Proper cutting tool form

Here is another option that has worked for me when cutting internal threads to a shoulder. Make your relief cut say .060 or whatever
width you're comfortable with and set a dial indicator at 0 just where the threading tool enters the relief cut. That way you know exactly
where the bit is in relation to the relief cut and have time to disengage the half nuts. You can then back off the carriage and withdraw the
tool. Hope this makes sense and will help.
 
I have cut the same thread without powering up the lathe. It is easy enough to turn the spindle by hand, using a T-handle inserted into the outboard end of the spindle tube. As you say, it's not a very long thread.
 
Steve,

The set I have is from grizzly http://www.grizzly.com/products/T10069. It does fairly well so far, and I've not needed any sizes not included, yet. SYIC is printed on the collets and holder, and a search turns up asian manufacturers mostly.

My second attempt earlier today ended in another failure, I had mistakenly used a smaller minor diameter and ended up making the inside threads too snug, though they're perfect in every other respect lol. I was at 1.345 when I should have been around 1.375. Not sure if I can salvage it yet.

After seeing your Hex collet holder, I am wishing I had a piece of it to make mine out of. Looks sharp, and would be easier to wrench off the spindle.

mtnlvr,

I have a shoulder cut in for the spindle thread, and I set my depth to cut to match it, and using the graduation marks on my boring bar make a plunge outward just past the area to be threaded. The tool cuts just over 1/16" and I make about a 1/8" relief. When cutting the thread, I line up the graduation mark with the end of the work, and as it passes I can hear the difference in the machine when it passes the threaded area. At that point I pop the half nuts, shift the cross slide in, and move back out of the work, and reset for the next pass.

I have only one DI mounted on a mag base, and with the way I've got my steady rest set up, doesn't lend itself well to checking either depth of cut or travel. I would love to do either, but I've not found a suitable way of mounting it yet to accomplish either.
 
Terry,

Don't give up!! :))

mntlvr brings up something that I just assumed you were doing. You need to make a holder for your DI that clamps to the front way of your lathe. They are easy to make out of a chunk of aluminum. I don't think I've posted a pic of mine but I'm sure I've seen others posted - so do a search. I made the hole in mine to fit the barrel of the DI and cut a short piece of drill rod so I can either use the DI for measuring carriage travel or use the drill rod as a hard stop. This is a must have in my opinion.

Those collets look interesting. Similar to ER's but with a much shallower taper. Do you know the taper angle?

Hang in there.

Steve
 
Steve,

Good ideas, and I'll do a search for the DI supports you mentioned. The taper angle on the collet appears to be 2º. I used the 3/4" collet with a 3/4"round fed through the spindle and used the marks on my compound to match the angle. I am lacking in any number of miscellaneous tools which would have made that easier. I attempted taking measurements off the collet itself, but wasn't able to find anything that matched up precisely.

The order of operations I had planned in making this tool was to first make the spindle thread and fit the work to the spindle. True the work to the spindle before making the taper and threads for the nut.

Terry
 
Nearly done.. parted the work and mounted to the spindle and trued.
DSCN0510.JPG

Then when I went to set up the gears to cut the metric thread, I realized I was one short of the little gear assemblies to mount all of the gears I needed. So turned a bit of aluminum to act as a bushing, and turned down a carriage bolt to fit into the banjo. I was fortunate that one of the locations only required a single gear, so I was able to get away without having to key the bushing.
DSCN0519.JPGDSCN0518.JPG

Only then was I able to thread the part to accept the nut from my collet holder. And that advice about making a handwheel for the spindle, next time I make any metric threads, I'm going to make one first. Other than the routine of stopping the motor, disengaging the back gears, pulling the carriage out, and then winding the spindle backwards by hand, it was fairly unremarkable. Meaning, I was successful in making my first metric thread on my first attempt. Somewhat gratifying after the aggravation I had with my inside threading attempts.
DSCN0517.JPG

One final step remains, and that's to put the taper in for the collet, but I'll leave that bit for tomorrow. That and doing something to the exterior to make it a bit less plain, and easier to remove. Even though I had snugged in on by hand, it took a pipe wrench to get it off.

Terry

DSCN0510.JPG DSCN0519.JPG DSCN0518.JPG DSCN0517.JPG
 
TO keep your tool post from rotating under pressure,simply take a couple of 1" wide slips of brown paper bag(it has no clay in it),and place them under each side of the tool post. Paper will grip like crazy and the tool post will not ever slip again,provided you tightened it down well. I also use this trick in the milling vise when milling slippery metals like brass or aluminum. It makes all the difference in the World.

You should go to the top of this forum and read ALL of my tips. It's a long list,made into a sticky by Tony Wells. It contains lots of valuable things to know,like using paper to keep things from slipping.
 
George,

Thank you, I will do that. And I'll use the paper trick too, in the future. After the tool post rotated, I tore it completely down, and gave it a thorough cleaning, it had little bits of swarf between the base and the compound. Seemed to do the trick.

Terry
 
You must log in or register to reply here.
Back
Top