Making Simple QC Tool Holders

[vtsteam]

I could swear someone asked me about making a tangential tool holder earlier in the thread, but I just can't find it....

Anyway, thought I'd try it.



The slot is angled 12 degrees in two directions. One side of the toolholder is beveled 12 degrees. The tool is ground at 30 degrees diagonally. I don't think I want to grind another one of those from a blank for awhile! It must have taken a half hour with constant dunking in water. And the tool is short., too. Has to be to clear the bottom of the toolholder, which must sit all the way down the post because of the tool height.

I haven't finished it yet -- need a button head screw to lock the tool into the holder.

[awemawson]

"awemawson, I agree. I'm not proud of the finish. Hoping Rob will at some point reveal all in a tutorial. I don't own a surface grinder, or a belt sander, and don't have a buffing wheel set up. My tool grinder needs both abrasive wheels. But I will work on these holders further by hand to get them more presentable when the whole set is done."

Hey no criticism of the finish - it's fine and certainly fit for purpose. Probably nitriding would be better anyway than nickel to give a harder surface.

[andyf]

Very neat, all of them 

If I've counted right, there's only one out of the original seven left. News of its fate is eagerly awaited.

Andy

[SwarfnStuff]

Great thread well written and love the Pics. Only comment about your Tangential holder would be that next time (If you make another) would be to not use a square blank but start with enough length to alow the tool to overhang the cross slide.  Another brain spasm, It matters not (I think) whether you overhang to the side - keeps max diameter, or the front - smaller max diameter. Great work any way I look at it. Thanks for posting,

JB

[black85vette]

I could swear someone asked me about making a tangential tool holder earlier in the thread, but I just can't find it....

Anyway, thought I'd try it.

That was me.   

The tool looks to have a little too much rake.   With the 12 degree angle of the holder I have mine set to just a few degrees, like 15.   Try a couple of settings.    In a holder without the additional side angle it can be hard to use for facing cuts.

Looks great and gives you some additional flexibility.

[vtsteam]

Funny you should say that b85V, I thought the rake seemed pretty extreme, too. But I've never owned a tangential tool holder before. I spent the day playing with it, and I'll get photos on later tonight.

It does facing cuts because it has a 12 degree angle both ways.

The source for my version geometry was here:

http://www.gadgetbuilder.com/ToolHolders.html#Tangent

But I'm beginning to think there was a mistake in the design of the sharpening jig. I believe it is giving a rake of 30 degrees from vertical instead of horizontal -- and I'm guessing that 30 deg from H was meant.

Suppertime -- back with more later.....

[vtsteam]

Okay, first photo, trying out a cut on some rusty hot rolled steel -- not particularly good stuff, hard to get good finish generally, but this tool bit is doing a pretty good job.

[vtsteam]

Here's what the finish looks like close up.

[vtsteam]

I found it would remove up to about 30 thou deep in one cut turning. Anything more broke the point of the tool. Which is a real pain because you have to grind a lot of material at this acute angle to get back to a point. Plus the tip tends to burn really easily. I now think it was too acute, in agreement with black85vette.

Facing provided a similar finish and limitation of depth of cut. It definitely wasn't a suitable tool for hogging metal off. The tool tended to jump under the cut if I tried to cut too deep as it approached the center. That would also break the itp.

[vtsteam]

Oh, thanks awemawson, I'll have to read up on nitriding. Is that just a commercial process, or is that something that we can do in our shops?

Thanks AndyF, I hope I can work on the last one tomorrow. 

SwarfNStuff thanks greatly! 

Here's a picture of the jig I used to sharpen the tool bit. It was taken from the site referenced earlier, and the pdf drawing it referenced though I didn't pay attention to the actual dimensions other than the 30 degree angle from horizontal.

[vtsteam]

Just now looking at the jig plan I thought I noticed a mistake. But I'm starting to think the mistake is mine.

I put a lip on the bottom of the jig assuming the tool would be sharpened pointing upwards. The lip is supposed to ride against the back of the grinder's tool rest.

But now I see in the drawing that the lip is at the other end of the jig. I thought that couldn't be right because the lip would hit the wheel between the gap with the tool holder.

But now I'm thinking maybe they meant for us to grind the tool facing downward in relation to the wheel, so they have the lip on the right side.

This might account for my too acute angle on the lathe tool ....

Here's the relevant part of the dwg.

[vtsteam]

If the tool is to be ground laying downward in relation to the wheel, it would naturally have a more obtuse angle because of the arc of the wheel. It would also make sense that the wheel diameter wouldn't affect the angle -- I was wondering about that. too.

Finally, a more obtuse angle would strengthen the point, reducing the tendency to break in deep cuts. It would also mean the point didn't burn as easily when sharpening,. And it would be quicker to profile to shape originally. The jig would be easier to use -- pushing down is easier than trying to keep a short bit pushing upwards against the wheel, etc.

So, I'm pretty sure that's what was intended.

As Bugs Bunny used to say, what a maroon!

Nevermind.....

[vtsteam]

Last photo tonight, showing how the compound 12 deg angle is achieved. The side face of the tool holder is beveled 12 deg, and then the tool channel is let into that at 12 degrees.

