Brown and Sharpe Taper Reamer: Straight shaft w/o spinning between centers.

Ray C

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Been meaning to re-make a Brown & Sharpe taper reamer, this time out of O1 tool steel that will be heat treated to RC 60+. This is will be used to make balancing grinder hubs for the B&S surface grinder in my shop. The angle is 7.125[SUP]o[/SUP] from centerline (14.25[SUP]o[/SUP] inclusive) which I believe is also known as 3 in 12 taper. Reamers with this angle are available but I can't find one with the right base diameters.

This metal is a little expensive so I'll want to use as short a piece as possible. To do that, I'll pass along a method of spinning between a 3J chuck and a dead center -and still managing to get perfect concentricity. I'll show step by step and it's useful for folks who prefer not to spin between centers. Normally, I would spin between centers but I'm trying to conserve this piece of stock.

It starts out with this, a hunk of O1 and a CAD drawing with the dimensions of the cutter. The cutting edge diameter goes from 1/2" to 1.1" over a distance of 2.4". I've chosen a 2" long shank to drive it and I'm giving myself a generous extra 1.5" of material for work holding in the chuck and dead center. You should be able to see this in the photo below.

BS1.JPG


First, lets see how much room there is and if it's even possible in this little space. Here, I'm taking a piece of old brass boat propeller shaft and seeing if there's enough room to work. After thinking things over, I'm going to splurge and cut my piece 7" long instead of 6".

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My 3J chuck (just the stock chuck that came with the PM/QMT lathe) is fairly well behaved after some minor tuning and balancing. If your 3J does not re-center well at the same diameter, you should probably switch over to a 4J and scrap your 3J. When a 3J does not re-center at the same diameter, it's got serious problems -probably with the scroll and/or jaw journals.

The trick to this is to always make a mark on the piece and put it in the chuck in the same orientation. Start by facing and drilling one end and making a mark (red spot) that lines-up, in this case, with the insignia on the lathe.

BS3.JPG

When you've done one side, flip it around and face/drill the other end making sure the mark is lined up with your landmark. Once that is done and without removing the piece after the second face/drill operation, I'm going to reduce the shaft to 1/2". This will later be used to grip the part with the 3J chuck. Note: At this time, we know 2 things for sure. 1) the center hole is concentric with the 1/2" stub 2) the 1/2" stub is concentric with the average outside diameter of the uncut shaft. -We also know that the center hole "should be" pretty well centered with the center hole on the other end. Here's the 1/2" stub:

BS4.JPG

Now, flip the piece around and grab it in the jaws by the stub. Bring-in your dead center and tighten things down. Make a light pass of about 0.005 DoC. Then measure the shaft left, center and right. On my first pass, I had difference of 0.0046", wide at the tailstock end. This means that the tailstock must be moved toward me by 0.0023".

The next sequence of steps, to move the TS 0.0023", are important to do in the proper order.
First, put a TDI on the end of the part and set it to a zero point (utilizing 1/2 the travel of the TDI). Second, slightly loosen the chuck jaws so they are still grabbing the piece but not loosely. Third, move the TS head by 0.0023". On my new TS, lateral adjustment can be made without unlocking the base from the ways. My finger is pointing to the lateral adjustment on this TS. If you have a traditional TS, making this adjustment may take a little trial and error. Once the adjustment is made, tighten everything backup. In my case, after tightening the chuck, I loosened the TS base slightly and re-applied sufficient dead center pressure. This TS does not lose center when the base is loosened and re-tightened.

BS7.JPGBS9.JPGBS8.JPG

And finally, take another pass and re-measure the shaft diameter at left, center and right.

In this particular case, the shaft came out measuring 1.3197" 1.3198 and 1.3199; thus, it is holding +/- 0.0001" -Good enough for this piece because it will be cut to rough form and about 10 thou oversize on the lathe, six fins will be cut on the mill, it will be heat treated then, finished to size on the tool cutter/grinder.

Here's the rough blank. In this position, the taper will be cut next and I know there will be enough clearance to do the work because the logistics were checked up-front. BTW, this metal is a joy to work on. This was spun at about 850 RPM and 0.004 IPR (left to right cut) with naked carbide TCMT 3251 insert. The insert I used was borderline shot but, the piece has a beautiful finish. It's practically hard to screw-up good quality metal.

BS5.JPG

We'll continue later... Please be patient because I gimped-up a few fingers and am on light duty these days...

Ray

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OK, time to cut the taper -which is very easy. First some easy math. The one side angle (for a Brown&Sharpe grinder arbor) needs to be 7.125[SUP]o[/SUP] and an angle is expressed as the Tangent of the Rise divided by the Run. We need to make two measurements from the compound. One measures the Rise (deflection of the compound) and the other measures the Run (distance traveled). You need to setup two travel indicators as shown. The bottom one measures the distance traveled and the top one (which is fixed to the tailstock) measures the run of deflection on the compound.

