Member postings for Neil Lickfold

Sam, What is your Milling machine? There is a big difference in rigidity between machines and in particular the rigidity of the column. I myself refer carbide cutters now days. Out here in NZ they are about the same price as HSS if they are 10mm and smaller and last a whole lot longer. Being as you are on a manual mill, the carbide will work very well. I don't think carbide cutters come in screw shank for Clarkson type holders though. All that aside, with you making the T nut exercise, in mild steel, 600 rpm seems about right. Depth of cut could well be on 0.5mm on your mill per pass if it is not rigid enough. If your machine has ball screws, that makes it very easy to climb mill. But a non ball screw mill, you are best to be conventional milling. If you can't make the pass in 1 go, ie you have a 12mm cutter and the part is 14mm wide, I would be cutting at just over 7mm wide pass each way at what ever cut depth that did not labour or load the machine too much. Coolant or one of those air misters that will blow the chips away from the cutting surface and cutter flutes as well. Milling on a manual mill in the home workshop is no where near the speed or feed of a substantial cnc machine. The Gibs on the X,Y,Z really need to be correct, ie there is slop in them. The gib lock or slide lock should take very little to create resistance on that slide. When we used to use old worn out bridgeport mills, we used to lock the axis we were not using, and the axis we were using used to just sinch up that axis, so it could be turned ok with a slight drag. Even with carbide cutters on your home mill, you probably will still use similar speeds and feeds and the cutters will last you 5 times longer over your HSS. Try using a smaller cutter like an 8mm or 10mm diameter cutter. They will put less load on your mill and are slightly cheaper as well.

The formula I use is (318.3 X cutting speed of material )/ diameter of cutter or work piece. For mild steel I use 25m/min eg (318.3X25)/12=663 So choose the closest to it, but I would not run 700 rpm , I would run slower with HSS cutter. Feed rate is from 0.03 to 0.1 mm per rev per tooth. In softer materials like free cutting MS the feed rate can go to 0.2mm per tooth, but the depth of cut is limited to how solid your machine is. If you are cutting harder / stronger materials, the cutting surface speeds go down and you may need a lower depth of cut. I suggest at 0.5mm depth and if all is good keep going deeper until it sounds loaded or as you have described, starts to really shake and rattle. There is no point in taking big cuts and wrecking the machine.

Neil

I look at it differently. If the part needs tensile strength, use a high tensile steel. If it needs to be rust resistant, stainless tool steels like Stavax is really good and very stable after heat treatment and ok to turn etc. Another good steel is P20 or 718 and other numbers. It is pre hardened to about 30 Rc and gives a very nice finish as well. I don't make much where MS is a good choice so I don't buy it. I can't see the point in making something and then making it again because that material choice was not the best. There are many things that MS is an ok or in some cases a good material choice. Learning what you need in a material is always a big help in what you are making, so is researching what the part has to do and the appropriate material for that situation. Neil

You can make scarping tools from O1 tool steel and double temper at 150C or very light straw colour. This will be about 61 Rc hardeness if it is good O1 steel. Scraping takes time to learn and it's work taking the time to learn it.

Neil

Thanks for the thread charts Rod. Neil

If you use 7075, I would recommend a bronze bush in the big end and little end. If you use 2024 or 2014, it will be ok without a bronze bush in the big end and little end. Make sure you have a good surface finish in the little end to help stop it from flogging out. Small end wants to be about 0.01mm max diameter clearance, The big end or the crank pin end wants about 0.05mm to 0.07mm diameter clearance.

Edit, Make sure you have the grain of the material in the line of the rod, ie, running length wise. If you do not know the grain direction of the material, I do not recommend using it for a con rod.

