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• koko

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Home built 17” vertical bandsaw. Preamble This machine has largely been made from parts that I had kept for a rainy day and bits out of the scrap box. The only items which had to be bought were the wheels, the saw blade and the motor drive V belt. Therefore much of the design has been dictated by available material. There are no drawings nor even rough sketches available because none were drawn. I mostly make things like this without sketching first. However I believe that the value of descriptions like this lie in the various ideas transmitted rather than in any detailed plans ready to be copied as presented. In any case everybody’s scrap boxes contain different stuff. My need for a bandsaw is primarily cutting metal, mainly Aluminium but also some mild and alloyed steel. Occasionally I will cut wood but I will be happy enough to run the band speed at the highest Aluminium speed for that. A saw principally for wood only can be more easily made using a single belt speed reduction thus simplifying the construction. I use a 25:1 reduction gearbox that I had, combined with a pair of 5 step belt pulleys which gives a nice speed range for my needs when driven with a 1500 rpm motor. I have made several video clips during construction and I’ll post links to one or more videos when I have had a chance to edit them together. This document is mainly a collection of photographs with some explanation of the thinking behind some features.

Wheels I wanted a bandsaw with a throat of around 16" and I thought that wheels from a moped might be a good starting point and i found a couple at a local Saturday flea market. They were from different mopeds but one was a front wheel with bearings and brake. The other was a rear wheel without bearings for a single sided mounting. The wheels turned out to give a 17” diameter.

The yellow wheel was a front with bearings, the blue was a single sided rear without bearings. Firstly I was disappointed with the absence of bearings in the rear, thinking that I would have to make a bolt-in bearing housing. However as we'll see, it worked out really well.

From the beginning I knew that the rim shape was not suitable as the surface for the saw blade to run on but I thought that it would be easy enough to fill the well with polyester car body filler. It is easy to apply, sets hard, easy to machine and adheres to metal very well. With a rubber belt glued on it would be protected from the saw blade teeth. Most ot the outer rim would need to be machined away. I am planning on running 1/2" wide blades and so a final rim width of a bit over double that seemed about right. I knew that holding the wheels near the centre would result in chatter on the rim when turning so to reduce the amount of turning I used my little 55 year old Burgess bandsaw to cut off as much of the surplus rim as possible. In the 1970s I had a business making cast wheels for motorcycles and so I was well aware of the machining requirements. Back then I had mounting fixtures which held the wheels by the inside of the rim to prevent chatter but to repeat similar fixturing for these two wheels would have been way too much work for a one off job.

On the left; is the original rim shape, centre; shows sawing the outer rim off, right; the cut down rim section. After sawing, the major part of the machining was to narrow the rims and chatter on the sides would only be a cosmetic issue and I decided to call it knurling. Only minimal machining was needed to true the outer diameter. I used paint stripper and finished with bead blasting to clean them up, with particular attention to the rim well to ensure a good surface for the filler.

On the left is the lower wheel after filling, to the right is the top wheel after machining the crowned surface.

Back in the 70s I had lathes big enough to swing wheels over the bed but those days are past and fortunately my current lathe has a gap bed, so for the first time since new I removed the gap to be able to swing the wheels. I jury rigged a tool holder extension to fit out around the rim, as shown in the following.

I had a 25:1 gearbox which looked to be a good way to get the blade speeds suitable for metal cutting, the output of which was a flange with 3 studs. After offering up the rear wheel it became obvious that I only needed to make a spacer to fit the wheel onto the gearbox, no need to make a bearing carrier after all.

Both sides of the unfinished spacer. The non-central hole and piece missing from one side is just something that was in the block out of the scrap box. Note the register in the centre of the wheel.

Each side of the finished spacer.

Spacer fitted to gearbox and wheel.

Wheel mounted on gearbox.

Table This was made from two pieces of 6mm steel plate to get the required width because that is what I had. The outer rim has angle iron around it for stiffening and also to give me something to attach guides and fences to in the future.

Size dimensions are given in mm.

