Monday, September 26, 2022

Bandsaw Log Sled

Work Holding Larger Logs on the Bandsaw

Since I own a lathe that can handle huge logs (Stubby) we are often confronted with the challenge of preparing large blanks. This usually dictates the use of a chainsaw and other means of wrestling the wood into a turn-able shape. Preparing large wood for me is the unpleasant part of turning.

While processing the large aspen logs for the lamps [previous posts] I broke a 3/4-3 TPI bandsaw blade. This isn't the first time! So at $30 a pop, I decided to pay more attention to the cause. Note: I did find a blade on Amazon for $16 that I am testing.

I decided that the reason the blade broke is that I was free-hand cross-cutting the ends of logs. Along with being an unsafe method of preparing wood, it is prone to twisting/binding the blade which leads to breakage.

So I proceeded to find a simple and better way to:
-Feed logs for cross-cutting on the bandsaw
-Weld bandsaw blades

Sled Design & Fabrication

After lots of internet research, I settled on a simple sled for the bandsaw that features two moveable horizontal stops with one edge cut at a 45. Most of the sleds I reviewed had a fixed V to hold the log. Logs generally are not the same diameter from one end to the other.

To allow a level of adjustment I milled slots into the sled and anchored the stops with carriage bolts. The stops are adjusted to fit the profile of the log and are then secured with a belt and an old ratcheting snowboard clasp. I knew there was a reason to keep that clasp.

There is a tenon screwed to the bottom of the sled that rides in the miter slot to keep the log square to the blade.

Now a clean straight cut

The miter slot keeps the log straight

Adjustable stops that you can align to the log

nice controlled clean cut

firmly attached and aligned to the miter slot

locked and loaded

Conclusions

Certainly, square log-ends can be achieved by cutting the log square when harvesting but most of the time the pre-cut logs I get from the trash are not cut straight. There are also times when the noise of the chainsaw is objectionable in the neighborhood.
You can also mount the log on the lathe and part away the angle if you can get it mounted straight and get enough bite from the spur center.
The band saw sled is just another option for processing logs.

I will employ a separate post sharing my experience with welding bandsaw blades

Enjoy and please comment;

Don

Welding Bandsaw Blades

Repairing Broken Bandsaw Blades

Braking a bandsaw blade is one of the most frustrating and costly events that you can experience while preparing logs for woodturning.

While engaged in a large lamp project I again broke a 3/4-3tpi blade which costs $35.

Along with making a jig to better feed the log into my bandsaw, I embarked on a project to weld broken blades.

I watched every YouTube video that I could find on methods and jigs for welding blades and settled on a design and method.

The jig needs these features:

A long base that allows clamping the blade in place
An open area where the seam can be welded
A reference edge that will register the top edge of the blade
A reference stop below the seam that holds the seam together while welding

The Base

Many of the jigs used a piece of angle iron for the base. This material is problematic as the inside corner has a radius that prevents a positive reference point for the top of the blade. The blade will tend to ride up this radius unless it is removed or other fixed reference points are provided.

I had a piece of stock in my bin that had tightly bent 90s that I used for the base. I think I go this either at a big box store or at McMaster Carr. Although I ended up milling the corners of this material [just for finese] the first blade I welded fine without it.

A square hole was cut in the upper center of the base and the bent edge was cut away to facilitate access to the edge of the blade while welding. I found that at the weld the upper edge had a tendency not to properly wick leaving a void when it is touching the base.

A small plate is welded on the bottom of the base to hold a "backing bolt". The plate is tapped to accept a section of 1/4-20 bolt which has one end grout to a point. This bolt is used to put pressure on the back of the scarf joint and hold it tight to the upper blade section while welding. The bolt is adjusted to touch the lower section of the blade at the scarf joint and uses a wing nut to lock it in place.

Simple Clamping

I clamped the blade to the base with hand spring clamps. Most designs I looked at had bolts or over-center latches to hold the blade. Spring clamps require no fabrication, worked fine, are simpler, and act less as a heat sync.

Preparing the Joint

The ends at the break have to be ground to provide a scarf joint. It's important that the resulting weld be very flat otherwise it can damage the bandsaw track and/or cause failure. The conventional thinking is that the scarf joint should be ground at 20 degrees with straight and square edges. Seems my jig ended up being 16.

I cut a slot into a sled to facilitate grinding this angle. This sled worked but I found that I need a better way to clamp and hold the blade while grinding. It was difficult to hold the large blade still while moving the sled. That's a planned enhancement that will precede the next weld attempt.

Welding Method

The popular methods included brazing, silver solder, arc, and tig welding. I judged that arc and tig welding would require skills well outside of my abilities and would result in a joint that was more difficult to grind. I tried silver solder without good results. It did not want to flow into the joint. I later realized that I was not getting the joint hot enough so I will try that silver solder again next time.

I ended up successfully brazing the joint with a brazing rod and LOTS of flux.

I purchased some silver solder and flux to perform the weld but ended up using a brazing rod and the flux instead. I used a map torch as a heat source.

