Milling Slots

This topic has 12 replies, 10 voices, and was last updated 2 April 2017 at 14:18 by ronan walsh.

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21 November 2016 at 11:05 #267679
simon Hewitt 1
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@simonhewitt1
I need to mill slots in 2 pieces of Gauge plate 1/8" thick. Slots are 3/32 and 1/2" wide and about 1" long (to make the base of a slide valve chest). I cannot get them neat,parallel, straight! what advice? I always seem to get the end cutting wider than the main length, or changing width along the cut, ….
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21 November 2016 at 11:05 #8402
simon Hewitt 1
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@simonhewitt1
Milling neat slots in Gauge Plate
21 November 2016 at 11:21 #267681
not done it yet
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@notdoneityet
Initially more narrow than required finished size, then clean up the slot sides to size. That is if all other tnings are satisfacory – support, rigidity of machine, tool quality, axes tightened down, etc
21 November 2016 at 11:22 #267683
Nick_G
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@nick_g
Posted by simon Hewitt 1 on 21/11/2016 11:05:27:

I always seem to get the end cutting wider than the main length, or changing width along the cut, ….

.

Have you got the table locked down in the axis you are not moving the cut in.?

If so are the gibs in the axis you are moving adjusted to give as little play / movement as possible while still remaining smooth to axis movement.

Nick
21 November 2016 at 11:42 #267689
Neil Wyatt
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@neilwyatt
Unless you are taking very shallow cuts a 3/32" cutter will flex on a tough material like gauge plate, especially if you are using an end mill rather than a slot drill.

Try using a short 1/16" FC3 cutter to mill out the centre then take a skim off each side.

Neil
21 November 2016 at 12:44 #267698
Hopper
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@hopper
As mentioned already, use a two-flute slot drill rather than a four-flute end mill when milling slots.
21 November 2016 at 13:23 #267712
Chris Evans 6
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@chrisevans6
O1 (gauge plate) is a bitch to machine even after years of experience so don't lose heart. Do as suggested and make sure gibs are adjusted/table locked and use a slot drill.
21 November 2016 at 16:15 #267742
JasonB
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@jasonb
Real question is why does it have to be gauge plate?

Bit of Mild steel would do or better still slice off the end of a bit of round cast iron, flat brass strip or plate.

If you must go with gauge plate then I would first drill the two ends of the slot 3/32, rough out the middle with a 2mm FC-3 cutter and then finish off with a 2-flute 3/32" cutter at 1/32" depth per pass.
21 November 2016 at 16:21 #267743
simon Hewitt 1
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@simonhewitt1
because I have some, and if I get it right, it will last forever.

But if I cannot get it right, i may start again with brass.
2 April 2017 at 12:29 #291782
Tony Pratt 1
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@tonypratt1
Posted by simon Hewitt 1 on 21/11/2016 16:21:48:

because I have some, and if I get it right, it will last forever.

But if I cannot get it right, i may start again with brass.

It make take forever to get it right Seriously for this application you would be better off using brass or mild steel.

Tony
2 April 2017 at 12:47 #291790
Ian S C
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@iansc
The gauge plate is susceptible to rusting, more so than mild steel, and even if your steam engine is only used with air, it will be subject to condensation.

Ian S C
2 April 2017 at 13:27 #291796
JasonB
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@jasonb
Denbeigh Drill question moved to here
2 April 2017 at 14:18 #291803
ronan walsh
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@ronanwalsh98054
Have you considered having it wire edm'ed ? But as people here have said, gauge plate rusts like billy-oh.
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