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Member postings for ChrisB

Here is a list of all the postings ChrisB has made in our forums. Click on a thread name to jump to the thread.

Thread: Case Hardening
05/12/2019 15:29:08

So are there two methods for case hardening? If I understood correctly some are saying to heat the part enclosed and let it soak, and then there is another process where I heat the part and dip it in case hardening material multiple times and then quench. Is this right?

05/12/2019 08:51:46

Thanks for all the replies, much appreciated. First thing I'm going to need is to get a proper gas torch and some fire bricks, think those will help concentrate the heat better as the parts are quite thick at 2 inches.

04/12/2019 18:51:04

Hi Clive thanks for the tip. By charcoal, would the bbq type do? And regarding heat, how hot should one go, does it need to be red?

04/12/2019 18:23:54

Hello, I have some parts made out of mild steel which I would like to surface harden just to avoid nicks and dents in them in general workshop handling and to attain some wear resistance.

I have done some reading on the subject but I would like some advice before I attempt anything.

I understand that I will have to heat the parts to a high temperature in a carbon rich material. I have read about Kasenit for carburizing material but I wouldn't know where to find that or something similar locally. I have some fine graphite powder (like talc) was wondering if it would make for a good case hardening material.

Chris

Thread: Cracking a bolt
02/12/2019 14:35:32
Posted by Nicholas Wheeler 1 on 02/12/2019 10:09:15:

ALL bolts are in tension and stretch; that's how they work!

My comment was in response to the above statement. In my opinion, bolts can be installed both in tension and shear, that's all. I was not referring to the type of joint being used - I'm referring to how forces can be transmitted to a bolt.

**LINK**

02/12/2019 13:10:01
Posted by Michael Gilligan on 02/12/2019 12:57:55:

With the greatest respect, Chris ... That seems a very inefficient way to use a bolt

It is effectively just a shear-pin with something to stop it falling out.

Could you give us an example, please

MichaelG.

You may call it a shear pin Michael, I called it a bolt as most are threaded and have a hex or 12pt head. My experience of these types of "bolts" comes from aviation - as to the efficiency of use of these type of bolts, I'm not the designer, I just encountered them!

02/12/2019 12:47:46

Well I have seen cases where bolts are used in shear. The bolt is retained by a castle nut which is tightened just for the purpose of not falling off and secured by a cotterpin or tab washer. All the load the bolt carries is in shear not tension in these cases I mention.

02/12/2019 12:14:34

If not referring to cylinder head bolts only, I wouldn't say all bolts are in tension.

Thread: Rake angle on Cutting Tools.....memory tips???
22/11/2019 08:21:23

I use TNMG inserts (negative) on all materials I use - stainless, brass, steel, alu, and they cut well and with a good finish. Most of the times the finish comes out like a burnished mirror finish. Down side is I cannot machine very small diameters as the tool creates quite a lot of side pressure, and it does not give a good finish with spring passes - but what I mean to say is, it all depends on the application - maybe rake angles come to play most when turning small parts etc but not much for larger work - my limited experience opinion.

So I would experiment with tool geometry, materials, speeds and feeds and find what suits my application best, as probably no book will have your exact conditions (type of lathe/tools/etc) and work requirements. I opted for TNMG inserts because as a beginner I was going to ruin a lot of inserts until I get a good feel of my lathe, so having 6 cutting edges on one insert and the negative insert being more robust, it made a good compromise.

Thread: DIY magnetic DRO
21/11/2019 16:13:57

Posted by Ian P on 21/11/2019 15:48:10:

As I understood it, whilst the tape has a magnetic pattern in it, the amount of magnetic force is so low its unlikely any swarf or chips would stick to it, maybe ferrous dust might accumulate but with the protective stainless foil over, it would be easy to wipe off once every few years.

You'll be surprised! Large pieces of swarf will not stick, but on a milling you'll be producing lots of small chips, and those will stick to the magnetic tape with ease. My reasoning goes: better have the tape visible and accessible where I can easily give it a wipe.

Chris

21/11/2019 14:51:47

I think it's a better idea to leave the magnetic tape accessible, small chips will find their way anyway and stick to the magnetic tape. So I'd rather have the tape mounted in a way I can easily brush or wipe off dirt and chips.

Also keep in mind that the encoder needs to have room for adjustment as it has to ride at a certain height and in the middle of the magnetic tape. I built the readhead case with this in mind so that I would require minimal setting up and adjustment.

Chris

17/11/2019 18:58:47

Hi Jed, I went for the 1μm resolution as the most common type of commercial read heads are 1 or 5μm. Don't know if higher resolutions are better but for what I do, the 1μm resolution encoder is more than enough.

Thread: Tramming The WM18 mill head
15/11/2019 14:15:54

This morning I had another attempt at sorting the mill tram, following the advice on this thread and other videos of similar mills on youtube.

Started off with levelling the bench and table which were out so I had to adjust a bit. Then checked the table and column, both were acceptable, the column has a nod of 0.05mm over a height of 200mm - I shall call that acceptable. Then I proceeded to tramming the head, left to right was easy enough, but front to back was a bit of a work out. As the column alignment was fine I was not going to touch it to fix the front to back tram, so instead I shimmed the head. I had to place a 0.2mm shim under the lower part of the head where the head lock bolt is located. Not an easy task as I had to do it about four times, and each time I had to support and slacken the head enough to slip the shims in.

