Kovant Report post Posted January 7, 2023 Hello I need a machine to polish and sand leather. I have seen that the usual is to buy a bench grinder, a sanding drum and a polisher. The problem arises because I need the sander also for sanding rubber soles. I have read some people that having a bench grinder over 3000 RPM is bad for the rubber soles. So I have 3 options and I don't know which one to choose. 1 - Bench grinder with variable speed. https://www.rapidonline.com/sealey-bg150wvs-bench-grinder-150mm-variable-speed-94-3199 2 - Bench grinder of about 2000 RPM (will it go well for leather and rubber sole?). 3 - Bench grinder of approximately 3000 RPM (will it go well for leather and rubber sole?). https://www.rapidonline.com/draper-29620-230v-150mm-heavy-duty-bench-grinder-91-5507 I also have a question regarding the sander. 1 - Sanding drum with groove. I can put any sander I want on it but I don't know if the slot will leave any kind of imprint on the leather or rubber sole. https://www.justwood.com/buy/75mm-sleeveless-drum-sander_34.htm 2 - The regular sander drum (there are less sandpaper grits to choose from). I would really appreciate it if any of you could help me with this. Thank you very much Best regards Quote Share this post Link to post Share on other sites
kgg Report post Posted January 7, 2023 3 hours ago, Kovant said: I need a machine to polish and sand leather. This is what I done which may give you some ideas: kgg Quote Share this post Link to post Share on other sites
Kovant Report post Posted January 8, 2023 Thank you! You have done a great job! But I still have the same doubts. Best regards Quote Share this post Link to post Share on other sites
kgg Report post Posted January 8, 2023 On 1/7/2023 at 10:39 AM, Kovant said: 1 - Sanding drum with groove. I can put any sander I want on it but I don't know if the slot will leave any kind of imprint on the leather or rubber sole. https://www.justwood.com/buy/75mm-sleeveless-drum-sander_34.htm You need to increase the speed slightly so the sanding drum acts like a sleeve drum. On 1/7/2023 at 10:39 AM, Kovant said: 2 - The regular sander drum (there are less sandpaper grits to choose from). The rougher the grid the faster the drum needs to spin or it can feel like you are hooking / tearing the material rather then sanding. Just my experience. kgg Quote Share this post Link to post Share on other sites
Kovant Report post Posted January 8, 2023 Thank you! I still have these doubts: Drum with or without slot? If I have not misunderstood if I give more speed to the one with groove it acts as one without groove, is it so? How many RPM for the leather and for the rubber sole? Thank you! Best regards Quote Share this post Link to post Share on other sites
TomBanwell Report post Posted January 11, 2023 I too would like to know the ideal rpm for sanding veg tan edges on shoes. Anyone? Quote Share this post Link to post Share on other sites
kgg Report post Posted January 11, 2023 On 1/8/2023 at 10:41 PM, Kovant said: Drum with or without slot? If I have not misunderstood if I give more speed to the one with groove it acts as one without groove, is it so? Yes the faster the slotted disc rotates the more it acts like a solid disc. kgg Quote Share this post Link to post Share on other sites
RockyAussie Report post Posted January 12, 2023 Rubber soles need fairly rough sandpaper to cut away well and that means the grinders you show above lack the horsepower to do the job. A 1 horsepower would be a better choice. The https://www.justwood.com/buy/75mm-sleeveless-drum-sander_34.htm link is reasonably useful up to a point and I have used it for sanding edges of leather when making belts etc. This link shows a video where I have used a couple of 1/3hp motors and similar sanding drums to sand belt edges if that helps - What rpm is ideal will depend on the diameter of the sanding drum as the surface contact area is what is what counts. The smaller the drum the slower the contact speed. On a 6" drum 3000 rpm will be too fast. I would think about running a transfer pulley set up to allow for changing speeds to what ever you find works best. As a rough guide I would expect a rpm of around 1500 would be a good starting point for most applications as long as the motor has sufficient horsepower. The pvc pipes do work well for the dust extraction and they are attached to a 2 hp extractor unit. Quote Share this post Link to post Share on other sites
Kovant Report post Posted January 12, 2023 Thank you very much The problem is that in Europe it is very difficult to find bench grinder with variable speed. Bringing it from the USA is very expensive because of shipping and taxes. I have asked to buy one with fixed speed and convert it to variable speed and the thing is quite complicated and the price goes up a lot. Unfortunately I will have to make do with what I can. Best regards Quote Share this post Link to post Share on other sites
Matt S Report post Posted January 12, 2023 @Kovant if you truly want a variable speed you might need to look at a 3 phase motor/machine and a variable frequency drive (VFD). Those little machines with "variable speed" tend to bog down under any appreciable load because they have a very simple variable speed circuit that just cuts out a proportion of the wave according to the dial setting. Also, in my experience, those small DIY/"light/occasional trade" bench grinders have a short duty cycle meaning you can't operate them under load for long before they overheat. Alternatively some higher-end machines are available which allow selection of a couple of speeds (using pole switching I think), but I don't know if these will give you the needed range or granularity of options. A pair of cone pulleys between motor and wheel will give you a wider range of speeds with the added advantage of higher torque at low speeds but the disadvantage of fiddly speed changes and general bulk. As I'm sure you know, professional shoe makers and repairers use a big finishing machine for this purpose, with wheels and attachments for grinding/sanding a polishing. They are large and expensive however. I believe that they turn relatively slowly, as I was recommended to not turn one of the big horsehair polishing brushes faster than 900RPM and they tend to share an axle with the sanding wheels. Depending on your budget and space, maybe consider a good quality belt sander with variable speed. The 2x72" types that knife makers use look great. Or, for a cheap option not used very often, stick a sanding drum in a basic bench/pillar drill with variable speed. Prolonged radial force will wear out the bearings but that'd take a while to do. Plus the drill has many other uses. 16 hours ago, TomBanwell said: I too would like to know the ideal rpm for sanding veg tan edges on shoes. Anyone? There is no particularly ideal RPM for leather. Machinists talk about "surface speeds" (how fast the cutting edge of their tooling moves) which I think is more useful, and use the spindle speed to calculate it. If you have a 2" sanding wheel and a 8" sanding wheel on a 3,000RPM motor the sandpaper on the 2" one will be doing 1,572 feet per minute and the 8" one 6,288FPM. With equal pressure applied the 8" wheel will remove material faster than the 2" one but will be hotter and more likely to burn. Within a certain window it's possible to adjust your pressure to not burn the leather on whatever speed sander you have. I have one of those ubiquitous little 1x30" belt sanders which can either burn leather in seconds or be make a beautiful clean edge depending how heavy handed I am that day. Quote Share this post Link to post Share on other sites
Kovant Report post Posted January 12, 2023 Wow, what a great explanation! It's all very clear to me. Thank you very much Best regards Quote Share this post Link to post Share on other sites
