Here is a list of all the postings IanH has made in our forums. Click on a thread name to jump to the thread.
|Thread: This months MEW are 3 CNC features two too many|
First off let me say that I haven't read the issue in contention because I let my subscription run out by accident.........doh! but as keen CNC user at home I can see little point and hardly any interest (even for me as an enthusiast) in pages and pages of G Code if that is what these articles contain. If you get into CNC you will very quickly realise that you will rarely go near G Code, the computer will look after all of that for you - the interest and challenge is in the new opportunities that are now open to you and sorting out how to exploit them on a budget (real 3D CAD and CAM software is extremely expensive and most home machines will be home brewed conversions of one sort or another).
I think that if we had articles on what folk were doing with CNC that might be a whole lot more interesting for everyone. Articles giving print outs of G code in past issues have left me wondering whether some of the authors have realy "got" CNC, or just got lost in it?
Iam going to vote for CNC here. I produce patterns for lost wax casting vintage car and engine parts - the patterns are always one offs - no repition work here. I moved into CNC milling simply to extend the range of geometries I could handle. Making a pattern for the expansion link illustrated earlier in this thread for example would be easily handled by my CNC mill.
What I don't do is reproduce the original parts themselves with CNC - there are folk doing this and to my mind the finished articles, whilst serviceable, do not make adequate reproductions of original parts. They shout out "billet made CNC" some indeed even make a virtue of this.
My approach is to come via the casting route - it is more expensive overall but you get a more authentic product. I am off to the foundry this morning to pick up some prototype Rolls Royce Phantom III oil pump castings - whilst some aspects of this pattern could have been done by hand, there were a series of ribs that curved and sloped that would be beyond me without my CNC mill.
Also don't underestimate the tooling challenges of using CNC machines - it stretches everything I have learned in many years of manual machining.
|Thread: BobCAM - ANy experience|
I have a busy CNC mill with Mach 3 on board and have found that almost everything I need to do can be achieved with 2 1/2 D machining. I bought Vectric Cut 2D and can not recommend this highly enough.
Looking now at true 3D machining I spotted BobCAM.
I have been searching the Internet for user reviews and have found little to commend this product.
I can't decide whether this is because the program is truly awful or because people are comparing it with commercial products at far highr prices. At the end of the day it has to work of course - does anyone have any experience of BobCAM?
|Thread: Thread tool form|
A few years ago I started machining threads for crank pins and main shafts in JAP engines - these are fine threads subject to very high loadings - I took the plunge and invested in some throw away tip tooling which I would say has been one of the best tooling investments I have ever made. In particular I invested in Carmex miniature and sub miniature internal threading tools and these have been a Godsend.
I standardised on 20TPI (although metric pitch options can be cheaper) and bought full profile tools for that pitch, but supplement this with partial profile tools allowing me to machine any other pitch I need.
My advice would be to invest in some decent tooling - it is worth it.
|Thread: Sheared Drawbar|
Just picking up on the "damping ring" - in case you don't read my reply on the other thread - the damping ring makes a fine puller to pull the chuck out of the taper. Plenty of chucks do without them but having one makes your collet chuck superior in that if nothing else it provide a means for you to remove the chuck without beating your spindle to death again in the future.
|Thread: Centec with Clarkson Collet|
I had a Centec with a Clarkson Autolock chuck - if by the "damping ring" you mean the large diameter threaded collar on the collet chuck, that buts up against the bottom of the spindle then I recommend that you use this to extract the chuck from the spindle. My method was (first of all not to overtighten the thing in the first place!) - loosen off the draw bar by about 1/8" leaving it engaged in the chuck body. Now with a peg spanner on the damping ring and an open ended spanner on the flats on the spindle, use the "damping ring" to pull the collet chuck out of the taper. The damping ring has a fine thread so not much effort is required. When it frees, the chuck will drop but ony as far as the draw bar will let it. Put the spanners down and spin the draw bar free whilst you hold the chuck with the other hand.
|Thread: DIY Vacuum heat treatment oven|
Thanks very much for all this information - I don't live far from Stoke so I guess I have no excuse but to make some contacts and see what I can find out there, I will post progress as it happens.....
Just wondering idly over the Christmas break abou the practicality of making a DIY vacuum heat t reatment oven. I saw one recently in another workshop based on a gas cylinder lying on its side - the "top" of the cylinder had been removed and flanges welded on the cylinder body and on the remains of the top. It was hinged to form a door and although there was a clamping arrangement - the vacuum kept it shut and sealed - there was an O ring seal in the flange.
Inside there were refractory bricks and some electrical elements - and there was also a control system.
Anyone have any ideas - how many KW woud I need to heat treat steel - the actual chamber needs to be no bigger than a coupe of house bricks. Sources of heating elements and refractory bricks etc etc?
Edited By IanH on 26/12/2010 14:13:32
|Thread: Drilling of 34CrNiMo6 4340 817M40 En24?|
I have recently had a bit of fun recovering a job which involved drilling into hardened EN 36B - my normal Dormer HSS drills wouldn't touch it, it was like drilling glass. I bought a cheap solid carbide drill off Ebay (harryuk123 store) for just under £5.00 and it was a piece of cake. Don't be scared of solid carbide.
|Thread: Need for recomandations on cut off or parting tool|
I am not sure what a Sieg C6 lathe is but I can recommend the Q cut tool from Greenwood without reservation. I have two of these, one for my Myford 254 and one for my Colchester Student - I would not be without them.
