Third Round, Lathe Bit Grind

In two earlier posts, I have shown tool rests that I made for my 6 inch grinder to help with lathe bit grinding. These have been satisfactory for grinding the end and side cutting edges, but are inadequate support for grinding the top rake angles (side rake, back rake).

I have been influenced by an article that shows how to take advantage of the slightly concave surface that a 6 inch wheel makes on bit surfaces. When this concave surface is stoned, the stone touches just at the top and bottom of the surface, making a cutting edges at the median angle of the ground surface. View the article to see some excellent pictures of the effect of stoning.

Here is my new setup. The grinder tool rest is replaced by a guide for tool holders.

Note the catch pan for grinding debris, a big help in clean-up.

During grind, bits are carried by holders that are guided by the base. Here is a protractor holder for end and side cutting edges and two other holders for the top surface (side rake and back rake).

The protractor makes end and side relief angles of about 9 degrees and adjustable side and end cutting angles. The other two holders make 15 degree back rakes and 15 degree side rakes, one holder for right cutting bits and the other for left cutting.

This is the back of the protractor showing the step that keeps it at constant distance from the wheel.

Here the protractor is used for an end grind.

And here it is used for side grind. For a shallow angle, this must be done with some care as it is possible to wedge the bit and stall the grinder motor.

The two holders for top surface grind have grooves to position the cutter for the compound angle (side rake and back rake) that is needed.

At first thought, it seems that the right cutter and left cutter top surface guides should be mirror images. But my grinder motor interfered with any approach to the wheel from its right side so both of these work from the left side of the wheel.

These sketches help to explain the side rake grinds.

Here the right cutter guide is being used to make the side and back rake angles.

And here the left cutter guide finishes a top surface.

Finally, two newly ground tools.

Yet to be made are two more holders for aluminum cutting bits that will have 35 degree back rake.

Update 28 Oct 2020: Here are the four holders for grinding tool top surfaces. All are 15 degree side rake (per the sketches above). The front two are 35 degree back rake for aluminum and the back two are 15 degree back rake for steel. The notches at one corner are needed for clearance from the wheel.

Posted in Abrading, Turning | Leave a comment

A Salmon Reel

This is the work of my friend Terry, for whom I have shown two other designs. It is a 4.5 inch diameter reel for “big game”.

Terry has several decades of experience with salmon fishing including regular visits to Alaska and Iceland. I think it is interesting that he chose to make a click type reel. Two pawls may be better than one.

The remaining pictures include his 2.25 inch reel for comparison.

Terry is doing his drawings with Autocad LT. I have reproduced them here but it took several steps to communicate them and turn into jpeg format. If anyone is serious about reproducing this design, contact me and I can provide PDFs with better legibility.

If you combed through this blog, you could find drawings for seven different reels. At the Categories list on the right side of the blog page, click on Plans.

Update 14 Oct 2020: Here is a communication from Terry after I made this post.
“The answer to your question regarding the 2 pawls is that very definitely yes, the 2 pawls make a huge difference in the clicker drag on this reel.. This is not something new to me. In my previous years of salmon and steelhead fishing, I have always turned both pawls on my old Hardy type of reels so they are in contact with the gear and set so they are working in the same direction. This greatly enhances the drag on the reel and with the overlapping palming flange, you can easily handle even the larger fish encountered. I like the clicker drag system, even on larger reel for larger fish because this system is about as simple and foolproof as you can get. I have never had a failure of this type of system, which is not something I can say about more elaborate drag systems on much more expensive reels I have used as well over the years.”

My observation on his pawls is that they are spaced 92.5 degrees apart. Because he has a 31 tooth ratchet, the pawls are exactly 8 teeth apart and so click over simultaneously. I would like to play around with 2 pawl placement and see what different sounds could be had. Maybe something like the Harley V Twin where the cylinders are 45 degrees apart.

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Terry’s Second Reel

Terry is bamboo rod maker in Idaho. In June I posted pictures of his first reel. Now he has produced a 2.25 inch diameter reel for a 5 foot bamboo rod.

This is about as simple and straightforward as a reel design can be.

He had this one engraved, and the engraver added some color. At this time I do not know the process; possibly just a chromate conversion coating.

