Needs Pictures: 0
Results 1 to 15 of 24
-
6th Mar 2021, 05:30 PM #1Member
- Join Date
- Feb 2021
- Location
- Australia Brisbane Qld
- Posts
- 51
Cleaning up surface of internal bores on lathe
If I make a cylinder that I want to fit inside a bore, and this is not specifically about pistons in blocks , just generally speaking, with my cylindrical rod in the lathe I use a file or sandpaper to clean up the outside diameter of the cylinder prior to attempting a press fit ......but if I have just used an internal boring bar to make a hole , how do I improve , smooth or polish the inside when it痴 tricky to see or get in there ? I知 not stupid enough to stick a finger wrapped in sandpaper inside the bore. I知 aware I値l just get my finger ripped off or broken. I have a very healthy respect for the torque of the machine
-
6th Mar 2021, 10:15 PM #2Most Valued Member
- Join Date
- May 2011
- Location
- Murray Bridge S Aust.
- Age
- 71
- Posts
- 5,945
There are several ways this can be done, using the boring bar with very fine feed, and a radiused cutting edge. Honing as per a car engine hone or a brake cylinder hone, or if it's a small diameter, reaming. Using a tool post grinder is another option, as a last resort as it's a VERY messy operation for the lathe.
There are others on here that are far better informed than I on this subject.
KrynTo grow old is mandatory, growing up is optional.
-
7th Mar 2021, 12:27 AM #3I break stuff...
- Join Date
- Aug 2010
- Location
- Toorloo Arm, VIC
- Age
- 39
- Posts
- 1,270
Piece of dowel with a slit hacksawed in the end, and a piece of sandpaper in the slit that then wraps around the outside?
-
7th Mar 2021, 12:57 AM #4
Hi Steve, Guys,
If you are just going for a press fit, then as Kryn says, use a well rounded tip on your boring bar cutter and a fine feed. You shouldn't need to do anything else.
If you are going to put a piston in there then as
Jekyll and HydePiece of dowel with a slit hacksawed in the end, and a piece of sandpaper in the slit that then wraps around the outside?Best Regards:
Baron J.
-
7th Mar 2021, 06:54 AM #5Member
- Join Date
- Feb 2021
- Location
- Australia Brisbane Qld
- Posts
- 51
I did not know about brake cylinder hones , but after reading about them here, I found a local supplier that offers one between 19-63 mm. That will cover most of what I知 likely to need. Most of my boring bars are insert type but I have a couple of brazed tip units that I can sharpen to a radius tip , and the edge of a reamer could also work , and good old sandpaper wrapped around a stub too .....good tips men, thanks
-
7th Mar 2021, 11:37 AM #6Gear expert in training
- Join Date
- Aug 2008
- Location
- Melbourne
- Age
- 34
- Posts
- 1,075
You should be able to get perfectly finished bores straight off the tool with the right insert and cutting parameters. What material, speed, feed and cut depth are you using?
-
7th Mar 2021, 01:21 PM #7Most Valued Member
- Join Date
- Nov 2017
- Location
- Geelong, Australia
- Age
- 57
- Posts
- 2,651
If you池e buying a hone that you think is likely to get a bit of use then make sure that replacement stones are available or that it痴 cheap enough to throw away if they aren稚.
A hone that will go as small as 19mm will only have small stones so you will wear them out pretty quickly on larger bores.
Like sandpaper, Scotchbrite or emery cloth in a split arbor also work well if the bore has just been machined and you池e only trying to improve surface finish.
Steve
-
7th Mar 2021, 06:03 PM #8Senior Member
- Join Date
- Nov 2019
- Location
- Brisbane
- Age
- 69
- Posts
- 452
bore finishing
Hi again.
A hone will correct out of round and concentricity as well as finish the bore. If you just want to improve the finish I have used pvc tube split at the end and wet and dry. if it is ferrous and 400 grit is fine enough then try alox no fill paper.
regards
BC
-
7th Mar 2021, 08:41 PM #9
Hi Steve,
The reason a rounded tip works well is because, when you are boring under power, you are actually cutting a very fine thread in the material surface.
