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I think you have had a great idea, the coating on drill bits does seem to hold up to really extreme wear doesn't it? I will do some searches and see what I can find about this. I have found out a bit about ceramic coating and whilst you can quite easily source the liquid product, it does seem to...

Sorry gearcutter I seem to have posted at the same time. Yes it amazes me as well about the screws being worn out and the machine still operates, we get an operating indication that the time has come to change auger elements by surging in the machine happening actually quite suddenly. Once it...

Yes, I have been really thinking about the case hardening aspect for the last hour or so, one point that keeps recurring is I SUSPECT that the outer extremities of the part, also the 0.5mm case are the bit that would see the fastest rate of wear, in fact a convo I had here 2 or 3 years ago keeps...

My mother has a furnace for firing clay porcelin dolls, I could probably quite easily set up some sort of temperature controller. My father uses sort of putty cones that collapse when a particular temp is reached but that would make keeping a constant temp difficult. I suppose any cracks would...

Thanks, first Q for gearcutter, when I have my gears made I have the gear guy case harden the spur gears (8620 if memory serves) I have wondered if the teeth are cut before or after hardening, or maybe a combo of both, rough cut, harden, finish grind?? The reason I ask is the actual gear teeth...

The parts that are wearing actually wear as much on the core diameter as the flights, I think I want to investigate the through hardening process. All I am figuring is that if I can harden them even a little bit then they should last a little longer. I figured that I would like to know what...

A number of years ago I designed and made an extruder for making powder coatings. I have been using the prototype machine for 5 years now and made a similar new machine two years ago and both operate well. I am now designing a beefier one that has a stronger gearbox to reduce breakage down time...

Thanks for you reply TVP. Am I right in saying?: "The method of hardening that we use is tempering, other methods of hardening are neutral hardening and carburizing"

Hello, I own a business that makes a plastic product and we are using self designed and made extruding machines. As part of our "machine design improvement" process we have come around to improve the quality of steel used, by heat treating and I am now coming across terms I only very slightly...

Thanks everyone. The EDM route has proved very costly. I have 12 pieces to do right now and then repeating in dribs and drabs over time. I can drill the hole within reason as deep as I like. I can probably increase the bore diameter after the 2" deep bit where the male hex will insert. From your...

I need some advise on how to broach a hexagon into a BLIND hole. The workpiece is 2" diameter, 22" long and I need to have a 3/4"AF hex Female hole put into both ends about 2" deep. Like a cap head screw. Can anyone advise me on how to do this?.

OK, thanks everyone for the advise. As I said earlier the shaft photos were of the old ones. On the new design I have consistantly doubled the cross sectional area of the shafts in almost all areas. I can change the keyway spec. What are you general feelings on doing away with key and using...

Sorry desertfox I didn't answer your question. The three shafts in question did fail at a shoulder and the two bigger ones (the input drive shaft) failed at the other end to where the pulley (sheave) is. The smaller shaft failed at the right hand side of the gear - the other side to where the...

Thanks Guys. I was concerned about the gears as well and I stripped the box down again with intention of changing them out. I agree and am going to impliment everything that you guys have advised. For the short term I have to get the machine running for production. Hopefully the NEW (today)...

Here is a picture of the intermeshing screws of the extruder. These are an old set but very similar to what is running now. The powder coat premix is intraduced into the auger flighting at the far right hand side and then conveyed towards the kneader blocks on the left side. Only the left side...

Here is a plan view of the gearbox with the top taken off. For scale the diameter of the input shaft is 40mm where the pulley or sheave sits. The gearbox output is 5/8" Hex. This is the "new" gearbox after 6 hours...

Here is the photo of the damaged shafts.http://files.engineering.com/getfile.aspx?folder=9351cb11-dff4-4b27-903e-57baf3da745f&file=DSC_0195.JPG

Ah. now that we are on load of bearings. The original small dia shaft gearbox bearings never failed, however I always changed every bearing everytime I changed a shaft ~ every two months ish. Now with the new big shaft gearbox I have had to change to a smaller OD/ID difference dimension, I mean...

Thanks Engineertex. Yes the shop next door said they could send away to case harden the shaft and then they could grind to size. I think he just said he could do it if I wanted it rather than really suggesting that I needed to do it. I get the impression that you lot know more abot the metal...

OK, I have found a supplier of 4340 with heat treated yield strength of 115K PSI and 112K PSI for 1.75" diameter and 1.25" diameter respectively. The metologist (sorry if spelt wrong) is on vacation until Tuesday. I wanted to check two things here: 1. Is the steel still machinable? 2. Can the...