Neil

Edited By Neil Lickfold on 29/09/2016 10:09:39

On larger calipers of repute, they will give you a formula to calculate the error due to temp of the part being measured and the error of the instrument itself at different intervals or lengths. We call calipers very nearly there's. If you are within 0.02mm that is about right. If a 100 mm gauge block shows to be either longer than 100.01 or shorter than 99.99 mm , either the temp range is way off, the instrument is junk or you are not operating it correctly. Some come with a sprung slider that allows the user to use a fairly constant pressure when taking measurements and setting the reference zero. A ball bearing race is a good easy way of checking for outside comparison dimensions and inside diameter comparisons. Of course if you are after precision, you would not be using a caliper anyway. I have had a really good run from Mitutoyo digital calipers and also with the cheaper Insize brand 0-200 caliper that brought a couple of years ago. The Insize come with a test certificate and it conforms well to the gauge block tests I have done with the instrument. The very cheap calipers I brought quite a few years ago, are just that cheap and are ok for wood work where you do not need better than 0.1 from size. You can use a piece low stretch fishing line, wrap it around the part 10 times is a lot more accurate on straight diameters and using a rule or tape measure to get the total line length.

Neil

Ray, with the ER series for work holding , you can make a set of collets that are only split in the front only. These will hold work pieces without needing a support ring in the back. But are only really any good for a small holding range. From size to about 0.05mm on diameter smaller. It will keep a concentricity of 0.01mm. The other option is to use a collet size bigger than you need and then make a series of split sleeves to hold the parts. The sleeve only needs to have a single slit and depending on the length of part the slit may only need to go 1/2 way to 3/4 down the sleeve.

In my experience with the Hardinge style C collets, they only are any good at size and up to 0.05mm smaller than nominal. At 0.1mm under nominal, they don't hold parts to better 0.01mm . The C series collets , they make blank collets in steel and Delrin. These come with 3 pins for boring to a particular size and geometry required. They are a lot more work to make in the home workshop compared to the simple ER series collets. Orientated collets when bored in position will be as accurate as you can achieve on your machine.

Neil

John, go for the slim line castle nut over the regular nut. It will give you more room to see what you are doing.

Neil

Hi John, Only the ER11 with the castle nut collet , has the front of the collet face recessed relative to the front of the collet nut. The regular or standard ER11 nut which is a larger thread on the collet holder, and uses a Hex nut design similar to ER16, 20,25,32, all are about flush or close to flush on the nose. This slim series nut came from some milling extensions that used ER11 collets on a 16mm shaft for getting down into moulding cavities. So when I made the tooling for the lathe just used the same nuts from the milling section. They also have a complete set of collets spare as well, so was a win for me. On the set ups I use, the parts generally indicate to better than 0.02mm TIR. The home made collets for specific jobs are better than 0.01mm tir and for most things that is plenty good enough. Most of the collet chuck bodies I have made are from stress relieved pre hardened P20 die steel, it is about 30Rc or so in Hardness. It is a very stable material and I feel that is very important factor in making tooling that it is a stable material. My home made cue lathe is made with an ER40 collet spindle that I made as a cartridge spindle and then mounted that cartridge onto the lathe bed. I also made various steady rests that also use the ER40 collet size and those used a 40X62 bearing from air conditioning clutches in cars. A really nice double row bearing. Other ones just used a pair of bearings but spaced as if they were angular contact bearings. I have pictures in my album on them. I also have alot of split sleeves for holding parts, so I for example a series of sleeves that are 19mm od with varying id's from 16mm down to 14mm. These sleeves are quite a neat fit onto the part and the collet is used in its nominal size range, ie from 19.05 down to 18.95 mm. The concentric sleeves are really easy to make and can be made from what ever material it needs to be, so can be steel, plastic or even wood, like I use on the pool cues. The sleeves can also have tapers to match that of the part being held like a cue where they have some quite shallow tapers for example. There is a huge list of things you can do with theses collet systems apart from just holding cutters and do it quite repeatably and with just basic lathe skills and a hacksaw.

