Adventures in Ogives

[customcutter]

I got the bright idea back when Cane Man and I were both trying to make reamers that I needed to make a radius cutter (aka ball cutter). I'm still trying to cut ogives and he's finished his point forming die. Go figure, but here's to you Cane Man.

I couldn't make any of my 3 different tool post holders work to cut an ogive so I decided to make a radius cutter. There were several issues, but one of the main ones was that the pivot point for the compound was short of the center line between the chuck and tail stock. So I made a new base and moved the pivot point closer to the rear of the lathe. Unfortunately, I forgot to figure the extra offset for the ogive. But no problem, I finally figured out I could run the spindle in reverse and put the radius cutter on the back side.

Here are some pics of the radius cutter. It didn't work well, so I decided to try a radius grinder.

Edit: Should have taken more pics but that 4" disc started as a 4X8X.75" block of aluminum. My first attempt at cutting a circle from a square. I cut 8 sides with the band saw and chucked it up in the 4 jaw and had a lot of "interupted" cuts. Also had to bore a 1" hole in the bottom plate and set that up in the 4 jaw but only had 3 jaws holding it, so I clamped it down tight and turned it at 70RPM.

[customcutter]

There was too much deflection with the radius cutter, so I decided I would try to modify it to make a radius grinder. I spent all morning machining a holder for a small pencil grinder I had bought with intentions of using it to lap the point forming die once I got it reamed. Still working on that reamer though. I tried mounting the grinder as low as possible to stiffen everything, but it created a problem with the center part of the diamond wheel not having any diamonds to grind with and also the center bolt to hold the wheel to the shaft was a problem, so I had to mill a slot and raise the holder about 1/2-3/4". I also milled a shallow slot in the grinder holder so that it could be attached to the fixture with a single screw and be a solid fit.

You can see there is one picture where I was trying to see if I could grind an ogive and ran out of room. It was really a set back for me because I thought that the fixture still wouldn't work. I thought there was something wrong with my dimensions, off set, design, or something. I spent an hour or so trying to figure it out and finally decided to simply raise the grinder to where I could cut with the lower part of the diamond wheel and it worked.

[customcutter]

Here are some pics of 2 different laps that I made using the radius cutter with a carbide insert. Then there are a couple of pics of the 2 points that I made using the grinder. The point that looks the closest to the factory 55 grain ogive is 6X the radius, the longer point is 6X the diameter. The same is true of the shorter points the smaller one is 6X the radius, the longer one with the ugly tip that has a booger on it is 6X the diameter.

These aren't going to be used for lapping but simply to confirm the procedure. I'll need to find a way of using a cut off wheel or maybe making a disc that I can attach 120 grit, 220grit, and 400grit silicon carbide too to polish the final laps and reamers with.

Here's the pics of the points.

[plus1hdcp]

I find these "how to" threads incredibly interesting. I am both glad and sad that I am not in position to try this in my shop. Maybe someday. But thanks for sharing and keep up the great work.

[Cane_man]

cc, looks like you are making good progress, that radial attachment looks great now chuck some O1 and see if you can grind an ogive on that... you will have to polish it smooth for your reamers, but you can leave it rough like that for the laps as it helps them to hold polishing compound and they get smoothed out anyway while lapping...

[teddyblu]

When you get the shank to size and start the radius, I have used superglue to glue a serria 52 hp to end and held in place with carriage till glue is thourghly set, Then you can adj the grinder to follow the ojive. When you have it like you want then just hand pull off the bullet.

I use a wider wheel and prob 120 + grit and grind with surface of wheel. I lock the grinder in place and use it to grind the shank to size like a tool post grinder.

You are getting it done looking good.
Larry

[customcutter]

Plus,
Just wondering why you aren't able to attempt them in your shop? Thanks for the encouragement, it helps keep us "rednecks" motivated.

Cane,

I saw those shallow groves in the point that I ground and was wondering if it would help hold the lapping paste also. I think that diamond wheel was either 60 or 80 grit, a little to rough possibly. Once I start making progress again I've got to get some ordered. What grits did you use?

[customcutter]

Larry,
I had the pencil grinder and modified my radius cutter. It is on the weak side to say the least. I've also got a slight issue with the hole that I bored in the rectangular base. The hole is slightly tapered, the only thing I can figure is the compound wasn't square to the hole. I should have set the compound and fed with the carraige instead of the compound. I may try reboring it and inserting a bushing or maybe a bearing. It works for now I just have to keep downward pressure over the pivot point while turning the points.

I looked at several rotary tools last night at HF trying to figure out another way mount something with a small grinding wheel like you used. Finally decided to just go with what I had for now. Maybe I'll look at something else if I decide to do this long term.

[Cane_man]

the first grit i use for lapping is the "course" valve grinding compound you can buy at the auto parts store just to get all the rough cuttings off...

then use 600 grit diamond paste, until you get to within 0.002 of your final ID, then heat treat...

that final 0.002 use 2000 grit to size and 8000 to polish...

it helps a lot to make a 0.223 test inserts to see how close you are getting, just get a brass rod and turn one to 0.221 and another to 0.2230 for testing... when the 0.221 can slip into the die the ID will be close to 0.222 and you can heat treat, when when the 0.223 inserts slips in you will be close to 0.224

here is the lady i get my diamond polishing compound from:

http://www.ebay.com/itm/5-gram-Diamo...item35b65207b3

when you make your reamers, they will ream about 0.004 too much, also you want to leave about 0.004 for lapping, so make your reamers have a shank OD of 0.224 - 0.004 - 0.004 = 0.216 and it will put you where you need to be starting at about 0.220 and give you plenty of room for lapping and polishing...

i used three sizes of laps, 0.210, 02.15, and 0.220 as you have to leave some room for the lapping compound


dude, i am getting pumped, you are taking serious steps to make this happen... wont be long now

[customcutter]

Cane,

Thanks, you really got me motivated with that last die and bullets. Those look better than any I've every bought. I only get to put in a few hours during the week and about half a day on Saturday. That's all my back can handle. Don't know why but just standing in one spot really strains it. I've had 3 herniated discs for almost 30 years now. Bouncing on the mower doesn't help any and I was thinking of getting into machining, beings I have a few pieces of equipment. However, this is showing me that maybe that isn't the way out. Maybe I'll finish them before the fall. But then I'll have to start on some dies for .40, .45, and 9mm. Maybe 6.5mm, 7mm, and .30 also.