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I'm going to use a travel distance of 1/2". First, set the compound manually to the angle of 7.125[SUP]o[/SUP] as best as you can. Second, set the bottom indicator so the plunger is depressed a good 1/2" and zero the scale. With the top one placed against the compound, move the compound until the bottom indicator shows 1/2" of travel. Now read the top indicator. 0.5 x Tan(7.125) is 0.0625. That is the number we're looking for on the top indicator. Keep resetting the carriage, adjust the compound and rezero the indicators until you get a measurement on the top indicator of 0.0625. When you get it, lock the compound down.

If you're looking to cut an MT2, the one side angle you need is 1.4307[SUP]o[/SUP] so, following the procedure above (with a 1/2" travel) you need to read a deflection of 0.01249. For MT3, the angle is 1.4377[SUP]o[/SUP] so, it's 0.01255.

When you make the cut, you will not move the carriage at all once it's been roughly positioned... you will turn the compound crank to make the tapered cut. First, you need to extend the compound all the way out. Get the bit close to the metal by positioning the carriage and crossfeed then, lock the carriage. Next, check for clearances (no banging tools now), turn on the lathe, make bit contact by moving the crossfeed in and crank backward on the little compound dial. It will shave off a ribbon and start to form the taper.

Please note, I've decided to cut the taper small end at the left. I could reverse that if I wanted to (by rotating the compound the other way, running the lathe in reverse and cutting on the far side. For this piece, it's not possible because the tailstock is in the way. If it were a short, unsupported piece like an MT2 stub, I would do exactly that.

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Here's a closer view and some progressions along the way. Normally, I don't like to run so close to the chuck but, theres is no powerfeed going on here and I'm working from left to right.

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So, here it is all done and I've cut a 1" shaft on the end. I'll mill a square on the end to drive it with a wrench. The area between the black lines is what I need to ream the grinder hubs. I'll leave the excess material in place. Later on, we'll toss this piece in the mill and make the cutting fins.

BTW, this is the color of good carbide cut swarf -beautiful blue indigo. Sadly, because of the angle of the cut, I could not utilize the chip breaker and that swarf is razor blade sharp. The blue glove does not provide protection; it's only there to keep my hand clean.

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Ray

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Here's a little more demo of how to cut a Morse stump. First, use the angle setting procedure described earlier. If you can run your lathe in reverse, set it up this way:

M2.JPG

If you have a forward-only lathe, set it up this way:

M1.JPG

Note the differences in how the compound angle points for each case. BTW, I just made that MT2 stump in about 5 minutes....


Ray

M2.JPG M1.JPG
 
I would definitely mill. A formed wheel will not keep its form very long. Probably just good for cleaning the milling scallops out of the cuts,if you get my meaning.
 
Definitely on the mill 60[SUP]o[/SUP] apart. I'm behind on this project. That one nasty looking finger had a blood clot and needed some special attention the other day so, I'm taking it easy these days.


Ray


I would definitely mill. A formed wheel will not keep its form very long. Probably just good for cleaning the milling scallops out of the cuts,if you get my meaning.
 
Hi... After a little pause, I decided to spend a little time on this today. The facets are basically cut and if the fingers are up for it, I'll clean them up just a little more and heat treat this part. After that, we toss it in the tool grinder and make it sharp.

Very simple procedures here to cut 6 flutes. I made passes with a side cutter, a dovetail cutter and a normal endmill. 6 flutes, 60[SUP]o[/SUP] apart. Very self explanatory except the first photo where I was running the table back/forth to find the counter-angle of the taper.

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Ray

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Hi ray:

I'm curious as to why you made it a left-hand cutter(if there was a reason). I know it will work in either direction.....
 
When I used some store bought (right-hand) cutters and used them in the lathe, the wrench slipped off and the knuckles went crashing into the lathe's splash guard. Pulling toward me, I'm less likely to end-up with more dents in the splash guard.

BTW, the reaming is not a delicate process and it takes some good elbow grease to cut the metal... So yes, they are left hand by design.


Ray


Hi ray:

I'm curious as to why you made it a left-hand cutter(if there was a reason). I know it will work in either direction.....
 
When I used some store bought (right-hand) cutters and used them in the lathe, the wrench slipped off and the knuckles went crashing into the lathe's splash guard. Pulling toward me, I'm less likely to end-up with more dents in the splash guard.

BTW, the reaming is not a delicate process and it takes some good elbow grease to cut the metal... So yes, they are left hand by design.


Ray

Makes sense; thanks!
 
Woops, I forgot to mill a square on the shank to drive it... Fixed!

C7.JPG

C7.JPG
 
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