Model Engine Maker

Help! => Mistakes, muckups, and dangerous behaviour => Topic started by: scc on November 21, 2017, 09:26:07 PM

Title: wrong size holes
Post by: scc on November 21, 2017, 09:26:07 PM
I must have improved, no cock-ups since April :ThumbsUp:    I've made up for it now :ThumbsDown:

Spotting through the cylinder covers into the cylinder casting for the 1/4 BSF studs I have somehow managed to drill both ends (that's for 36 studs) with a 6mm drill :facepalm: I have no idea what  or why :Mad:

I thought if I tapped the holes 7 x 1.0 I could get away with by just making 7mm studs and nuts with the same A/F as bsf.   Can I find 7mm mild steel rod??? nobody seems to do it., or 9/32" for that matter.  I did not want to "slim down" 5/16" rod but it looks like I may have to.

Any advice people?                   Terry
Title: Re: wrong size holes
Post by: Admiral_dk on November 21, 2017, 10:07:31 PM
Heli-coils  :ThumbsUp: (goes under different names too) are a wire coil made from a diamond shaped, plus a thread tool 1mm. bigger in diameter than the defect one, plus and insert tool, plus the right diameter drill. These can be bought as a kit in one ore more sizes in a box.

First drill the hole, cut the new thread, place the coil in the insert tool and screw it in, Remove tool and take a punch, place it next to the tab on the coil that was used to screw the coil into position, use a hammer and give it a smal wack and the new thread is ready  :whoohoo:

There are other options, as in plug the holes and start again, for one, or your own suggestion comes to mind.

Best wishes

Per
Title: Re: wrong size holes
Post by: RayW on November 21, 2017, 10:12:03 PM
I just searched on eBay and found item number 272045668356
This is a company selling mild steel rod in lots of sizes including  7mm.

Ray
Title: Re: wrong size holes
Post by: Bluechip on November 21, 2017, 10:15:24 PM
I got some 7mm 303 Stainless from here:

https://www.aluminiumwarehouse.co.uk/stainless-steel/round-bar/diameter/7-mm/unit-of-measurement/metric

Some 2.61 for 1500mm.

Beware, shipping cost is somewhat ferocious if you only want a small order ...  :'(

Dave

Title: Re: wrong size holes
Post by: scc on November 21, 2017, 10:18:39 PM
Thanks  Ray and Dave,     Ebay looks favourite .            Forum personnel extracted me from the brown stuff again :cheers:    Terry
Title: Re: wrong size holes
Post by: jadge on November 21, 2017, 10:30:35 PM
Is your cylinder block to the LSM design or the earlier Filby design with the thick liners? If there's room I'd drill and tap 8mm, or preferably 10mm. I'd also use 8mm fine (1mm pitch) or10mm in constant pitch, ie, 1mm or 0.75mm. Then I'd make and screw in plugs and then drill and tap " BSF. Alternatively you could use 5/16" or 3/8" by 32 ME threads. I've checked that some of those threads have Coventry diehead chasers available - shall I warm up the repetition lathe?  ;)

Andrew
Title: Re: wrong size holes
Post by: scc on November 22, 2017, 05:08:06 PM
Hi Andrew,    It's the early type with the thick liners.  I'd weighed up the plug option, but now having found 7mm rod I think I'll go down that route. :thinking:    Not finalised yet.   Wish I had a repetion lathe :)     Regards     Terry
Title: Re: wrong size holes
Post by: scc on November 25, 2017, 03:50:41 PM
Apologies Per,      I seem to have missed your reply and hence ommitted my thanks :facepalm2:  Thank you.
Best wishes..........Terry