They transform parting off from a tense operation at best to a complete no brainer. I have no qualms parting off alloy steels (EN16, EN24) and stainless steels at high speed (800 plus RPM).
Defintely worth the money! I have no connection with Greenwood tools by the way other than being a loyal customer - I generally stock up once a year at Harrogate 4 SCLCR tips and a couple of Q cut tips every other year (they last and last).
|Thread: CNC engraving|
Well, no good reason for not using doube sided tape really - I have used double sided tape in the dim and distant past on something or other but found it was less than happy with coolant around so I have not used it since. There was no coolant on this job of course but I didn't consider tape. I will remember this for next time.
Just looking back at this post I thought it would add interest if I added a photo of an engraving project. This is a reproduction dash board badge made on the Denford that now adorns my Morgan.
|Thread: Slotting Tool Design|
Cooking on gas now. Here is a photo of the tool.
Tool body maximum diameter to fit into the hole with just enough space for the cutter to project - tool body machined out of EN16 for toughness, bottom face and slot for tool steel angled at 8 degrees giving "top rake" with a chunky cap to hold it all together with 2 M5 cap heads. Easy to grind - just provide a bit of "front" clearance on the vertical face then off you go. FInal step was to tighten up the belt on the slotting head so all the power of the motor was available.
Just need to make another now for the 3/16" slot
Thanks for all the ideas
Thanks for this. On an earlier job I managed the keyways on the lathe racking the saddle back and forth with a home made tool holder with a piece of 1/4" sq HSS tool. This approach is just like the text books suggest.
I used this same tool in the slotting head and found that it tended to be pushed away from the cut until it finally bit, then at that point it dug in. I am now making a more robust version of the tool and if it works out I will post a picture here so you can see what it looks like.
Edited By IanH on 23/06/2010 17:52:08
Some few years ago I bought a slotting attachment to hang off the back of my Bridgeport. I now find myself wanting to create some 3/16" and 1/4" keyways in 1" and 1 1/4" bore holes in EN24 and am astruggling a bit with the design of the tool/tool holder. The slotting head has a 0.625" socket for the tool holder to sit in. Can anyone provide a sketch of something that will work?
I am anticipating using 1/4" square HSS tool bits for the 1/4" keyway and had thought of clamping it horizontally in the bottom of the tool holder. My first attempt has not been rigid enough allowing the tool to dig in and jam everything up. I can't find any pictures of commercial designs so thought I would turn to the forum.
Thanks in anticipation
|Thread: Roller bearing cages - full size|
Another attempt at the photo....
I think a final scheme is emerging. Moving up to a 40mm od crank pin and using a stock needle roller bearing get you up to 45mm od. If you then add in a hardened ring in the conrod eye you are looking at boring the conrod something like 0.15" over the iriginal dimension. At ths size the conrod is looking rather delicate and as this all started with a fork rod failure,,,,,
New conrods with a bigger "big end" would be required.
Plan B then is to go to a 35mm crank pin allowing me to use 42mm od needle roller bearings which can be accommodated by opening out the existing big end sleeve by only .030 on diameter. I am pretty sure the sleeve is hardened right through so this should be achievable. The od of the sleeve doesn't change so the original pattern conrods will do. If I stick with the bronze bush in the blade rod then it should be straighforward.
Thanks for all the information - I would love to see a sketch of the broach and die set up Ian is suggesting - any chance of this Ian?
I have sent a message to mgj to check out the woodruffe cutter proposal - I think we have different ideas of what a woodruffe cutter is although I suspect it is because the cage is relatively thick compared with its diameter rather than being a thin shell as he suggests.
At the Three Wheeler Opening run today concensus of opinion amongst the racing fraternity was to use an INA caged needle roller bearing running directly on the crank pin. The proposal for the crank pin is to go to a parallel pin with .004" interference and press it together in the hydraulic press - no tapers, no threads! I have to admit that this is tempting......
Question is whether the blade rod will be ok on its bronze bush or should this be sleeved and a crowded needle roller arrangement be put in place - it only rocks back and forth when all is said and done.
Thanks very much for this John,
This was the idea I had in mind talking about a two piece cage but I wasn't thinking of leaving the washer floating.
Reducing the inertia by going into a lighter material might be an idea?
What did you do in terms of clearance between the cage and the crank pin and the cage and the big end sleeve for both the cage and the floating washer? I am thinking of "Tuning for Speed" where there is discussion about the cage wearing the pin away,
What clearance did you use between each roller and its slot? I am thinking that using shaped slots like this you could keep the cage off the pin and sleeve, but the washer would be free to run on the crank pin.
What do you think of giving the washer a register to held it in position on the cage - the register would need to be deeper than the end float on the big end to keep it in place.?
Lots of questions I am sorry!
I am approaching a big end rebuild on my JAP LTOWZ engine (1000cc water cooled V Twin from the 30s). The original big end bearing was a crowded roller bearing (loads of rollers no cage) but I would like to modify this to add a light alloy cage.
The cage then is an annular ring with a series of rectangular slots to take the rollers.
Phil Irving in his seminal work "Tuning for Speed" recommends milling out the slots with a woodruffe cutter then filing the ends square but I am afraid I don't have it in me to do all that filing.
Do we have any alternative techniques for forming the cages without the filing? I have milling (manual and CNC) and turning of course.
I have wondered about making the cage in two pieces - a plain ring on one end to close off all the slots, but am not sure about how to secure it.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.