The button head screw tends to roll the tool upward slightly when tightened. I'm going to add a thin washer to prevent that. I noticed one in a photo at the website previously mentioned.

The tool bit was a broken piece I happened to have. Guess I'll be making a new one tomorrow and a new sharpening jig....

[black85vette]

You can also slightly round the edge making the point so that it is not as sharp.

Here is the one I made to mount directly on the Atlas/Craftsman 12";



IMG_5874 by black85vette, on Flickr

And one I made for the 4 way tool post that will hold round stock to make an elliptical cutter:


IMG_5875 by black85vette, on Flickr

[SwarfnStuff]

Hi Vsteam,
Your tool pictured looks way too steep. So I went to me shed thinking I could easily find the paperwork that came with my tangential tool from Eccentricengineering.com.au here in OZ. I know the angle is stated in said paper work. Alas I must have put it away carefully (never to be seen again) . I seem to recall a mention of 28 deg and when this is inserted in the holder with 12 deg it would come back to 16 deg. You will also grind less of your tool steel off although grinding a new piece still is a fair grinding job even with the 8mm stuff I use on my 7x lathe.
Cheers,
Swarfnstuff

[vtsteam]

Thanks black85vette, nice tool holders. I like the way that round one is trapped by the slide. I'm guessing there is a screw in back that pulls it in. The square one looks nice and solid and simple as well. I think I remember admiring those on CSEE. I did try radiussing the corner a little -- helped with finish, and burning the tip and well, made it easier to grind back a chip!

SwarfnStuff, thanks greatly for the actual commercial angles. To check the 12 + 12 deg compound in 3D I did a little drawing in Sketchup and the actual resulting compound angle is 16.7 degrees normal to the tool.

this gets subtracted from the grind angle to get the actual top rake. 28- 16.7 = 11.3 -- well wht do you know, the tool is practically 12, 12, 12 all around.

Making a new sharpening jig today.

[vtsteam]

I ended up making a new tool rest for my bench grinder. I had been using the stamped metal bracket that came with it. I didn't make a super fancy replacement capable of sharpening end mills, etc. -- that's a project for another day.

I just put together materials on hand, namely some angle iron sections of a bed frame, a spare strap hinge, and some steel cutoffs, spot welded together. But it's a hundred times better than the grinding rest that came with the machine!

Then I was able to make a new tool bit for the tangential tool holder, and I got a true 28 degrees, measured, for the cutting face.

I honed it on a little diamond hone and tried it out on the same chewey steel test bar I had earlier. It gave the smoothest finish I've been able to achieve so far --  a personal best. Probably not as good as others can achieve, but It feels shiny smooth, which is a big improvement for me. I do see some slight regular variation in surface appearance, but I'm thinking that is probably due to lathe vibration and lead screw. I need to make a more solid base for the lathe than I have right now. The whole table top shakes.

Very happy with this  tool post! I might reserve it for finish use, though. I'm not sure it's suitable for taking heavy cuts.

Here's a current picture:

[black85vette]

The tool looks correct at that angle and the results confirm it.   Depending on the metal and how secure the tool is held, I have found that I could take pretty deep cuts with mine.   Your entire setup is great and would be excellent for someone starting out.

It would be cool if the tool holders were mass produced so someone could just make the post to fit their lathe and buy holders cheap if they didn't have a mill.

[awemawson]

There was a chap in Australia selling them complete with a sharpening jig a few years back (maybe 7)

If I remember correctly they featured in an article in Model Engineer

[RussellT]

Good job VT.

B85V.  These tool holders can be made without a mill.  There is also a similar commercial design - http://www.krfcompany.com/ but I don't think it includes a tangential tool holder.  It is indexable though.

Russell

[black85vette]

http://www.krfcompany.com/[/url] but I don't think it includes a tangential tool holder.

They are pretty expensive.   Looks like $38 to $43 per tool holder.   I can get holders for my BXA type QCTP for $9 each.

Looks like shop made is the way to go.

[vtsteam]

Thanks B85V and RussellT! 

Started roughing out the last toolholder. I milled slots in the block and brazed in some upright pieces. Soaked the arm stock in dilute muriatic acid to get the mill scale off before working them further. But they fit in place nicely.

I'm sure you can guess what this one will be!

[SwarfnStuff]

Hi Vtsteam;
As for the depth of cut have a look here, http://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=22&Itemid=42 Hopefully this will take you to his demo of the 8mm tool for mini lathes. He states that the lathe used is as it came out of the box. Prices are not cheap but his stuff is good. I am way pleased with the Crobalt tool blanks.

I Agree with Black85vete that the tool grind after your new jig now look much better.
Awemawson: The company in Australia is eccentric engineering.  As in the link above.
Regards.
Swarfnstuff

[awemawson]

That's that's the chapie ! So my grey cells haven't all died yet 

[vtsteam]

Hi SwarfnStuff thanks again for all your info. My concern re. depth of cut has more to do with the holding screw on this one. It seems to slip, and that was mentioned also re. interrupted cuts in the article I linked earlier, whose design geometry i adopted. I added a washer, and we'll see how well it does.

Thanks for replying, all!