The table is clamped to the pillar of the drill to hold it true for drilling the bolt hole to stiffen the table at the slot cut for blade replacement. My experience with bandsaws has taught me that I rarely need to set the table at an angle and for simplicity of construction I was tempted to make it fixed to only allow cutting at 90 deg. It is usual for bandsaw tables to be mounted on trunnion style bearings with the centre of rotation in line with the blade at or near the top surface of the table. This ensures that the blade remains reasonably centred relative to the hole in the table. To make a quality implementation of such a system would require more time than I was willing to devote to a feature that I am unlikely to use often. I wondered if a tilting table could be made with a simple pivot. Also if I was to make a tiltable table I would want it to tilt up to 45 deg. The obvious place for the pivot would be as close to the underside of the table as possible and inline with the blade. This would work but the hole in the table for the blade would move sideways relative to the blade. That could be accommodated by making the hole wider, but I

didn’t like that idea. Then it occurred to me that if I offset the pivot appropriately, the degree of lateral blade/table mismatch could be reduced to a trivial amount as shown below. The secret is to mount the pivot as high up as the table would allow and then calculate the offset to give a +/- 22.5 deg movement either side of mid tilt.

The completed table shows the two short tubes near the blade slot which form the tilt pivot. To the left of the picture there is a short bracket which is used in conjunction with the stay shown below to set the table tilt angle.

Gearbox and table mounting subassembly This is probably the most complex part of the whole job because it performs many functions and much of it must be made very true. In some cases that requires milling welded tubular structures with the attendant potential problems of chatter.

The previous photos show the gearbox mounting bracket, made from 3 mm steel sheet. Below we see the bracket welded to its support tube and then with wheel and gearbox.

The next stage to this subassembly was the addition of the table pivot mounting tube and a block for attaching the lower blade guides. Both sides are shown above. The guide block mounting was milled squared to the gearbox mounting surface, and drilled and tapped for mounting bolts, as shown in the following..

Guide block mounting and the guides. The slots in the guide block carrier will be made after the saw is assembled and the blade aligned. The slots will allow height adjustment which is necessary when using the bandsaw with the table tilted.

Showing the multi task subassembly fitted to the table, in both the 90 and 45 deg positions. Remember that these pictures are inverted. Note how the table pivot works.

The next feature to sort out was how to mount the drive pulley. The input shaft of the gearbox was just a short piece of hexagon shaft, not at all suitable for holding the pulley. I decided to mount the pulley on a shaft supported by bearings on each side. The question then became “how to hold the bearing in mid-air”. The inner one turned out to be fairly easy. Surronding the gearbox input shaft was a shallow circular recess which was concentric with the shaft. I mounted the gearbox in the mill with the shaft upright and centred it with the recess, fitted the gearbox support bracket and bored a concentric but smaller hole in that. A top-hat style bearing bush could then be pressed into the gearbox bracket and sandwiched between bracket and the recess in the gearbox. I fitted two small bearings to take the inner end of the pulley shaft. The shaft extends through the bearings and had an internal hexagon cut to match the input shaft. A quick test showed that the shaft would spin with minimal friction indicating that both the pulley and input shafts were aligned very well.

Showing the recess.

Checking mill alignment.

The inner bearing housing. On the left is the gearbox side, the OD spigots into the gearbox recess and acts as a large aligment dowel. On the right the pulley side is shown. After being forced into the hole in the steel plate from the other side a sleeve with an interference fit is pushed over for additional rigidity and security. The outer bearing mounting was more of a problem because there was no nearby or obvious support structure. I welded some stand offs on the support tube, the outer ends were drilled and tapped to bolt on a plate to hold a bearing boss. The gearbox was squared up on the mill again and the ends of the standoffs were milled parallel to the gearbox mounting face. Then the mill was centred on the inner bearing boss. The plate was bolted in place and the hole for the outer bearing boss was bored concentric with the inner one.

The scrap box yielded this piece of 6 mm aluminium plate for the bearing boss carrier.

Double checking horizontal alignment.

Aligning to the inner bearing bore. Note the two standoffs to hold the outer bearing plate.