Neil

The lathe is a 19 year old Nakamura lathe ,71mm spindle bore, with their LucBei software on a Fanuc control. I also have made ER16 to ER11 for my cnc router at home. I really like the ER system, especially the ease at making special sized collets. On the smaller ones, I ruf them out and drill/bore /ream the holes and for the final finishing, do that between centres on the hole that was created to finish the outer front 30deg and rear 8 deg tapers. I do this on the collet sizes smaller than 4mm. I always slit them last if they are collets.

Neil

Edited By Neil Lickfold on 19/09/2016 20:24:02

If you have a lathe, just make a couple of form tools and turn up the ring to the profile and diameter that you want. I made my wife a Titanium wedding band for our 15th anniversary . I made a form tool for the inner shape and a form tool for the outer shape, parted it off. Then set it onto a mandrel and blended the side that was parted off. To get the size I just asked her to take a ring to the jeweller in town and got the sizing off them. They told her how many mm diameter it was.

Neil

Raymond, I put a piece inside the collet that is about 0.01mm smaller than the bored collet. I just cut them slowly with a slitting saw on the cuter grinder, so not milled. Then debur them. I also make adapters from the ER40 to ER11 for holding 1mm drills etc. I also use them in the collet chuck when holding small parts, less than 6mm diameter. I wish that I had live tooling but it just has a 12 station VDI 50 turret, 6 outer and 6 inner.

Neil

http://www.model-engineer.co.uk/forums/postings.asp?th=120333&p=8

This is where I posted about the ER40 collect chuck that I made for holding parts at work.

Neil

The collet blank is just from P20 tool steel. I put in 4 slits from the front to about 4mm from the back. Most times the parts are better than 0.02mm diameter and the 4 way slit is good enough. If more range is needed, I add 4 slits from the back and finish at the retract groove. The blackened collet chuck body, sits into 50mm bored softjaws that are torqued to 90NM on the M12 capscrews to keep it all the same. The hydraulic chuck pressure is set to #10 of 24. It was bored and threaded in the softjaws when it was made. It has dedicated softjaws and is always set in the same radial position. A really important and often over looked aspect of the chuck body is the concentricity of the outer thread for the nut and the 8 deg bored taper. If these are out, it will not work as well as when it is actually concentric. I make the thread to be quite a neat fit to the nut that is going to be used and only use the one bearing nut in this case, as it is used to hold parts and not cutters.

The plate sitting on the nut is the standard stop and can be used with the tube as an extension needing greater than 25mm diameter but less than 30mm. The cap-tube is the standard extension that takes 25mm diameter stop blanks and can be used with the other tube as an extra 75mm extension to the cap-tube.

I have made for carbide cutters with my CNC router which uses the ER16 collets, I made some shrink holders. They work really well. But I have access to the use of an induction heating unit which makes it easier to heat and get the cutters into the holder. Also I needed to modify the diameter of the collet at the front of the groove, otherwise you can't the nut onto the collet. There is a limit as to how long of an extension nose you can make and it's diameter in order to get it all together. I also made some other tools, like a 4 mm ball end with the ER16 shank to use as a setting piece to touch off with and finding the work piece position.

Neil

This is what I made for holding various parts at work. I make support pieces to support the collet at the back end, either as a button or as a combined end stop and collet support. For some jobs I make a collet specific to that part with a step in it or what it needs. The outer shape of the ER40 blanks is a standard program in the lathe, so just need to edit the ID detail. These normally work over a small part size range, less than 0.1mm variation. I have also made some Delrin solid colets, and use them as distortion collets. The part neatly slides into the plastic with an end stop on the collet chuck body. So makes it into a dead length set up. Then the plastic distorts and holds the part nicely. With a steel step collet and stop I can hold and second op some quite thin parts down to about 1mm thick. Neil