Say you were using 2 thou per turn, then the rounding on the tool tip should be about three times that. The idea is that the rounding is greater than the width of thread produced by the feed and removes them giving a more smooth finish ! Its also more easily lapped/polished when finished if needed.
HTH.Best Regards:
Baron J.
-
7th Mar 2021, 09:41 PM #10Golden Member
- Join Date
- Sep 2008
- Location
- Riddells Creek, Vic.
- Posts
- 831
I wouldn't expect too much from a simple spring loaded brake cylinder hone, they are not designed to remove material like a proper honing mandrel such as a Sunnen etc.
-
7th Mar 2021, 10:07 PM #11Gear expert in training
- Join Date
- Aug 2008
- Location
- Melbourne
- Age
- 34
- Posts
- 1,075
If it's just to smooth the bore out, rather than to open the bore out to size, a cheapy might do the job.
Just remember that your bore size WILL grow a little, regardless of how you do it, so it might be prudent to work to the small end of your tolerance range until you determine how much material your hone is removing.
-
7th Mar 2021, 10:47 PM #12Intermediate Member
- Join Date
- Aug 2020
- Location
- Cowaramup WA
- Posts
- 28
For the sake of completeness, there are also available flexible Ball hones which individually suit only a small range of diameters and tend to be expensive.
It is also relatively easy to make expanding laps to polish bores. They can be purchased, but don't seem to be readily available in Aus, (though I haven't looked too hard.)
Dave.
-
8th Mar 2021, 09:34 AM #13Mechanical Butcher
- Join Date
- Oct 2004
- Location
- Southern Highlands NSW
- Posts
- 1,894
I have made some motorcycle small end bronze bushes, finishing freehand with a brake cylinder hone, fine stones.
An old engineer who used to race bikes taught me this method:
- Chuck a piece of leaded bronze, face and turn OD to size plus one thou.
- Still in chuck, bore ID to gudgeon pin size, part off.
- Press into conrod. The bush ID will decrease by about a thou.
- Use brake hone with kero, reciprocating, until pin fits nicely.
This has worked for me every time.
I don't think I could provide the reciprocating action in a lathe, unless with a special complicated arrangement.
-
8th Mar 2021, 01:16 PM #14Golden Member
- Join Date
- Dec 2007
- Location
- Adelaide
- Posts
- 574
I use indexible tip type boring bars and don't have too much trouble getting a good finish, from experience, once I'm within .0015' - .002" of the final size I take another 3 or 4 more cuts at the same setting - finest feed with the cross slide locked - this usually brings it to the correct size, if not then a few more cuts at the same setting - the theory being that you will always get tool spring with a boring bar - the amount will depend on the length and size of the boring bar, so it is best to set the length just enough for the hole depth and use the biggest boring bar that will fit even if it means changing up to a bigger bar as the hole gets bigger. With a bit of experience you get to know how much spring to expect.
-
8th Mar 2021, 08:57 PM #15Most Valued Member
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 3,228
Similar Threads
-
Measuring bores
By morrisman in forum METALWORK GENERALReplies: 16Last Post: 1st Feb 2016, 02:26 PM -
Lathe Chuck Internal Lubrication
By electrosteam in forum METALWORK GENERALReplies: 11Last Post: 2nd Feb 2015, 08:54 PM -
cleaning surface plates and gauge blocks
By markgray in forum METALWORK GENERALReplies: 3Last Post: 27th Oct 2014, 04:12 AM -
Using an internal tap with a lathe
By nearnexus in forum METALWORK GENERALReplies: 13Last Post: 1st May 2014, 11:58 AM -
lathe cleaning
By tanii51 in forum THE HERCUS AREAReplies: 4Last Post: 4th Jan 2010, 06:46 PM