Here is a list of all the postings John McNamara has made in our forums. Click on a thread name to jump to the thread.
Thread: How to seal a lathe headstock |
07/05/2016 09:22:16 |
Hi Raymond Anderson My VDF was made by Heidenreich and Harbeck As you might guess the machine did not look like the picture when I got it. Many happy hours months! have been spent refurbishing it. It is powerful and accurate. The finish is 2 pack epoxy machinery paint from Dulux closely matched to the original colour. Regards |
06/05/2016 14:58:06 |
Hi Rainbows Plain tapered roller bearings are a fraction of the cost of an NN type. many high quality lathes use them. One thing to consider when selecting bearings is the maximum speed for a given size, Tapered roller bearings size for size have lower maximum speed ratings than angular contact ball bearing sets, the reason they are used in CNC machining centre spindles. on the other hand tapered rollers will carry higher loads. Lubrication plays an important role keeping bearings cool. grease is fine at lower speeds however churning it causes heat build up, oil lubrication allows for higher speeds, after that oil mist lubrication ceramic balls and other exotic systems are used. The one thing I miss with my lathe is higher speeds, I would really like a small lathe that could do at least 3000 rpm ideal for turning small parts. Oh and I need more room to house it. Smaller diameter bearings in most cases have higher speed ratings and cost less. The major bearing manufacturers all have excellent downloadable application manuals; worth reading. Regards Edited By John McNamara on 06/05/2016 14:59:55 |
06/05/2016 08:24:09 |
Hi Rainbows The problem with a separate shaft collar is getting it sit perfectly on the shaft, even with a press fit there is a chance it will be slightly canted, if it is there will be a cam action forcing the spindle to move in and out as it rotates. It behaves like a micro version of a swash plate, often used in car aircon compressors. The same laws apply to the nut and lock nut used to set the preload on the bearings against the shoulder, for better quality machines sometimes these nuts are turned or more likely ground while mounted on the spindle as a set. Maybe you can find a local model engineer with a larger lathe to make the spindle. Regards |
06/05/2016 01:03:03 |
Hi Rainbows You really do need to keep the swarf out there are dozens of inexpensive mechanical seals available. Regards
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Thread: View from my shed |
29/04/2016 08:50:55 |
Overuse? |
Thread: Ball bearings between pulley and spindle |
14/04/2016 00:10:33 |
Hi Rainbows I am sure there are other members that may remember other companies that did this. From Memory the German company VDF did this with one of their lathes? They also offered plain bearings for some of their lathes the objective being a finer surface finish. Even super precision bearings create some bearing noise that may affect the work finish. The Diamond turning lathes used to turn computer disks do not use ball bearings, Air or magnetic levitation bearings are used for mirror finish required. |
Thread: Steel quality |
04/04/2016 14:15:13 |
Hi Sam My memory needed jogging too. If you Google the following 3 searches.... steel stress strain graph images You will see various representations of the stress strain graph for Steel. While strain hardening does occur it is past the point of no return, there is a permanent change in the dimension of the steel part. Up to the yield strength knee in the graph the material under load will return to its original size, obeying Hooks law. Long term there is also creep, particularly if the load is near the yield point. Normally in a design a safety factor is applied depending on the use. Creep will be less with lighter loading factors. Where human life is involved a factor of 2 even 3 or more is common. A steel part may pass the tests for a specific load and still not be satisfactory if it bends (Deflects) more than a particular design can tolerate. For high accuracy machinery Deflection is the main concern of the designer. A lathe bed is a good example, clearly there is no risk of it failing due to the load applied by the cutting tool and saddle. The designer made it massive to reduce deflection. Regards |
Thread: Drill press vice positioner |
01/04/2016 08:00:16 |
My solution is two pieces of 25 x 12 x 130mm steel bar with threaded hole set in the centre of one end forming a lever nut, round of the sharp edges to protect your hands. I just loosen the clamp levers and vice and all drag the vice into position. Much stronger than a G clamp and no spanner needed. Only a few minutes to make. cost from the scrap bin....nil. Regards Edited By John McNamara on 01/04/2016 08:02:19 |
Thread: Bedway vee angle |
30/03/2016 11:21:36 |
Great Idea! Regards |
Thread: Perpendicular Drilling |
29/03/2016 12:48:14 |
