Member postings for Mark Davison 1

Issue resolved. Cheap bearings replaced with FAG bearings and everything is now fine. The surface finish of the track on the cheap bearing is very poor in comparison to the FAG bearing. They might as well have been ground with a rock. I need to find who I bought them from and ask for a refund. They are the last 'Dunlop branded bearings that I'll waste my money on.

They will just be general purpose, i didn't order anything special. I can accept microns of runout, it 100s of microns of radial runout that I didn't expect! I'll see what these are like and reconsider the cylindrical roller bearing if they aren't considerably better.

I found cylindrical roller thrust bearings the same size as the ball but they are between £15 and £25 each. They seem to be designed for almost complete overlap between the opposing surfaces and I have dont have that, in fact I have slightly less on the spindle than that required for the ball thrust bearing. I've ordered some FAG 51102 and will keep my fingers crossed that the are better than the (cheaper) first pair.

Edited By Mark Davison 1 on 28/06/2020 07:23:53

I was just considering putting an online bush in there actually. There is about 13mm length between them so possibly. The only limit to the OD is the need to support the washers.

Yes the washers are located on their OD in the steel block, I suspect the tracks aren't concentric with the OD, or with the ID on the spindle washers. They look OK to the naked eye but something is clearly wrong!

unfortunately i don't have the height above the spindle centre line,it would break through the top surface of the mounting block, hence using the thrust bearings (28mm OD as opposed to 32mm).  There is a plate that slides over the top of the block, it prevents swarf gettting into the leadscrew/nut.  That's what the recess is for in the top of the block.  The 6002 bearing sits further forward and I have the height there.

Edited By Mark Davison 1 on 27/06/2020 18:21:53

I haven't left room for the tracks to float, neither on the spindle or in the housing, should I have?

Yep, they are in the right way round, the one that is the snug fit on the spndle went on first and the one with the clearance on the spindle went in the housing, visa versa the other side.

I'll look and see if they do needle thrust bearings in this size and I'll try those as well if they do.

I'm converting my Harrison vertical mill to CNC, triggered by the original lead nut having about 0.050 of back lash and needing yet another VFD if I wanted to use the power feed. I've replaced the X axis lead screw and gear box with a 2005 ball screw and NEMA 34 stepper. I used standard fBK15 and BF15 fixed and floating bearing blocks (that I made myself as no-one had the size I needed) and a pre-machined ball screw. All was well. I'm now in the process of doing the Y axis. I can't use the standard bearing blocks as I'm very restricted for bearing height (shaft centre to top surface of knee), so rather than use angular contact bearings I've used a pair 51102 thrust bearings, mounted into seats in a 35mm thick block of steel that mounts to the front of the knee. This is a very similar setup to the original design but the larger block allows me to mount a plate/box that will house the timing belt/pulleys and serve as a mount for the stepper. To take the radial load from the timing belt I've used a single 6002 ball bearing on the same 15mm journal that the trust bearing are on. The problem I have is when I bolt the 10mm thick aluminium plate to the front of the bearing block (this plate has the seat for the 6002 bearing) the spindle/bearing assembly acquires a considerable tight spot. When I remove the 10mm plate from the front and reassemble everything with a dti, the 6002 bearing is out of concentricity by almost 0.25mm. all 3 bearings are on the same 15mm journal and it is spot on size (15.00mm). the only plausible explaination I can think of is that the thrust bearings are duff, or one of them is. They are supposed to be 9mm thick, and one is spot on 8.99, but the other is 8.89 which is quite some error for a bearing surely? The other explaination, would be my bearing seats in the 35mm block aren't concentric, but surely this would just serve to give me a spindle that isn't perpendicular and bearings that aren't loaded evenily, it wouldn't cause 0.25mm of concentric error? I'm pretty sure the bearing seats are within 0.02mm or less anyway, so I can't see how that could cause the massive error I'm seeing.

Thoughts anyone?

I'm going to order a pair of FAG of SKF thrust bearing (these were Dunlop) and see if that fixes things.

The spindle in the first photo is the original lead screw, the other photos are my 1605 ball screw with an entension sleaved and bonded onto it to give the additional diameter i need to mount the thrust bearings.  I've spent today remaking the spindle/extension thinking that was the problem, which it wasn't (and couldn't have been, 4hrs wasted).