Welding

I flailed on the first band repair but finally realized that the problem was that I was not getting the blade hot enough. The process that worked the best was:

Clean all surfaces of the blade with an 80-grit wheel.
Clean surfaces with acetone
Clamp one end of the blade hanging over the edge of the base with the surface to be welded facing upward
Heat the scarf area to red hot with flux applied
Tin the blade with flux and brazing rod by applying the rod with the heat until it flows naturally across the joint
Repeat tining the other side of the scarf joint
Clamp the blade on the base with the scarf joint aligned but the blade surface not overlapping. Slide the blade left-right until the combined thickness is the same as the blade.
Apply heat to the joint until both the top and bottom are cherry red. Use plenty of flux. When the joint is fully red touch the solder onto the surface and into the flame. It should melt and suck into the joint. The key is to allow enough solder to flow into the joint to make it strong but not so much that the joint is too thick.
After cooling grind the joint flat on both sides

Annealing

This is important. Since the repaired area has been hardened from the welding temperature the metal at and around the joint needs to be annealed so it is not brittle and prone to breakage.

This is the method I use:

Grind the surface 3-4 inches from the joint so that it is bright metal. Removing oxidation facilitates seeing the subtle color transition.
Use a butane torch on low heat or alternately a map torch with a careful and intermittent application of the flame to the blade.
Slowly heat the blade to a straw color about 3 inches away from the joint. Then move the torch up the blade toward the joint. This should cause the straw-colored area to move to the joint.

The straw color transition is subtle and quick. It's easy to overheat the metal and when you do it will turn blue. The blue color means you have gone too far and potentially hardened the metal.

When the straw color encompasses the joint stop, and allow the blade cool. DO NOT QUENCH!

Results

The first blade I welded turned out too thick. On this blade, I did not tin the joint and tried a suggested method where the solder was placed in the joint before heating. I later realized I did not allow the joint to heat up enough and also suspected that the C clamps were acting as a heat sync. In this attempt, there was no backing bolt in the base.

Too much overlap at the joint makes it too thick.

Good coverage but to thick

The silver solder attempt did not work.

The second blade welded easily. I waited until the joint was fully cherry red, used a lot of flux, and has spring clamps vs C clamps. In this attempt, there is a tiny discontinuity visible at the joint and on the top edge. I was surprised that this tiny notch creates a ticking noise in operation.

Mounted on the saw, good connection, just a tad too thick. Runs with a small tick.

Enjoy and please comment.

Don

Thursday, January 7, 2021

Making a Faceplate Chuck

I am not sure what I should call this tool as it's not really a Cole chuck and its also not a Longsworth chuck so I call it a "Faceplate chuck".

It is used to hold a bowl, bottom out, for finishing the foot. I have a vacuum system but wanted something simpler to set up and use. Sometimes out of round and leaky vessels make a vacuum chuck a challenge.

I also wanted to get more experience designing and routing using my CNC machine and this seemed like a good learning project.

The Design

The design. The plate is 16" in diameter (the swing on my Stubby with the bed in the home position).

The 8, .25" wide fastener slots are routed through the material every 45 degrees. The slots start 1 inch inside the perimeter and end 2.25" from the center.

The plate is designed for a 2" faceplate, specifically this one: https://amzn.to/3nn52VZ

There is a recess milled into the plate so that the faceplate can be located accurately on the center of the plate.

The plate was then cut out of Luan using this bit: Freud 75-102: 1/4", 2 flute carbide bit https://amzn.to/3nxaXbj

I used Fusion 360 for the CAD-CAM and drawings.

https://drive.google.com/file/d/1AHNkIav3f0J2ErfndpXrMwa7eNC-mwS9/view?usp=sharing

Faceplate Attachement

The faceplate holes are very near the edge of the faceplate and their are 8 of them.

The chances of getting 8 holes manually aligned and drilled so the faceplate fits is pretty unlikely.

Therefore I created a 1-1 template on Fusion 360.

Print out this file 1-1 to use hole placement:

https://drive.google.com/file/d/1ZM4RyZdgSYWH6dYlcCnHW2RmWlh8mpGR/view?usp=sharing

The attachment of the faceplate to the chuck is done with 10-32 cap screws that are bolted through a plate on the front with nylon locking nuts on the back. I got the screws at Ace hardware, they were a strange length but fit perfectly.

Front Pressure Plate

I made the front pressure plate from 1/8 inch aluminum scrap. I cut it with my favorite nibbler and used the template for hole placement.

Drilling the Plate Holes

I took extra precautions to drill the plate accurately. The challenge is that there are 8 radial placed holes that are dangerously close to the perimeter of the faceplate. A small deviation from the center and/or improper spacing meant the screws would not align with the pressure plate and the faceplate. There is no tolerance to enlarge the screws to account for misalignment.

Therefore I made 2 awls from #10 bolts and ground the ends to a point.

Grinding a point

With the faceplate in the recess, one awl tapped through the hole and into the wood plate. This awl pins the faceplate in place while the other holes are marked

The second awl was used to mark the remaining holes while the first awl is left in place.

Holes marked accurately

Use a brad point bit for accuracy

The Fusion design files can be obtained by requesting such in the comments.

