BobL

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About BobL

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  • Location
    Perth, Australia
  • Interests
    metal, wood, stone, images, problem solving, free wheeling projects, measurement, improvements.

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  1. Artist has pretty well nailed it, especially his point number 3 about It is much better all round to more blade exposed not less. I agree that newbies have to be looked after so for anyone contemplating this idea I would not recommend doing this with any wheel other than a thin (1mm) kerf wheel which is capable of handling these higher revs and if it does shatter represents a much lower risk than thicker wheels. Perhaps a bit of background, I have a variety of metal cutting gear, e.g. plasma cutter, a bandsaw, angle grinders and a 12" chop saw and have used all of these extensively and are used to cut larger pieces. This saw is only used to cut small pieces of tool and other steel that are difficult to cut with these other machines. One incentive for doing this is that I have hearing damage and even though I have several good pairs of ear muffs I dislike noise so the angle grinders and chop saw rarely get usedl. I measured the sound pressure levels of my saw compared to the angle grinder. At 4000 rpm my saw is is 25 dB less and at 9000 it is is 15dB less than the angle grinder. This may not seem like much but it is significant. Comparisons between these thin (1mm) kerf wheels and any thicker wheels are limited. A better comparison is with the 30,000 rpm cutting wheels used on Drenels with no guards. I don't know about others but I struggle to use these wheels on a Dremel without them breaking. Do parts of the wheels fly off in all directions across a workshop ? No - why? read on, Do I use appropriate safety gear when using these - yes of course a full shield - that is all that is needed. There is no need for a leather apron or other protection when using these wheels. As I said before I have been hit a number of times on the hand and forearm by piece off these thin wheels and it is about the same as being hit by wood chips from a fast revving chainsaw. If you leave skin exposed to a continuous stream of chainsaw chips it will eventually draw blood but there is no stream of pieces coming of any broken wheels. The reason they don't do much damage to skin is they have a high surface area to mass ratio so their coefficient of air resistance is very high. as they leave the wheel they immediately tumble and turn and slow down rapidly. Do I use appropriate safety gear when using a chainsaw - of course I do, full chaps, full face shield and ear muffs - people that know me think I am a safety sissy. Do I recommend appropriate safety gear when using this saw - yep a full shield - that is all that is needed. The downside of the slower speed is there is more wheel grit and dust generated which represents some sort of health risk but I have good ventilation and dust extraction. To demonstrate good safety practice I have made a guard for the top of the saw and am in the process of making one for the underneath - however that is mainly to collect the grit and metal dust. The transparent shield is polycarbonate so even though it is thin it it very tough.
  2. Well I also have plenty of experience with these wheel and have used many hundreds of them on an old table saw and in angle grinders. Of the several hundred I would say I have broken at least several dozen and I can reassure you that at low speeds the breakage has always been a non- event. I Have never seen one shatter at any speed and when they do break they usually break of at the arbor mount but they don't fly off in all directions and just flop onto the floor. Any pieces of wheels have broken off have very low momentum and a high surface area so they slow down rapidly in air. The pieces that have hit me (usually I am just wearing a T-Shirt) have never even broken the skin. I do ALWAYS wear a full face shield when using these wheels whether it's on the table saw or using them in an angle grinder.
  3. I know you guys like home shop made gear. Here is a thin kerf metal cutting saw attachment for a grinder that I made recently. The first photo shows the grinder is one of two 1HP 3Phase grinders connected to one VFD with a cross over switch between them. The grinders were originally 415V 3phase and have been converted to run 240V 3 Phase . One grinder was free and the other cost me $40. The VFD converts 1P 240 to 3P 240V and provides variable speed so I can run the grinders a bit slower - much less noise, better control traded off for a bit more blade wear. Apart from the VFD, all parts were either made from scraps or found in my spares box except for the countersunk SS screws which I paid $2.50 for. The large pulley and belt come from a running machine. I machined up the rest - the bearing housing and wheel collars/flanges have also been fume blued. Mitre slide is made of scrap ally. first photo shows how table flips up out of the way for wheel change.
  4. Here's a simple mod to a small bench grinder based linisher I thought you guys might like to see. The top roller (comes from an Aussie wood working sanding accessory to a drill press ) is spring loaded and provides the necessary tension. The roller is are chain clamped to a metal pipe which is itself bolted to a vertical piece of HD Unistrut. The pipe position can be moved up and down the Unistrut to accommodate different length belts (shown is a 48" belt). Belt tracking is handled by the front roller of the linisher.
  5. I have wire wheels on a bench and angle grinder in my shop and I do use them a fair bit, with a full face shield and with a lot of care. Increasingly I find I'm using a wheel that is made up of tightly packed tough pot scouring pads. It has enough abraviseness to clean up flat surfaces without obvious scratch marks (especially on brass and copper) and instead leaves an attractive matte finish.