This video shows the issue.  Here the dti is on the 12mm part of the shaft that carries the taper bush for the timing pulley, but the same thing happens with the bearing that is on the 15mm journal.

https://www.youtube.com/watch?v=HC2h8gP6kkQ

Edited By Mark Davison 1 on 27/06/2020 17:16:11

Edited By Mark Davison 1 on 27/06/2020 17:18:29

In the end Evolution cancelled my order as they didn't actually have any. They sent me a 20% off code as an apology so I went and bought a new one with 4 carbide burrs , some flapper wheels and cut off disks for £52. Still 110v but I can live with that.

I used a mounted point to get through the skin rather than risk wrecking a new burr. In hindsight I think that was overly cautious. I then switched to the burr and it does remove material quite quickly and under control.

I've taken more off since I took this photo (theres plenty left) and tidied up the shape a bit. I now have (just) enough depth. Oily rag - the mounting block is as slim as I can make it already.

Edited By Mark Davison 1 on 14/05/2020 19:42:40

Edited By Mark Davison 1 on 14/05/2020 19:44:23

Just ordered an evolution die grinder. C grade (refurbished stock) direct from evolution, £40 with free postage. . Downside is that it is 110v so I'll need to hire a transformer but luckily our local tool hire shop has just reopened today.

Now to find some burrs, the Garryson ones arent that easy to find on line, at least not at prices I can afford.

Edited By Mark Davison 1 on 11/05/2020 05:49:19

I need to remove a couple of millimeters of material from the floor of this cutout (the ledges at either end) in the knee of my Harrison mill. I'm replacing the lead screw and bronze nut with a ball screw and I've not quite go enough room. Would i get by with a Dremel for fourty quid or am I best of with a die grinder (a cheapish one, no more than a hundred quid). The surface is as hard as nails. I tried to scrape it with the end of a file as it didn't even scratch it. I assume it has sand in it as it is 'as cast'. The ribs/floor is about 8mm thick and most of the material that I'll remove is in the center to allow the underside of the cylindrical ball nut carrier to clear. The trough/cutout is about 40mm wide/35mm deep, 220mm long to give you an idea of size.

I'm using the app with a Teensy 3.2 micro controller reading chinese 5um optical scales (3 off on my mill, cost about £40 each before china shut down) directly (encoder library handles them with no additional hardware). I then broadcast the data over bluetooth to my android phone.

Teensy 3.2

There is now a much faster Teensy 4.

Edited By Mark Davison 1 on 26/04/2020 22:18:34

Thanks folks. I've ordered some 0.1mm shims which will get me started. I may try and turn down some sheet shim stock that I have whilst I'm waiting.

I have a pair of SKF angular contact bears that I am trying to use to secure the end of a ball screw. I've tried to replicate a BK15 fixed bearing block where the bearings are mounted face to face. Trouble is I seem to have a lot of end float. Almost 0.2mm. The outer races are clamped tight so im pretty sure the movement is between the inner and outer races. Should I expect to have to separate the inner races and then apply fixed preloaded on the outer races? I was expecting almost no end float. 15mm ID, 35mm OD, 11mm width bearings with a 20mm dia ball screw.

Its NOT OZ25 after all. I found out the hard way, bought another only to find out it doesnt fit (too small).

Can anyone help identify this?

Edited By Mark Davison 1 on 16/12/2019 21:10:22

I recently bought a harrison vertical mill that came with an Osborn tools collet chuck with a single collect inside it. It looks a bit like an ER collet but I believe it may be an OZ25 collet chuck. The taper appears slightly less than on an er collet and the length slightly longer. The collet appear to have an internal bore of 1", but the are no markings on the collet itself. Does anyone know what the clamping range of one of these collets is, is it likely to hold a 25mm dia end mill? ER collets have a stated range of 1mm but I cant find much info on these.

I have 2 fake cheap no name clone VFDs from Banggood, about £55 each delivered from China. I would normally buy products from close to the top of the range but took a punt on one of these instead of an Optidrive. I must say, for the money I cant fault them. Neither gets hot, run the motors quiet happily etc. They don't do vector control but neither the lathe of mill motors get a hard life (3hp and 2hp respectively). I've just bought a new mill so will try a branded VFD with proper braking and sensorless vector control on the lathe and move the cheap one to the new mill, but it isn't going to be easy to justify the extra expense.

The VFDs I have are (supposedly) 2.2kw and the motor is only 1.5kw. What happened to yours Dave?

I think I've found the start point ?

Should there still only be 3 wires even on a 6 pole motor ?