When contemplating how to process a job accuracy beyond what is needed can be a great time waster. does the job really need to position the hole with pinpoint accuracy or will within maybe .0015" to .002" do? achievable on a good day if my glasses are clean. I can set a drill in key less chuck on the pillar drill in a few seconds, Maybe a spotting drill first if needed, Position the work in vice and set the centre pop on the work under the drill in less time than it takes to write this. If needed In goes a chamfer cutter to remove the sharp edges around the hole flip the work do the same on the other side and the job is done. Alternatively do it in the vertical mill this will require centre finding the punch mark locating x and y, the big table is heavy and there will be a fair amount of winding. then Fitting a drill chuck in quill and tightening up the the draw bar.... as we all know the wrong tool is always in the draw bar... then finally drilling the hole. Yes with care I can get better accuracy maybe one or two thousandths of an inch better, The purists will claim they can do .0001" (In their dreams) unless they have a jig borer in temperature controlled room! yeah. Regards |
29/03/2016 07:51:49 |
Hi Daniel The Drill press looks a little like my Rexon a Taiwanese made drill I have had for maybe 20 years, It has given good service within its capabilities. Yes I have scraped the swivel bearing face to make the table a true right angle. With smaller drills I like it for the light and sensitive touch. For heavier work I use the milling machine but the quill is a lot heavier and less sensitive. There will be some deflection of your drill table with heavier drills say over 10mm particularly if you bear down on them trying to push them into a piece of tough steel or grabby Brass. The drilling pressure can be significantly eased by drilling a smaller pilot hole first, to drill through 25mm steel you will need to peck drill to clear the chips or you may get a jam. It is important that drills are kept sharp. The smaller drill will also find the centre of your centre punch marks more easily, the web of a 12mm drill may miss unless you punch heavily. So the smaller drill is acting as a spotting drill as well, it should result in more accurate work. Regards |
Thread: Windows 10 - A Warning |
28/03/2016 13:40:25 |
From Steve Withnell "Sky Broadband connection with a 2GB usage limit"
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Thread: Bending 4mm steel rod by 90 degrees |
27/03/2016 13:09:45 |
I agree with Paul Lousick, A hot bend is far less likely to cause stress fracturing that is often created when cold bending steel to a sharp corner. |
Thread: Turntable truck bearing |
27/03/2016 02:49:47 |
Dollar for Dollar or Pound Pound in the UK a pallet truck is to me one of the most useful ways to move things around, It will not work on soft surfaces so you will also need a few sheets of strong plywood and a number of chocks to create a level surface if moving over say grass. Needless to say if there is more than a mild slope, it is better to use a professional machinery mover. They are available fairly cheaply. I have a storeroom that abuts a driveway that is packed so tight I can only just close the roller door! there is no passage way inside, It is stacked to the roof. with all the goods stored on pallets and shelves made to fit on pallets. It only takes a couple of minutes to drag out a few pallets to access the ones at the back the pallet truck makes it so easy. it is left parked under one of the pallets with just enough room to shut the door. as long as the floor is flat you can move a ton quiet easily. Regards
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Thread: How to cool a piece for a shrink fit? |
23/03/2016 13:20:11 |
An alternative..... Cut a step in the shaft making it a couple of mm oversize, a light press fit will do, it will be tightened up by peening. Then bore the plate to fit and put a 1.5mm 45 deg chamfer on one side of the bored hole. I would do this in the lathe with the plate resting against the face of the chuck jaws, the main thing is to keep it from canting. Tidy up face of the rest of the projection in the lathe. if looks are important. If you peened it well you will only see a fine line. Regards |
22/03/2016 03:33:07 |
Dry Ice? You should be able to get it. |
Thread: Rotary Table Scales |
21/03/2016 11:58:34 |
Hi A while back I made up a spreadsheet to calculate the required angles for dividing. using a Vertex type Rotary Table. Its an excel spreadsheet. Enter a number to divide and It will only show the needed settings for that number. Best to print it out and mark the rows off as you do them. (Always turn the handle one way, if you overshoot reverse well back then try stopping on the exact mark again to avoid backlash) Link Regards |
Thread: Which version of the Victoria U2 milling machine is this ? |
21/03/2016 11:32:28 |
Hi Alan There is something very satisfying about heavy Iron,
I googled victoria U2 Milling machine Worth a browse A good find. Regards
Edited By John McNamara on 21/03/2016 11:35:00 |
Thread: Ferrite rings |
19/03/2016 09:56:08 |
Many computer power supplies have leads wrapped around ferrite rings, they are used for reducing electrical noise Regards |
Thread: Model Engineer – Editorial direction |
15/03/2016 05:55:25 |
Gee..... Regards Edited By John McNamara on 15/03/2016 06:07:00 |
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