Thanks for the tips, I know they will help lower the learning curve. I couldn't get both brain cells to fire at the same time this AM, and it had me stumped for a little while.

CC

Edit: Did that modified tree burr do anything or was it a waste of time?

[Cane_man]

cc, the modified tree burr worked really well for rough hogging the die... i sort of abandoned the idea when i decided to do the rough hogging out with the d-reamer and finish ream with the 2-flute reamer... i ended up grinding down the burr until the max OD was about 0.210 or so, but one problem is that is leaves a really rough finish... it is worth looking into

[aaronraad]

What is a tool post grinder worth?

[customcutter]

It would depend on the make, model, manufacturer, condition, etc.

[customcutter]

Got back into the shop for a couple of hours and decided to try and make a couple of points to make D reamers with. I sat up the .250" W-1 exactly like I did the .250 brass. I cut about 1.5" down to .218-.219 and proceeded to install the radius cutter. The abrasive wheel is offset 6 X the radius of the pivot point, then I advanced the crossfeed on the abrasive wheel till it just barely made contact with the .219 rod. I moved the carriage feed toward the chuck until the abrasive wheel made contact at about a 45* angle to the rod. I started grinding the ogive, swinging around the pivot point and advancing the carriage slightly till I got a very small meplat. It didn't look right (looks like a 3-4 ogive)so I decided to reverse the rod and make another on the other end, but trying for .220" this time.

Same set up as before except that I hit .220" instead of .218" after filing. Set up exactly the same on the radius cutter, and this one looks fatter than the first one. Maybe a 3 ogive.

I would say this is because I need to have 6 X the diameter instead of 6 X the radius. But the 6 X radius in the brass rod at .250" looks perfect. Is the .030" affecting the ogive that much? EDIT, brass rod was set up at 6 X .112"

I guess tomorrow, I'll chuck them both back up and turn them at 6 X the diameter. Sorry no pics for now, got to get ready to take the wife and her best friend out for supper.

CC

[Cane_man]

imo, i think you need to aim for 0.216 as these reamers tend to cut oversize by about 0.004 or 0.005, this way you will have plenty of ID for rough sizing, then heat treating and any warping that may occur, and then to final lapping... make your die ID test probes as you dont want to get this far and then oversize your die, ask me how i know

did you get your diamond lapping compound yet? $22 gets you the three grit sizes you need and you are good to go

[customcutter]

Haven't ordered the lapping compound yet, But maybe later tonight. I thought some of the other threads had said to try for around .220, but I'll go with .216. You can always take more off, but it's hard to put some back on.

The only other thing I noticed was the diamond wheel has a slight grove worn in it where the diamonds are being removed. I may try moving the wheel up or down to a "fresh" spot with lots of diamonds. I still may try and make a disc that I can mount silicon carbide sand paper on.

[teddyblu]

Customcutter I mentioned glueing a 52 hp to the end of your sized shank, then see if your ojive setup will trace the outline, adjust or change until it will.

[customcutter]

Teddyblu,
I had to pull a 55 gr bullet from a loaded round to have one to compare to the brass ogives that I cut. As stated the 6X radius was almost a perfect match. I used the same set up for the W-1, and it looks like it's cutting a 3X ogive.

Thanks for the tip, I may have to try that.

[customcutter]

OK, I adjusted the pencil grinder up about 1/16", also found that the pivot rod had backed out about 1/2 turn due to vibration from the pencil grinder. Left it at 6X radius, and tried regrinding both points. They look much better. I think the pivot point backing out had elevated the upper part off of the base and exaggerated the "rocking" possibly, causing it to grind something other than 6 ogive.

Back to the garage to see if I can grind them in half + .001-.002 , heat treat, temper, and make a couple of D-reamers now.

[customcutter]

NO JOY

Got 3 points made, ground them in half +.001" (ie, .216" point ground to .109"). Heated them to orange for +/- 30 seconds, dropped them into a 5 gal bucket of water (W-1). Stuck them into the oven for 1 hour on 350*. Polished all the scale off and sharpened them up on a hard Arkansas stone. Placed the smallest one in the drill chuck in the tail stock on the lathe and put the step drilled die into the 3jaw chuck and started it up at 70rpm. Filled the die with cutting fluid and started feeding the reamer in. I attempted to ream the hole for probably 15 minutes and all I was getting was very light scrappings near the tip of the reamer. Kept pulling the reamer out inspecting for shavings, blow out the hole, and reapply cutting fluid. Applied just a little more pressure with the tail stock and snapped the D-reamer. 70rpm and feed rate incredibly slow (IMHO immeasureable). I grabbed a Nicholson file and easily cut the die, tried it on the reamer, and probably could have cut it, but wasn't going to be easy. I'm just thinking I should start over with another die material instead of the 4140PH? It cuts easy on the lathe, drills easy with some cheap chinese drills I have (109pc set, I won years ago at a vendors party).

This die is killing me.