Posted in Reels by Readers | 1 Comment

Anodizing Temperature Control

DIY anodizing of aluminum parts is a practical process for home shop reel makers. These earlier posts provide background:
Technical Data on Anodizing.
Water Cooled Cathode
Cool water

I anodize reel parts in a 32 ounce polypropylene jar, and the lid assembly has several features. A reel spool is suspended from the lid by an aluminum “rack”, which both supports the spool and provides an electrical path.

Also visible here are 3 tubes: the big looped tube passes cooling water through the acid solution, an open ended tube is for bubbling air to keep the solution stirred, and a closed end tube is for temperature sensing. These three tubes are electrically connected together to serve as the cathode.

Here is the acid jar with lid and an auxiliary jar for ice and cold water. A small 12 volt dc pump circulates water between the jars.
Two additional connections are provided on the cold water jar, a normally plugged outlet for system drain and an overflow for excess melt water.

This is the complete setup, adding a current controlled power supply, an aquarium air pump for bubbling, my new temperature controller, and an IR temperature gun for casual monitoring.

Before I made the controller, I kept a glass thermometer in the closed end tube and turned on the pump when the temperature reached 21 deg C, and turned it off again at 19 deg C. This required constant vigilance during the one hour process.

This is a close-up of the controller, it is just a resistor bridge (one leg is a thermistor in the closed end tube), a voltage comparator, and a power transistor to switch the pump.
This automatic control makes running the process much more pleasant; I can leave my garage for a while (88 deg F in the summer) and just periodically check on whether ice should be added to the auxiliary jar.

When the process is started, the acid needs to already be at 20 deg C (68 deg F). I get it there by holding it in an insulated chest with some blue ice for about an hour.

Recently I had been getting some cosmetic failures of the process, dark smudges under the anodize coating. I have been able to eliminate these by switching from titanium to aluminum for the anode rack. Not sure why the smudges were developing; I was using grade 2 titanium and so not introducing rogue metals.

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Chuck Spider

I finally sold my Sherline lathe, my first machine tool. I could do this because I have made enough upgrades and fixtures for my newer minilathe to produce all reel parts with just it and my mill.

The last consideration was making a thin (.110 inch) disk as the blank for the front end ring. To do this with the Sherline lathe I bought soft jaws for the 3 jaw chuck. The jaws step was .080 inch and that was enough to firmly hold the disk.

More about soft jaws at this post: Custom Jaws.

This would be a good solution for the minilathe also, but there seems to be no source for minilathe soft jaws. I found a good article on DIY soft jaws: Harold Hall’s Soft Jaws. But I did not pursue this because it appears to require a surface grinder.

Instead, I have made a chuck spider.

This is the spider: a hockey puck with milled grooves to clear the jaws. It works with diameters from 2.25 to 3.0 inch.

I had made a similar spider to use with the Sherline 3 jaw chuck, but it was a loose part in the chuck-spider-work assembly and did not work very well (i.e., disk sides did not come out as parallel as I wanted). The improvement here is a draw bolt to keep the spider firmly against the chuck face.

To make the final facing cut on the spider, I removed the chuck jaws and held the spider against the chuck face with just the draw bolt.

And it worked, I got a disk with sides parallel to .001 inch.

The spider has a witness mark for angular positioning on the chuck. This eliminates the effect of any chuck face axial run-out.

Posted in Ring, Turning, Work Holding | Leave a comment

A “Perfect” Reel Configuration

An iconic reel design is the Hardy Perfect. I have never had one in hand to photograph but I did borrow a Hardy Bougle from a friend, and it is the same thing except that the frame is raised pillar instead of round.

What is unusual here is the winding plate that carries the knob, the ratchet, and a spindle that reaches through a frame mounted bushing to drive the spool.

Another notable feature in this design is the ball thrust bearing. I have never really understood the reason for this bearing; seems that if you wanted a ball bearing for axial forces, you would want them for radial forces also. I have never used ball bearings, too many tiny moving parts.

What is the real advantage of this design? I don’t know, but I do observe that one face of the spool is accessible for “palming”, to create additional drag.

Here is my take on a Perfect reel.