The bearing plate being bored to accept the bearing boss. The plate is held onto the standoffs by counter sunk screws because they are quite repeatable for positioning and do not relay on a tight fit which is necessary with normal bolts or dowels.

Machined outer bearing plate with and without the bearing housing fitted.

Although the bearing housing was a loctited interference fit I added a couple of 4 mm insurance screws on the circumferal junction.

The above two photos show the pulley and shaft supported in the bearing housings.

Upper wheel mounting subassembly. This is to hold the upper wheel in place, tension the blade, permit blade tracking and support and adjust the blade guide block. There are several possible designs that one could use for this but my decision was based on what I could find in my scrap box.

Once I saw this bent lump of steel I formed an idea of how to support and adjust the wheel. The design of everything else on this subassembly then followed logically.

A rod was welded across in the corner and will run in a pair of channel guides. The hole to the right of the picture was already there and will be used for the blade tensioning rod. The hole at the top of the picture is for the wheel axle.

On the left is a trunnion which is cross drilled and tapped to take a piece of 12 mm threaded rod. To the right is shown how that is used with the wheel support bracket to tension the blade. Although shown horizontally in the picture this will be mounted vertically on the saw.

Shown here are the guide channels for the wheel bracket. I didn’t have any square section bar large enough to mill these from so I fabricated them by welding two lengths of angle together. I made the width slightly undersized and after welding I made a couple of light passes of the mill to clean up and size the rubbing surfaces. The one to the left is prior to machining, to the right is after.

Basis of upper subframe, ready for the guide channels. The extension to the right on the lower member will be used to support the blade guide mounting.

Upper subframe with guide channels and wheel support bracket in place.

Main frame construction

The basic support frame, the previously described upper and lower subframes will get welded to the large upright.

Lower subassembly supported by a clamp to the left and a pole on a screw jack to the right. The subassembly was adjusted to be true to the base of the main frame and then welded.

Left, the frame with the subassembly welded in place. The dark coloured tube is for support. Right, the wheel is has two black straight edges clamped for alignment of the upper wheel.

Showing how the upper wheel gets aligned with the lower one, using the clamped on parallel upright bars.

The upper subframe was carefully aligned using the uprights and then welded in place.

Once the top frame was welded, the final job was to align the top wheel to the lower one and then fix the axle to maintain the alignment. By fixing the axle last, any welding distortion that occurred when adding the upper frame is compensated for. That concludes the main structural aspects of the saw, all that remains now is a safety blade cover on the non cutting side, adjustable upper blade guide mounting and the motor mount.

The previous four photos show the motor mount from folded 3 mm plate, the non-cutting side blade cover to prevent accidental hand or work piece blade contact. The cover was made by slotting some rectangular tube. The blade guide support is more fully described next.

To hold the aluminium block with the guide rollers I machined a clamp from a block of steel which was welded to the support tube. The hole in the clamp was machined after welding to ensure squareness.

Machining the hole for the guide block after welding.

Two views of the guide support after machining and associated components.

The guide support tube runs in this bushing made from two pieces of angle iron. The internal surfaces were milled prior to welding. The side is fitted with a 2 mm “shim” for two reasons. 1. It widened the necessary tolerances on the width of the bushing. 2. It spreads the locking bolt loads and prevents marking the support tube. Two short pieces (around 8 mm) of the same shim material are welded into each end of the bushing to prevent the shim sliding out during use.

Blade guides, guide block and vertical support. To the left is shown the bushing for the support prior to welding to the main frame.

The following photos shows the completed frame, ready for assembly and then the completed machine.

I searched the net for specs on 16” bandsaws to ascertain typical table heights. They seem to range between 900 and 950 mm. Even though I am average height at 1.74 m those table heights seemed a bit low and I made this one to be 1 m, which feels ideal. I tend to make my work benches higher than most people also, it is much easier on one’s back. I added some finishing touches. A storage box for spare blades etc. and a top wheel safety guard.

Build videos is now available on YouTube at https://www.youtube.com/playlist?list=PLyn2snGjYlHwAxRqLijO1hdmUIYO28Def