Boring a taper

Most of the guys I know, me included, would just buy a reamer.

For setting the slide to a male taper, mount a dial indicator on the slide and adjust until you see no movement indicated when you traverse the lenth of the "master". I suppose a test bar between centers and two indicators (one to follow along the test bar and the other to measure the travel of the slide accuratly) could be made to work. Measure the given taper per inch in an accurately measured inch of travel. Cumbersome, but workable without a master to work fron.

That does not even start to deal with the amount that the boring bar has to hang out of the tool holder to reach the bottom of the taper socket. It would not surprise me to find that the bar is flexing quite a bit in the hole. That's going to cause its own set of issues.

Have you considered making a reamer?

Cheers Trevor Jones

Are you sure that the taper you are measuring against is running true? A dial indicator against a true running shaft and some simple math will get you the taper per inch that will be read on the dial indicator. Remember that the dial will read half the amount of taper per inch.

John

Bob,

Lose the layout blue idea. How in hell that got started is nothing short of a mystery to me. It's WAY too thick to be of any value, and doesn't tell you anything, anyway. It balls up prematurely and tells you nothing about how the metal parts relate to one another. The proper thing to use is Prussian blue, a very thick oil product that comes in a small tube, much like a small tube of tooth paste. It's the stuff guys are supposed to use when scraping. You put it on VERY thin, and look for an interruption in the pattern when you wring the parts together. When it's properly applied, only the highs will transfer, very unlike the other stuff that are often used, with results much like yours.

Another option is to use a sign plate or bar and a surface plate setup to determine the proper angle, but that demands you be able to set up the parts perfectly square, otherwise you introduce error. The typical home shop would be unlikely to be able to make a reasonable setup by that method.

You'll get acceptable results with the Prussian blue, assuming you're willing to go through the struggle of getting the angle right in the first place.

Don't make random changes of your compound when setting the angle. Use a dial indicator against the side and move it a prescribed amount and see what it does for your fit. You'll quickly come to see how much a thou changes the angle. Could be a couple of repetitions and you'll have it.

Remember to keep your boring tool at the same height at all times, otherwise there will be a minor change in the angle.

Harold

Too thin a boring bar and too flexable a lathe. Shrug.. Its actually better to drill and ream a #1 cause the tooling is by nature gonna be pretty thin

I was having the same issues with a #2, even when doing it on a Hardinge HLV-H..the best results were with very high spindle speeds and tiny cuts towards the end. Stuff was deflecting.

So I scounged a set of #2 roughing and finish reamers.

This works SO much better now

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Your standard MT may not hve been aligned well with the spindle, and I would prefer using a test indicator to feeling drag on a bit of paper.

I would use a piece of cylindrical stock and set the compound with a test indicator so it shows the right taper for MT#1 which is .04988" (diameter) per axial inch. This has worked for me.

Boring tools do spring some, so you need to make finish passes without increasing the cut until you get a pass that removes no material. A sharp HSS bit works a lot better than carbide here.

Yup, here's how I did it, also without a taper attachment.

I had a male taper of known quality that I used as my master. I set the compound as accurately as I could, and then cut the taper socket. I then applied Dykem "Hi-Spot blue" dye to the male taper, and put it in the socket with a light touch and a twisting motion. It will show a ring of color on the taper you just cut, either that the outer end or the inner end. That tells you where it is too tight, so you adjust the compound angle in painfully microscopic increments, and do it again. When you get close, take off the tool, and rig a Dremel tool or other similar high-speed spindle to the toolpost. (OK, I cheated here, I have a toolpost grinder, and I'm not using a Sherline, but a lathe

Jon

Dykem, the famous maker of blue layout dye ALSO makes "Hi-Spot blue" a prussian blue dye sold specifically for spotting work. So, the confusion between the same maker's two blue dyes is pretty easy. And, yes, they are totally different materials for totally different purposes.

Jon

You've got plenty of good suggestions above.

I'll add that when I did a job like this, I finished by lapping the last 1/2 thousand in. Just take an old drill, cut the tang off, grind a couple pockets along the side of the drill. Then apply lapping compound, clamp the drill in the tailstock drill chuck, and run the lathe slow. You'll have a mirror finish and a perfect taper.

Karl

Any suggestionss - please. Is there a better way

Better- I'm not sure. I can give you different. I had a problem checking the fit on the(close to)B3 end mill holders I made. I cut them by setting the compound with an indicator using a B3 collet for reference. Checking the fit was a problem as the collets use a key, and I couldn't rotate the workpiece in the spindle to get clean rub marks using HI-Spot. I had some 20 year old Plastigage. I put a piece on opposite sides of the end mill holder and tightened the drawbar a bit. The Plastigage deformed, showed how far off the taper was, and where it needed to be corrected.

I have not heard of anyone using Plastigage in a machining context. There may be good reasons not to use it, but it worked for me.

Kevin Gallimore

I agree with Harold. The sine bar method will set the exact taper angle, then use very fine cuts and Prussian blue to make the final passes. Bugs

What brand of Prussian Blue are you using? I haven't found anything currently that matches it.

Hul

Bugs wrote:

I can't speak for others, but the tube I have in my toolbox was made by Permatex. I've had it for, easily, 40 years. It's old enough that the address is listed as Brooklyn 35, N.Y., before zip codes.

One need not buy much of this stuff. A small tube, when properly used, is capable of covering the earth a couple times over.

Harold

I use Canode spotting dyes because they are less messy. They are not as good as real prussian blue, but then I'm not scraping things to the single micro-inch level. But, I used to use Dykem brand "Hi Spot Blue" in little squeeze tubes of 4 Oz ea, I think. But, I HATE the mess. MSC, J&L, Travers, etc. all carry the Dykem brand. The Canode is hard to get ahold of in small quantities. I just found some at the Cummins outlet store, but I have no idea if they have this at all branches.

Jon

Go to any art supply store. They will sell you as much Prussian Blue [oil color] as you can use in a lifetime. Bugs

And a hearty "Thanx guys" to all respondents!

All of your insightful and informed replies caused me to rethink the crux of that particular biscuit. Bottom line: I was doing it wrong!

Although I couldn't see anything wrong with the idea of a "paper-drag" gage, your suggestions to go with a dial test indicator really straightened me out. I applied my little Starret Last Word indicator and surprise! surprise! . . . it showed me I was trying to set up on the wrong angle. The angle given in the handbooks for a plug taper is an "included" angle, thus my method of paper-drag gaging was way uncool. Half the indluded angle must be used when setting up to cut tapers.

So, by switching to the advice of experts, and a little common sense, the error of my ways soon became apparent. I should have used a dial test indicator in the first place. I have cut tapers before but always with the compound on my 13 x 40 lathe. This time I wanted to practice with the Sherline and its compound. Sherlines don't ordinarily come with compounds. I bought the optional Sherline compound some time ago and never really tried to do any serious work with it. Sherline suggests cutting tapers by setting the head stock over or turning "between centers". There is no way to cut an internal taper between centers. Besides, there is something alien to me about turning anything between centers. Maybe next time I cut internal tapers I will try Sherline's recommended method of setting the head stock over. In retrospect, that is what I should have done in the first place. It would be very easy to place the work in a collet or 4-jaw chuck, meter with an indicator, and set the head stock over 1/2 the published taper angle.

Bob Swinney

Ignoring the comments and advice the others have given, there is one other thing.. If the tool is above or below the centre line at all, the taper will be large at the small end. The taper will also not be a conical shape. So that's another thing to check.

Regards Mark Rand RTFM