

Tom

[dalee]

(11-10-2012, 11:42 PM)EdK Wrote:

(11-10-2012, 10:06 PM)dalee Wrote: I guess it will be another trip to the big evil city to go to the steel store.

dalee

Where are you getting your steel from? Midway Steel in St. Cloud has much better prices than anything in the Twin Cities so if it's convenient you might want to check them out.

Ed

Hi,

St.Cloud is the big evil city to this old country boy. And at 70 miles one way, a "fur piece to go" for just small random purchases. Lazy old sot that I am.

I was just up there and bought some aluminum 2" round from them. I wish their stock wasn't quite so limited sometimes, (no brass or bronze stock), and only a tiny bit of stainless. But I do buy a lot of material from them. Very nice to deal with and open on Saturday mornings.

I don't have their stock racks memorized yet, but I think they should have the aluminum stock on hand for this project. But it will be a week or so before I can get back up there.

dalee

[EdK]

(11-11-2012, 11:03 AM)dalee Wrote: Hi,

St.Cloud is the big evil city to this old country boy. And at 70 miles one way, a "fur piece to go" for just small random purchases. Lazy old sot that I am.

I was just up there and bought some aluminum 2" round from them. I wish their stock wasn't quite so limited sometimes, (no brass or bronze stock), and only a tiny bit of stainless. But I do buy a lot of material from them. Very nice to deal with and open on Saturday mornings.

I don't have their stock racks memorized yet, but I think they should have the aluminum stock on hand for this project. But it will be a week or so before I can get back up there.

dalee

I didn't realize they didn't have brass or bronze in stock. That seems rather strange, especially the brass. I've bought a bunch of tubing and round and square solid stock from them. I was buying the same stuff from Discount Steel in Minneapolis but when I moved out to the small town where I live now I tried Midway Steel and found their prices to be about half of what I was paying at Discount Steel.

Ed

[dalee]

Hi,

Well not all is totally lost for brass and bronze pieces. The recycling place across the street often has random drops they pull out. But it's quite catch as catch can.

When I picked up the aluminum round I stopped to see if they had any small diameter, (under an inch), brass rounds. Alas none of that stuff, but they had a goodly sized pile of brass flats that were 5/8"x5"x3' or so. Not having a need for such material, I didn't ask price. But I did find a small piece of 1 1/2"x2" rectangle I bought and a 6" piece of 3/4" copper round that I have no idea why I bought.

dalee