The adjustment was done with all locks on the column and quill tightened and the quill at the retracted position. I could not find a way to fix the quill misalignment (0.3mm over it's full travel) but I reasoned I will use the column rather than the quill to take milling cuts.

I did some test cuts, first with a 50mm face mill and then with a flycutter. Judging from the machining marks it looks like the tram is fine in all directions ( that's no expert judgement btw!)

This is a 50mm face mill, probably I could do with some more speed. No noticeable ridge at the cut intersections.

20191115_125333.jpg

Flycutter at approx 6" diameter left a nice smooth and flat surface.

20191115_133121.jpg

Thread: Warco WM 250 problem?
15/11/2019 13:15:42

As mentioned above, add a piece of plywood under the tray otherwise you'll be tightening the lathe against a piece of sheet metal with a 3/8" air gap, most probably that's the cause of your lathe wobble.

This is the gap I had between the tray and the bench top.

20170903_132145[1].jpg

Thread: Tramming The WM18 mill head
11/11/2019 21:31:49

Thanks Nigel for the detailed explanation. Will try to get the head off and check if there are any nicks or anything under it. Below I took a short video clip of what's happening, the first part is the travel of the head up and down movement, the second is the Quill. It looks a bit strange.

I'm using a precision vice on its end as a square, might not be perfect but it's close enough, it's about 200mm tall.

Edited By ChrisB on 11/11/2019 21:33:24

11/11/2019 19:08:54

Can anyone with a WM18 or similar mill measure their quill out of squareness for me please? I have a feeling that this movement is coming from the rack and pinion pushing the quill towards me.

I'm tramming the head with the quill retracted and locked, this gives me 0.02mm left to right over an 8 inch diameter, front to back I'm getting 0.05mm...I would be happy with these readings, however when extending the quill to its max extension and locking it the readings change drastically, the left to right becomes 0.05mm, but the front to back goes over 0.30mm.

If I use it with the quill retracted I think I should be fine but I would like to know if this is normal for this type of mill or I'm getting this totally wrong.

10/11/2019 16:03:32
Posted by mgnbuk on 10/11/2019 12:22:32:

As often seems to be the case, you appear to be trying to correct one error by introducing another - in this case mucking up the column to table squareness to "solve" a spindle alignment issue.

 

Below is an extract from the PM-30V manual which is a similar mill to the WM18. Basically it's telling you to move the column to tram the Y-axis - now instead of shimming the column I jacked it - same result as shimming I think. But still the quill out of alignment will not be resolved by the procedure in the manual as you clearly explained Nigel.

"A procedure similar to the above may be used to check tram
in the Y-axis, front to back. The difference here is that there
is that Y-axis tram is established in manufacture, and can be
adjusted only by these shop methods:


1. Shimming between the dovetailed Z-axis saddle casting
and the headstock itself. It is more likely that the headstock
is nodding forward rather than leaning backward,
so start with (say) a 2 mil shim in line with the underside
(central) headstock nut. This is a temporary fix that will
need to be checked if the headstock is tilted again.


2. Shimming between the underside of the column and the
main base casting. This is a long-term fix. It is a two-person
procedure, requiring an engine hoist or some other
means of un-weighting the headstock (see Section 1, Installation).
As an alternative to shims, which do not provide
a uniform bearing surface, consider injecting a metal-
filled two-part polymer. "

 

So the question is, is there a way to adjust the quill?

I have checked the table movement and the difference I could read in the FWD to AFT direction was 0.02mm over the whole travel - which I should regard as negligible. In the Left to Right direction did not get any deflection.

The column is square to the table in the Left to Right direction. In the Fwd to AFT direction it is tilted 0.02mm over a height of 80mm towards the front. (negligible?)

The quill is out by 0.30mm towards me over the same height of 80mm, which compared to the column out of squareness is enormous. Have no idea how to adjust this.

Edited By ChrisB on 10/11/2019 16:04:09

10/11/2019 11:34:12

Well just back from the workshop....as usual, Jason is right embarrassed

I removed the screw jacks from the column and checked the column and quill. Found that the column was almost spot on straight, while the quill is tilted backwards (that's why when I jacked the column I got the tram right in the fwd to aft direction)

The tilt in the quill is significant, I mounted the test indicator on the quill at a diameter of 8 in, and on the full travel of the quill the indicator would read +0.3mm a the front and -0.3mm at the rear. The column max reading was 0.02mm.

Now how to adjust the quill if it can be done at all is beyond me!

Chris

10/11/2019 06:11:22

One thing I noticed is the ammount of flex the column has. Pushing the column by hand forwards or backwards I could see the test indicator give a reading of about +0.05mm and -0.05mm , that is by applying a moderate force, it would deflect more if I pulled harder. That got me thinking....could it be that the column is in fact machined true to the base and table, but the weight of the head makes it nod that tiny ammount?

09/11/2019 21:58:45
Posted by JasonB on 09/11/2019 17:17:02:

As well as checking the tram you should check the head moves true and that the quill movement is true to the table

Ah, didn't think of that, will have a look at that tomorrow and take a couple of passes and measurements.

Agreed George, I'm not moving the head again unless really necessary. I got a digital angle gauge which should be enough for my needs.

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