If you use the BIG brand ER colets, they are far better than the Regofix and all others. I don't have them myself as they are too expensive for me. These hold cutters a lot better than any other ER collet and their collets only have a 1/2 mm range in size with a recommendation of using them on the nominal sizes. For holding milling cutters, you can't beat a shrink fit system with good quality shrink holders and an induction heater system for installation and removal. Mainly carbide cutters are held in the shrink system. The earlier video was a bit misleading by not showing the 1st test at real speed and sound. The second cutter should have been in a new path instead of going in an existing slot. For home use the appropriate ER collet system size is important to get the most out of the holders for cutters. Using a bigger longer collet is only good if the cutting tool is still held by the full length of the collet. I don't see any point using an ER32 as an example when the length of the 4mm end mill does not allow the too shank to be fully supported. Then you are better off to have a shorter collet chuck like an ER16 collet chuck for example or the even smaller ER11 collet chuck.

Neil

With ER collets. I have made a collet fixture, I use at work. it goes into a dedicated set of softjaws. It has on the back a plate that is used as a stop. This is for ER40 collets. I have a set of spacers and also spacers that have the diameter of the work piece that locates into the last 5mm or so of the ER40 collet, with the front of the stop being used as a true face for the part to sit against. The area between the part and the 5mm engaged with the collet diameter is relieved a little, I make it smaller by 0.2mm in diameter. This allows me to hold onto parts sometimes only 2mm length to hold. Of course you only take cuts according to the ability to hold the part.

This effectively makes the ER collet like a fixed length collet chuck, which is great for repetition of parts. I also make my own ER collets for specific tasks and only takes parts to a tight limit, Exact size or smaller by 0.02mm max. The collets I make , I only slit them from the front and leave the back as a single ring. The slits only go to about 5mm from the back of the collet. I drill a hole for the end point of the slots. If the parts need to all be the same length, then I make a stop block to suit. The stop blocks are held by a M8 capscrew. But a smaller similar system could be made fro ER30 or any other ER collet size.

I can take some pics if anyone is interested and then add them tomorrow.

Neil

There are optical tacho's available that go off the light from the prop and will go to 50k or so rpm.

Mine is a futaba and is about 34 yrs old. I think place like hobby king sell them and maybe model shops inthe UK might also sell them.

Neil

This is an interesting thread with loads of varying opinions. It seems to me that a lot do not realise how much skill is required to make something cnc and to make it accurate and have the really nice finish. There is the design or cad skills as well as the cam or cutter path skills. Of course to a great extend the shape as ling as the tool can access it, it will create the geometry. Accurate things need cutter compensation and radius compensation, if not on the machines controller on the cam package making the part. If you can measure the geometry of the tools being used, and create a cutter library with the tools of the correct geometry, then the cam side will create the compensating code. Depending on the equipment being used but the path may need to be modified to compensate for the idiosyncrasies of the machine tool itself. I make stuff on my myford with no digital read out is one end of the scale and make parts on a cnc lathe or a cnc wood router. There are some precision parts that just can not be made by hand and do require the control of cnc equipment to generate the geometry to the level of precision that is required.

The final answer has to be how to you weight the varying skills to make the same item ?

What weight do you give to the person who can 3d draw a propeller with the correct sections and geometry and then program a machine tool and create the tooling and method to make it over someone who hand carves an approximation of the same propeller . The hand carved prop will be not be as equal in performance and will not have the same precision in it's manufacture. The person who used the computer and cnc has a far greater skill set than the person who just carved one up. In this example I know as I have done the hand carved props and they are way easier than the skill set to learn to draw it all up and then create the cutter path. I just don't have the cad skills to draw the props, but do have the cam skills to create the part from a solid model if it were supplied to me as has been done on my cnc router at home.

Which leads to the next part, if you do not make the cad models yourself, then in reality, you have just copied a part and got it produced which is essentially my cnc made carbon props.

Neil

There was a chinese made sets of ER32 collets about 2-3 years ago and they were just terribly made. The front 30 deg taper was not concentric to the 8 deg taper. The other issue was the groove was cut too shallow for the collet retract. It may be possible that you got one of these collets or one with similar problems.

I have learnt that cheap is just wasting time and money if you are expecting any level of precision.

Neil