Because this reel is left hand wind, I had to make left hand threads on the end of the spindle and in the bronze spool insert. Otherwise, line tension might unscrew the spool.

Instead of the ball thrust bearing, I have a plain bearing of Delrin (the ratchet face) running on bronze.

If the reel is palmed, then axial thrust is in the direction that the thrust assembly does not support. On a Hardy reel, this load is taken by a small area of spool aluminum running on the end of the frame bushing. Here, the bronze spool insert runs against the bushing.

This reel is cosmetically defective due to failure of my anodizing process. There are stains embedded in the oxide layer. I think that the aluminum alloy may not be 6061, which is a good anodizer. But it seems quite unlikely that something else would have been supplied.

I did not make drawings of all the parts, but here is what I have.

The pawl is drawing 1090 : pawl. The ratchet is 36 teeth, 36DP 20 degree.
Click hardware is drawing 1091 : hardware.

Finally, this sketch shows overall arrangement and dimensions.

Update 18 Aug 2020: The cosmetic defect in the anodizing must be due to the aluminum alloy. I don’t think it is 6061, which is well known as a good anodizer. I have never knowingly ordered anything but 6061 in this large diameter.

Posted in Frame, My Reels, Plans, Spool | 4 Comments

Threading with the Minilathe

I have had reason to single-point some threads recently. This was motivation to further improve my Minilathe so that threading is easier.

First, the spindle that carries the intermmediate cluster gear needs a brass shim (oblong) to bring the two meshes into axial alignment. The shim here is .062 inch thick. If this is not done, some gear arrangements are bound up with gear faces rubbing. The same axial alignment would be achieved with a simple round washer shim under the mounting plate for this spindle, but this would also reduce the space available for puller jaws.

I also replaced the thin washer at the nut with a thicker one.

I am not so bold as to try threading under power; there is not enough control. Fortunately, Little Machine Shop sells this spindle crank, part 3897.

Pull the line cord plug while you have this installed.

The plastic first gear and last gear (A and D) require a puller to remove. I bought this one at the auction site, but it was entirely unworkable.

Here I have modified the puller to make it easy to use.

1. Discard the two cross bolts.
2. Grind the jaws at the end of the arms so they are thin enough to get behind the gears.
3. Install two pins in the cross bar so the arms do not fall off.
4. Cut off the flimsy tommy bar and replace it with a knob.

Finally, I made my own chart of change gears.

Note that there are two setups for 1 mm pitch, one if you have bought the 21 tooth gear from Little Machine Shop and a somewhat less accurate setup if you do not have it. None of the the metric pitches are exact, but close enough for most purposes. The last column of the chart shows the ratio to true pitch.

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Terry’s First Reel

Terry is an active bamboo rodmaker, now from Idaho but with background in Michigan. I met him once at the RKP rod shop. He has equipped himself with Grizzly mill and lathe and is starting out on reels. This is his first.

The pawl and ratchet are Delrin, an application that I strongly advocate.

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Internal Grooving

When I first got a lathe, I bought a group of randomly selected turning tools from the auction site. These two were a mystery to me and I never tried to use them.

This morning I was browsing through Youtube videos and I came across this one: Making Grooving Boring Bars
Duh. They cut an internal groove, as you might want for an o-ring. Might be useful on a reel where the o-ring is a substitute for a “tolerance ring”, allowing a low precision press fit.
The small one makes a 3/32 wide groove and the bigger one makes 1/8.

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Lathe Bit Grinding, Redone

I posted the article “Lathe Bit Grinding” on 1 July 2013. Since then I have arrived at a better scheme, as described here. Bit grinding is somewhat an art and you will find many alternative styles of lathe bit. My goal has been to find a method that is quick and repeatable, producing a bit that is easily re-sharpened. All grinds are made with the tool held firmly against a spacer plate on top of the tool rest.

Here is a borrowed illustration which establishes nomenclature for lathe bits ground from high speed steel:

Image taken from the web site

My first metal lathe was a Sherline. You can buy pre-ground bits from Sherline, one is shown here. Initially I tried to reproduce this grind myself.