Enjoy and Comment

Don

Wednesday, December 30, 2020

Shop-made carbide tools

I have been experimenting with the use of carbide tools for some time now.
As a traditional turner, I use conventional bowl gouges for most everything I turn.
I don't do much spindle work so the bowl gouge is my go-to tool.
That said, I have a set of carbide tools that I keep trying in different situations.
Last time I tried my carbide set while on my small Jet lathe I realized that the tools were just too big!
So I decided to fabricate smaller versions of the carbide tools that I use on my stubby.

Short tool

Materials

1x 1/2 square stock: McMaster https://www.mcmaster.com/9143K17/

1x 1" round alum tube with 1/2" ID: https://www.mcmaster.com/9056K28/

4x 1/4-20 set screws

Carbide cutters*: https://amzn.to/3pzTKiD

* Caution: I have ordered these cutters twice and have gotten two different sizes of cutters and screws. Check your cutter order before you start this build.

Design

The tool consists of a 1/2 x 1/2 bar with a cutter recess and a milled tang which is fit into a handle insert. The 3.5-inch handle insert is epoxied into a turned wood handle.

Cutter mounting

A cutter recess is milled into the cutting end of the bar stock. The recess is made slightly longer than the cutter that will be mounted. The recess depth is less than the thickness of the cutter. The cutter will be mounted touching the edge of the recess but the recess must not be so deep that the cutters cutting edge touch the bar. Meaning, when mounted the cutters cutting edge must be proud of the bar's top surface.

For square cutters, the recess is milled perpendicular to the bar

For round cutters, the mounting recess is milled from the tip of the bar toward the tool's tang leaving a half-round surface for the cutter to index against. The end mill's diameter should match the diameter of the cutter.

The cutter is then positioned in the recess and the mounting hole is marked and subsequently drilled and tapped to match the size of the mounting screws. Mine was a 4mm-.7 screw.

The tool that mounts the round cutter is subsequently modified to mount the pointed V cutter. This is done by milling down the center of the tool so the back of the V cutter is relieved. The end mills diameter depends on the size of your V cutter. I lay the cutter on the tool and mark where the Vcutter intersects with the 1/2 moon recess. Then using that size end mill cut a recess along the tool's length and through the 1/2 moon long enough for the V cutter to mount flat on the tool.

The cutter, slightly proud of the bar top surface

Modified bar to fit point carbide

Shaping the bevel

The face of the tool is then ground to a shape to match the cutter's bevel angle and shape.

Handle Insert

The handle insert is made from the 1" aluminum stock. A 3-inch piece is mounted in the lathe and the center hole is drilled out to 1/2inch. The raw tube stock had a slightly undersized 1/2 inch ID.

A 1 1/2 inch long tang which is 3/4 inch in diameter is turned on one end.

The part is then turned around and the front of the handle insert is finish turned to create a smooth surface.

Four holes for the set screws are drilled and tapped to 1/4-20. The holes are positioned 1/2inch back from both ends of the main body of the insert.

Tool

The toolbar is made from a 1/2inch x 1/2inch steel bar. The cutter recess is at one end and a tang is milled in the other. The tang on the tool is milled to a square such that it fits into the 1/2" hole in the insert.

The tang is milled to the largest square that is inscribed in the inserts 1/2 inch hole.

Calculate the Tang Size:

The problem is to calculate the size square that will fit snuggly into the 1/2 hole in the handles insert. We will mill a tang on the 1/2 x 1/2 inch toolbar the size of this inscribed square. The tang is inserted into the handle insert and set screw'd in place.

What we know:

Tool bar crossection = .5 x .5

Insert hole r = .5 / 2 = .25 = hypotnuse

angle theta = 45 degrees

Calculate the size of the inscribed square

We need to find the side opposite the angle theta (see sketch above) .

Once found 2x that value is the length of one side of the inscribed square.

Using this trig function: sin theta = Opposite/Hypotnuse

Then transposing to find the Opposite: Opposite = sin Theta x Hypotenuse

Since:

sin 45 = .707 and Hypotnuse = .25

Opposite = .707 x .25

Opposite = .1768

Therefore:

One side of the inscribed square = 2x opposite = (.1768 x 2) = .3535

The inscribed square i.e. the tang needs to be milled to .355 square.

How much must be milled off each side of the toolbar to create the insert tang?

Bar = .5" square

Tang = .3535" square

Mill off each side = .5 - (.3535/2) = .07"

Mill .070 off each side of the toolbar to make a tang that fits the 1/2 inch hole in the handle insert.

Handle

The handle is turned from the appropriate wood blank in the shape and length that matches your turning style. I used maple and since this was for my small lathe the handle was turned just long enough to fit my hand.

A 3/4 x 1 1/2 hole is first drilled into the blank with one end in a chuck and Jacob's chuck in the other. The blank is then held between centers with a cone in the tailstock live center. This cone is inserted into the drilled end of the stock for turning.

The handle is then turned to shape making sure that the insert end of the handle is the same diameter as the insert's tang.

The adapter is then epoxied into the handle.