  6. I started building a belt sander/grinder about 8 months ago but apart from the frame and a view bibs and bobs it's still in pieces awaiting a few components to be turned up. It's designed to be used more for wood than metal so it's current design is for a two roller with 48 x 6 belt, but I was thinking of adding a 3rd outboard belt roller so I could put a longer narrower belt on it. Speed control wise I bought a never used used 3phase 2HP motor for $35 and a new VFD so it can run on single phase and provide a comfortably X5 speed range. I plan to get back onto it in the new year. I'll post some pics
  7. Assuming the connections, wiring, the outlet and breaker are OK. 100ft of 10 ga copper has a resistance of about 0.1 ohms (8 gauge is 0.06 ohms) When carrying 15A this is Voltage drop of about 1.5V for the 100 ft long extension lead. In other words the wire is not going to be a problem Connections could easily double this but should still not be a problem.
  8. Some photos of your setup would allow folks to provide better advice. By a 2ft shop fan, I assume this is some sort of a axial or propeller type fan? If so, these fans cannot generate much pressure and so are poorly suited at moving air along any ducting that is substantially narrower than their propeller diameter. What would be better is a fan that can generate a reasonable pressure in a narrow duct such as an impeller type fan that is used in dust extractors. Whatever you do, if you don't have enough air coming into your shop this is going to cause a problem. Also I notice a lot of folks don't always take preferred wind direction into account. If a shop that is exposed and the preferred weather/wind side comes from the opposite side to the usual opening into the shop this can suck air out of the opening which will reduce chimney draw.
  9. UPDATE The high reached here was 103, tomorrow the forecast high is 106, the day after it's 103.
  10. This might warm you guys up a bit. I was over 100F here yesterday and forecast highs for the next 3 days are 100, 100 and 102F.
  11. I agree with Rich. While zinc Melts at around 790F the amount of Zn vapour produced at its melting point temp is extremely low and the amount of ZnO produced at this temperature would be less than what would be coming out of your forge fuel or is present in normal air (see below). To make significant quantities of ZnO the Zn has to be at higher than boiling (1650F) e.g., commercial production of Zn uses about temperatures of 1750F. If the chain was at that temperature whatever was cooking in the pot would be well and truly on fire. On this basis I'd say you would be quite safe to use it for your purpose. BTW few people realise that air already contains relatively high amounts of Zn and ZnO dust. It comes from a wide variety of sources including natural and man made fires, soil/rock dusts, and exposed galvanised metal, but more significantly in urban settings from something called zinc stearate dust generated by motor vehicle tyre wear where Zn stearate (a form of soap) is used as a vulcanisation and tyre mould release agent. As tyres wear, thousands of tons of rubber and accompanying Zn are produced as a fine dust that moving vehicles throw up into the atmosphere and any light breeze will carry it for miles. The grey gooey dust that sticks to insect screens and air filters and computer fans contain significant amounts of this stuff. On its own Zn stearate is not considered dangerous but any of this dust that enters a flame or high temperature zone will be converted it into ZnO. I don't wish to scare anyone but to demonstrate that humans are already exposed and seem to tolerate some ZnO.
  12. I agree with DanielC. In my limited experience I found I can get much finer control by letting a blower run at it's most comfortable speed and setting up an extra outlet and tap or flap that enables excess air to be spilled rather using a dimmer or restricting inlet or outlet flow.
  13. "Lead free brass" is a matter of interpretation. Just about all brass has at least 2% lead added to it to improve its machinability, but brass may still be called "lead free" even if it contained higher amounts than this - as much as 4% in some places. In 2010 CA introduced a mandatory max of 0.25% lead on so called "lead free" brass but there is a heap of old stock out there apparently still being used up and I guess one question to ask is, who if anyone is keeping an eye on this? I wonder if it really matters in the case of gas fittings, unlike chlorinated/carbonated water it's not like the lead is going to be that easily leached from the metal.
  14. Another issue not thought through with wire wheels is the use of guard that can cause the wheel to grab some objects and drag them around inside the guard and fling them back at the operator.
  15. My favourite metal cutting saw is this used small metal cutting bandsaw that I paid $100 for. I added an aquarium pumped coolant loop that does increase cutting speed but the blades last a lot longer It's supposed to be limited to cuts that are 6 wide x 4" tall but I have modified it so it can cut 7.5" wide. It's slow but quiet and accurate and you can leave it do its thing and it turns itself off when the cut is finished. It also stands upright and can be used to cut curves. I used this saw to cut the 6" radius of curvature curves in 1/4" steel plate for the back and front doorway flanges for my gas forge. The other metal cutting saw that I have thought about getting rid off several times but doubt I ever will, is a small (8" 1.5 HP) woodworking table saw in which I put thin kerf 5" cut off wheels. Because it's belt driven, the motor is well away from the blade so I can use water cooling and cut small stuff and hold the pieces quite close to the wheel without cooking ones fingers. The water cooling also suppresses the grit and dust thrown into the air but cut off wheels. The standard fence and mitre slide can be used and it's much easier to use than an angle grinder to ripping up small/medium pieces of sheet metal. Being only 2850 RPM it's slower slow than an angle grinder but It's MUCH quieter and I have less concern about getting my hands close to the wheel. I have used 100's of wheels on this saw. Since I got my bandsaw I have used is mainly to cut stuff like tool steel that is too hard for the bandsaw.