These bits have zero Back Rake (see nomenclature illustration) and the entire cutting edge (intersection of side and top surfaces) is very near the height of the bit blank. When the bit is sharpened by additional grinding of the side, the height of the cutting edge is reduced (as the edge moves down the Side Rake) and shimming of the bit (for use in a simple tool post) will be needed. But what is difficult about sharpening this bit is that the ground surface on the side is flat, whereas a grinding wheel has a radius. It would be difficult the hand hold the bit and make new side surface that is flat. Sherline undoubtedly has good tooling for producing this grind.

The grind pattern that I am using includes some Back Rake, and reduces the cutting edge height by .020 inch or so right from the start. So I am always shimming underneath my lathe bits.

It is easy to measure the edge height with a micrometer and determine the amount of shim required. My frequently used Sherline tool post needs the edge to be at 0.250 inch (i.e., the full height of the blank). The larger tool post for my Minilathe requires 0.332 inch. I think that it was designed for 8 mm tool blanks (0.315 inch) so at least 0.017 inch shim is always needed.

I made a selection of shims from brass shim stock and scrap material.

You could make a very complete set of shims from a feeler gauge kit.

These are Sherline tool posts for 1/4 inch bits, for 3/8 inch bits, and a “rocker” tool post.

The rocker is supposed to eliminate the need for shims but I find it to be fussy to set tool height and so seldom use it. Much quicker to measure the edge height and then select a few shims.

This is the Minilathe standard tool post. I use 1/4 inch bits in it, which need at least 0.082 inch shim. The greatest part of this shim pack is in a brass part with a step that provides an alignment edge. The step width is set to locate the bit under the clamp screws.

My grinder is a Delta that you would find in many hardware/home supply stores. The tool rest angle can be set in increments by the radial serrations you see on the mounting lug. The increments are too coarse for the purpose of bit grinding.

One of the increments sets the surface of the rest in line with the center of the 6 inch diameter wheel.

Here is a sketch of the grinding geometry. I have made a 1/8 inch thick plate to set on top of the tool rest. If I hold the bit flat against this plate, the relief angle of the grind is asin(0.125 / 3.0) = 2.4 degrees at the bottom of the bit. (3.0 is the wheel radius.) But at the top of the bit, 1/4 inch higher, the relief angle is asin(0.375 / 3.0) = 7.2 degrees. This is the effective relief angle at the cutting edge.

So here is a view of my cover plate for the tool rest.

It has some lines engraved as guides for grinding.

Following are the steps in grinding. I show a tool bit that is already ground, rather than a new blank.

The first grind is on the end. I hold the bit flat against the cover plate. The End Cutting Edge Angle is 25 degrees. The End Relief Angle is 7.2 degrees at the top of the bit.

The second grind is on the side of the bit; again I hold the bit flat against the cover plate. The Side Cutting Edge Angle is 10 degrees and the Side Relief Angle is 7.2 degrees at the top of the bit.

When re-sharping a bit, this is often the only grind that needs a re-touch.

Finally, grind the top of the bit, again holding the bit flat on the cover plate. The Back Rake Angle is 10 degrees and the Side Rake Angle is about 7.2 degrees at the cutting edge.

This grind can be eliminated for a tool meant to cut only brass.

End Relief, Side Relief, and Side Rake are all curved surfaces (3 inch radius). This makes no difference in how the tool preforms.

My grind pattern has a 75 degree included angle at the tip, and that seems to be good for getting into a square step. But the tool post has to be turned at a small angle, as shown here.

Quick Change Tool Posts have height adjusters that eliminate the need for shims under the bit. But, if I understand them correctly, they have to be mounted square to the cross slide and so some special bit shape would be needed for corners, perhaps a negative Side Cutting Angle. The freedom to rotate the tool post seems to me to be so important that I have never invested in a QCTP.

Update 20 Aug 2020: I just found this article, Hoffman Article. It says that I am wrong on tool height above the grinding rest, that instead of aiming for 7 degrees at the top of the bit you should have 7 degrees at the mid point. This is because a properly stoned tool will have a little material removed at the top and bottom of each face, and the true relief angle will be midway between the top and bottom angles that the grinder produces. He has some good photos that show this. So maybe my tool rest cover plate should be 1/8 inch thicker.

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