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Member postings for colin hawes

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

Thread: Magnetic chucks on lathes
16/02/2012 14:51:26

I have used double sided tape to hold shims for skimming to a thinner size. Can only take max 2 thou cut though using a sharp tool.With a magnetic chuck I would have thought magnetic swarf could be a problem.You could ,of course, hold brass etc. using double sided sticky tape.

Colin

Thread: 3 - Jaw chuck on Clarke 300 lathe / cutting speeds for brass / steel.
13/02/2012 16:17:33
The speed for cutting a metal bar depends on its diameter and material.Also the rigidity of the machine. Using HSS tools on mild steel ,about 700 rpm would be ok for 3/8" to 3/4 dia 500 rpm up to1" dia but cutting the larger sizes you should use a cutting fluid of some sort to maintain tool life and finish. 50% higher speeds for brass and aluminium. Note that, without lubrication, aluminium tends to weld itself to the tool causing a torn finish. Smaller diameters will be cut at proportionally higher speeds. I hope this gives you a good starting point! Of course ,you can't achieve ideal speeds when facing the end of a bar because its diameter is not constant.
Colin.
Thread: What cutting tools for mini - lathe (HSS or Carbide Tipped ?)
13/02/2012 15:35:40
Don't get bogged down with "recommended rake angles" my experience indicates you are better off with more rake for non heavy- production work the recommended figures are designed to allow the heaviest possible metal removal with best tool strength and heat dissipation. Our hobby does not create such conditions.Your tools will give a better performance with lots of rake, like a slicing knife rather than a hammer and chisel Try it.
Colin.
13/02/2012 13:21:40
hi Chris: I recommend starting with HSS tools as these are more than adequate for your application. Tipped tools are expensive to buy and use and offer little advantage on most machining operations, the exception being cast iron if you want to remove metal quickly or if it has commonly found hard spots in it.Stainless steel comes in many grades and i'm assuming you intend to use a free-machining type.HSS tools should be kept razor sharp so touch them up on the grinder before you start a job ,making sure you have plenty of rake on all cutting faces and a good finish should be attained on the workpiece.Industrial machining is done with tipped tools to get very fast metal removal with minimum tool wear and the best results are attained on very rigid and powerful machines
Colin
Thread: What size do i drill a brass cylinder in order to ream it 5/16 "
11/02/2012 16:25:36
The amount a reamer should take out varies wih its diameter, about 5 thou for small ones eg. 1/8"dia , 8 thou up to 3/8" and 8 to 12 thou above that .The drilled hole has to be a reasonable finish and should be done with an undersized drill first then opened up with the reaming size drill.Reamers over 5/8" dia should be o.k. at 1/64" undersize hole.As with all cutting tools, the reamer needs to be sharp.
Colin
Thread: Fine Finish on Crankshaft
11/02/2012 15:56:41
I agree that a sharpened HSS tool will produce a better finish in this instance provided it is ground with a good rake in all cutting directions.Hard-tip tools are ,in my opinion, very much overrated for use on most materials used in our hobby.Cast iron is the most likely metal give you the benefits of carbide tips .HSS tools are easy to sharpen and that is most important for a good finish.
Colin
Thread: Countershaft pulleys for Grayson lathe
31/01/2012 19:04:37
I made flat belt countershaft pulleys for my lathe and horizontal mill using 1/8 steel sheet rolled and welded .They have been going for 40 years with no trouble.
Colin
31/01/2012 19:04:34
I made flat belt countershaft pulleys for my lathe and horizontal mill using 1/8 steel sheet rolled and welded .They have been going for 40 years with no trouble.
Colin
Thread: Myford Lathe Problem
28/01/2012 17:23:16
Idon't have experience of the Myford,but it is not uncommon for the dial to be fitted with a spring- loaded ball for friction.This ball can be lost on dismantling.
Colin
Thread: Steel boiler for 5" loco
28/01/2012 17:15:22
There are regulations that will make it very difficult for an amateur to manufacture a welded steel boiler.eg You have to be able to prove competance at welding, you have to use the correct grade of steel which is certified,you need to produce test welds for inspection,and it it has to be examined during construction.I don't know about rivetted steel boilers. If it is for a small scale such as 5" the required thickness of steel is likely to make it impractical.
Colin
Thread: Issue 4422
28/01/2012 16:57:22
It seems to me that a flat belt stays on a convex pulley simply because it is forced to stretch to a longer length at the middle of its width than at the edges,a bit like wearing in a new pair of shoes ,so the edges of the belt being shorter than the crown means they don't easily slide across the crowned pullies.
Colin
 
Thread: gland nuts
28/01/2012 13:19:57
I agree with John,the answers "yes".
Colin
Thread: Manky External Threads
26/01/2012 18:00:31
A blunt die can sometimes be sharpened with a Dremmel type grinder if it has not been used for too long in a blunt state.
Colin
Thread: Double thread T- nuts
26/01/2012 17:53:28
Make sure you can get a longer nut into the T slot! There is not enough space on my minimill.
Colin
Thread: Another broken tap thread
26/01/2012 17:46:48
Has anyone tried to grind out a broken tap with a Dremmel-type grinder?This tap seems big enough; at least it could produce a dimple to start acarbide drill.Before we had carbide drills stellite was used to drill through any hard steel even hss.
Colin
Thread: Stress relieve in castings.
25/01/2012 13:20:32
I can remember castings being left outside to rust .I was told that this was to stress relieve them by virtue of the rust eating away at the hard skin.Not much use to us though; they had to be left for several years for a good result! It seems that embedded sand was also removed by this process.
On second thoughts I have taken so long on one project it might have been a good idea! 

Edited By colin hawes on 25/01/2012 13:26:50

Thread: Making your own case hardening compound.
24/01/2012 15:11:36
I have had great success using charcoal from a bonfire and slivers of leather from an old belt to case harden a roller bearing race for an ancient vehicle. The part was packed in a tobacco tin and sealed with yellow clay from my garden. It is important to seal the tin. I can't remember how long the tin was kept at red heat but I got a deep enough case to grind the part in my lathe after hardening.
Thread: Is it just me
28/12/2011 15:38:20
I've got so many scrapped things I can't bear to get rid of that I forget what I've got and go and buy one!! £!x%!!!. It hurts.
Colin
Thread: Reamers - hand vs MT
28/12/2011 15:26:19
Reamers are intended to produce a very close tolerance hole and are most likely to do this if allowed to float a little, to follow the drilled hole, by holding them the minimal amount in the drill chuck.Reamers with a taper shank are more likely to have a tendency to bore the hole due to inaccuracy in a tailstock.
Colin
Thread: Slitting saw thickness
01/12/2011 10:35:04
Rigid workholding is of utmost importance. Vibration can easily come from a flimsy setup.
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