Tuesday, January 12, 2016

Wood Lathe Duplicator with Angle Grinder

My version of a Lathe Duplicator was inspired by The Homestead Craftsman, and his video entitled Homemade Wood Lathe Duplicator using an Angle Grinder.  Basically, the only things I changed from the original design is the grinder blade, and the table surface of the duplicator.  My modifications were made to create turnings with a little finer detail and less clean-up, which the carbide cutter provides, and more versatility and adjustability for mounting the pattern to the table top.

Laminated 16ga steel table top and pattern secured with Magswitch Model 150 magnets.
The angle grinder has a Viel Tools Model D-15-80-5 Carbide Cutter.

While searching the internet for Lathe Duplicators using Angle Grinders, I ran across the Viel Tools Lathe Duplicator, and was very impressed by their Angle Grinder Carbide Cutter.  It is the Model D-15-80-5 Carbide Cutter which has 5 diamond shaped carbide inserts (probably a VCGT-332 35° Diamond Carbide Insert), and the cutting radius of the tips are 1/32" for getting into those small details of a pattern.  Secondly, the cutter is capable of cutting with the side of the insert, which makes removing material much easier.  I recommend cutting the finer details in the clean-up phase with the tool rest and spindle gouge or skew chisel.  Details like small birds beaks and such are too delicate to cut with the duplicator.

One big advantage of duplicating with an angle grinder is the slow RPM speed of the lathe (~650 RPM).  This reduces chatter and vibration, and allows you to cut thinner and longer spindles.  Thus far, I have cut spindles with sections as thin as 5/16" (as pictured above and below), and as long as 24". Currently I'm building four Windsor Chairs, and the duplicator made turning the spindles, 13 per chair a breeze.   I highly recommend using the Woodturning Live Center with Collet Chuck and Drawbar to reduce chatter and vibration on the spindles.

I don't think the direction of the lathe makes a difference at 650 RPM because the grinder is turning a 4.5" Diameter cutting wheel at 9,500 RPM (measured with no load).  If my calculations are correct, the tips of the cutters are moving at 127 MPH (57 m/s), and the outside of a 1" Diameter dowel turning at 650 RPM would be moving at 1.93 MPH (0.86 m/s).  The surface of a 3.5" Diameter dowel would turn at 6.77 MPH (3.02 m/s). I'm not sure if plus or minus 2-7 MPH will make much difference, but it could with the larger diameter stock.  As mentioned before, the low RPM of the lathe probably reduces chatter and vibration.  I tried turning in both directions with the smaller stock, and I haven't noticed a difference.

Turning a spindle with 1/2" diameter on left, and 5/16" diameter on right side (length = 11").  I realize that the pattern should
have been flipped, but the duplicator was capable of cutting it with this orientation with very little chatter...as long as you
remove the majority of material on the photos left prior to removing it from the right side.
24" Spindle with 1/2"D on left side and 5/16"D on right

Duplicator Templates

The 1/4" thick patterns are attached to 19mm thick piece of plywood with 10-24 threaded brass inserts to secure them to the base.  Thus far I have two bases.  The base pictured above is 19mm x 85mm x 458mm, and the larger base is 19mm x 85mm x 712mm, and uses four Magswitches.

The bottom of each pattern base has 100 grit sandpaper glued to the surface for extra holding power.

Operation of the Duplicator

WARNING! - The Viel duplicator blade is very aggressive, and can remove a lot of material at once.  You must, and I repeat MUST remove the material slowly and with shallow passes, or the blade could grab and cause some damage to the work piece OR worse yet - YOU.  Use shims similar to those I'm using below to reduce the possibility of the blade grabbing.  These shims provided a guide for the removal of material in 1/8" - 3/16" increments, which was speedy yet safer.  Version 2 of the Template Follower reduces the use for shims, and provides and incremental method of removing stock with the Depth of Cut Turret.

Roughing the stock is much easier and safer if shims are used to guide the duplicator along the piece in order to remove only the desired depth of cut.  The duplicator is capable of removing large amounts of wood, but the results are better and the process is much safer if smaller amounts of material are removed in a more controlled manner.  I cut several thicknesses of shims that fit beneath the pattern, and can be removed as needed to control the cutting depth.  This can be seen in the photos below.  The need for shims are less likely with Version 2 of the Template Follower and the Depth of Cut Turret. The STL files for these parts may be downloaded from Thingiverse "Wood Lathe Duplicator Components".

The follower is in contact with the shims to control the depth of cut.
Version 2 of the template follower with depth of cut turret.

Close up view of template follower and depth of cut turret.

Depth of cut turret.  This device will eliminate the shims used in the picture below.

Tool Rest

One other item I added to the original design is a tool rest which is attached to the table top with Magswitches.   I used an old tool rest from a previous lathe to make the following rest, which works very well.

Tool rest with Magswitch base.

Grinder and Mount Assembly

One major disadvantage to this duplicator is the price of the Viel Carbide Blade, as well as the price of the Magswitches.  However, the blade is well worth the investment.  If you compare the price of this blade with any milling tool with carbide inserts, you will realize this item is reasonably priced.  As for the Magswitches, you will discover from some of my other post that these should be a 'must have' item for every shop.  I highly recommend the 40mm Magswitch (Model 150) because they have more holding power on 16ga steel.

I tried using a inexpensive import angle grinder, but found the quality of the cut was unacceptable.  There was far to much play in the arbor, and it resulted in a very rough cut.

In order to stabilize the grinder in the mount, I added a piece of plywood to the front to reduce any twisting action of the grinder within the mount.  The photo below shows the piece of wood I added, and the bolt I screwed into the threaded handle hole on the bottom.

Bolt that attaches grinder to base

Duplicator Table Construction and Assembly

The bottom of the lathe mounted duplicator table.  This is 3/4" Melamine board, which was the flattest and largest piece of scrap sheet good that I had in the shop.  I biscuited a couple of wings on the side to give me more table surface to support the grinder.  The top of the table has a small sheet of 16ga steel contact cemented to the surface for use with the Magswitches. The duplicator table is fixed to the lathe bed with the a piece of plywood that fits tightly in the slot between the lathe bed ways.

Slot for 7" long carriage bolt head to be inserted.  A large washer with a slot cut in it to
for the carriage bolt is sandwiched, screwed and glued between the two pieces of plywood.

Carriage bolt and nut

Carriage bolt in slot - Bottom of table

Examples of Turnings and Templates

These are some full scale patterns I'm currently using to duplicate the spindles, balusters, legs and stretchers
for a Windsor Chair.
Windsor Chair Spindles 24" and 22".

WARNING! - Read and follow all manufacturer instructions, and use this Lathe Duplicator at your own risk.

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